Chucks and adjustment?

They are retaining screws to hold the pinions in. Position doesn't matter as long as they are not proud.

Cylindrical grinders with chucks on have to be set on very job for run out as these need to have the work running to tenths or better.

They achieve this by having a slightly undersized register on the back plate and clearance in the 3 or 4 holding bolts. The operator chucks the job up and puts a clock on the diameter he needs to run true, then thumps the chuck into place with a block of lead. Sounds crude but this is standard practice.

-- Regards,

John Stevenson Nottingham, England.

despite the name self centering chucks aren't ... Only Sc chuck Ive seen that is any good for that kind of work is a 6 jaw from kitigawa used on the Brierly drill and tool grinders

cheers d

Scroll chucks are for idle apprentices. If you want accuracy, you can't beat independents!

Which are also only as accurate as the bloke on the end of the chuck key

-- Regards,

John Stevenson Nottingham, England.

Has your backplate been machined on your lathe & chuck correctly fitted ? If the chuck just falls off when the screws are removed it is not fitted properly to the register faces & will never run true.

Yes, but at least the guy with the chuck key can set them as accurately as a DTI will register. With a scroll chuck, you're stuck with it - short of wielding a big hammer!

What are they for? one is screwed in more than the other . Are the just fixing for the adjusting bolts or do they have another purpose such as adjusting the centricity of the scroll either as straight run out or longitudindal alignment?

any advice most welcome

Mike D

ps I have nearly finished making the Hemmingway backplate adjuster which will solve the centre run out.