Dies

[BOB BLACKSHAW 1Participant @bobblackshaw1]

[BOB BLACKSHAW 1Participant @bobblackshaw1]

I have all the metric dies up to 12mm, but noticed that several have the start front and back. I needed a flat shoulder on a 8mm shaft but have ended up with a small tapper, I got around this by using a small parting tool. My question is how do you know what type of die will be supplied, or do they have a special name.

[Rik ShawParticipant @rikshaw]

Only two types I know of are the split adjustable die designed for cutting a thread from scratch or a solid die nut – more suited to cleaning up or finishing an existing thread.

Rik

Edited By Rik Shaw on 20/11/2017 08:59:58

[larry PhelanParticipant @larryphelan54019]

Same here !

[richard 2Participant @richard2]

Just for pleasure I usually screwcut a thread and run a die on to finish.

I ground a fine pointed tool to provide a totally flat shoulder.

But my greatest pleasure is in using my lathe – (Myford S7B) for which I enjoy making attachments.

Richard 2.

[KWILParticipant @kwil]

A die is not just a set of teeth, they work because of the taper. So there is no way you can get a die to cut square to a shoulder. Hence we put in the undercut when we need a square shoulder.

+1 for screwcutting, then topping (ie profile) with a die.

[Anna 1Participant @anna1]

Hello Bob.

I have noticed the same thing as yourself regarding double tapers on some dies supplied in the past 2 or 3 years. I have never seen this before. All are c/steel cut thread dies from the same British manufacturer.

Traditionally the thread is started from the taper side and then the die is turned around and cut from the unchamfered side of the die, which will reach almost up to a shoulder as you say, and a radiused undercut formed under the screw head as needed. Some of the tapers on the dies I have are so long that it would take a very wide undercut to clear the partially cut thread. Unfortunately I suspect it is just poor manufacturing of the dies. I guess the only option is to buy from one of the major manufacturers where quality control will probably be tighter.

Regards

Anna

[MWParticipant @mw27036]

Posted by Anna 1 on 20/11/2017 17:23:51:

Hello Bob.

Unfortunately I suspect it is just poor manufacturing of the dies. I guess the only option is to buy from one of the major manufacturers where quality control will probably be tighter.

Regards

Anna

Hi,

I've got the double taper on good quality presto HSS dies too. So I think it is more a standard practice than a quality issue.

Michael W

[SillyOldDufferModerator @sillyoldduffer]

Couple of wild guesses:

• the dies are made for an auto-changing machine like a Machine Centre. Saves time because It doesn't matter which way up they are loaded.
• You get a bit more life out of the dies by reversing them after the first start gets worn.

Dave

[BazyleParticipant @bazyle]

The leading edge will wear. Having two is cost efficient. Most threads do not need to be up to a shoulder.

[Anna 1Participant @anna1]

Hi,All

If as it would seem from Michael W,s post, tapers on both sides of a die are becoming common even on premium dies, they are of little use to me, Is there a manufacturer who is known to put a taper on only the one side of the die? For the most part having to screw cut smaller BA sizes on the lathe would seem to be a bit over the top.

regards Anna

[JasonBModerator @jasonb]

I have a few dies that I have ground down the "back" of which allows me to get closer to a shoulder and a 1.0mm parting tool gives a wide enough runout for the thread to cut into. These are mostly ME dies where I want fittings to screw up against something.

The other option if you want to screw upto a mating part is to drill a mil or two at clearance size then the rest of the way tapping size so that any unthreaded length on the male part goes into the shallow clearance hole. Also stops you getting a raised "burr" around the tapped hole if working in a soft metal such as GM and some aluminiums.

The third option is to cut a female thread into both parts and use a separate threaded nipple to join the two.

Edited By JasonB on 21/11/2017 07:24:10

[HopperParticipant @hopper]

Can you grind down one side of the die to get rid of the tapered section? An angle grinder would make quick work of it, if you have a steady hand. Otherwise, some kind of holding jig and grind it down on the bench grinder?

[Anna 1Participant @anna1]

Thank you Jason and Hopper for the suggestions and I concur, Jason, re ME dies. Grinding the face of the die is probably the best suggestion as once done it solves the problem for the future. I on occasions use the counterbore technique where practical. I looked at some the work I have done in recent times and quite a high proportion of the threaded parts are cut up to a shoulder.

For the most part c/steel dies are probably only used in the model world so I still wonder why the need to manufacture a double taper on the dies.

Thank you

Anna

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