The Home Machinist!

I like those jaws!

Some aircraft engine manufacturers of that era used standard size studs screwed into undersize threaded holes in castings to obtain an interference fit to retain the studs. Others used standard taps with over sized studs to obtain the desired interference fit. Over sized taps are also used on some a...

Sounds a bit like chip welding where a small chip welds itself to the cutting edge of the tool for a short duration and then breaks free.

You're welcome, Harold.

I did it back in the 80's when I had discovered Silicone Bronze filler rod for TIG brazing steel. It was only an experiment, as I had a short piece of 2" brass tubing and a small piece of brass sheet and wondered what would happen if I tried welding them together. It worked pretty well as I was able...

I've TIG welded brass using silicone bronze filler rod so that may be an option depending on the repair needed.

I'm not yet too familiar with them, but have a Smith Tool floating reamer holder that I'm not quite tooled up enough to use yet that will allow .030" radial misalignment, but it does not compensate for angular misalignment.

That's where things can still go bad when using one it seems.

That wouldn't show vertical error in the tailstock axial alignment either parallel or angular.

A gauge pin was then inserted into the barrel bore and indicated concentric to the lathe spindle axis. https://i.imgur.com/nONBiCil.jpg The reamer was then plunged to the desired chamber depth. https://i.imgur.com/jTJBsogl.jpg The barrel was then flipped around and the crown was cut using the same t...

Finally had some time to tinker. Plugged the lathe spindle and turned the plug to just slide into the barrel. https://i.imgur.com/oo1KjUEl.jpg Took a boring bar holder and indicated parallel to the Z axis and plugged it with round bar. Then indicated the round bar in so that it was concentric with t...

It's a bit confusing, as your title states a four jaw chuck, but them you quote runout specs.

Are you looking at four jaw scroll chucks?

You should be looking for a four jaw independent chuck for chambering use, not a scroll chuck.

Pistol or rifle barrel?

I'm in total agreement with Mauro, but I'd also try a smaller radius on the tool. Maybe about half of the radius you are using to start.