Can a small lathe handle a tail stock die holder?

[Howard LewisParticipant @howardlewis46836]

You have a small lathe and cutting a 3/8 BSW thread in one pass would probably at or more than its limit.

As already said, open up the die, and take more than one pass.

Use a proper lubricant, such Trefolex , Rocol RTD, or if none is available, bacon fat will probably suffice.

use a SLIDING Tailstock Die holder. That relieves the machine or you of dragging the Tailstock along.

The load can easily strip a fine thread as you cut it!

Yes, make up a mandrel Handle, so that you can turn the lathe by hand. It has the advantage that you can feel how much torque is needed. You will break fewer taps that way!

Turning the chuck on a small lathe, to cut a 3/8 coarse thread will require a lot of torque. Probably more than you can apply with a hand gripping the small chuck.

Do check the die, I have had one where the lead in chamfer was not on the marked side, which made life difficult until the error was spotted!

If you do become brave enough to Tap or Die under power, (Be very careful if working upto a shoulder ) use back gear, to reduce the load on the motor.

My lathe is a Craftsman lookalike (6 " swing over the bed ) and with a 1.5 hp motor, I do thread cut under power, using a sliding Die or Tap holder, and plenty of lubricant, at low speed.. If in doubt, the Mandrel Handle is pressed into use.

Being a coward, wherever possible, I avoid screwcutting and use Taps and Dies

But it has just cut a 8 mm pitch half round thread 1.5 mm deep, in several passes using back gear, under power.

You will become more expert as you become more familiar with the machine, and its limitations. Rome was not built in a day!

Howard

[Mick B1Participant @mickb1]

Posted by JA on 02/08/2020 12:55:38:

I am unable to cut a 3/8”BSF thread using a good split die in a good die holder mounted in the tail stock by hand. Full stop. I use a mandrill with a handle having a large swing – I just do not have the strength and I am a big person.

If I want to cut such a thread, and I will be doing so in the next few days, I turn a thread and use the die to finish it off.

JA

I'm astonished. I can tap 1" BSW into a blind hole so long as I've got a good square start and some lube.

Oh, and 18" long tapwrench handles, and 2 mugs of coffee and a good breakfast inside…

If I was doing 3/8" BSF in the lathe, I'd make sure the tailstock dieholder was well seated by a smart rap with a nylon mallet, and I'd turn the chuck using a stick of 10mm bar in the chuck key hole.

[JAParticipant @ja]

Die cutting a thread using a lathe tailstock is harder than tapping. With a taper tap you get a good lead in.

I may have exaggerated but die cutting a 3/8” BSF is something I do not do in the lathe (note change of wording). I have done it but with lubricant and good equipment (Araand die holder) I find it difficult. Far more difficult than cutting such a thread using two handed die holder and a vice.

JA

[Nick WheelerParticipant @nickwheeler]

Posted by Mick B1 on 02/08/2020 20:00:00:

Posted by JA on 02/08/2020 12:55:38:

I am unable to cut a 3/8”BSF thread using a good split die in a good die holder mounted in the tail stock by hand. Full stop. I use a mandrill with a handle having a large swing – I just do not have the strength and I am a big person.

If I want to cut such a thread, and I will be doing so in the next few days, I turn a thread and use the die to finish it off.

JA

I'm astonished. I can tap 1" BSW into a blind hole so long as I've got a good square start and some lube.

Oh, and 18" long tapwrench handles, and 2 mugs of coffee and a good breakfast inside…

 

If I was doing 3/8" BSF in the lathe, I'd make sure the tailstock dieholder was well seated by a smart rap with a nylon mallet, and I'd turn the chuck using a stick of 10mm bar in the chuck key hole.

I'm also astonished. I use M12x1.5(common on cars for particularly for fuel systems) a lot, along with M10 and M8 on my WM250. I push the handheld die holder onto the stock as I don't have a tailstock holder. The larger threads I turn the chuck with a 17mm spanner on the end of a jaw; M8 and smaller get done with just my left hand. Taps go in the drill chuck. The issue with larger threads isn't cutting them, but whether the chuck is gripping them enough. As cutting threads is usually the last operation, I now give the chuck key an extra tweak before starting. Or ise the ER collet chuck if making several parts.

 

A tailstock die holder is on my list of things to make, but I want one that doesn't need lots of large diameter material for the holders; I want a holder for every one of the dies I'm likely to use, or it isn't worth having. I don't do a massive amount of thread cutting, so the time/cost ratio of sorting such a tool isn't really in my favour.

 

I don't see the point of single pointing a thread and then finishing of with a tap/die; the whole reason for having a screwcutting lathe is to make oddball threads(M14 and 25 by 1mm for use on Yak18s as examples) without any issues. If I have the tap or die, I'll use it for the whole thread.

Edited By Nicholas Wheeler 1 on 02/08/2020 20:18:48

[Howard LewisParticipant @howardlewis46836]

My like of using Taps or Dies in the lathe is to avoid the drunken threads that happen so often when using a tap wrench on work held in a vice.

A sliding holder for Taps or Dies, held in the Tailstock provides alignment and minimal load on the newly cut thread, since it does not have to drag the Tailstock along the bed of the lathe. In particular, ME 40 threads being shallow, will not withstand this.

Proper lubrication makes life so much easier for raw material, Tap/Die and operator.

Howard

[Mick B1Participant @mickb1]

It's true you may need to pull up the chuck pretty tight to avoid leaving scored rings where the chuck slipped around the bar.

I thought about making a die holder, but decided that paying out 30-odd quid to save myself the work made sense. My personal reason for being in the hobby is to make models and projects for family and friends, so I'm miserly with time spent on tooling and will avoid it when I can.

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