Double Taper (DT) Collets

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Double Taper (DT) Collets

This topic has 10 replies, 7 voices, and was last updated 8 February 2023 at 01:17 by John Reese.

Viewing 11 posts - 1 through 11 (of 11 total)

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6 February 2023 at 16:17 #632276
Grindstone Cowboy
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@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
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6 February 2023 at 16:17 #20913
Grindstone Cowboy
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@grindstonecowboy
Worth pursuing, or just go the ER route?
6 February 2023 at 17:40 #632292
Baz
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@baz89810
Go for ER32. Never seen a milling cutter of any size with 7/16 dia shank.
6 February 2023 at 17:45 #632294
noel shelley
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@noelshelley55608
3/8" and 1/2"! Milling cutters were not normally made with a 7/16" shank. Noel
6 February 2023 at 18:45 #632312
old mart
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@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.
6 February 2023 at 19:06 #632320
Grindstone Cowboy
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@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
6 February 2023 at 20:22 #632334
Gavlar
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@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
6 February 2023 at 20:42 #632336
Grindstone Cowboy
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@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
6 February 2023 at 21:33 #632341
Grindstone Cowboy
Participant
@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
6 February 2023 at 21:51 #632343
Les Riley
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@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!
8 February 2023 at 01:17 #632536
John Reese
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@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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