Lathe chuck backplate question

[RussellT]

Some time ago I was given a 6 inch 4 jaw chuck.  This is a solid bodied steel chuck - no cut aways or lightening holes anywhere.

It came without a backplate and so I bought a backplate casting.  I followed the advice on lathes.co.uk on machining the thread and register and it fits nicely.  So I took it out of the 4 jaw chuck I was using to machine it.

When I mounted the new backplate I could see that the backplate was about half an inch thicker than it needs to be.  I can't machine that off the chuck side of the backplate and machining it off the headstock side would require very accurate clocking in two planes.

So, does it matter? Is it an advantage as I can get larger stock through the chuck further? What does anyone think?

Russell

[caskwith]

Personally I like the extra length on my backplates, allows me to hold larger stock deeper in the chuck as you mention. I don't think 1/2" will make a whole lot of difference to rigidity.

[Jonny]

When you face off the rear and front, turn the register, counter bore for fixing it wont leave a great deal.

[RussellT]

I'm still thinking about this - although I have worked out how to hold it to machine some off the back.

Russell

[Jonny]

Mount it on the spindle and machine o/d some where near, then machine back then front with register.

Can improvise with tooling to machine the back as there may not be clearance to head stock using a left hand tool. Or right hand tool on a rear tool post.

[RussellT]

I decided that for this chuck I ought to reduce the overhang a bit.

I bored another register in the front of the backplate and put it on the spindle backwards.  Turned off enough to remove my first register and then bored a new one.

Put it back the right way round and started cleaning up the front.  I estimate that by the time I've skimmed the front the backplate will be about 5mm thicker than the spindle nose which is OK.

But while I was cleaning up the front - the lathe motor started playing up.  I suspect the capacitor.

Russell

[micktoon]

 Sorry to hear about your motor problems Russel , one job ALWAYS leads to another , fi not a bloody chain reaction I find  Good luck with getting it fixed with out too much hassle.

 Cheers Mick

[vtsteam]

Isn't that the way! My lathe motor just started acting up, too. Somewhere in the starting bits. I have to give it a spin by hand to start it. Will be taking it apart to see what's up.

Anyway, enjoying reading about your backplate procedure! 

[RussellT]

Thanks Mick and Steve.

It was indeed the capacitor.  One of the terminals had corroded and dropped off.  I think it was shorting to the other capacitor terminal so there was no phase difference on the start windings.  I think that stopped it reaching enough speed to open the centrifugal switch when I started it by flicking the pulley.

Fortunately there was a spare terminal on the capacitor  .  Unfortunately it too was corroded and broke when I pushed the spade on. .

I soldered a new terminal on and reassembled.  Unfortunately the capacitor leads are so short that I had to take the motor off for the repair but it's all working again now.

I hope to finish the back plate tomorrow.

Russell

[RussellT]

Done!

Now I just need to drill the mounting holes.

Russell

[Manxmodder]

 Nicely done Russ    looks good to me.....OZ.

[RussellT]

Thanks Oz.

Russell

[RotarySMP]

Nice work Russell. Is this one of the cast iron blank backing plates off ebay UK? How did it machine?

[RussellT]

Thanks RotarySMP

Yes and No.

It wasn't off ebay but it could have been.  I bought it from RDG at a show and they also sell them on ebay.

It machined fine once I'd got the speed right - I used HSS tools and they cut fine.  There was a defect in part of the threads but no worse than on some of my genuine Boxford back plates.

Russell

[RotarySMP]

Thanks for that. I'll need a few for my lathe.