Un-split, split die

[JonBerkParticipant @jonberk]

[JonBerkParticipant @jonberk]

I've asked this question before elsewhere and had a couple of answers but I still feel there must be more information out there.

I have several threading dies that I inherited that are not split, but they should be.

The 'new old stock' un-split die I've just started using is a 1/4" BSF but I do have other sizes. It works OK, but being able to adjust it could be useful.

They are 'normal' HSS round dies with dimples on the circumference where the die-holder adjusting screws fit and vee slots where they should have been split for the spreading screw.

I have an instruction from the manufacturer stating that the die should be split before use. No instructions were given on how to actually split the die and I'm reluctant to give it a whack with a cold chisel or similar. Other split dies I own have obviously been split after manufacture and not by cutting a slot but by splitting them.

Although I could split the die with a Dremel or a 1mm angle grinder blade, I would like to know how it was done properly.

Does anybody know how this was done?

Thanks in advance.

John

[Phil WhitleyParticipant @philwhitley94135]

Very interesting John, I think I have vaguely heard about this. Also seen new old stock half nuts for a Colchester that were in one piece as they had been machined and were split just before fitting. If you think about that of course although the half nuts would be identical, only those machined together in one piece would have a matching thread on both halves as there would be know way of telling where the thread would start. Can't see the point of not splitting a die though, unless they got a lot of breakages in packing or transit.

Phil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Phil Whitley on 17/11/2015 21:46:21:

Can't see the point of not splitting a die though, unless they got a lot of breakages in packing or transit.

Phil

.

… or unless it was a brilliant cost-saving initiative by the Bean-Counters [?]

MichaelG.

..

[John] … How old, or recent, are these? . and can you let us know the manufacturer?

Edited By Michael Gilligan on 17/11/2015 23:03:57

[Enough!Participant @enough]

Just a thought. Some manufacturers produce both adjustable (split) dies and solid (unsplit) dies – the advantage of the latter being, I suppose, that they cut accurately to the final size.

If I were such a manufacturer, I would probably make a single product and simply omit the final slitting operation. The dimples will be there on both as they are needed to prevent rotation in the die-holder. As for the v-slot, it might simply be an artefact of when they separate the two versions in the manufacturing process.

I know that many people are dead set against solid dies but I think they have their uses. You can get a nice, accurate thread by first cutting with a split die opened up a bit, then finishing with a solid die. Or screw-cut the thread on the lathe and finish with the solid die.

[AlanWParticipant @alanw96569]

Not so long ago, I bought a (very) cheap 1/2" NPT die on eBay from a source in China. It looked OK in the photograph but the one that eventually arrived had a dimple in the wrong place and no split. A couple of minutes with a diamond cut-off disk in a mini drill had it useable and it actually cut very well.

I only needed it for a one-off job, so it wasn't worth opening a dispute (especially over a fiver including postage). My thought is that someone is supplementing their meagre income by selling the contents of a factory scrap bin. It would make sense; if a dimple is out of place, why bother to complete the rest of the manufacturing processes.

Alan

[David Clark 13Participant @davidclark13]

I think split means adjustable for cutting a thread and unsplit is used for cleaning up a damaged thread.

[KWILParticipant @kwil]

I have a number of excellent swiss made BA dies which are not split nor have any indication they need to be.

Even the so called split adjustable ones can cut undersize when opened out. Hence I screw cut when ever possible.

[mickParticipant @mick65121]

Solid dies are by their nature dead size, which makes them extremely useful for finishing and cresting a screw cut thread when you don't have a full form threading tip. They should really be reserved for sizing operations, as using them to cut a full thread will only blunt them making them useless for their intended use. A round split does give a very small amount of adjustment, which can be beneficial when cutting a thread in hard steel, as the first cut can be made with the die as open as it will go using the central screw, then finished off by loosening the central screw and tightening the side screws while sizing the thread using a standard full nut as a gauge.

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