Model Forum / General / Models / May 2008

On 23 May, 06:46, Richard Edwards
<poundeaterbu...@burrsblueyonder.co.uk> wrote:

Richard Hi, I made one of this type of collet chuck several years ago
for my Boxford which has the same spindle nose thread as your Viceroy.
I adapted a design that was published in EIM in 2003 (check your mail)
and it has worked hard with no problem whatsoever. I made mine from a
piece of "free cutting mild steel" I bought from my local stockholder;
at the time enough to make three bodies cost £15. The nuts were made
from the same material. While I haven't been in the shop much over the
last 6 months prior to that they were in almost daily use for three
years and show few signs of wear. I do take the trouble to keep them
really clean though as the relatively "soft" collet seat would no
doubt mark with any chips. I did think of using a "hardening" steel
but decided that I could just recut the seat if, at any time, it
showed any damage; it hasn't yet. If you are using these in a
professional shop then something more exotic might be justified.

The closing force required on the nut, particularly when holding
imperial sizes in the metric collets is quite large and I'm not sure I
would be confident using Cast Iron. I've not got time to "do the
maths" on the thread strength but just feel that steel would be much
better in this situation, particularly if you ever need to hold a
milling cutter in the chuck. These nuts which are the most "trying"
part to make are now available form several suppliers at reasonable
cost if you feel flush, I found the exercise interesting so made my
own.

The last collet chuck I needed was for my BH600 and as time is
currently short I bought a backplate mounted version from
ArcEuroTrade. This has been excellent and once set up (easy with the
backplate mounting) has proven to be accurate and repeatable. While
many think the overhang would be increased with this type it is
actually the same as the Boxford one I made.

Apologies for another rushed response and on this occaision my
"opinion" is born purely of experience, I just haven't had the time to
do the research and thought for a "theoretical" response.

Best regards

Keith

Thanks for all the comments with a particular "thank you" to Keith for
a long scribe and a PDF.
I will be using steel, got an offcut allocated.
I will buy the nut, in fact a bearing type which increases the
available clamping force.
I did consider the backplate and bought collet chuck option but felt
it looked "ungainly".
The "bought direct from Hong Kong" items were interesting.
Particularly as the ER11 range did not go as small a bar size as the
ER16 and ER20. My collet set is 18 off from Nominal 3 to 20. If I find
I need smaller then a few ER16 plus another "home made" chuck would be
the way to go. The vendor is noted.

All I need to do now is work out the change wheel set to give me 8 TPI
from my 3mm leadscrew.

BTW If anyone needs any 1 3/4 brass bar I know of a source at a good
price. 4 foot lengths. (they are bar ends!)
--

Richard

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