Colchester lathe bits

Anyone know where to get 'em?

specifically, the tool for loosening the chuck retaining ring (giant C-spanner, I assume) and the internal parts for the drum brake.

for a Mk1 student.

I bought a set of NOS jaws for the Pratt burnerd 8" 3-jaw, which failed to stop it running off-centre. can't see anything wrong with the chuck body and mechanism, and the chuck body runs true. more or less solved by gripping a large ex-bearing race on the outside steps of the jaws and then running a carbide boring tool down the resultant "hole" in the middle. It now runs more or less true.

Is this normal practice, or should I look in more detail at the internals of the chuck?

Reply to
Austin Shackles
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Pretty close to normal.

Accept that a 3 jaw chuck is not normally a precision instrument, a couple thou runout is about normal.

You can improve things a bit if you work with one size commonly, by setting up your jaws so that you are tightening them, then boring the working faces of the jaws to the size of your stock, or using a toolpost grinder.

Of course this means setting the jaws as near to the size of the stock as you can, first, to minimise the amount of material taken off.

There are sets of assorted size washers sold for the purpose, to be held between the three jaws, at the back, while working on the front part of the jaw. Some use spacers between the jaws, others have drilled holes for pins on the outer face of the jaws and used those pins to grip a ring, similar to what you did, but squeezing inward.

Because the scroll wears more in the areas it is used the most, the accuracy will vary with different diameter work anyway, so you can either work around it, or set it up to get acceptable accuracy for a size that you commonly work with.

If the jaws are two piece, you can get or make soft jaw tops for them.

Cheers Trevor Jones

Reply to
Trevor Jones

Hi Austin, I said at the time that your were buying your Student make sure you get that big C spanner and any other bits. Regards. Ben

Reply to


When I had a Student, I forged mine from a length of 3/4" rebar, and case hardened the 'tooth' - worked fine on two Students over about 15 years.


Reply to
Andrew Mawson

On or around Mon, 6 Nov 2006 20:17:44 -0000, "Ben" enlightened us thusly:

heh. the spanner wasn't available, unfortunately. Mind, judging from the look of it, others have employed the "big hammer" method before me, and I at least use a bronze drift on it.

Reply to
Austin Shackles

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