I use a Comec Auto I 1000 High Speed Milling Machine with CBN insert for Cast Iron OR a PCD Insert for Aluminum Heads

This machine is double adjustable, I can adjust the spindle speed and the table travel speed to achieve the surface finish that is required.

http://www.joebakerequipsales.com/AutoI1000.htm


The first thing to do is check the valve cover surface for any burrs and remove them.

Next is to mount the head in the machine and check the level of the head in both directions.



Then the other way, this head was not out that bad from the last time it was milled.



I did a “getting to know you” pass of .002 to see how square the head was. This was done on a faster setting.
Notice the upper and left side of the head is dull, this is a low spot. The head was not index properly and did not maintain a proper “square” to the valve cover surface.



I made another cut of .003, I sped up the cutter, and slowed the table speed.

This is the end result.



Another different view.



Now with a proper surface, and the head re-squared, The customer will have no issues with a MLS gasket sealing, and also having a closer to equal combustion chamber size.

 

So if my machine shop says they use a broach machine that would be this correct?

 

It depends on the surface finish.

Most rotoary broaches were designed to cut cast iron, and composite gaskets.
Alum. Heads for the most part do not cut well on one.

Also most broaches have several carbide cutters, 10-14 of them, How hard do you think it is to get the same width cutting edge on the blade, along with having them all set at the same height?

This head, 4.0l Jeep was cut on a Van Norman Rotoary Broach


See how much more corse the finish is? A composite will seal, But I doubt a MLS would,