I moved this from the builds board.
I thought you chevy guys would find this useful.

Ok guys I thought some of you would like to see some
piston fly cutting in action.

I took a few pic's this afternoon of me making an off the
shelf J.E. part # 170818 23deg piston work with my 18X
Brodix heads.

Here is a pic of the jig I made to hold the piston without
putting a mark on it. It works grate!

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The two aluminum blocks I made in my CNC mill and they square the piston in the vise but the piston is not allowed to touch the back jaw of the vice, it clears it about .050.

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The first thing I done was put some clay on the piston and let the valve mark the clay that next I put a transfer punch in the valve guide and marked the centerline of the valve,
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Here you can see the market clay and where I circled the
punch mark with a Sharpie
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Here is how I set the head on my mill to the correct angle (18 deg)
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Next I line up the spindle on the mill with the punch mark. Notice the felt between the piston and the vice jaw, the felt is .125 thick so when it is squished down
so the jig blocks are held tite the piston is rock solid.

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After all that is done I setup the fly cutter just a little past where the valve marked the clay, about a .075
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This will give you an idea of how much the cutter will be removing.
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Here is a close up of a finished piston.
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Re: Fly cutting my pistons with pic's

awesome writeup! should help many people save soem $$ since they can use off the shelf 23* pistons with 18* heads!

 

Re: Fly cutting my pistons with pic's

Nice! Youare goin to finish those right?

BTW, how many smokes did it take to finish the job?

 

Re: Fly cutting my pistons with pic's

Where's the body grinder?

Just Kidding... Nice Work.

 

Re: Fly cutting my pistons with pic's

I've still got to round the sharp corners and
# then but other than that there done.
The exhaust valve clears by a mile so no work needed
for that.

I cut on a few old TRW's testing the setup but when
the J.E.'s went in the mill the Marlboro consumption
whet way up!

 

Re: Fly cutting my pistons with pic's

Is that a Tormach PCNC in the back ground? How do you like that little mille?


Jess

 

Re: Fly cutting my pistons with pic's

Yes it is! It's does a good job for it's size and price.
There has been some growing pains mainly with learing
cam software.

The Y axes gibb was not fitted correctly, I
had to remove it and hand fit it.

This is the case with most import machines.

 

Re: Fly cutting my pistons with pic's

How thick is the piston at the base of the notch? We have done something kinda similar, except the cutter we made was a valve with a slightly bigger diameter than what we were actually using.

Good job!

 

Re: Fly cutting my pistons with pic's

J.E. leaves a little extra meat in this area plus I didn't go as deep the factory, I should be fine.
When I clayed the motor I had about .020 clearance and this was with no gasket @ 0 lash. I cut the new relief's are .250 deep I should have plenty.