Making Round Threading Dies

[old toolmaker]

I would make the thread with a follower right on the other side or all around in front or back of the 60° tool bit. Both following together. And both on the tool post. The tool bit would advance on its own translating set-up and not with compound or cross. With this method no taper in threads. And work is not between centers. Good Luck…Dave.

Hi Dave,

I appreciate your input but I don't quite understand what you have in mind. I would like to learn more if you can explain what you mean by follower.

Thanks, Dick

 

[chips&more]

Hi Dave,

I appreciate your input but I don't quite understand what you have in mind. I would like to learn more if you can explain what you mean by follower.

Thanks, Dick

Hi Dick, well, I tried to find mine? I found a pic on the net (below). It’s NOT the set-up, but has the same principle. Mine has an easily retractable tool bit so you can pull the tool bit away and go back to the start with no hassle. And darn it, now I won’t sleep tonight till I find mine…Dave

 

[4GSR]

Change the screw size to 7/16-20 left hand thread. And I can send you a tap to tap out the thread to 7/16-20 LH. I may even have a left hand die for this thread too.

 

[old toolmaker]

Change the screw size to 7/16-20 left hand thread. And I can send you a tap to tap out the thread to 7/16-20 LH. I may even have a left hand die for this thread too.

Change the screw size to 7/16-20 left hand thread. And I can send you a tap to tap out the thread to 7/16-20 LH. I may even have a left hand die for this thread too.

Hi Ken,
Thanks very much for the offer. I appreciate it, but there wouldn't be enough wall section left in the nut nor enough space in the casting to allow a larger nut to be used. I do already have a 3/8-20 L.H. tap though.

Dick

Hi Dick, well, I tried to find mine? I found a pic on the net (below). It’s NOT the set-up, but has the same principle. Mine has an easily retractable tool bit so you can pull the tool bit away and go back to the start with no hassle. And darn it, now I won’t sleep tonight till I find mine…Dave
View attachment 257786

Hi Dave,
I think you are on to something here that I could benefit from owning now and in the future. If you do find yours I would like to see it, but don't loose any sleep over it. I have seen and read about a device like this but don't know what it is called. I think I will pursue info also.

Thanks
Dick

 

[Tony Wells]

Do a bit of research on "backing off" cutting. It is not simply the minor diameter of a die that is tapered and relieved, but the PD as well. This allows a cutting edge be to be formed, and in the case of adjustable dies it lets them be readjusted after sharpening, which is done by grinding the ID of the relief holes. Many people believe the adjustment is for varying the PD as cut, and while it does affect it, the adjustment it primarily for setting the PD cut to fall within standard parameters.

There is a rather long-winded approach to substitute adequately for the dedicated backing off mechanism that was available for a few lathes, but It's kind of a cheesy cheat, even though it works. For a handful of parts, it probably isn't worth the effort, but if you were going to produce a heat treated tool steel long life die (or tap using the same principles) it might be.

 

[old toolmaker]

Hi Dick, well, I tried to find mine? I found a pic on the net (below). It’s NOT the set-up, but has the same principle. Mine has an easily retractable tool bit so you can pull the tool bit away and go back to the start with no hassle. And darn it, now I won’t sleep tonight till I find mine…Dave
View attachment 257786

Hi Dave,

I understand your system and how it works now. You mentioned you have a means of retracting the tool and go back to the start. Do you have a means of resetting the tool with micrometer accuracy when back at the start point? If so is there a dovetail slide involved?

Dick

 

[chips&more]

Hi Dave,

I understand your system and how it works now. You mentioned you have a means of retracting the tool and go back to the start. Do you have a means of resetting the tool with micrometer accuracy when back at the start point? If so is there a dovetail slide involved?

Dick

Hi again Dick, I made it about 20 years ago? At the time, was making a lot of feed screws, RH & LH and it was invaluable! I felt it was the definitive way of doing it for my needs! Have not used it for some time now. I put it somewhere safe!...LOL. It’s so safe, I can’t even find it!

Yes, it had a dovetail slide that was lever operated to re-track the tool bit. The lever turned an eccentric pin that moved the slide. And the whole slide moved with a micrometer feed for depth of cut. All to the best of my memory anyway, sorry…Dave.

 

[old toolmaker]

Hi Dave,
Thanks for the answer. That is good enough for me. I believe George H. Thomas described a device like this in his book "The Model Engineer's Handbook. I have a copy and will read that section again and try to adapt his method. I am going to abandon the tap idea for now as your method is the best one. A good lathe cut thread is better than a die cut thread any day.

Dick

 

[old toolmaker]

Hi Dave,
Thanks for the answer. That is good enough for me. I believe George H. Thomas described a device like this in his book "The Model Engineer's Handbook. I have a copy and will read that section again and try to adapt his method. I am going to abandon the tap idea for now as your method is the best one. A good lathe cut thread is better than a die cut thread any day.

Dick

Sorry! I meant "The Model Engineer's Workshop".

 

[benmychree]

Do a bit of research on "backing off" cutting. It is not simply the minor diameter of a die that is tapered and relieved, but the PD as well. This allows a cutting edge be to be formed, and in the case of adjustable dies it lets them be readjusted after sharpening, which is done by grinding the ID of the relief holes. Many people believe the adjustment is for varying the PD as cut, and while it does affect it, the adjustment it primarily for setting the PD cut to fall within standard parameters.

There is a rather long-winded approach to substitute adequately for the dedicated backing off mechanism that was available for a few lathes, but It's kind of a cheesy cheat, even though it works. For a handful of parts, it probably isn't worth the effort, but if you were going to produce a heat treated tool steel long life die (or tap using the same principles) it might be.

To my knowledge, the only button type dies that are relieved on the PD are tapered pipe dies, dies for straight threads are not relived on the PD; they would "shave" threads if forced forward or also if dragged back. Button dies are a very poor choice for cutting long threads from scratch; they tend to "camming", that is they start to wobble as the cut progresses, getting worse as the cutting continues. Cutting the thread by single pointing is the best way for accuracy, cleaning them up with a die for considerations of taper, well maybe, button dies are not known to give a particularly nice finish on a thread. The method of using a follow rest is a good one, but as the thread nears completion (in the case of a vee thread), there is very little bearing on the tops of the thread crest; with square or Acme threads this is not so much of a problem.