A different kind of head fixture for machining
 

Here is a different approach to a fixture that allows machining the heads even fully assembled while giving total support.

I took an old cam tower and cut off one third and machined it flat. I welded it to a 1" piece of aluminum plate and machined it flat in the lathe. I set up the first head and dialed in the cylinder locators. Removed the cylinder and bored a hole in the fixture so the next time set up will be easy to dial in off the hole.

Although it looks rather crude, the results were perfect. Once the first one is set, the dowel pins allow instant location for each remaining head.
http://forums.pelicanparts.com/uploa...1201323331.jpg
http://forums.pelicanparts.com/uploa...1201323343.jpg

So next time you set up, you will use a test indicator with the ball tip in the hole in the fixture, so you can tell if the cylinder bore is concentric with the lathe? I think I get it.

How much play is there between the head and the fixture when it's set up? Will you just locate off the dowel pins or can you clamp to the fixture using the bolts?

Neat idea, thanks for posting.

Yes, a dial indicator in the center hole will line up the fixture concentric with the cylinder bore. Only important on stepped heads.

The dowel pins in the head fit snug in the fixture so every head repeats exactly the same. Look at the picture and you can see the four bolts inside at the circles. You can easily reach them from behind the fixture to snug the head to the fixture while in the lathe. The rubber band is used to prevent the bolts from coming out when I faced the fixture true.

Rather than dialing in the face of the fixture each time it's used (not too often in my case), I would probably take a skim cut off the face to assure it's perfect.

http://forums.pelicanparts.com/uploa...1201328853.jpg

I have seen that somewhere before:D Nice setup, do you leave it on the 4 jaw and remove the chuck from the lathe and keep the setup as a unit?

http://66.236.61.177/showthread.php?t=383811

Craig

Unfortunately my chuck bolts on to the taper on the lathe and does not screw on like yours. However, with the hole in the center of the fixture and the fixture machined parallel, you simply loosen the chuck jaws, force the live center in the hole (and fixture against the chuck) and tighten the jaws and you are within a couple thou.

The good news is that I used to grind crankshafts for a living (30 years ago) and you learn to dial things in VERY quickly or you are unemployed so I can have it set up in just a few minutes.