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DA collets

This topic has 9 replies, 5 voices, and was last updated 12 July 2019 at 23:22 by Cornish Jack.

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10 July 2019 at 11:23 #26707
Cornish Jack
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@cornishjack
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10 July 2019 at 11:23 #418154
Cornish Jack
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@cornishjack
I have some DA collets which were bought secondhand. Checking against the published dimensions I appear to have a partial saet of DA200s. The checked dimensions are CLOSE TO the published for that range, but not exact. What degree of tolerance should one expect for the D1, D2 and L values ? (I'm assuming the holding value will be to spec)

Any advice appreciated

rgds

Bill
10 July 2019 at 18:09 #418209
Neil Wyatt
Moderator
@neilwyatt
Hi Bill,

Is it possible they have been over stressed?

Googling the beasties it appears they have a tendency to crack at the nose if used to hold milling cutters, presumably because they aren't designed to collapse for their full length like ER collets. So be aware of this!

Neil
10 July 2019 at 18:32 #418214
Cornish Jack
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@cornishjack
Thank you Neil – I appreciate what you say about possible fragility but my query is actually about identification. The D1 etc. values shown on the 'net are Imperial to 3 decimal places and the items I have differ by 2 or 3 third place values. They are not marked as to type so I'm wondering if I actually have DA200s or some other type? The closeness of approximation is such as to generate a doubt but I can't find acceptable tolerances for collets and holders. Hope that makes sense – (got to be a first time for everything!!)

rgds

Bill
10 July 2019 at 18:52 #418217
JasonB
Moderator
@jasonb
Depends on what published sizes you are looking at. a quick google for DA200 gives the larger dia as 0.531", 0.532" and 13.7mm ( 0.539" ) and lengths of 1.188", 0.19" and 30mm (1.811" )
10 July 2019 at 18:56 #418218
Emgee
Participant
@emgee
Hi Bill

This may help, if your collets are close to these dimensions should be OK, also remember there is a max tightening torque.

Edited By Emgee on 10/07/2019 18:59:28
10 July 2019 at 21:19 #418236
Cornish Jack
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@cornishjack
Thank you Jason and Emgee – " if your collets are close to these dimensions should be OK, " ,,, that's what I was after; Yet another raid on the piggy bank!

rgds

Bill
10 July 2019 at 22:03 #418240
Phil P
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@philp
Posted by Neil Wyatt on 10/07/2019 18:09:02:

Hi Bill,

Is it possible they have been over stressed?

Googling the beasties it appears they have a tendency to crack at the nose if used to hold milling cutters, presumably because they aren't designed to collapse for their full length like ER collets. So be aware of this!

Neil

These collets are actually designed to collapse over the full length, they have a double taper where they get pushed into the collet holder, and a single taper that the nut pushes against.

Probably not quite as effective gripping power as an ER but still pretty good, I have used them for years with no problems. If you make your own collet holders the two internal tapers have to be precisely located with respect to each other to ensure they share the load and collapse in a parallel manner. I have made special reamers with tapered depth stops to facilitate this.

It is the middle two at the bottom of the next photo, they are for DA200 and DA300 collets.

I also use DA180 for work holding.

Phil
11 July 2019 at 16:20 #418344
Cornish Jack
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@cornishjack
Phil – very impressive. The sort of thing I would like to do but age and incompetence rule against!. My query was a roundabout way of finding out if a sale item would be suitable for an existing collet holder.

rgds

Bill
12 July 2019 at 23:22 #418575
Cornish Jack
Participant
@cornishjack
Just to tidy this one up – the DA200 published dimensions are NOT exact. The new and old sets are interchangeable as regards holders.

rgds

Bill
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