Turning question follow-up


E A
 

First, when I asked for ideas for turning down some stainless steel tubing, you all gave me a bunch of great pointers, so thank you all!
The first picture shows a section of tube going down from 1.25" to 30mm. The second shows the end product. You can see the ratty part I was replacing just to the left of the shiny one.

A couple of questions.... you can see from the pic I was using a carbide insert tool. Was taking cuts of aprox .005" at a pass. 244 rpm...
So...
Is it normal for the work piece to get kind of hot? I used tap magic, and it was smoking some, and the metal was fairly hot after one pass...
Rather than chips, I was getting long springs of metal.... so what does that indicate?
And lastly, when I tried to use a TS cut-off tool to put in a light groove (just as a mark to go by for facing to correct length) the tool did not want to bite in at all. Possible causes?
Erik A


Ondrej Krejci <okrejci@...>
 

Howdy,

Without flood coolant, parts will get hot.
Stringers, instead of broken chips, are caused by low feed and small cut depth, which sometimes cannot be avoided.
Positive rake is generally prefered for stainless steel because it needs to be sheered away not torn off.  Most inserts are made with negative rake for steel.

OK

On Wednesday, November 9, 2022 at 10:10:15 AM EST, E A <b-arch@...> wrote:


First, when I asked for ideas for turning down some stainless steel tubing, you all gave me a bunch of great pointers, so thank you all!
The first picture shows a section of tube going down from 1.25" to 30mm. The second shows the end product. You can see the ratty part I was replacing just to the left of the shiny one.

A couple of questions.... you can see from the pic I was using a carbide insert tool. Was taking cuts of aprox .005" at a pass. 244 rpm...
So...
Is it normal for the work piece to get kind of hot? I used tap magic, and it was smoking some, and the metal was fairly hot after one pass...
Rather than chips, I was getting long springs of metal.... so what does that indicate?
And lastly, when I tried to use a TS cut-off tool to put in a light groove (just as a mark to go by for facing to correct length) the tool did not want to bite in at all. Possible causes?
Erik A


Rogan Creswick
 

The cut off tool may not be right on center, vertically.  If it is even slightly above center it won't cut, because the clearance of the tool will hit the material before the cutting edge.

Be careful, though, since being to low can cause the material to climb up the tool, and with a part like that it *could* climb up, buckle, and crash.

I use a magnifier and compare the tool height with the point of a good center in the tailstock.

It could also just be that the tool isn't sharp, and it needs ground/honed.

--Rogan 

On Wed, Nov 9, 2022, 8:06 AM Ondrej Krejci via groups.io <okrejci=yahoo.com@groups.io> wrote:
Howdy,

Without flood coolant, parts will get hot.
Stringers, instead of broken chips, are caused by low feed and small cut depth, which sometimes cannot be avoided.
Positive rake is generally prefered for stainless steel because it needs to be sheered away not torn off.  Most inserts are made with negative rake for steel.

OK

On Wednesday, November 9, 2022 at 10:10:15 AM EST, E A <b-arch@...> wrote:


First, when I asked for ideas for turning down some stainless steel tubing, you all gave me a bunch of great pointers, so thank you all!
The first picture shows a section of tube going down from 1.25" to 30mm. The second shows the end product. You can see the ratty part I was replacing just to the left of the shiny one.

A couple of questions.... you can see from the pic I was using a carbide insert tool. Was taking cuts of aprox .005" at a pass. 244 rpm...
So...
Is it normal for the work piece to get kind of hot? I used tap magic, and it was smoking some, and the metal was fairly hot after one pass...
Rather than chips, I was getting long springs of metal.... so what does that indicate?
And lastly, when I tried to use a TS cut-off tool to put in a light groove (just as a mark to go by for facing to correct length) the tool did not want to bite in at all. Possible causes?
Erik A


Payson
 

To find center, not using carbide and with the machine not running, bring the cutoff tool (or any cutting tool) to the metal, and insert a short piece of feeler gage between the two. The feeler will angle up down or straight. Down is below center, etc.

Payson. 


Stuart Wilby
 

I use my 6” rule which is always on the machine,  this tip was given to me 55 years ago by a 75 year old instructor ( Clifford Bosworth)


E A
 

Ondrej - Good to know. Since my part is probably too unstable for heavy cuts, I will have to accept stringers. At least I now know the proper term for them!
Rogan - Helpful pointers re the cut off tool. Still not working for me, but then my grinding wheel may be too course (60 g) or the part is too flexible. I was trying to use the parting tool just to make a slight cut, as a guide for facing to finished size. Even at a really slow speed via the back gear was a no go. Reverted to a pointy turning tool to score the tube.
Payson - Neat tip...
This is a great place for help!
Curious if anyone is in the northern DC area?
Erik A

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of Payson <egreene104@...>
Sent: Thursday, November 10, 2022 9:48 AM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] Turning question follow-up
 
To find center, not using carbide and with the machine not running, bring the cutoff tool (or any cutting tool) to the metal, and insert a short piece of feeler gage between the two. The feeler will angle up down or straight. Down is below center, etc.

Payson. 


Stuart Wilby
 

To explain, the 6” rule fits between the cutting tip and the work, trapping it with the crosslide, if it is not vertical then adjustment is needed until it is, simple, works every time.


Stuart Wilby
 

I use my 6” rule which is always on the machine,  this tip was given to me 55 years ago by a 75 year old instructor ( Clifford Bosworth)


Rogan Creswick
 

I suspect you will need to hone the cut off tool on a stone to get a sharp enough edge, but I don't know enough to say what grit that would correspond to.  (Maybe 1000-3000?)


On Fri, Nov 11, 2022, 5:29 AM Stuart Wilby via groups.io <stuartawilby=aol.com@groups.io> wrote:
I use my 6” rule which is always on the machine,  this tip was given to me 55 years ago by a 75 year old instructor ( Clifford Bosworth)


eddie.draper@btinternet.com
 

I've had similar trouble trying to get a freshly ground HSS parting blade to start cutting into medium strength steel. This was cured completely by polishing it with a fine diamond file.


Eddie




------ Original Message ------
From: "E A" <b-arch@...>
To: "SouthBendLathe@groups.io" <SouthBendLathe@groups.io>
Sent: Friday, 11 Nov, 22 At 13:26
Subject: Re: [SouthBendLathe] Turning question follow-up

Ondrej - Good to know. Since my part is probably too unstable for heavy cuts, I will have to accept stringers. At least I now know the proper term for them!
Rogan - Helpful pointers re the cut off tool. Still not working for me, but then my grinding wheel may be too course (60 g) or the part is too flexible. I was trying to use the parting tool just to make a slight cut, as a guide for facing to finished size. Even at a really slow speed via the back gear was a no go. Reverted to a pointy turning tool to score the tube.
Payson - Neat tip...
This is a great place for help!
Curious if anyone is in the northern DC area?
Erik A

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of Payson <egreene104@...>
Sent: Thursday, November 10, 2022 9:48 AM
To: SouthBendLathe@groups.io <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] Turning question follow-up
To find center, not using carbide and with the machine not running, bring the cutoff tool (or any cutting tool) to the metal, and insert a short piece of feeler gage between the two. The feeler will angle up down or straight. Down is below center, etc.

Payson.


eddie.draper@btinternet.com
 

Absolutely fine if your workpiece is a.) circular, b.) concentric, and c.) smooth. If you don't remember to set up all the required tools with a ground bar in a concentric chuck before mounting and spending eternity setting up a casting, you're back to spotting it against a tailstock centre.


Possibly the best method is a custom height gauge that sits on a ground surface on the lathe, such as the bed or (if flat) cross slide. If you have a vernier height gauge, record the exact centre height and set it to that on each occasion of use. I know that my 18" Broadbent, for example, wants its tools set at 18.08" for small work such as truing the home made centre before installing a wheelset, although for the usual diameters of workpieces on that lathe, within 1/4" is good enough. I keep a collection of worn out / broken machine hack saw blades as tool shims. For some reason, there never seems to be a shortage of these...


Eddie




------ Original Message ------
From: "Stuart Wilby via groups.io" <stuartawilby@...>
To: SouthBendLathe@groups.io
Sent: Friday, 11 Nov, 22 At 13:28
Subject: Re: [SouthBendLathe] Turning question follow-up

To explain, the 6” rule fits between the cutting tip and the work, trapping it with the crosslide, if it is not vertical then adjustment is needed until it is, simple, works every time.


Ondrej Krejci <okrejci@...>
 

You could try using a more acute insert, D or V , 55* or 35*, with a small tool nose radius, 0.005", to make more controllable chips.

On Friday, November 11, 2022 at 11:43:26 AM EST, eddie.draper@... via groups.io <eddie.draper@...> wrote:


Absolutely fine if your workpiece is a.) circular, b.) concentric, and c.) smooth. If you don't remember to set up all the required tools with a ground bar in a concentric chuck before mounting and spending eternity setting up a casting, you're back to spotting it against a tailstock centre.


Possibly the best method is a custom height gauge that sits on a ground surface on the lathe, such as the bed or (if flat) cross slide. If you have a vernier height gauge, record the exact centre height and set it to that on each occasion of use. I know that my 18" Broadbent, for example, wants its tools set at 18.08" for small work such as truing the home made centre before installing a wheelset, although for the usual diameters of workpieces on that lathe, within 1/4" is good enough. I keep a collection of worn out / broken machine hack saw blades as tool shims. For some reason, there never seems to be a shortage of these...


Eddie




------ Original Message ------
From: "Stuart Wilby via groups.io" <stuartawilby@...>
To: SouthBendLathe@groups.io
Sent: Friday, 11 Nov, 22 At 13:28
Subject: Re: [SouthBendLathe] Turning question follow-up

To explain, the 6” rule fits between the cutting tip and the work, trapping it with the crosslide, if it is not vertical then adjustment is needed until it is, simple, works every time.