Stuck Chuck Follow Up Part 2

[porthos]

ok guys , first thanks to those of you that submitted advise. Here's where I stand.
1. I scraped the surface area of the backplate that seats against the back register of the spindle. Took about 5 on and off installations of the back plate , using Prussian blue to make "rub" marks on the surface of the back plate. I scraped the blue area of the backplate with a carbide insert that I made a scraper out of. With each scraping I got more bearing surface between the two surfaces. Now I have full face to face rub marks with the blue.
2. Now I recut the surface that corresponds to the back of the chuck and bolts to it. Everything should be square, right?
3. Bolted the chuck to the back plate. Chucked up a .500 pin gauge. I now have .008 runout. A real letdown.
4. However the chuck does come off easily . Thanks for the scraping advice.

I've got a couple more things to try. but in the meantime I've still got a 4 jaw chuck and collets

I learned a neat trick to keep that disgusting cast iron cuttings and powder off most of the ways and carriage.
Saran Wrap. taped it to the headstock under the spindle (after degreasing). Over and around the compound.
Even poked a hole in it for the toolbit . Worked pretty good.

porthos

 

[brino]

A "lathe bib"

Neat trick, I'm gonna use that.....
I should have thought of that as I already cover the shop PC's keyboard in a layer of plastic wrap.

thanks,
-brino

 

[joshua43214]

Well Done!

Clever tip on using Saran wrap. Will have to try that on my compound. I always just lay paper towels spritzed with WD40 on the ways to catch most of it and vacuum off the rest.

Your run out could be caused by a number of things.
You should be able to loosen the mounting screws and shift the chuck around on the back plate to minimize the run out. If the chuck won't move, or won't move enough, then it might be mis-drilled.
There are two type of mountings for chucks, front screw (the back plate is threaded) and back screw (the chuck is threaded). If you have a front screw, then either the holes are in the wrong place, or the chuck is just low quality. The holes could be properly placed, but the chuck just has that much run out. If you have a back screw, just drill the holes in the backing plate out a tiny bit and you should have some more wiggle room.

 

[porthos]

Thanks Joshua. that is one of my things to try. I had the holes drilled by someone else with a Bridgeport with an indexing table. The are just about to size. Most of the bolt holes have thread marks on them. So, there is no wiggle room. I 'll drill them a little bigger. I'm going to take a couple days off and move to another project. I'm fitting a carbine stock to a 30-40 Krag that will become a faux carbine

 

[DoogieB]

I learned a neat trick to keep that disgusting cast iron cuttings and powder off most of the ways and carriage.
Saran Wrap. taped it to the headstock under the spindle (after degreasing). Over and around the compound.
Even poked a hole in it for the toolbit . Worked pretty good.

Yup, I keep a roll of stretch shipping wrap down in the shop for just the same reason. Works great when sanding as well as it keeps the grit off the ways and you aren't ashamed to throw it away immediately.

 

[Bob Korves]

Check to see if your runout is because the work is orbiting off center but parallel to the spindle, or instead because it is not in line with the spindle axis (or maybe both.) Carefully chuck an accurate ground round rod and check the runout close to the chuck as well as at several distances from the chuck, unsupported by the tailstock. Scraping the spindle to chuck interface would more likely affect the work being off axis. Those two variations require quite different fixes. The indicator readings will tell you how to proceed to make it right.