Grinding a carbon steel die

I have a 1/4" long plug that needs a 10mm thread right up to the shoulder but my die will only allow me to cut about 1/8" before it butts up against the head. I've tried the usual dodge of reversing the die but that doesn't work either.

I don't want to undercut the plug or counterbore out the first 1/8th of the thread so the only thing I can think of is fabricating a plug by making some 10mm studding and threading it through some hex or grinding away the back surface of the die - which might be more useful in future (except that would mean packing it up in the die holder thereafter). My question is, how tricky is this likely to be given that I'll just be using a small bench grinder?

(and why don't they make dies that will cut right to the end anyway?!)

Cheers

Paul

Hi Paul, but usually I would fit a copper or aluminium washer to the plug as that helps seal as well as getting rid of the thread problem. Just a Thought!

David

Paul

I have used both the methods you are considering. For the studding method I use some Loctite to keep the bits together with some success.

For grinding the back of a die I hold it in a tailstock die holder to save my fingers from the wheel and the heat generated and the fact that you have a small grinding wheel is an advantage as you will form a concave recess on the die. Just make sure you grind the unmarked face!

Even with a ground die I doubt you will get your plug to seat unless you either undercut the male thread or recess the female.

Jim

Thanks David - not a bad idea but a 1/8" washer is probably a bit too thick as it would be almost the same thickness as the head!

Could you remove the first thread in the socket to help with the Clearance?

David

Edited By David George 1 on 10/02/2017 20:11:28

Hi Paul, whats the reason for not wanting to either undercut the plug or recess the socket thread ?

John

It's for the end of a pump valve chamber so I'd like to keep as much thread as possible on the plug - the part it screws into is already made and threaded. In light of Jim Nic's comments I think I'll make some studding, thread it through a bit of hex and silver solder it together.

Thanks all.

Paul are you using a standard M10x1.5 die? For things like pumps, glands and general steam fittings a finer thread is more appropriate. Something like M10 x 1 is easy enough to pick up and allowing for either a 1mm undercut or counterbore then you would get 5 full turns of thread which would be more than enough for this application.

I have ground out teh backs of several of my ME dies with a Dremel.

Yeah it's a standard die... spent a shed load on tooling in the last few month so the finer stuff will have to wait - but point taken thank you. Also need to make up a suitable tool for boring such 'small' holes!

Is it that new dies these days have a lead on both sides since most of the old dies I have only have a lead on one side which very usefull if you want to make a thread go up to the shoulder. Niko.

Seems to be little difference between the two sides on the dies in this set - the last ones I bought about 10 years back only had a small lead-in on the back.

Paul,

When thread milling has not been an option I have occasionally had to tap a full thread profile to the bottom of a blank sight mounting hole, the process involves grinding off a little from the end of a plug tap, cutting the thread as far as possible, cleaning the work then repeating the process until you have a full thread form right to the bottom, the tap is then only good for cleaning and restoring threads as it has no lead-in.

If you cut a tap, or die, down in one go to the point where it will cut a full thread to a shoulder you have removed all lead-in and it is unlikely to work.

Thanks Nick. I've got a couple of ground down taps that are very useful. I won't be grinding this die down however - it's now a properly split die! I made the first plug which seats beautifully but as I started the second there was a sharp snapping sound and the die was no more (it died ). First time I've ever done that... that's the price of carbon steel I suppose. So now I need 1x coarse to finish the job and 1x fine (+ tap) for next time. Grrrrr!