So where am I going wrong

I am trying to replicate a small - 22mm long 3mm diameter - adjusting screw.
Left Hand Thread. Split Die bought from RDG - Not UK Made

I have made it twice now, both times they made it to the scrap bin!

I am turning it from a piece of EN3B, down to 2.9mm the first time 3.1mm the second time. and both times I ended up with something that vaguely resembled a thread, about 2.5-2.6 mm in diameter and it fell through the threaded hole both times.

Any pointers gratefully received. I was thinking maybe the steel was too soft?

graham.

Is that the steel teh die is made of or the EN3B

I did have similar problems with a 5/8x40 die from RDG a couple of months back and ended up screwcutting it on the lathe

J

A problem I've experienced is that either one or more of the securing-screw holes in the die-holder, or the 'dimples' around the die are not aligned, so when they're tightened down they tend to distort the die and make it cut a horrible thread. It might be worth your while to check it out.

Martin.

I did think it just might be the Die Jason

Snag is that it is 3mm AND left hand thread.

Bugger.

graham.

This is why I love this place. Great thinking Martin and certainly a possibility.

I was just thinking myself there - always a danger - could it be that the die is also faced? What I mean is, there is no lead in on one side?

graham.

I got my best results by roughing most of it out on the lathe, then finishing with a die

If I wanted a nice tight thread, I never used a die, the ones I have always overcut a bit too much

No doubt they cut "within acceptable tolerances", but still too much for the more precise scenarios

Edited By Ady1 on 09/12/2013 19:55:47

EN3B will tear a bit, but you should get better than you have done.

Are you using any tapping fluids.

Are you using a tailstock dieholder, if not are you using something behind the die to keep it square.

EN3B allows you to have a second stab at it, so you can open up the die, take a cut and then close down the die for a second cut. Don't try this in stainless.

Is the die, carbon steel or HSS

It's not cutting within any tolerance Ady, it's turning the screw down from 3.1mm to 2.5 mm and unable to function as a screw..

Al, yes I use cutting fluid and a Die stock holder. Rather, I hold the Die in a Die stock and then against the tailstock, it works well and I have always done it this way with 100% success. I suspect the die is carbon steel. Also tried the light cut/heavier cut scenario you describe.

Doyou think it's worth buying another die? Left hand - 3mm?

graham.

Edited By jason udall on 09/12/2013 20:50:29

From my own experience these budget dies do have 'issues', they do a job but not always very well. If you turned the job the wrong way as suggested the left hand die wouldn't go on. Try turning to 2.9 mm and have a nice 45 deg. chamfer on the end, open up the die for the first pass, hold it in a tail stock die holder if possible, use cutting oil and not too fast on the spindle speed.

Tony

Hmm, Graham, did you forget to let the lathe running backwards for the left hand thread???

Hansrudolf

I had something from Tracy Tools do something odd once. They exchanged it straight away. Good customer service. See what RDG say before shelling out on another.

With a small dia. thread there is a lot of metal to bend when opening the split. It may be that cutting grooves, with a thin cutting disc, will allow the die to open a bit more. I've done this with some success, but not if the die is going to be returned!

This:

"turning to 2.9 mm and have a nice 45 deg. chamfer on the end, open up the die for the first pass"

and This:

"and shouldn't be overtightened. In fact, I only ever use one screw, not all three"

worked for me.

Opening the die - quite a bit actually - has stopped it 'overcutting' the small rod i turned. I now have a workable thread. Bit of a result really as I really didn't want to be shelling out for a new HSS die and hoped the steel one would work. It can now go into the drawer for the next millenia to come along when I might need it again.

This is the problem when you are spoiled with first class kit and you buy something "on the cheap" just to get you away on a job. I really should know better. Not to worry, something else I have learned. Bit of a result really.

graham.

If it was mine it'd be going straight into the bin.

Andrew

In a perfect world do this:

Put a "good" split die in the holder and use the centre screw to slightly spread the die. Cut the thread. Use a die nut to remove the last little bit down to size. Works for me every time (Where I have a die nut the correct size that is).

Rik