Fly-cut for flat face


On this second attempt to create a chuck adapter, I first fly cut the blank so I'd have a flat face to position against the lathe spindle, and bolt in place. This way the drill holes should be parallel to the lathe bed, and when the register (shallow flat-bottom hole) was turned, it too would be concentric and parallel.

Sad to say, when I used the DRO to drill the bolt-holes, I managed to loose center!  And while the holes were space accurately - the adapter 'circle' was off-center to the blank diameter, and I had to figure out how to remove the excess metal.

Fly-cut for flat face
3-jaw chuck adapter

The Mill table is christened


The mill table is christened!   I managed to run the drill through the work and into the table - despite every precaution! I had so not wanted to mung up that pristine table...  but as luck and my 'not being in the moment' would have it, it is no long virgin.    :-(  

I had the blank centered for the bolt-hole circle, then decided I needed to get it up off the table so I wouldn't drill into the table.  So I managed to raise the blank up on 1-2-3 blocks, but in the process lost center, and STILL drilled thru into the table.   Sheesh!

The Mill table is christened
3-jaw chuck adapter

Recovering from off-center bolt holes


To recover from the off-center holes, I ended up doing a trepanning operation using a cut-off tool.  I did a lot of reading on the web and 'official' trepanning tools are way too costly.  And after some thought, figured I could carefully plunge the 1/16" cut-off tool into the easy-cutting CI; Occham's Razor - "the simplest solution is the best".

As it turned out it worked perfectly, and now I have a 6" CI disk with an off-center, 5" hole in it!

Recovering from off-center bolt holes
3-jaw chuck adapter

Machining the lathe register


This is the lathe setup to machine the flat-bottom hole for the lathe register on the spindle.

A brazed-carbide boring bar was used to make the cut.  In my early attempts to do this, there was a lot of rubbing and bad cuts...  couldn't quite figure out what was wrong, so I abandoned the bar.

On subsequent attempts I discovered the boring bar was positioned in the tool holder incorrectly!  I had the flat top of the carbide insert parallel with the bed.  As the cut got wider, this allowed the metal beneath the carbide to rub against the work.  By simply rotating the bar in the holder into a 'negative rake" position, (flat tipped down a bit, toward the front of the lathe), the cut became sweet and easy, and I was able to get a perfectly square shoulder.

Machining the lathe register
3-jaw chuck adapter

Finished Adapter & blank


Here is a view of the 5" adapter plate - chuck-side up, with the original 6" blank and off-center hole.

Finished Adapter & blank
3-jaw chuck adapter