Double Taper (DT) Collets

[Grindstone CowboyParticipant @grindstonecowboy]

In the pile of bits and pieces that came with my Boxford lathe, there is a nice MT3 collet holder with drawbar – I have deduced that it takes Double Taper or DT collets in the Z size range.

Unfortunately I only have one collet, a 7/16" and it looks like they are not all that common and not cheap when you can find them – around £25 each or more.

Do you think it's worthwhile trying to get any more, or should I just go for ER32 instead? Which would also make it possible to pass material all the way through with the right sort of holder.

Bonus question – if I keep it just for doing some light milling with a vertical slide, what diameter milling cutter would have a 7/16" shank?

Thanks,

Rob

[Grindstone CowboyParticipant @grindstonecowboy]

Worth pursuing, or just go the ER route?

[BazParticipant @baz89810]

Go for ER32. Never seen a milling cutter of any size with 7/16 dia shank.

[noel shelleyParticipant @noelshelley55608]

3/8" and 1/2"! Milling cutters were not normally made with a 7/16" shank. Noel

[old martParticipant @oldmart]

The er sizes are very easy to get hold of, being so widely used. The er 32 go up to 21mm and the er40 go to 26mm. If you also have a mill, they can be used on both machines which is convenient.

[Grindstone CowboyParticipant @grindstonecowboy]

Thanks chaps! As I suspected, it's essentially useless – I was kind of hoping someone might suggest a source of collets at £1 apiece, but…

I'll revert to my original plan of ER32.

Thanks again,

Rob

[GavlarParticipant @gavlar]

I have no experience of DT collets. So at the risk of embarressing myself, could your collet set possibly be 3c? The standard Boxford collet holder and drawbar are for 3c collets

[Grindstone CowboyParticipant @grindstonecowboy]

Hi Gavlar

No, afraid not – I think it's something the previous owner (a lifelong engineer) acquired somewhere along the line. It's definitely one of these.

Rob

Links to http://www.tools-n-gizmos.com/specs/DT_Collet.html

[Grindstone CowboyParticipant @grindstonecowboy]

Unfortunately not got one of these though

Rob

Links to https://www.cutwel.co.uk/dkf65-a6-quick-gun-change-direct-mount-fixed-length-lathe-collet-chuck-dkf-series-klamp

[Les RileyParticipant @lesriley75593]

Some years ago I too got a DT chuck and one collet. Not much use so I put it in the cupboard. More recently, I bought a machine that came with a big box of DT collets so I am glad I didn't throw it away!

[John ReeseParticipant @johnreese12848]

The DT collets have a clamping range of only a few thou from their nominal size. ER collets in the larger sizes will hold work up to 1mm below nominal. That is a big advantage for holding drills or taps.

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