Machining a 10" chuck on a 12" lathe

[SteveM]

Had a deal on a practically new 10" 4-jaw chuck.

I really can't use it on my 12" Atlas as it would probably bend the spindle.

I bought it to use on a 9" rotary table.

Got it home, went to put it on the rotary table and the flange in the back stick out further than the backplate mounting surface. The rim around the back is 8-7/8" inside diameter, which prevents the chuck from sitting flat on the rotary table. I need to take 1/8" off the diameter, so it will only make the rim narrower by 1/16" (the rim is about 1/4"
wide, so no problem there).

Problem is how to hold it.

I was worried that if I tried to hold it in one of my other chucks, I would risk having it fall out, given the weight and not a lot of place to grip it.

I took a piece of 1-1/2" or so 4140 that I had on hand, bored out the soft jaws to fit so that it would hold it concentric, drilled a center in the other end, slipped the 4-jaw over the bar and supported the other end of the bar with the center.

It was weird centering the chuck, as everything worked backwards, as you weren't centering the work, you were centering the chuck.

I realize that I didn't need to get this precise, but figured it was good practice and got it to within 3 thou total reading.

Then I realized my cross slide doesn't pull back far enough, so I had to turn the toolpost 90 degrees and mount a boring bar backwards in the toolholder.

Turned it all by hand to check clearances, particularly with the live center. Set up a stop so that I don't send the tool in too far.

Ran out of time tonight to do the actual boring, so I will do that tomorrow.

Steve

[Russ Hanscom]

Sounds like you are on the right path.

[SteveM]

I marked two points on the back of the chuck at 180 degrees by putting a level on a chuck jaw, leveling it out, using the insert to scribe a line on the chuck, rotating the chuck 180 degrees and leveling it, and scribing the other side. My 12" vernier caliper was able to measure to those lines across the support rod and the backplate I forgot to remove first.

So I machined the back of the chuck with the CPxx3 insert in the boring bar. Then I used a VBxx insert in the corner to relieve the corner.

When removing the chuck, I used a plywood cover that I made to keep the ways from getting dinged if I dropped a chuck.

I dropped the chuck on the rotab and it dropped right on.

I put an indicator on it, and it was oversize by a few thou.

Since it's a 4-jaw, centering wasn't as important as it would be for a 3-jaw, but it's always good practice to get it better than it needs to be.

Steve

[RSG]

Nice job Steve!

[spro]

Very nice work Steve M. You had to be creative along the way. Don't we like Timken roller bearings.