A Collet Chuck for the Colchester Lathe
by John
I recently bought a blank chuck backing plate on Ebay, hoping that it would fit my Colchester lathe. It was $AUD110 plus postage, which, if suitable, would be an excellent price, but it was a gamble. It was old new stock.
When it arrived I cleaned off the old, hard grease, and nervously presented the backing blank to the lathe headstock. It fitted perfectly! The seller had another identical blank backing plate, so I bought that one too. Components for the Colchester are not readily available, so I was very happy with this find.
I had a use in mind for both of the backing plates, and a few days ago I machined up the first one as per the following photos.
The cast iron backing plate blank had a tough skin which a high speed steel cutter would not penetrate. So I use a carbide insert tool cutting 1mm deep to break through the skin. I finished the contact surface with a HSS tangential tool. (A diamond cutter from Eccentric Engineering)
The C5 collet chuck. I have had this chuck for a few years, purchased from CDCO Machinery (USA), but rarely used it because I was not satisfied with the accuracy. I was very interested to see whether a very careful installation on the Colchester lathe might be more satisfactory than on the previous lathe (a Chinese lathe).
Checking the runout off the newly installed collet chuck. With a piece of 10mm diameter silver steel, the total measured runout was about 0.005mm. Good enough. The backing plate is larger than required, but I will leave it as is in case I ever use it for another, larger chuck. C5 collets will hold round stock 2-26mm diameter, and some common square and hexagonal sizes. Very useful.
johnsmachines 
Watch out for that Huck towel. If it gets caught in the works it might be a problem. Elfin Safety Officer wouldn’t approve.
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Quite right. It is there only while I was turning the very abrasive cast iron. I will soon make make a metal cover for the ways.
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I thought about one of these but it was about .he same price which I thought was too much. If I need a collet chuck I fit an error collet chuck on a parallel shank into a four jaw chuck and center it properly. I used to have c5 collet but I replaced them all with er ones. The only snag is that er collet only hold round shapes.
John f
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