Making an accurate spindle with an innacurate chuck.

Gallery, Projects and General > How do I??

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Joules:
If you have a short length of silver steel or other ground stock. Mount it in the three jaw chuck, clock the run out and mark it on the shaft. Now clamp the four jaw chuck onto the shaft and clock the body run out, then the rear (that should have been set the body so it has the same runout as the shaft, set true to it) This will give you a rough estimate of it being parallel, as the run out should be constant from the three jaw chuck. Is the three jaw chuck also running out much ?

I hand scrap machined!!! faces to get them as accuratly as I can measure. Had to do this with a cheap ER collet holder that fitted on the lathe spindle and had horrendous runout.

Just make sure the bar you use is stiff so it doesn't flex under load.

S. Heslop:

--- Quote from: awemawson on November 22, 2013, 04:05:39 AM ---I wouldn't write off Chronos on a single issue. I've had very good service from them recently - admittedly only on small stuff but the service has been very good and amazingly prompt.

--- End quote ---

To be fair I did get a box of cheap drill bits and a box of taps from them on the same order, both of which are serving me well.

I've also removed the chuck from the back plate and placed it on a piece of plate glass to check the error with the indicator, and got a similarly large reading. I also took care to clean the bottom and make sure no swarf got under it. I also checked the float glass before doing so and it was as flat as I could measure.

It does surprise me that it'd be so far off kilter. Can cast iron shrink that much as it settles?

lordedmond:
Have you blued the mounting face of that chuck to your surface plate?
is it flat?

Stuart

awemawson:
If you are measuring the front and rear faces as significantly none parallel then even after this period of times I'd get in touch and open negotiations as that situation would suggest that the chuck is not fit for purpose. If you explain that you've only just got round to mounting it then you never know they may take pity on you .....

Andrew

Fergus OMore:
Simon,
Whilst Stuart is right in seeking important answers, I think that a further lecture is called for.

The first is 'cast iron' and by the very nature of the substance, both it and rolled steel can be very unstable.
If you cut into either, the stresses will start to release. Correctly, cast iron should be rough cut to almost size and put out to weather in the factory yard. This what happened only a few miles from you when the 'Tyne' had factories. Again, when steel was red hot going through the rolling mills and came out, it had received built in stresses to be released later. Bright steel is worst whilst black steel is less unstable.

Steel will do a lot of funnier things than that- but enough for the day.

The next bit of the lecture is Pythagoras and the Euclidian propositions of straight lines which your lathe should adopt. Again, I question whether yours runs parallel to cut correctly. Others have expressed similar points- but much the same really.

The final point is whether your lathe is sufficiently 'man' to support a 5" disc and to machine it- by hand.

This all suggests that you have a lot of testing and alignment before you commit tools and so forth to a replacement chuck.

I can only apologise but I feel that you should begin to grasp these concepts.

Again, my best regards towards your future success

Norman

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