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Advice on chuck modification

Making a disc chuck fit on a D 1 3 backplate

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Plasma30/03/2019 19:54:26
198 forum posts
26 photos

Thinking caps on please.

I have a Smart and Brown model L headstock going spare and a disc chuck that fits the spindle nose of that lathe, needing a draw tube to tighten it.

I'm thinking it might be nice to mount this chuck on a D 1 3 backpkate so I can use it on my boxford.

What's the best way to proceed?

Butcher the spindle and work out a way to fit it to a backplate, or have a false spindle nose made to fit on the backplate?

I do not think I'm accurate enough to make a false nose myself so would have to find a firm to do it for me.

Any thoughts woukd be most welcome.

Thanks Mick

Hopper30/03/2019 22:29:51
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3529 forum posts
68 photos

Pics would help. Can't visualize exactly what you need otherwise.

Would be a good practice piece to make yourself and save a hundred quid.

Martin Connelly31/03/2019 00:06:02
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839 forum posts
93 photos

Are you talking about a step chuck?

Martin C

Plasma01/04/2019 11:37:02
198 forum posts
26 photos

20190401_110252.jpgHi guys,

Sorry been busy buying a pillar drill off fleabay and got sidetracked.

Yes its a step chuck, as I said I have a scrap spindle I could butcher but that seems a waste.

20190401_110302.jpg

Plasma01/04/2019 11:38:49
198 forum posts
26 photos

That's the kind of thing I'm after, easy to pop on my boxford for use with thin pieces. I have the draw bar tube for it too so should be a straight forward job.

Cutting the thread is what scars me.

Mick

Hopper01/04/2019 12:46:44
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3529 forum posts
68 photos

No time to learn like the present. You should be able to cut the thread and use the chuck to test it for final size. You can make it a bit on the loose fitting side if the spindle uses the usual method of a stepped collar that does the locating. The thread is just there for retaining purposes.

To get best concentricity you should make the other end of the false shaft first and press it or weld it to the D13 flange. Then mount that on the spindle and turn the business end with thread and collar in situ.

Get some material and make some test pieces up for practice, cutting the thread etc.

If you are not confident of your skill levels, you could hold off until you have more experience.

For the time being, simply hold the body of your step chuck in the jaws of your regular three jaw chuck (or four jaw if super fine concentricity is essential). This would be good enough for most flat washer type jobs in the hobby workshop.

Clive Foster01/04/2019 13:09:56
1667 forum posts
46 photos

Lower (in your pictures) part of the closer unit looks to be a plain cylindrical section. If this is true to the collet then simply boring out the backplate to a nice sliding fit and fixing into place with a strong version of loctite or similar adhesive should work fine.

Cutting forces on things held instep collets are generally low and the drawbar will hold it back against the backplate so spinning is very unlikely. Does need to pull back against a solid shoulder tho' or the drawbar pull will eventually work it loose.

Due to the way these things are made the odds are that the cylindrical part is true to the collet closer cone.

Clive

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