Doing a little Tri-Z head milling!

[bkm]

I’m not sure if I’m going to be able to explain this without a drawing or sketch, but here goes anyway.

Imagine a round plate that was the size of whatever the maximum your bed will allow on that lathe which had a short hollow shaft (pipe if you will) the largest diameter that the chuck will acsept welded to it. Now imagine that you have perforated that large round plate with a whole bunch of different hole patterns that are threaded, as well as one large one (unthreaded, maybe 1” día.)in the center.

You would need an assortment of angled slugs that would match the angles of the various spark plugs in the heads that you planned to do machine work on. Those slugs would have the angle on one side and be cut straight on the other.

If you only wanted to face the mounting services of the head the slugs could just have a small hole in the center that would allow you to draw at T shaped rod through the combustion chamber side of the head, through the spark plug hole and through the hole in the slug which could then be tightened with a nut. However, if you wanted to reshape combustion chambers you would need to have a rod that could thread into the spark hole from the top. Not sure if your lathe would afford enough room for that.

One way to make the tools would be to smash a bunch of spark plugs up and just weld some threaded rods to the remaining threaded metal portion of the plugs to make your tools.

So focusing just on a setup to face the mounting services of heads with non-perpendicular spark plug holes, the remainder of the threaded holes in that round plate would be used to thread rods, or bolts into it to press up against various points on the top side of the head which could then be locked into place with nuts. These would be used to properly locate the head parallel to the mounting plate as well as stabilize it during the machining process.

Does this make sense?

Yep, makes perfect sense. In essence it's kinda the same thinking as my idea with the angled slugs. I'm just skipping the plate idea. I think we're on the same track here. The biggest problem is the capacity of my lathe. If I had a bigger lathe with a 4 jaw, this wouldn't even be an issue.