Fitting a Unimat chuck to a Cowells

[Jo]

I picked up a bargain last night a Unimat Sl1000 three jaw chuck for ?11. No one wanted it because of the 12mm * 1mm thread. I can never understand these people chucks have back plates, you just remove the old plate make up a new one to fit your lathe and fit it.

For this chuck I took a 40mm noggin cleaned it up:



As you can see I actually made two backplates rather than one, it just meant that I had an opportunity for some character building to hand hacksaw the two plates apart. Back to the lathe and then used a 14mm * 1.5mm tap to tap the thread for the nose:



People have told me that using a tap to cut the thread for a backplate is bad practice but they seem to forget that the nose on the lathe has a register as well so the chuck is centered on the register not the thread. So using a boring bar the register was cut in the back of the plate and checked using the nose on my dividing head (sorry forgot the photo )  and the surface skimmed to chick it was square with the register.

The the new backplate was then put on the Cowells and the register for the back of the chuck cut on the new backplate before drilling and cutting the three 4mm screw holes. So a new chuck for my Cowells:



My plan is to use this new chuck on either my indexing head or the dividing head.

Jo

[ScroungerLee]

Nice job.  And you got to buy something, woo!!!

Lee

[Jo]

I also picked up a 24" height gauge for ?5  I now just have to find something big enough to build to use it on

jo

[steamer]

I need to make a mandrel to adapt from my F1 to the Southbend....probably with the M22 x 1mm thread on F1 dividing head.


Nice Job Jo!



Dave

[Raggle]

It's a shame that all new replacement chucks for 21x1 and 14x1 on offer these days seem to be screwed body and not backplate mounted.

While playing with my Super Adept, which came with only a faceplate, I made a backplate to fit my Uni SL 3-jaw, using only a 3/8" BSF tap and fair bit of close measuring and fitting, finishing on the Adept with treadle power. I was rewarded with almost negligible runout, which was a surprise as it was awful on the Unimat and had been for years. Naturally I then made a new backpate for the Unimat.

Part of the backplate design was the ability to use the chuck on the Uni's dividing plate, each of the "gears" matched the lathe's backplate and used the same screws. The threading masters also required the chuck's 3-screw fitting.

And you're right about the register being most important. A quite sloppy thread will do the necessary guiding until the register locks. Too close a fit can interfere.

Ray

[Goldstar31]

I suspect that I have a three jaw and a four jaw independent chuck for Super Adept. Solid chucks scewed 1/2" BSF?
Could be a liitle Enox10, however. Kept top slide for my Quorn

[Dan Rowe]

Jo,
Thanks for the tip. I had forgotten that the Unimat SL chuck had a backing plate .

Now I have another job on my list.

Dan

[craynerd]

Nice work Jo. I`ve just been doing something similar but didn`t post up because I also cut the thread with a tap and thought I`d get slated. Thanks for the post.
Chris

EDIT: Jo, 

So using a boring bar the register was cut in the back of the plate and checked using the nose on my dividing head

   I can`t picture that and I know you said you missed the photo, but could you explain a little more about your setup here?