I got a deal on an entire Sherline machine shop some time ago. It came with a Sherline boring head. I've tried to use it but it was quite frustrating for me. Hard to accurately adjust. (This was my experience and may be due to lack of skill. No knock on Sherline.) Poking around the Internet, the bane of my existence, I found that Criterion makes a 1 1/2" boring head which works well on the Sherline. It is a Criterion S 1 1/2A Boring Head. Again poking around, it's the Internet's fault, I found one on EBay and couldn't resist. It's a beautiful piece of tooling.

I made an adaptor which threads onto the Sherline 3/4-16 spindle and takes the 7/8-20 boring head mount.

It accepts 3/8" boring bars. Finally a picture mounted on the mill.