First Cut


G K
 

Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


Andrei
 

Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 


From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000@...>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


rlm_mcv
 

My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000@...>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


George Steube
 

What kind of steel?  If it came from Lowes or HD it will never cut smooth.  Get some leaded steel (12L14) before you worry about adjustments. 

George

On 6/24/2021 4:33 PM, G K via groups.io wrote:
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


G K
 

No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv@...> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000@...>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


david pennington
 

9C only has half nuts for power feed.

David W. Pennington
Denver, Colorado
720-442-3744


On Thursday, June 24, 2021, 04:10:23 PM MDT, rlm_mcv via groups.io <rlm_mcv@...> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000@...>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


david pennington
 

Also try the other two spindle speeds. Looks like you may have tool chatter going on, which can be a function of the free air resonant frequency of the tool and the surface speed of the work piece. 

Changing the speed can sometimes eliminate that form of chatter by moving the stimulus along the frequency spectrum to get it away from the resonant frequency.

Changing the free length of the tool--if that's possible--will change its resonant frequency.


David W. Pennington
Denver, Colorado
720-442-3744


On Thursday, June 24, 2021, 04:21:01 PM MDT, G K via groups.io <bug_hunter2000@...> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv@...> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000@...>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


Bruce
 

You need a center hole and use the tail stock.


Steven H
 

410 rpm is about 160 sfpm for a 1.5 inch diameter. Way too fast for HSS. Try cutting the rpm in half and see if that makes a difference.

Steve Haskell


Bill in OKC too
 

for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000@...> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv@...> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000@...>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


m. allan noah
 

Add tailstock support, vary spindle speed, add cutting oil, reduce feed rate, change cutter geometry, sharpen cutter. Some mix of those ideas will help.


On Thu, Jun 24, 2021, 7:40 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv=yahoo.com@groups.io> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000=yahoo.com@groups.io>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


Sam
 

Putting a large radius round nose on the cutter, hone it sharp enough to shave fingernail.


On Thu, Jun 24, 2021 at 8:48 PM m. allan noah <kitno455@...> wrote:
Add tailstock support, vary spindle speed, add cutting oil, reduce feed rate, change cutter geometry, sharpen cutter. Some mix of those ideas will help.

On Thu, Jun 24, 2021, 7:40 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv=yahoo.com@groups.io> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000=yahoo.com@groups.io>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


G K
 

Thanks to all.  We've moved a long way in the right direction.  I believe the biggest issue, as a lot of you mentioned, was spindle speed.  I reduced it to 244 rpm, and it is a lot better.  Not consistent through the entire length of cut, but much better.  Would the finish improve with depth of cut?  How deep a bite can I go?  I've read the maximum cut is 0.125 on a SB9, but no way am I comfortable with that.  What is a good, safe, deep cut?  I'll start to play with the depth of cut, and feed rate and see where she leads.

Thanks a bunch for all the help.

For those that recommended adding tailstock support, I agree that when working a piece of steel with greater stick-out than 3-4 times the diameter, you should have tail support.  But given that nature of the two disc headstock to bed alignment test, no tail support should be used.  The next step would be to run a piece between centers in a similar test to align the tailstock.

Thanks again,

Greg

On Thursday, June 24, 2021, 07:48:39 PM CDT, m. allan noah <kitno455@...> wrote:


Add tailstock support, vary spindle speed, add cutting oil, reduce feed rate, change cutter geometry, sharpen cutter. Some mix of those ideas will help.

On Thu, Jun 24, 2021, 7:40 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv=yahoo.com@groups.io> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000=yahoo.com@groups.io>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


Ondrej Krejci
 

Greetings,

For testing the spindle-to ways-misalignment, which I believe you are trying; hence, no tailstock support, a sharp tool, about thirty degree tip, with 0.005" radius, will relieve tool pressure.
Appropriate speed for part and cutting tool material should be used, about 100 fpm for 10 series steel using HSS, and a fine feed, less than the tool nose radius.

Enjoy,


OK

On Thursday, June 24, 2021, 09:27:26 PM EDT, G K via groups.io <bug_hunter2000@...> wrote:


Thanks to all.  We've moved a long way in the right direction.  I believe the biggest issue, as a lot of you mentioned, was spindle speed.  I reduced it to 244 rpm, and it is a lot better.  Not consistent through the entire length of cut, but much better.  Would the finish improve with depth of cut?  How deep a bite can I go?  I've read the maximum cut is 0.125 on a SB9, but no way am I comfortable with that.  What is a good, safe, deep cut?  I'll start to play with the depth of cut, and feed rate and see where she leads.

Thanks a bunch for all the help.

For those that recommended adding tailstock support, I agree that when working a piece of steel with greater stick-out than 3-4 times the diameter, you should have tail support.  But given that nature of the two disc headstock to bed alignment test, no tail support should be used.  The next step would be to run a piece between centers in a similar test to align the tailstock.

Thanks again,

Greg

On Thursday, June 24, 2021, 07:48:39 PM CDT, m. allan noah <kitno455@...> wrote:


Add tailstock support, vary spindle speed, add cutting oil, reduce feed rate, change cutter geometry, sharpen cutter. Some mix of those ideas will help.

On Thu, Jun 24, 2021, 7:40 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv=yahoo.com@groups.io> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000=yahoo.com@groups.io>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


Bill in OKC too
 

The bigger machines I'm playing with at school will do a cut of .100 to .050 fairly easily with a sharp HSS tool. NOT a large radius tool, but a fairly small radius. Unless you're in a hurry, and need to do a lot of roughing, I generally prefer a .020-.040 depth of cut. When I want a very fine surface, I'll do .005-.015 DOC, followed by a cut under .005", and then a spring pass. Feed it again without adjusting the depth of cut. THEN check your surface finish. This is very much an area where YMMV!

If you still don't like the surface finish, check all the gibs, and adjust them to just a bit too tight, and then slacken them just a teensly bit. Then try again. Might also need to adjust the spindle bearings.

If you turn between centers, you eliminate many of the variables. Once you can get a good finish that way, branch out to see what other things you might need to adjust. And lube the heck out of it all! ;)

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 08:27:27 PM CDT, G K via groups.io <bug_hunter2000@...> wrote:


Thanks to all.  We've moved a long way in the right direction.  I believe the biggest issue, as a lot of you mentioned, was spindle speed.  I reduced it to 244 rpm, and it is a lot better.  Not consistent through the entire length of cut, but much better.  Would the finish improve with depth of cut?  How deep a bite can I go?  I've read the maximum cut is 0.125 on a SB9, but no way am I comfortable with that.  What is a good, safe, deep cut?  I'll start to play with the depth of cut, and feed rate and see where she leads.

Thanks a bunch for all the help.

For those that recommended adding tailstock support, I agree that when working a piece of steel with greater stick-out than 3-4 times the diameter, you should have tail support.  But given that nature of the two disc headstock to bed alignment test, no tail support should be used.  The next step would be to run a piece between centers in a similar test to align the tailstock.

Thanks again,

Greg

On Thursday, June 24, 2021, 07:48:39 PM CDT, m. allan noah <kitno455@...> wrote:


Add tailstock support, vary spindle speed, add cutting oil, reduce feed rate, change cutter geometry, sharpen cutter. Some mix of those ideas will help.

On Thu, Jun 24, 2021, 7:40 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv=yahoo.com@groups.io> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000=yahoo.com@groups.io>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


ww_big_al
 

My estimate is: Stick out is too far without support. Tool my be ground wrong and/or dull. Other causes could be loose gib or bearings. Tool rakes incorrect,  or not on center.

 

Try chucking it up with only 3” sticking out. If cut is good, then center drill for a tailstock support. If cut is bad, use a different tool bit.

Al

 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of G K via groups.io
Sent: Thursday, June 24, 2021 5:34 PM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] First Cut

 

Afternoon Guys,

 

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

 

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

 

I've been running at 410 rpm

Depth of cut between 0.003 and 0.005

Feed rate of 0..0031

Using a HSS cutter that came with the lathe

 

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

 

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

 

Thanks a lot for whatever input you may be able to provide.

 

Greg


Nick Andrews
 

I will say that while I haven't tried any cutting with it yet,  just applying Vactra 2 on the ways of my lathe sure seems a lot smoother than the ole 30wt I was using.  

One of the first things I tried on the lathe was turning a new detent pin for the left gearbox lever from O1 3/8".  Too much flex.  Cut the mangled end off, center drilled and supported with a live center.  Then I turned it near the end at around 8" away from the 3-jaw.  Turned out pretty well,  and it was cool to use the lathe to make a repair part for itself. 

On Thu, Jun 24, 2021, 9:15 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
The bigger machines I'm playing with at school will do a cut of .100 to .050 fairly easily with a sharp HSS tool. NOT a large radius tool, but a fairly small radius. Unless you're in a hurry, and need to do a lot of roughing, I generally prefer a .020-.040 depth of cut. When I want a very fine surface, I'll do .005-.015 DOC, followed by a cut under .005", and then a spring pass. Feed it again without adjusting the depth of cut. THEN check your surface finish. This is very much an area where YMMV!

If you still don't like the surface finish, check all the gibs, and adjust them to just a bit too tight, and then slacken them just a teensly bit. Then try again. Might also need to adjust the spindle bearings.

If you turn between centers, you eliminate many of the variables. Once you can get a good finish that way, branch out to see what other things you might need to adjust. And lube the heck out of it all! ;)

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 08:27:27 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


Thanks to all.  We've moved a long way in the right direction.  I believe the biggest issue, as a lot of you mentioned, was spindle speed.  I reduced it to 244 rpm, and it is a lot better.  Not consistent through the entire length of cut, but much better.  Would the finish improve with depth of cut?  How deep a bite can I go?  I've read the maximum cut is 0.125 on a SB9, but no way am I comfortable with that.  What is a good, safe, deep cut?  I'll start to play with the depth of cut, and feed rate and see where she leads.

Thanks a bunch for all the help.

For those that recommended adding tailstock support, I agree that when working a piece of steel with greater stick-out than 3-4 times the diameter, you should have tail support.  But given that nature of the two disc headstock to bed alignment test, no tail support should be used.  The next step would be to run a piece between centers in a similar test to align the tailstock.

Thanks again,

Greg

On Thursday, June 24, 2021, 07:48:39 PM CDT, m. allan noah <kitno455@...> wrote:


Add tailstock support, vary spindle speed, add cutting oil, reduce feed rate, change cutter geometry, sharpen cutter. Some mix of those ideas will help.

On Thu, Jun 24, 2021, 7:40 PM Bill in OKC too via groups.io <wmrmeyers=yahoo.com@groups.io> wrote:
for that diameter, cutting mild steel with HSS tooling that's properly ground, you should be using about 275rpm, according to my little Feed&Speed calculator. Try dropping the speed, and try running it faster, and see if you get an improvement in finish.

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)




On Thursday, June 24, 2021, 05:21:00 PM CDT, G K via groups.io <bug_hunter2000=yahoo.com@groups.io> wrote:


No clutch on a 9c, so half-nut is the way to go.  I believe it is 1018, that I bought as a drop from a fab shop.  I could be above center, I'll check and lower the bit.  I will also switch to a slower feed (quick swap of a one gear).  After that I'll look at trying a different cutter.

Thanks and keep the suggestions flowing.

On Thursday, June 24, 2021, 05:10:19 PM CDT, rlm_mcv via groups.io <rlm_mcv=yahoo.com@groups.io> wrote:


My thoughts cutter ground wrong and above center.  Also looks like using 1/2 nut instead of clutch for feed.  Not a pro but my guesses.

On Thursday, June 24, 2021, 5:06:22 PM CDT, Andrei <calciu1@...> wrote:


Cutter problem and/or feed problem. Fix one and do another test cut, then fix the other and cut again. 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of G K via groups.io <bug_hunter2000=yahoo.com@groups.io>
Sent: Thursday, June 24, 2021 5:33 PM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] First Cut
 
Afternoon Guys,

Just made my first cuts on my rebuild South Bend 9c.  First off, thanks to all who have helped me along the way with eh clean-up and reassembly.

Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter.

I've been running at 410 rpm
Depth of cut between 0.003 and 0.005
Feed rate of 0..0031
Using a HSS cutter that came with the lathe

You can see from the photo that the surface finish is for sh$t.  Looks almost like a reverse thread.

Any suggestions relative to machine setup adjustments, machine tuning, spindle speed, feed rate, depth of cut, cutter, etc. would be appreciated.  Also, if I can answer any questions, send them on over.  Tough to troubleshoot when you've never done it before.

Thanks a lot for whatever input you may be able to provide.

Greg


eddie.draper@btinternet.com
 

Dear all,


There seems to be a lot of missing the point here. The test that is being attempted requires a very light cut WITHOUT the benefit of tailstock support. The purpose is to detect (effectively) whether the headstock spindle is truly parallel to the surfaces of the bed ways, and detects wear and distortion. I would apply the following criteria:


The bar should be a free machining steel so that it encourages a good finish. Preferably mild steel, but something a bit harder will do. NOT EN8, for example.


The tool should be as stiff as possible, i.e as large a section as can be accommodated, with as short an overhang as can be accommodated. Mounting the tool straight to the compound slide top rather than in a fancy tool post will add some stiffness.


The tool shape should be a "knife" tool, ground correctly for turning (not facing) steel. The top rake should be about 7 degrees, front and side clearance between 3 & 7 degrees, the cutting edge should be set square to the axis, the side that is nearly parallel to the axis wants 5 - 10 degrees clearance. Leave almost but not quite a sharp point on it (no radius). Just one rub with a smooth slip at 45 degrees to the axis, maintaining clearance. Polish all faces with a slip or diamond lap after grinding. Set it DEAD on centre height, by first taking a light facing cut to see where it ends up at the distance from the chuck where you are working.


This shape of tool end is not robust and should be used for only the lightest of finishing cuts, with lubricant. No more than about 0.005" at a time, reducing towards finishing. The overhang of the job will limit what you can do, anyway. The sole purpose of the design is to minimise tool forces.


In order to allow rapid traverse between the chuck and outer ends of the bar, reduce the diameter of the centre part SLIGHTLY (with a more robust tool) below that at which the measurements will be made. Only slightly, because diameter reductions have a disproportionate effect upon stiffness.


If your lathe does not have a very slow power feed, only the screwcutting apparatus, use manual feed as slow as you can. Make a number of passes at the same setting as final cuts, until no further swarf is created. Re-polish the tool before you take the last cut with added cut depth on both ends of the bar so both ends are seeing the same sharp tool protrusion. Use a cutting speed as recommended for the tool, workpiece and lubricant material combination. If still no good, try slower & faster. If that doesn't cure it, there is probably some slack somewhere.


If you have a badly bell mouthed chuck, that will add further difficulties. You can detect this by lightly closing it onto the bar and attempting to wobble the bar. If the chuck then wobbles, you're on a hiding to nothing, as it means the headstock bearings are shot, and that should be your starting point for further work. If only the bar and not the chuck wobbles, try wrapping a shim around the bar where the jaws are slack.


The diameter differences between the chuck end and outer end is the answer you are looking for. There is a quicker and easier way if you have a dial gauge, as follows:


Supporting the outer end with a centre, machine both ends to the same diameter. Remove the outer centre to allow the bar to spring to its natural shape. With a DTI mounted on the saddle, try it at both ends and note the differences in readings. If the needle wobbles at the outer end, just take the average. The needle wobble will just mean that the tailstock wasn't centred when the centre drill first made contact and it pulled the bar over a bit.


To centre the tailstock, you need the bar turned or measured with the DTI between centres, not in the chuck. My advice is that if you have a taper turning attachment, NEVER displace the tailstock centre, as it can take days to get back right again. On common user lathes, permission from the gaffer should be sought before shifting a tailstock sideways, and (s)he who shifts it puts it back right before they go home.


Hope this helps,


Eddie



m. allan noah
 

Really well written, Eddie, but I think you might also be missing the point. It makes sense to learn to take a cut and read the material, before worrying about precision alignment.


On Fri, Jun 25, 2021, 4:57 AM eddie.draper@... via groups.io <eddie.draper=btinternet.com@groups.io> wrote:

Dear all,


There seems to be a lot of missing the point here. The test that is being attempted requires a very light cut WITHOUT the benefit of tailstock support. The purpose is to detect (effectively) whether the headstock spindle is truly parallel to the surfaces of the bed ways, and detects wear and distortion. I would apply the following criteria:


The bar should be a free machining steel so that it encourages a good finish. Preferably mild steel, but something a bit harder will do. NOT EN8, for example.


The tool should be as stiff as possible, i.e as large a section as can be accommodated, with as short an overhang as can be accommodated. Mounting the tool straight to the compound slide top rather than in a fancy tool post will add some stiffness.


The tool shape should be a "knife" tool, ground correctly for turning (not facing) steel. The top rake should be about 7 degrees, front and side clearance between 3 & 7 degrees, the cutting edge should be set square to the axis, the side that is nearly parallel to the axis wants 5 - 10 degrees clearance. Leave almost but not quite a sharp point on it (no radius). Just one rub with a smooth slip at 45 degrees to the axis, maintaining clearance. Polish all faces with a slip or diamond lap after grinding. Set it DEAD on centre height, by first taking a light facing cut to see where it ends up at the distance from the chuck where you are working.


This shape of tool end is not robust and should be used for only the lightest of finishing cuts, with lubricant. No more than about 0.005" at a time, reducing towards finishing. The overhang of the job will limit what you can do, anyway. The sole purpose of the design is to minimise tool forces.


In order to allow rapid traverse between the chuck and outer ends of the bar, reduce the diameter of the centre part SLIGHTLY (with a more robust tool) below that at which the measurements will be made. Only slightly, because diameter reductions have a disproportionate effect upon stiffness.


If your lathe does not have a very slow power feed, only the screwcutting apparatus, use manual feed as slow as you can. Make a number of passes at the same setting as final cuts, until no further swarf is created. Re-polish the tool before you take the last cut with added cut depth on both ends of the bar so both ends are seeing the same sharp tool protrusion. Use a cutting speed as recommended for the tool, workpiece and lubricant material combination. If still no good, try slower & faster. If that doesn't cure it, there is probably some slack somewhere.


If you have a badly bell mouthed chuck, that will add further difficulties. You can detect this by lightly closing it onto the bar and attempting to wobble the bar. If the chuck then wobbles, you're on a hiding to nothing, as it means the headstock bearings are shot, and that should be your starting point for further work. If only the bar and not the chuck wobbles, try wrapping a shim around the bar where the jaws are slack.


The diameter differences between the chuck end and outer end is the answer you are looking for. There is a quicker and easier way if you have a dial gauge, as follows:


Supporting the outer end with a centre, machine both ends to the same diameter. Remove the outer centre to allow the bar to spring to its natural shape. With a DTI mounted on the saddle, try it at both ends and note the differences in readings. If the needle wobbles at the outer end, just take the average. The needle wobble will just mean that the tailstock wasn't centred when the centre drill first made contact and it pulled the bar over a bit.


To centre the tailstock, you need the bar turned or measured with the DTI between centres, not in the chuck. My advice is that if you have a taper turning attachment, NEVER displace the tailstock centre, as it can take days to get back right again. On common user lathes, permission from the gaffer should be sought before shifting a tailstock sideways, and (s)he who shifts it puts it back right before they go home.


Hope this helps,


Eddie



comstock_friend
 

Allan, Greg, the OP, did say: "Can't seem to get a nice, smooth cut.  Chucked up a 7-inch long, 1-1/2 inch diameter piece of steel I had laying around in an attempt to do the two-collar alignment test.  I used a four-jaw chuck, and adjusted it to sub .001 runout near the chuck.  No support on the tail end.  I faced it off, then started reducing the diameter."

But as you say, maybe some experience is in order "
before worrying about precision alignment."

John