ME thread dies

[ridleyian]

Did dies used to have a tapered start one side (normally the marked side) and a non tapered start the other side, enabling one to cut the thread one way and then reverse the die to finish up to a shoulder, or have I dreamed the whole thing?
The ones I have have a taper both sides.
I have recently been making some boiler fittings and the amount one has to undercut with a parting tool to enable the fitting to screw in up to the shoulder seems to seriously reduce the number of threads left to engage.
I have even considered finding someone with a surface grinder to skim off enough of one side of the die to take off the tapered lead in.
I was in Dartmouth a couple of weeks ago and browsed around Tracy Tools where I found a 10 BA domed die specifically designed for cutting up to a shoulder,but that was the only size available.
Any Comments?
Regards
Ian

[gwrfan]

Hi Ian,

Certainly as far as I know, all my BA and ME sized dies are recessed, as you describe, and that's exactly what I do, turn them around! Haven't bought one for a while, but the last, from Tracey Tools was a 1/2x 32, and that was recessed.

Geoff

[ron]

Ian, this seems to be a problem with modern dies, the ones I have had for years are tapered on one side only but the newer ones are tapered both sides, I'm afraid the only answer I've come up with is to gently hold it against the side of a grinding wheel [naughty, naughty], at least dies are relatively cheap nowadays.
Ron

[paul]

I recently bought a set of metric dies and they are as you descibe (i.e. one end tapered one not. As a newbie I wondered why they were like that! I did try them both ways but there was no tangible difference when threading the end of a rod). I bought them from Halfords.

On the question of threading a rod is there a 'recommended' size (max rod diameter) as there is for dilling a hole for tapping? For example, if I wanted to put a 4mm threaded end on a 8mm rod would this be a practical possibility or would I need to work the part to be threaded down to a smaller diameter before threading??

[jgb7573]

Normal practice is to have the rod that is to be threaded of the same diameter as the thread itself. So in your example with a 4mm thread on an 8mm rod, you would turn down a length of the 8mm rod to 4mm, long enough for the amount of thread you need. You then use the die to create the thread on this reduced part. Of course, there is now a shoulder between the 4mm part and the 8mm part, and getting the thread up as close as possible to that shoulder is where this discussion started.

The reason for reducing the rod to the thread diameter is that it reduces the amount of work that needs to be done (i.e. metal removed) by the die, and hence reduce the stress on a relatively expensive tool.

[paul]

Thanks jgb7573! 'Turn down' in my case means file (or bring file to piece held in the drill chuck - I know it's not recommended but needs must...). I figured trying to cut away that much with a die would be a problem which is why I haven't tried it, although I will shortly need to thread the end of an 8mm rod to 5mm.

[houstonceng]

Paul

The "bind moggles". How would you start a die with a 4mm dia thread onto a rod which is 8mm dia without turning it down first.

Tip. Back when I were a lad and didn't have a metal lathe, I used to "turn" brass in an electric hand-drill (my dad's 3/8" chuck Van-dorn) using a wood chisel like a graver. I think, also, that there was a design of steam engine tthat could be made purly with "hand tools" - can't remember where.

Andy

[alanstepney]

That was Handmaiden, by Tubal Cain. Full "words and music" appeared in ME.

Looking back further, many models were built using a hand drill, files, and lots of patience.!!

[houstonceng]

Sorry. Should have included these observations in my previous mailing.

I, too, have observed that some dies are now recessed on both faces. The old, expensive, HSS ones I inherited from my dad (in BSF, Whit and a few "spark plug Metrics") were flat-backed. On odd occasions I have turned these over to get "another half thread" to the shoulder but was warned by my dad that this was NOT good practice.

I can't remember where, maybe Quorn Owners Yahoo Group or similar, there was an article about the shape of the cutting faces on a die and the fact that some have a lot of positive rake and/or have "backed-off" clearance from the cutting edge (some taps ditto). If this is the case, I can see why turning the die over could be "bad practice"; since the die would rub, rather than cut, in this direction.

Whilst on the subject - maybe a little OT if you will forgive me - has anyone noticed that there are a few "odd" metrics taps around. I bought some HSS ones from Chronos and the only one that cuts full-size is the Plug/Bottoming/3rd one. The thread on the taper/1st is ground away after the taper part so it's "flat-topped" and just floats into a correct sized tapping hole without cutting. The 2nd cuts, but not to full depth. This is not what my other screwing tackle does. Were these made for a special purpose and "dumped" on the ME market.

Finally, stuck one day with all the shops closed, a few months ago, and without a 6x1mm tap, I was forced to go to the local "go faster car accessories shop" - not the well-known chain (Halfords). He sold me a metric Tap/Die set, with which I attempted to cut a thread, only to find that the tap was worn ouwn by the mild-steel I was trying to tap. I doubt the carbon steel tap had ever been near a flame. Needless to say, I got my money back.

Andy

[paul]

Andy, I was thinking of tapering the end obviously! I just had no idea what diameter I could reasonably expect to run through a die.

After two hours messing around I now know the answer - very little!! To someone armed with handtools and a drill press only, the image below represents a lot of work (probably knock it off in a few minutes with a lathe?). Started with 8mm brass rod cut to size (plus a bit), drilled centre 5mm to 18mm depth. Turned down 15mm off the other end to give 6mm dia, threaded 12mm of that with M6.

I tried a few experiments on the bit of surplus length - trying to cut M6 thread with 7mm or even 6.5mm diameter proved impossible - it all got chewed up and stripped the thread as it was cutting. Actually I had to turn down the rod to a tad under 6mm to get a decent thread.

Still, at least it fits into the boiler bushes... one day it'll be a safety valve!!

[greasemonkey]

Hi All
I found this on the web..
Note: the chamfer-relief is to facilitate cutting which for dies is 45 deg on the stamped-side and 60 deg on the back-side of the die....
for more handy info about tapping etc visit www.tapdie.com and click on technical data on the left hand side.

Andy

[Ianb]

Hi,
I too have noticed that modern dies leave rather an annoying amount of unthreaded material next to a shoulder. I also encountered an even more curious problem that I think I solved but I'm not sure. I had bought a set of ME taps and dies in carbon steel, all of which produced nice threads except the 3/16 die. This would apparently cut the thread but when unscrewed off the work would reveal two or three turns of perfect thread tapering off to an undersize mess behind the die. An examination of the die revealed nothing out of the ordinary, the threads on the lands were uniform and well defined and there was nothing jammed in them that might be chewing off the formed thread. In the end I bought a replacement at Harrogate and solved the problem. After a lot of reflection I came to the conclusion that the thread in the die was out of alignment with the faces. I generally cut these small threads by leaving the work in the chuck and running the die, in a wrench, up it using a tailstock chuck with the jaws retracted to keep everything square. If I had let the die align itself it might have behaved.

Ian

[GeorgeRay]

My left is on the opposite side to yours Andy, I found the info though.

[Ansty]

I have looked at my dies today and agree that older dies inherited from my father have only one side tapered. Most of my dies bought from the seventies onwards (CS) have two tapered sides whilst those, admittedly HSS, obtained prior to this have not.
My taps have also a slightly different shape between older and newer designs.
Is this an improvement with new design techniques or just to aid production? My thoughts are of the latter.
Thanks greasemonkey for the link to the charts.

Brian