work slipping while threading …

[Howard LewisParticipant @howardlewis46836]

Unlike S O D, my work is mostly in Imperial, but often where threads are concerned Metric.

Whichever system is most suitable for the job in hand.. (Not unknown for the two system to be present on a particular project intended for my exclusive use. )

But an otherwise totally Imperial machine will be modified / repaired to Imperial standards. The same applies for a Metric device. In this way.

I have experienced mixtures on vehicles, and the concern as to whether a particular gadget used Whitworth or Unified threads. Even worse when the Whitworth standard power unit was replaced by a Metric one, on a Unified standard chassis!

Howard

[BASS 666Participant @bass666]

to answer a few questions …

the die was open and the correct way round ..

there was a good chamfer on the job ..

the die is new and i used cutting oil …

i think it's the jaws because as i said before the jaws would not hold six washers at a time the last couple or three fell out when i tightened the jaws …

i have schooled myself about doing the jaws so i might got that done in the very near future …

[Howard LewisParticipant @howardlewis46836]

At least you have eliminated most of the possible causes, and can concentrate on rectifying the fault.

In the meant time, you could drill a piece of bar 3/8 , mark no 1 jaw on it, hacksaw it and then replace it use to act as a collet to hold the workpiece for turning to size for cutting the thread.

Aluminium, being softer, may accomodate the bell mouthed jaws better than steel.

Howard

[SillyOldDufferModerator @sillyoldduffer]

Posted by Howard Lewis on 17/04/2022 15:07:06:

…

I have experienced mixtures on vehicles…

Tell me about it, can't remember which it was but one of my 1970s old bangers had everything. Might have been a Chrysler Sunbeam, which I just read was spawned from the Rootes Hillman Avenger, after Rootes were taken over by Chrysler, who later sold the firm to Peugeot. Mostly British, including UNC and UNF and some Metric. Didn't sell well abroad…

Dave

[Martin KyteParticipant @martinkyte99762]

Far simpler to use the 4 Jaw Chuck for this operation. The grip is much better.

regards Martin

[Nick WheelerParticipant @nickwheeler]

Is a 3/8 thread really that big to die cut in a smallish lathe? I've made a number of M12x1.5 parts in both my wm50 and the mini-lathe that I had first.

And I really can't see why you'd faff about screwcutting something only to finish with a die. The reason for having the die is to save the extra work

[Tony Pratt 1Participant @tonypratt1]

Posted by Nicholas Wheeler 1 on 17/04/2022 18:02:22:

Is a 3/8 thread really that big to die cut in a smallish lathe? I've made a number of M12x1.5 parts in both my wm50 and the mini-lathe that I had first.

And I really can't see why you'd faff about screwcutting something only to finish with a die. The reason for having the die is to save the extra work

Screw cutting removes the bulk of material & the die allows you to size the thread with relative ease.

Tony

[bernard towersParticipant @bernardtowers37738]

If you do intend to regrind your jaws look up the article in MEW that gives instruction on how to make a petal; plate. Its brilliant and I have since reground 6 chucks with it and the results are superb not only improving grip but concentricity as well.

[Anonymous]

As an aside, if it hasn't already been covered, I wouldn't size the rod to 3/8 anyway. I'd go under that by at least 5 thou (if not a bit more). It won't noticeably change the strength and makes die-cutting much easier.

[HuubParticipant @huub]

Above 8mm, I do not use a die but cut the threads on the lathe using a threading tool.

For more grip, I use a hex collet holder (ER32) placed in the chuck.

[Author]

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