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Make-shift surface grinding of a threading die face

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Greensands14/06/2020 14:35:35
263 forum posts
50 photos

Hi - I have a number of standard threading dies in the usual ME sizes, some of which have a generous lead-in on the front face for easy starting and effectively a zero lead in on the reverse face which is very useful when threading up to a shoulder. With more recent purchases I notice that dies now now come with a lead-in on both front and rear faces making it a lot more difficult to continue the thread up to a shoulder.

What I would like to be able to do is to grind off the lead-in from the back surface of these dies but in the absence of a surface grinder I am loathed to try any lash-ups for fear of having a disaster on my hands. What have been other peoples experiences in this regard and can anyone suggest a simple and safe way of achieving the desired effect.

Mike Poole14/06/2020 14:48:12
3095 forum posts
72 photos

You could try machining a recess with a carbide tool, just facing off the back will compromise the dimple positions in the die holder. HSS will machine with a carbide tool and carbon steel should be ok as well. An alternative to threading up to a shoulder is to machine an undercut as would be required if screwcutting.


Pete Rimmer14/06/2020 14:49:19
1096 forum posts
69 photos

If I was compelled to attempt something like that, I would turn up a make-shift shallow die holder with a spigot to hold it in my battery drill. Mount the die in the holder, cobble up a rest and spin it in the drill whilst pressing it against the wheel of my bench grinder.

10ba12ba14/06/2020 17:25:41
32 forum posts
19 photos

I have a few of these "double lead in " dies and as it happens I also have a surface grinder, so tomorrow i'll have a go at one.

The only snags which come immediately to mind are that the dimples will the lie further back in the die stock (sort that out with a washer) and that the die will have become magnetised.


Greensands14/06/2020 18:08:30
263 forum posts
50 photos

In the absence of a die having a zero lead-in on the back face a useful dodge I have found certainly for brass, is to tap the mating female thread into a short length of BMS Hex stock and face off the end to leave a well defined cutting edge. Works well with brass.

BOB BLACKSHAW15/06/2020 02:50:23
435 forum posts
104 photos

That's a good idea Grensands, I suppose silver steel hardened off with two slots for a spanner would work on steel.I to have a number of ME dies with a double lead, I would like to know why they are made like this.


JasonB15/06/2020 07:09:40
21636 forum posts
2493 photos
1 articles

Unless you are threading to a very large shoulder then a Dremel can be used to hollow out the back of the die but leave the outer edge untouched so it still sits right in a diestock when used the right way round. You can then flip it around to finish the thread but I still tend to add an undercut or ease the female thread.

Lainchy22/02/2021 10:29:13
271 forum posts
103 photos

I have exactly this issue on a very small part that requires 7/32x40ME... It only projects about 3/32nd - 1/8"

Did anyone manage to grind or mill out the lead out from a carbon steel die?

I notice also the post from Greensands... my brass hex external is 7/16. I'm guessing I could make just a 7/32x40 threaded bar, and silver solder a 7/16" brass nut to it. Got me thinking, but.... bit annoying that I can't just buy one as needed.

Cheers chaps

JasonB22/02/2021 11:04:21
21636 forum posts
2493 photos
1 articles

As I said above if shoulder is not too large a diameter than Dremel does the job, dimples stay in the right place and you still have a flat back face do die sits square in the holder


Lainchy22/02/2021 11:40:29
271 forum posts
103 photos

Looks fine Jason. I'd wondered if you'd built some sort of grinding jig for the toolpost.

Many thanks

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