Cylinder Head Machining 1

[mburgess]

I have been searching for tooling setup to skim cylinder heads on a mill. I have been told that you turn the head of the mill 1/2 deg to prevent backcut on the surface & use a large radius cutter with only a single cutting tool. But this would leave the decking surface slightly curved. Is this the correct method?
Does anyone have any pointers
The application is on small aluminium in line 4cyl motorcycle heads.
Thanks,
Michael

 

[patdaly]

Tilting the head will cause the back cut, not prevent it. Get it as square to the world as possible. They sell, or you can make really nice tramming tools to improve your accuracy.

As for the tool, a single cutter would work exactly as a multiple cutting head, it just requires a far slower feed.

Make sure, be very sure, of what the OEM is asking for in terms of surface finish, and follow it exactly.

 

[Majik]

Sounds like CBN Surfacer. Large round bit. If your refering to the fact that the cutting head on a CBN surfacer only contacts on one side so it should be lower in the middle than on each side. I agree and it probably is but not a noticeable ammount and nothing that would effect performance. Square it upto the rig and go. My berco makes no mention of tilting the head 1/2 a degree.

 

[mburgess]

So a standard three tool surface cutter set up square, with tool & bed speed adjusted for required surface finnish is the go?
Thanks,
MB

 

[Warpspeed]

Yes. If the head and cutter are dead square it will work fine, if it is very slightly tilted (and it usually is) just reverse the direction of feed.

Half a degree tilt is too much, you only need tool clearance. And I agree that the resulting curvature is so small as to be insignificant. Finish is much more important.

 

[larrycoyle]

There are a couple of companies that make fixtures and cutters specifically for this purpose.

Larry

Larry Coyle
Cylinder Head Engineering, LLC

http://www.cylinderheadengineering.com

 

[BCjohnny]

My Zanrosso head and block surfacing machine has a small amount of tilt (will try to dig out the figure; it's a measurement not an angle) but having an 11" head this is unmeasurable on the milled item. Theoretically the surface will be "low" in the middle of the head.

I would be more worried about how accurate your mill will cut over the length of the head. "Knee" type milling machines (Bridgeport etc) tend to produce a "crowned" cut as they age. The weight of the table causes this.

Also with milling alum, if surface finish is critical, blow the chips away as you cut, otherwise as the head moves along the cutter picks up chips on the back cut and rubs them across the milled portion, giving ghosting.

A nice tip I saw on another site suggested using an old flywheel as the cutter body. And carbide does work very well, but cbn can work better.

John.

 

[mburgess]

Thanks for the responses. Obviously you need to skim the whole surface in a single pass, is there any specification as to how wide the dia of the cutter to the width of the head should be?
Thanks,
MB

 

[malbeare]

I set up my bridgport type mill by putting a dial gage on the cutting tool about 6 inches from the spindle center and giving the head about 5 thou forward tilt compared to the back cut , just enough for clearence. I made a single tooth cutter out of 2 inch heavy wall RHS and filled it with lead to stop vibration. Works well


A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare