johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most.

Tag: collet chuck

A Collet Chuck for the Colchester Lathe

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.

 

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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)

 

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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).  

 

 

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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.

TCL lathe renovation 1

I CNC’d a new handle to replace the broken one on the little lathe, but the new one made the old ones look a bit shabby, so they will all be renewed.  The new, deeply waisted handles are very nice to use.

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The headstock shaft was 3/8″ and was a bit undersized due to wear, and I intend to use a collet chuck with a 10mm shaft, so I decided to increase the shaft size from 3/8 (9.525mm) to 10mm.

The headstock bearing housing is split, to permit some adjustment with wear.  I used a reamer with spiral teeth to avoid the teeth snagging the split.  And all seemed to go very well using the setup in the photo below.

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…Until I finished and raised the milling machine head out of the work.

Due to my lack of familiarity with the CNC mill controls I  activated the X axis rather than the Z axis.  The side movement broke the reamer and partially gouged the newly reamed lowermost housing.  Bugger.  Bugger.

What to do.  Throw the whole project into the scrap bin?  (following a few others).  Change the shaft to the next size (12mm) and enlarge the housing holes to 12mm?  That would thin and weaken the housing.  And would be tricky machining.  Also, due to the damage in a lateral direction caused by the mishap, I was not sure that drilling and reaming, or boring and reaming, would not follow the same lateral path.

At least the uppermost housing  was undamaged, so whatever tool was used would be held concentrically, as long as the cutting edge extended the distance between the 2 housings.

So I very slowly drilled 11.5mm (the 11.5mm drill did span the distance between the 2 housings) and re-reamed to 12mm, again as per the above photo. Despite my misgivings, this time it all went well.   The 12mm shaft is rather tight, and the housings will need some lapping.  The housings appear to have enough thickness remaining, but time will tell in that regard.   The lateral direction of the shaft is not perfect, but in such a small lathe that is not a big consideration.

As a consolation, and to retore some self esteem after this muck up, I made a new chuck key.

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The chuck is held onto the shaft with a 3/8″ x 24tpi thread.  That thread was cut on the CNC lathe, and is probably fairly accurate.  The oil cups are spare from the beam engine build.

I plan to lap the housings, install a thrust bearing behind the chuck, and make a drive pulley.  I have a spare 12mm shaft ER 16 collet chuck, which will probably be used more often than the 4 jaw chuck.  Then a new handle for the longitudinal feed, a paint job, a motor and belt…