What sort of chuck is this ?

Anyone know what type of chuck this is, its MT4 and described as type B Dormer chuck, i have only found one other described as series 2.

Much appreciated.

Edited By mark smith 20 on 09/09/2017 16:50:21

Mark,

I think it's missing a collet insert that holds a tap

MichaelG.

So is it for holding collets for tapping?? The only other i can find a photo of one is this MT5 one ...

I think so, Mark ... but it's a faint recollection.

MichaelG.

.

Edit: Maybe not ... This ebay listing suggests it may be for [screwed shank milling] cutters:

http://www.ebay.ie/itm/UNUSED-DORMER-TYPE-B-COLLET-HOLDER-No-4-MORSE-TAPER-SHANK-/352127397720?hash=item51fc6daf58:g:VQ0AAOSw5gxZcQFW

Edited By Michael Gilligan on 09/09/2017 19:55:32

Well i can find any mention on google other than whats been refered to .So its a puzzle ,is it designed to hold one size or was it originally to come with extra screw on front pieces. I cant tell if the front piece is design to hold screw in collets or cutters?

Believe its similar to a Clarkson in that you screw the cutter into the holder, bottom the holder out into the body and tighten the cutter until it hits the point at the end of the bore. Theoretically cutting loads tighten the cutter up increasing the grip of the collet on the shank until all is solid.

I don't really understand how it works tho'. Clarkson is bad enough to get your head round until you twig that trying to twist the milling cutter drives the whole collet forward under the influence of the thread at the end so the taper in the end-cap closes the collet.

With the Dormer the collet just screws direct into the body so where does the self tightening action come from?

Can you still get cutters with the right size thread on the shank?

Clive

Thanks Clive , ive no idea about what cutters fit it or their size , i was basically interested in anything which will fit in my MT4 Alexander spindle MT4 stuff is never cheap when you find it and most of the hobby machinist shops tend to stop at MT3. The seller of the chuck knows nothing ,just found it in a box of stuff apparently unused.

Think you probably have two thirds of some variety of one of these:-

Extract from 'Dormer milling cutter information handbook' Edition M.C. 776

Mike

Thanks for that it looks more like what i posted , also looks very different to this. there must have been more than the one or two actual chucks i can find ,very strange that there is no info on google or all the other forums. Especially as to what an actual collet looks like. In your illustration it appears to have collets a little like the clarkson `c` type chuck i have but with a taper at the back.

Edited By mark smith 20 on 10/09/2017 16:06:07

A bit more detail - you are right about two tapers.

Took me a little while to work out how it auto locks.

One thing im still confused about in my original photo the threads on the nut are at the front and it has threads on the inside at the back, different from your last photo?????

Instead of searching for Dormer ... I went back to the 'previously known as' name, and found this patent:

**LINK**

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=1067698A&KC=A&FT=D&ND=3&date=19670503&DB=EPODOC&locale=en_EP

MichaelG.

Ah the best of British Engineering Design! Nothing more precise than a few sharp taps with a hammer and you won't find smiley faces on far-eastern milling chucks!

Thanks Michael, i looked on patents and was searching for dormer. There is still a slight difference though between the holder nut i originally posted and the ones illustrated . Seems collets are impossible to source

Mark, the first and second photos you show are of different collet/chuck systems.

The former is a "Type B"; note the cross cut in the end. It's complete, not requiring another sleeve.

I have one on the desk in front of me as I'm tying this, but with a 1/4" collet.

The taper end of the collet is threaded and will accept a 1/4" Clarkson Autolock type endmill, so I assume the one Keith is/was selling will be correctly threaded for a 1" end mill.

I bought mine as part of a job lot, and just have the one body and collet; immediately after taking delivery I was browsing ebay and found a couple more collets for sale, but I didn't bid on them, as I've no current use for another holder, all my stuff is MT2; I've 3 working collet chucks in the right size anyway, plus a couple of compatible larger bodies ready to go if required.

From what I can see, all posts after your very first one, have gone off at a tangent, and are discussing a different system entirely, albeit from the same manufacturer. The only other direct similarity is the square nut on the end.

Unlike the Clarkson and similar, there is no obvious pip in the end of the body, for the mill to centre on, just a plain machined face with a very small hole in it. I'm not sure if that hole was for the original machining operation, or if there is a removable/replaceable pointed insert, which in missing in my example.

I can come up with detailed photos and measurements later, but I'm off out for the day after this coffee.

Bill

Bill thanks very much ,i thought something didnt add up with the other styles of holder. So the front piece is both a nut and collet combined?

Bill , i bought the one in the first post, very happy with it,and yes appears to be threaded for 1" threaded cutters. It is just flat bottomed inside and there is a hole. This holder  fine by me as it allows me to use larger cutters than what im limited to with the small clarkson `c` type i have and the er32.

One question though is that the draw bar thread doesnt appear to be M16 which i was expecting for MT4 . A M16 thread on a boring head i have only goes in about one thread then stops. Is it 5/8" BSW or other????

I need to make a pull stud on the lathe with thread for the holder on one side and alexander 20 x 2mm on the drawbar end.  Tried the 20 x 2  thread cutting on my southbend which is imperial ,the pitch i got almost dead on but the saw tooth thread wasnt up to much , unsure about cutter shape.Ive attached details of the alexander /deckel thread in case anyone has any tips on cutting this thread.

Edited By mark smith 20 on 13/09/2017 16:31:02

Edited By mark smith 20 on 13/09/2017 16:36:04

Edited By mark smith 20 on 13/09/2017 16:39:59