Chuck reverse options

[minilathe22]

Hello everyone

I am trying to secure my chuck for reverse rotation. I drilled and tapped an M5 thread through the side of the chuck backplate, which appeared to hold it securely. However, due to the design of my spindle, this throws the chuck off centre, and prevents me from accurately realigning my chuck. I would like to secure the chuck for reverse, and solve my chuck alignment problem.

You can see in the photo below that I have wrapped some tape around part of the spindle, so that the chuck backplate fits centrally. Tightening the grub screw pushes this off centre.

I am planning to add three grub screw holes equidistant in a triangle, then I should find it very secure in reverse, and I should be able to adjust them to prevent any runout and remove the tape.

Is this the best option? Any better ideas?

 

[dickm]

That whole setup looks a bit odd to me. Surely the chuck backplate/adaptor should sit on the parallel section of the nose to provide a proper register, and pull up against the bit that has the tape stuck to it. Or is that how it is when fully tightened? If it is, and the grubscrew throws it off line, then it suggests that the register of the chuck is a bad fit.
Or am I barking (probably!) up the wrong tree?

 

[minilathe22]

Apologies, What is not clear from my photo is that the chuck is not fully threaded on, to show the tape. When fully tightened, the back of the chuck plate squashes up against the brown fibre washer and completely obscures the tape from view. The hole in the smaller part of the back plate is the threaded hole I added, and the grub screw comes into contact with the tape.

 

[minilathe22]

See photo fully tightened:

 

[SVB]

Do you have ideally inside & outside micrometers but if not a vernier? Worth measuring the bore of the chuck recess and the register OD on the spindle (without the tape). Should be pretty similar within 0.2mm I'd guess.

S

 

[minilathe22]

I have vernier calipers, but I can say that the difference in diameter is at least 2mm, as I had to wrap several layers of electrical tape round to get a good fit. Unfortunately the tape unravels either when tightening or loosening the chuck, depending on which direction you wrap it on, so is not a permanent solution.

I wonder if I could find a thin strip of sheet of metal and solder it into the chuck backplate?

 

[CHJ]

... I had to wrap several layers of electrical tape round to get a good fit. ..

This is undoubtabley your basic problem, the chuck backplate should as SVB said should be a good fit on the spindle register.

What is the Spindle nose thread, are you sure you have the correct ISO backplate? some threads had different standards of register.

I don't think you are going to get a satisfactory long term solution using plastic tape to shim the difference.

You may be able to get a metal foil self adhesive shimming material that would be a better 'fix' with care.

Personally if the spindle nose is not a currently available standard for a backplate match I would get a slim walled sleeve turned up to go between the chuck and the spindle nose register.

 

[minilathe22]

It is a Union Graduate 1 1/2" x 6tpi thread, RH on one side and LH on the other. Register problem is apparent on both sides. The backplate is dual threaded from The Toolpost. I have not seen anyone else that sells the dual threaded backplate for this thread size.

I will measure the diameters tomorrow. If the gap is the same on both threads, then I will consider adding metal in some way to the inside of the backplate, while still keeping the grubscrew.

 

[graduate_owner]

Axminster used to sell back plates with L / R threads to match their discontinued super precision chuck. They were on special offer a while back which might mean Axminster were getting rid of discontinued stock.
I bought one of their evolution chucks with L / R thread and it fits nicely on both threads, and can he swapped from side to side without loss of concentricity.

K

 

[SVB]

I'd give Peter a bell at toolpost first. Sounds like wrong backplate spec to me. 2mm is at least order of magnitude too big and time, trouble and effort to fix may be greater than a new backplate imho.

S

 

[CHJ]

Note the different register dimensions for 1-1/2" threads.

http://www.quest42.co.uk/woodwork/bin/A ... hreads.jpg

Also some older 1-1/2" threads are Whitworth (55deg.), dependant on the machining tolerances fittings may be usable on the 'wrong' thread.

 

[minilathe22]

All good information, thank you. I will mull it over.