Making an accurate spindle with an innacurate chuck.

Gallery, Projects and General > How do I??

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S. Heslop:
I went and stole back a gift i'd made for my grandparents.

I made it to test out the 4 jaw chuck when it was new. Checking it with the indicator, it's off by a fair bit as well. I remember taking care to ensure it was properly bedded against the chuck body when I was making it. (I'll make a new stand for it before I give it back. The last one went missing)

I also found that the mounting face of the chuck rocks quite a bit, so that's maybe where the innacuracy is from. The surface of the back looks (to me) like it was flycut, with radial machining marks. Maybe I could try the gripping it on a bar thing, but as Norman has suggested my lathe might not be up to the task, even supporting with the tailstock.

Or I could maybe have a go at adjusting it parallel with shims between it and the backing plate.

I'm still waiting for that steady rest to arrive before I make a move though.

lordedmond:
Simon

this may help

Stuart

S. Heslop:

--- Quote from: Fergus OMore on November 23, 2013, 01:49:59 PM ---Simon,
We've reached the stage of 'workarounds' rather correct machining. So please don't get at me -anyone- I'm trying to help!

--- End quote ---

I appreciate the help and I don't mean to sound ungrateful, but I don't want you thinking i'm stone ignorant either.

I'm aware of what the 'correct' methods are, and have done plenty of reading on the subject (with access to a university libary). But with the budget, time, and equipment I have available I have to find compromises and alternative ways to solve problems. Plus by the end of the day that's what I really get out of this hobby. It's like a puzzle. It'd be unsatisfying having all the ideal equipment and following the instructions in a book.

I am aware that my lathe isn't very rigid, and have done tests in the past, but it doesn't account for all the error in the chuck and it can be worked around. I've also done tests available to me on the chuck, its backplate, and the lathe register (feeler gauges, felt tip pen as machinist's blue, dial indicator, surface plate, etc) to pinpoint the problem (that being that the chuck is all warped and none of the faces are parallel or even flat).

Sorry to be blunt but I just want this to be clear.

--- Quote from: lordedmond on November 23, 2013, 01:12:24 PM ---this may help

--- End quote ---

If i'm understanding this right, then I don't think it applies to my chuck. The inner face is a rough machining with 4 holes bored in that parts of the mechanism are pressed into. Thanks though.

lordedmond:
Ok Simon

that was from my Myford book

the Chronos chuck clearly do not follow the norm

IMHO
you have two choices find someone with a larger lathe clamp the chuck on the car and spin it up between centres and face the rear to the jaws and you will be sorted
or get a new chuck

All my working life I have worked to this principle if its K for not working I cannot make it worse so any repair is liable to improve things

I hope you sort it out with the minimum of fuss

Stuart

PS why don't you PM double boost (John ) he is in your neck of the woods to see if he can help sort out the chuck

PekkaNF:
hmmm....

If we are now on workaround route....and the chuck is expendable?

Because now it is concluded that front, rear and jaws are not to be trusted, only way up is to true everything on jaw ways.

Do you have a some parallels or ground key stock? You could rest the chuck on your surface plate on the jaw ways on the parallels and clock the rear mounting face of the chuck.

Can you mount the chuck on the lathe face plate on parallels touch the jaw ways?

I don't think you can true this four jaw chuck clapped on the arbour, because I don't think you can trust jaws being true to jaw ways.

What do you think?

Pekka

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