Date   

Re: Metric thread dial

ww_big_al
 

Get yourself a left-hand threading tool. Turn it upside down on the tool post. Run the lathe in reverse and cut the thread towards the tail stock. Should not do this with a threaded-on chuck.

 

Here is a video from Joe Pi demonstrating it.

(29) Threading on a manual lathe BEST TECHNIQUE EVER !!!! - YouTube

Al

 

 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of William Nelson
Sent: Sunday, January 3, 2021 2:36 PM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Metric thread dial

 

Almost every thread I cut is to a shoulder. How do you go about that if you can't disengage the halfnuts? Do you stop the lathe some distance from the shoulder hoping you stop in time or stop far enough to not crash and then hand turn the spindle to get to the shoulder? Perhaps this would be a good operation for left to right threading? I have had the occasion where I would have loved to metric thread but don't have the gears. Maybe in the future. 

Bill form Socal


Re: Metric Thread Dial

sblatheman
 

There is such a thing as IN/METRIC thread dial 



Ted
_._,_._,_


Re: Metric Thread Dial

Bill in OKC too
 

That should work fine, IF you have a reverse switch. My TH42 does not. Isn't a problem for the Heavy 10L yet, as it's not assembled, so when I get close to that, I can start hunting a reversing switch. As they say, YMMV. I'm looking for a reversing switch for the Atlas, but haven't had the intersection of available money and a proper switch happen yet. Some day, if I live long enough... 

Having all the different ways that a job can be done is a good thing, though! Just because I can't make it work just yet doesn't make it not good. Thanks for posting this, too!

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 Sunday, January 3, 2021, 01:42:13 PM CST, Dallas <dallas@...> wrote:


I’ve cut dozens of metric threads on both my Southbend and Atlas lathes. You don’t need metric change gears, metric lead screw or even a thread dial at all.  

Find a gear combination that gives you close to the metric lead you need (.5mm, .75mm, 1mm etc) you can calculate these, but the closest gear combinations are published or there are PC programs that will tell you.

Install the gear combination on your lathe to produce the desired lead (.5mm/revolution etc)

Turn your stock to the correct major diameter

Turn a short section to the minor thread diameter on the left end of the threaded section. You need this to let the lathe stop and not hog into the stock at the end of each cut.

Put the lathe in the slowest belt pulley combination and engage the back gear.  You are looking for the slowest chuck rotation & carriage movement.

Carriage should move toward the headstock when the the chuck  is rotating normally (top coming toward yo)

Adjust compound cross feed to be 29-1/2 degrees (assuming standard 60 degree thread)

Set up a single point thread cutting tool on center, perpendicular to the work piece, with point just touching workpiece. To do this set the MAIN CROSS SLIDE DIAL on Zero first then use the COMPOUND CROSS SLIDE to move the tool in until it just touches the workpiece.


Move carriage past the right end of the workpiece.

Using the COMPOUND CROSS SLIDE handle dial in a small cut (0.001 inch)

close the half nuts and NEVER TOUCH THIS HANDLE AGAIN until you are totally finished

Turn the ELECTRIC POWER SWITCH ON FORWARD to begin forward rotation with cutter moving toward the headstock. 

The cutter should make a light cut and you should see your thread stripe appear.

when the cut is nearing the end and is approaching your minor diameter relief cut, Turn the ELECTRIC POWER SWITCH OFF and let the lathe coast to a stop in the relief area.

Using the MAIN CROSS SLIDE DIAL move the tool away from the workpiece by turning the handle one complete turn from zero, one turn out and back to zero.  You have moved your tool away from the work one turn of the main cross slide

Turn the 
ELECTRIC POWER SWITCH TO REVERSE.  Allow the tool to move to the right until it is past the right end of the workpiece.  Approximately where you started.

Using the MAIN CROSS SLIDE DIAL move the tool back toward the workpiece by turning the handle one complete turn from zero, one turn IN and back to zero.  You now moved your cross slide back where we started.


Using the COMPOUND CROSS SLIDE dial in the next cut (approximately 0.005)

Make the second cut as before, stopping in the runout area. Move the tool out one turn main compound, reverse motor to beginning, move main compound in, dial in third cut etc. repeat this until your thread is complete. You can continue to cut until you hit your minor diameter.  You can also check fit with a nut or mating piece with part still in the lathe.

leaving the half nuts closed all the time ensured the timing of the gear train is correct. 

Dallas Shell



Re: Metric thread dial

Bill in OKC too
 

You can cut threads to driving the carriage from left to right, i.e, towards the tailstock, too. Eliminates the problem. Saw it mentioned on one of the many groups I belong to just a few days ago, IIRC. Could not tell you exactly how, off hand, but I think you'd use a rear tool post with the cutter upside down. I'll see if I can find it. 

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 Sunday, January 3, 2021, 01:37:11 PM CST, William Nelson <wnnelson@...> wrote:


Almost every thread I cut is to a shoulder. How do you go about that if you can't disengage the halfnuts? Do you stop the lathe some distance from the shoulder hoping you stop in time or stop far enough to not crash and then hand turn the spindle to get to the shoulder? Perhaps this would be a good operation for left to right threading? I have had the occasion where I would have loved to metric thread but don't have the gears. Maybe in the future. 

Bill form Socal


Re: Metric thread dial

m. allan noah
 

You CAN disengage the half-nuts when cutting a thread whose type does
not match the thread dial. But, you must then immediately stop the
lathe, and run it in reverse. Then re-engage the half-nuts on the
original mark, and run the tool back out of the thread. See the bottom
of this page for more info.
http://conradhoffman.com/metricthreading.htm

allan

On Sun, Jan 3, 2021 at 2:37 PM William Nelson <wnnelson@sbcglobal.net> wrote:

Almost every thread I cut is to a shoulder. How do you go about that if you can't disengage the halfnuts? Do you stop the lathe some distance from the shoulder hoping you stop in time or stop far enough to not crash and then hand turn the spindle to get to the shoulder? Perhaps this would be a good operation for left to right threading? I have had the occasion where I would have loved to metric thread but don't have the gears. Maybe in the future.

Bill form Socal
--
"well, I stand up next to a mountain- and I chop it down with the edge
of my hand"


Re: Metric Thread Dial

Dallas
 

I’ve cut dozens of metric threads on both my Southbend and Atlas lathes. You don’t need metric change gears, metric lead screw or even a thread dial at all.  

Find a gear combination that gives you close to the metric lead you need (.5mm, .75mm, 1mm etc) you can calculate these, but the closest gear combinations are published or there are PC programs that will tell you.

Install the gear combination on your lathe to produce the desired lead (.5mm/revolution etc)

Turn your stock to the correct major diameter

Turn a short section to the minor thread diameter on the left end of the threaded section. You need this to let the lathe stop and not hog into the stock at the end of each cut.

Put the lathe in the slowest belt pulley combination and engage the back gear.  You are looking for the slowest chuck rotation & carriage movement.

Carriage should move toward the headstock when the the chuck  is rotating normally (top coming toward yo)

Adjust compound cross feed to be 29-1/2 degrees (assuming standard 60 degree thread)

Set up a single point thread cutting tool on center, perpendicular to the work piece, with point just touching workpiece. To do this set the MAIN CROSS SLIDE DIAL on Zero first then use the COMPOUND CROSS SLIDE to move the tool in until it just touches the workpiece.


Move carriage past the right end of the workpiece.

Using the COMPOUND CROSS SLIDE handle dial in a small cut (0.001 inch)

close the half nuts and NEVER TOUCH THIS HANDLE AGAIN until you are totally finished

Turn the ELECTRIC POWER SWITCH ON FORWARD to begin forward rotation with cutter moving toward the headstock. 

The cutter should make a light cut and you should see your thread stripe appear.

when the cut is nearing the end and is approaching your minor diameter relief cut, Turn the ELECTRIC POWER SWITCH OFF and let the lathe coast to a stop in the relief area.

Using the MAIN CROSS SLIDE DIAL move the tool away from the workpiece by turning the handle one complete turn from zero, one turn out and back to zero.  You have moved your tool away from the work one turn of the main cross slide

Turn the 
ELECTRIC POWER SWITCH TO REVERSE.  Allow the tool to move to the right until it is past the right end of the workpiece.  Approximately where you started.

Using the MAIN CROSS SLIDE DIAL move the tool back toward the workpiece by turning the handle one complete turn from zero, one turn IN and back to zero.  You now moved your cross slide back where we started.


Using the COMPOUND CROSS SLIDE dial in the next cut (approximately 0.005)

Make the second cut as before, stopping in the runout area. Move the tool out one turn main compound, reverse motor to beginning, move main compound in, dial in third cut etc. repeat this until your thread is complete. You can continue to cut until you hit your minor diameter.  You can also check fit with a nut or mating piece with part still in the lathe.

leaving the half nuts closed all the time ensured the timing of the gear train is correct. 

Dallas Shell



Re: Metric thread dial

William Nelson
 

Almost every thread I cut is to a shoulder. How do you go about that if you can't disengage the halfnuts? Do you stop the lathe some distance from the shoulder hoping you stop in time or stop far enough to not crash and then hand turn the spindle to get to the shoulder? Perhaps this would be a good operation for left to right threading? I have had the occasion where I would have loved to metric thread but don't have the gears. Maybe in the future. 

Bill form Socal


Re: Metric Thread Dial

Steven H
 

And the same method (engaging the half nuts and leaving them engaged) is one sure method to use when cutting imperial (inch) threads with a metric lead screw lathe.

Steve Haskell


On Jan 3, 2021, at 1:13 PM, Jim_B <jim@...> wrote:



On Jan 3, 2021, at 1:02 PM, Bill in OKC too via groups.io <wmrmeyers@...> wrote:

Somebody is sure to pipe up that they prefer doing this with inch threads even if they have a thread dial. This definitely works.

End Quite

Definitely!!!!!

But only if the thread length is short. 

Perhaps less than 1”, Much longer and the thread dial is a better choice. 

I do use this procedure quite often.


Jim B.





--
Jim B


Re: Metric Thread Dial

Jim_B
 



On Jan 3, 2021, at 1:02 PM, Bill in OKC too via groups.io <wmrmeyers@...> wrote:

Somebody is sure to pipe up that they prefer doing this with inch threads even if they have a thread dial. This definitely works.

End Quite

Definitely!!!!!

But only if the thread length is short. 

Perhaps less than 1”, Much longer and the thread dial is a better choice. 

I do use this procedure quite often.


Jim B.





--
Jim B


Re: Metric Thread Dial

Bill in OKC too
 

Thanks for at least trying! I have to admit to being seriously math-challenged. I know what prime numbers are, but have to refresh (i.e., relearn) what LCM and LCF are. Sad part is I was certified as a math teacher, at one time. For some reason my brain doesn't retain such info unless I'm continually using it. I'm told I was severely anemic as an infant, and had to have blood transfusions to survive, so likely oxygen starved for a while. That may be why. My kids do a great deal better at math than I do. Though they may have gotten their mom's math gene. Eldest daughter is a Navy Nuc Electrician's Mate. Was the first person to attend that school who hadn't had calculus and calc-based physics in high school and passed.

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 Sunday, January 3, 2021, 11:20:59 AM CST, Davis Johnson <davis@...> wrote:


I don't think I have the right words to explain.

Too long, don't read warning....

The thread dial indicates the phase of the cutter with respect to a thread being cut.

With the half nuts unlocked moving the carriage or rotating the spindle changes the phase.

With the inch lead screw cutting inch threads the spindle the ratio between the spindle and the lead screw is simple. More importantly, you can lock the half nuts anywhere the appropriate mark lines up and be in sync with the thread you are cutting. About every 1/8th inch or so. I think. Need to check. In any event -- places you can lock the half nuts are separated by a fraction of a lead screw turn. HTRL has some notes on which marks you can use for which threads per inch (multiples of 2, 4 or 8tpi make a difference). The marks where you can engage the half nuts are the ones where the spindle has rotated back around to where you can pick up the thread.

Add the metric transposing gears, or one of the approximations, and the ratios get really messy. So messy that there is no simple, usable, relationship between the phase of the spindle and the thread dial indication. Spindle rotations don't divide evenly into lead screw rotations.

There are three solutions to cutting metric gears that I have heard of:

1) Don't disengage the half nuts while cutting threads. When done with a pass run the lathe backwards to return the carriage to make another pass. This is the most commonly suggested method. Somebody is sure to pipe up that they prefer doing this with inch threads even if they have a thread dial. This definitely works.

2) I have heard (but not tried) that starting with the carriage at the same position (perhaps using a carriage stop to the right of the carriage, or the tail stock as a carriage stop) AND always using the same mark on the dial (perhaps the 0 mark) will work. This makes sense to me mathematically - I won't bore you with the details)

3) I have also heard (but not tried) of a method where you turn off the lathe at the end of a pass, note the thread dial position, disengage the half nuts, move the carriage right to a position where the thread dial is the same as where it was when the half nuts were released and engage there. Then turn the lathe back on. I think there may be more to it than that -- it seems at least semi plausible to me.

The safe thing is to go with #1.

I'm amazed if anybody has managed to follow all of this. The math of this fascinates me, but if I start blathering about Stern-Brocot trees, prime factors, smooth numbers, least common multiples and largest common factors I'll deserve to be banned from this list.


On 1/3/21 10:56 AM, john kling via groups.io wrote:
Hm I don't feel particularly sharp today and have  not in the past thought about why the thread dial works - But would the imperial still coordinate the position of the carriage and the lead screw in metric operations on the imperial lathe. -if this is completely silly, ignore.

On Sunday, January 3, 2021, 10:08:19 AM EST, Steven H via groups.io <stevesmachining@...> wrote:


I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell
Troy, MI

On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Re: Metric Thread Dial

ww_big_al
 

I think you did a good job. I’ve seen (haven’t done) #1 & #3. #2 is a new one for me. I don’t have the gears so I haven’t cut any metric. I purchase a die as I need them.

Al

 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of glenn brooks
Sent: Sunday, January 3, 2021 12:38 PM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Metric Thread Dial

 

 


On Jan 3, 2021, at 9:20 AM, Davis Johnson <
davis@...
> wrote:

I don't think I have the right words to explain.

Too long, don't read warning....

The thread dial indicates the phase of the cutter with respect to a thread being cut.

With the half nuts unlocked moving the carriage or rotating the spindle changes the phase.

With the inch lead screw cutting inch threads the spindle the ratio between the spindle and the lead screw is simple. More importantly, you can lock the half nuts anywhere the appropriate mark lines up and be in sync with the thread you are cutting. About every 1/8th inch or so. I think. Need to check. In any event -- places you can lock the half nuts are separated by a fraction of a lead screw turn. HTRL has some notes on which marks you can use for which threads per inch (multiples of 2, 4 or 8tpi make a difference). The marks where you can engage the half nuts are the ones where the spindle has rotated back around to where you can pick up the thread.

Add the metric transposing gears, or one of the approximations, and the ratios get really messy. So messy that there is no simple, usable, relationship between the phase of the spindle and the thread dial indication. Spindle rotations don't divide evenly into lead screw rotations.

There are three solutions to cutting metric gears that I have heard of:

1) Don't disengage the half nuts while cutting threads. When done with a pass run the lathe backwards to return the carriage to make another pass. This is the most commonly suggested method. Somebody is sure to pipe up that they prefer doing this with inch threads even if they have a thread dial. This definitely works.

2) I have heard (but not tried) that starting with the carriage at the same position (perhaps using a carriage stop to the right of the carriage, or the tail stock as a carriage stop) AND always using the same mark on the dial (perhaps the 0 mark) will work. This makes sense to me mathematically - I won't bore you with the details)

3) I have also heard (but not tried) of a method where you turn off the lathe at the end of a pass, note the thread dial position, disengage the half nuts, move the carriage right to a position where the thread dial is the same as where it was when the half nuts were released and engage there. Then turn the lathe back on. I think there may be more to it than that -- it seems at least semi plausible to me.

The safe thing is to go with #1.

I'm amazed if anybody has managed to follow all of this. The math of this fascinates me, but if I start blathering about Stern-Brocot trees, prime factors, smooth numbers, least common multiples and largest common factors I'll deserve to be banned from this list.

 

On 1/3/21 10:56 AM, john kling via groups.io wrote:

Hm I don't feel particularly sharp today and have  not in the past thought about why the thread dial works - But would the imperial still coordinate the position of the carriage and the lead screw in metric operations on the imperial lathe. -if this is completely silly, ignore.

 

On Sunday, January 3, 2021, 10:08:19 AM EST, Steven H via groups.io <stevesmachining@...> wrote:

 

 

I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell

Troy, MI



On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:

For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Re: Metric Thread Dial

glenn brooks <brooks.glenn@...>
 




On Jan 3, 2021, at 9:20 AM, Davis Johnson <davis@...> wrote:

I don't think I have the right words to explain.

Too long, don't read warning....

The thread dial indicates the phase of the cutter with respect to a thread being cut.

With the half nuts unlocked moving the carriage or rotating the spindle changes the phase.

With the inch lead screw cutting inch threads the spindle the ratio between the spindle and the lead screw is simple. More importantly, you can lock the half nuts anywhere the appropriate mark lines up and be in sync with the thread you are cutting. About every 1/8th inch or so. I think. Need to check. In any event -- places you can lock the half nuts are separated by a fraction of a lead screw turn. HTRL has some notes on which marks you can use for which threads per inch (multiples of 2, 4 or 8tpi make a difference). The marks where you can engage the half nuts are the ones where the spindle has rotated back around to where you can pick up the thread.

Add the metric transposing gears, or one of the approximations, and the ratios get really messy. So messy that there is no simple, usable, relationship between the phase of the spindle and the thread dial indication. Spindle rotations don't divide evenly into lead screw rotations.

There are three solutions to cutting metric gears that I have heard of:

1) Don't disengage the half nuts while cutting threads. When done with a pass run the lathe backwards to return the carriage to make another pass. This is the most commonly suggested method. Somebody is sure to pipe up that they prefer doing this with inch threads even if they have a thread dial. This definitely works.

2) I have heard (but not tried) that starting with the carriage at the same position (perhaps using a carriage stop to the right of the carriage, or the tail stock as a carriage stop) AND always using the same mark on the dial (perhaps the 0 mark) will work. This makes sense to me mathematically - I won't bore you with the details)

3) I have also heard (but not tried) of a method where you turn off the lathe at the end of a pass, note the thread dial position, disengage the half nuts, move the carriage right to a position where the thread dial is the same as where it was when the half nuts were released and engage there. Then turn the lathe back on. I think there may be more to it than that -- it seems at least semi plausible to me.

The safe thing is to go with #1.

I'm amazed if anybody has managed to follow all of this. The math of this fascinates me, but if I start blathering about Stern-Brocot trees, prime factors, smooth numbers, least common multiples and largest common factors I'll deserve to be banned from this list.


On 1/3/21 10:56 AM, john kling via groups.io wrote:
Hm I don't feel particularly sharp today and have  not in the past thought about why the thread dial works - But would the imperial still coordinate the position of the carriage and the lead screw in metric operations on the imperial lathe. -if this is completely silly, ignore.

On Sunday, January 3, 2021, 10:08:19 AM EST, Steven H via groups.io <stevesmachining@...> wrote:


I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell
Troy, MI

On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Re: Metric Thread Dial

Davis Johnson
 

I don't think I have the right words to explain.

Too long, don't read warning....

The thread dial indicates the phase of the cutter with respect to a thread being cut.

With the half nuts unlocked moving the carriage or rotating the spindle changes the phase.

With the inch lead screw cutting inch threads the spindle the ratio between the spindle and the lead screw is simple. More importantly, you can lock the half nuts anywhere the appropriate mark lines up and be in sync with the thread you are cutting. About every 1/8th inch or so. I think. Need to check. In any event -- places you can lock the half nuts are separated by a fraction of a lead screw turn. HTRL has some notes on which marks you can use for which threads per inch (multiples of 2, 4 or 8tpi make a difference). The marks where you can engage the half nuts are the ones where the spindle has rotated back around to where you can pick up the thread.

Add the metric transposing gears, or one of the approximations, and the ratios get really messy. So messy that there is no simple, usable, relationship between the phase of the spindle and the thread dial indication. Spindle rotations don't divide evenly into lead screw rotations.

There are three solutions to cutting metric gears that I have heard of:

1) Don't disengage the half nuts while cutting threads. When done with a pass run the lathe backwards to return the carriage to make another pass. This is the most commonly suggested method. Somebody is sure to pipe up that they prefer doing this with inch threads even if they have a thread dial. This definitely works.

2) I have heard (but not tried) that starting with the carriage at the same position (perhaps using a carriage stop to the right of the carriage, or the tail stock as a carriage stop) AND always using the same mark on the dial (perhaps the 0 mark) will work. This makes sense to me mathematically - I won't bore you with the details)

3) I have also heard (but not tried) of a method where you turn off the lathe at the end of a pass, note the thread dial position, disengage the half nuts, move the carriage right to a position where the thread dial is the same as where it was when the half nuts were released and engage there. Then turn the lathe back on. I think there may be more to it than that -- it seems at least semi plausible to me.

The safe thing is to go with #1.

I'm amazed if anybody has managed to follow all of this. The math of this fascinates me, but if I start blathering about Stern-Brocot trees, prime factors, smooth numbers, least common multiples and largest common factors I'll deserve to be banned from this list.


On 1/3/21 10:56 AM, john kling via groups.io wrote:
Hm I don't feel particularly sharp today and have  not in the past thought about why the thread dial works - But would the imperial still coordinate the position of the carriage and the lead screw in metric operations on the imperial lathe. -if this is completely silly, ignore.

On Sunday, January 3, 2021, 10:08:19 AM EST, Steven H via groups.io <stevesmachining@...> wrote:


I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell
Troy, MI

On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Re: Metric Thread Dial

Bill in OKC too
 

Disclaimer: I have never cut an English thread on a metric machine or vice versa, but with the metric change gears it seems to me that it SHOULD work. When I say things like that SWMBO says I'm "shoulding all over myself." ;) Anyone who knows better, feel free to school me. In the mean time, I would suggest trying it, and seeing. I hope to be finding out for myself, one of these days soon. I have an HF mini-lathe for which I still need to print a 100-tooth gear to go with the 127-tooth gear I already have. The lead screw on mine is 16tpi. I've also got a single-tumbler SB Heavy 10L that I hope to be able to add metric transposition gears to once I finish the restoration project. I seem to recall reading that it's not quite so straight forward on the single tumbler gearbox machines, but if I can print a gear for it, it won't be too expensive to try. 

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 Sunday, January 3, 2021, 09:56:36 AM CST, john kling via groups.io <jkling222@...> wrote:


Hm I don't feel particularly sharp today and have  not in the past thought about why the thread dial works - But would the imperial still coordinate the position of the carriage and the lead screw in metric operations on the imperial lathe. -if this is completely silly, ignore.

On Sunday, January 3, 2021, 10:08:19 AM EST, Steven H via groups.io <stevesmachining@...> wrote:


I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell
Troy, MI

On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Metric thread dial

Jim_B
 


There are metric thread dials. As noted they are for metric threaded lead screws. Also they are quite complex and have multiple gears depending on the thread pitch.








Sent from my iPhone-8 no
Jim B,

--
Jim B


Re: Metric Thread Dial

joel wahl
 

sadly, there is not metric thread dial, the lead screw is Imperial (8 tpi, if i remember correctly).....the numbers just won't work out....the lead screw would need to be metric for a thread dial to work on it...... for metric threads you would need to never dis-engage half-nut.


Re: Metric Thread Dial

john kling
 

Hm I don't feel particularly sharp today and have  not in the past thought about why the thread dial works - But would the imperial still coordinate the position of the carriage and the lead screw in metric operations on the imperial lathe. -if this is completely silly, ignore.

On Sunday, January 3, 2021, 10:08:19 AM EST, Steven H via groups.io <stevesmachining@...> wrote:


I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell
Troy, MI

On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Re: Metric Thread Dial

Steven H
 

I have never heard of a metric thread dial. When cutting metric threads with an imperial lead screw lathe, one normally engages the half nuts and leave the half nuts engaged until you are done cutting the thread. Do not disengage the half nuts. Reverse the lathe to return the carriage to the starting point after backing out the cross slide. 

Steve Haskell
Troy, MI

On Jan 3, 2021, at 9:57 AM, Davis Johnson <davis@...> wrote:



The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Re: Metric Thread Dial

Davis Johnson
 

The metric thread dial is intended for use with a metric lead screw, not transposing gears.

Conventional wisdom is that the normal threading dial is not useful with the transposing gears, no doubt why you are interested in the metric thread dial.

I have read a contrary opinion, that it will work if you reposition the carriage the same place for every pass (perhaps a carriage stop to the right of the carriage? might have to go on the rear v-way.) AND start on the same dial mark each time. It sounds reasonable to me.

I have been wanting to try this for some time, but haven't done it yet. Next best thing for me would be for you to try it.

On 1/3/21 8:58 AM, Al Costich wrote:
For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan


Metric Thread Dial

Al Costich
 

For some silly reason, I am in the hunt for a metric thread dial for a 9A.
Some time ago I acquired a 127/100 transposing gear set and some additional
gears.
Thinking forward, i would like to single point some metric bolts.
I'm not confident enough to make a thread dial myself.
So, should anyone have one that is superfluous to their needs,
contact me.

Thanks.

Alan

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