What about using an engine valve as milling cutter?

[Cadillac]

They will cut anything not as hard as the valve itself. So yes they will work. I’ve seen videos of people doing exactly what you ask. Have I done it No but I do have a bunch of valves sitting around waiting to be ground some day if needed. Is it okay ideal No but if you need a special lathe tool to get into a tight spot it just might work.
I wouldn’t write it off.

 

[great white]

They will cut anything not as hard as the valve itself. So yes they will work. I’ve seen videos of people doing exactly what you ask. Have I done it No but I do have a bunch of valves sitting around waiting to be ground some day if needed. Is it okay ideal No but if you need a special lathe tool to get into a tight spot it just might work.
I wouldn’t write it off.

I've done the same thing before, using a scrap valve to clearance pistons. Usually brazed a small cutter on the valve face rather than cut the valve.

But it's a "get ya by" type of thing. Not recommended for regular use.....

 

[Suzuki4evr]

Back in the bad old days, when we were modifying stock parts for racing, when installing a camshaft with more lift and duration, the pistons would have to be notched to clear the valves. We'd take an intake and an exhaust valve and grind reliefs in the face to make a cutter. Put the valve in the guide in the head, run the piston up in the cylinder, chuck the valve stem in a drill motor and presto, notches cut. After the first cut too deep, one fits a stop collar on the valve stem. The really good machinists would braze HSS cutters to the valve face.

jack vines

That is a good idea for that purpose. When I was still working as an automotive machinist, I would clock up the pocket of the pistons in a four jaw using the valve in the tailstock as a rouhh to pretty close guide and the dial it in a little closer. Then machine to depth and pre-top the pistons as usal in the three jaw if necessary. Your Idea sound a bit quicker though.

 

[Suzuki4evr]

I did ask the question in the title of the thread and got the answer,but now I have found this on youtube and I must say this guy is thinking out of the box and I like it.