Fixing Ralph's Chucks

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Bogstandard:
Jack,

I am doing a rescue here, and by making the spindle nose perfectly true, as I did, is the only way it could be done. We all know that it is always better to use the original machine, but in this case it was just not possible. Anything will be better than what the chucks are like before the fix.

rleete,

Ralph told me he will be answering your question later.

Anyway, back to getting the job done.

So Ralph eventually arrived, clutching his duff chuck, plus a few other bits as well. Choccie scoffed, drinks drunk, gums well beaten, and then we got going into the shop.

I was going to be grinding the first chuck, and with a little instruction, Ralph will be doing the second.

The first job was to mount up the toolpost grinder and to dress up the mounted point to run true and be true to the bedways. Very slow power feed will be used during the grinding exercise.

This is the shot from the other direction, showing how the stone is fed down into the chuck. As you look at it, the stone is rotating clockwise and the chuck in it's normal direction, anti clockwise, at a speed of 65 RPM. The initial cut feed was 0.01mm, and the stone was turning at around 25K RPM

This is a much closer shot, action stopped by using flash. At the 1 o'clock position at the top of the chuck face you can just see a spark burst. It took 0.3mm before all jaws were sparked out down the whole depth, slightly more on the second chuck, mainly because of the bodge job I did a couple of weeks ago.

Here is a very rare shot of Big Ralph, happily sitting there, twiddling a knob and pushing a handle every so often. It seems like he has found a job that isn't too strenuous.

This shot shows the finish obtained on the jaws. On checking with a DTI and test piece before taking them off the stub spindle, the first, much less than 0.001", the second, a little more, and as I told Ralph, I suspect the scroll has been damaged slightly somehow, because it sparked out perfectly, but when the jaws were closed down to fit the test piece, the jaws moved out of position from each other. But still within expected runout tolerances.

Rescue done and dusted.

But before I finish, this does prove that Ralph did occasionally move.

He will kill me for showing this. Click the picture.

So anyway, the job got done on time, hopefully Ralph is happy, and we spent a few hours afterwards just beating our gums, putting the world to rights, hence the late timing of this post.

Hope you enjoyed this short journey with us.

Bogs

ozzie46:

Enjoyed it a lot Bogs. Thank you.

Ron

John Stevenson:
John,
I was told when grinding chuck jaws you had to load up in the direction they are closing because of any differences in the scroll.
Using a ring on the outside of the jaws is forcing the jaws open but you are grinding the part the is the closing element.

We were told to put the ring inside on the bottom of the jaw teeth, doesn't matter if the ring doesn't run true the jaws will do. This way you still have clearance to get all the way thru to clean the jaws up.

Divided he ad:
Ok.... Firstly.... Thanks for the debut video appearance John :bugeye: :palm:

Now, to answer a few queries... I screwed up the 80mm chuck long ago when not having a clue I tried to remove the runout and true up the jaws with a carbide tipped boring bar :doh: :wack: I know!

The 125mm chuck was not running as it should, probably me and my over eager need to "secure" stuff in the jaws!? (it was perfect to within all tolerances when new... There's a thread out there somewhere of me fitting it!) and had picked some steel up badly on all jaws, attempts to remove said welded matter were not good and ended up in poor condition (to be conservative with language) of the jaws. Marking all of the work I was producing.

So, chucks well and truly bu663rd, I asked John if he could help me get them into a better shape.... Else new chucks would be purchased. (not what I wanted to do without trying!)

The rest... You can read above.

Very happy with the process myself. The test of runout was well within tolerances on the little chuck and pretty close on the big un... (as said... Probably me screwing up the scroll! :loco: ) will prove if it worked or not on my lathe, I'll be testing them hopefully tomorrow evening.... I'll tell you all about it if you want?

Thank you John for being so patient and sparing me so much of your workshop time :thumbup: For those who would doubt it.... A proper gent :beer: (even if he did record me sitting on my ar53! :lol: )

Ralph.

Sorekiwi:
Thank you for a very imformative thread. I have a chuck that I need to do this to, just havent had the Ba11s to do it yet!

Quick question, any reason why I couldnt use the inner race of a big roller bearing instead of the brass ring that you made?

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