View Full Version : BIG fly-cutter

02-02-2008, 04:06 PM
After reading the recent posts on fly cutters I made my own large one to try and deck a cylinder head for a John Deere.
Its just made out of some 1" and 6" scrap mild steel I had with a 1/2" HSS toolbit so I could flycut the desired 8" for my job. It cuts really well so far in 6061 Al but it is yet to be tried in cast iron which is what I really need it for. I just went for the most rigid design I could think of with the material I had around.



-Robert Comer

Peter S
02-02-2008, 06:25 PM
Could I suggest getting a scrap cylinder head from any other engine and trying your fly cutter first? You don't want to do trial runs for finish and cutter life on the real thing in my opinion.

When I was a young and helpful apprentice I was talked into milling a Dodge flathead 6 head - thats when I learnt how reasonable, cheap, troublefree and downright sensible it is to take your head to someone who does it for a living. For a start (with a flathead anyway), the head doesn't necessarily stay flat while you are milling. And holding it down/setting it up is another curse. Fortunately my job was just to remove the material bulk (it was for a 'hot' engine), and it was finished elsewhere. Oh yeah, boring out the cam bearings in a Honda motorcycle head and hard chroming and grinding the camshaft journals - another one of those never again jobs done to help a friend.

02-02-2008, 07:20 PM
That's a big honker all right. Do try it on something else first as suggested. Ought work fine though. Take 'er easy on depth of cut.

I love working with cast iron except for the mess. It machines really nicely. You do have to clean up carefully afterward though--will grind up your machine.



j king
02-02-2008, 07:33 PM
make sure your head is trammed in perfectly or you will cut a dished or scalloped surface.Wont work like that.

02-02-2008, 08:43 PM
I could be wrong, but it looks to me like you have the front face of the cutter ahead of the central axis of that flycutter. With that diameter it probably isn't going to matter much, but with a smaller radius it would represent a negative rake as seen from the end of the cutter. If you were to be cutting inside a cylinder for example, that would have an impact.

Other than that, I certainly like the weight of it- should help to control the cutter and make the surface smoother. Have you figured out what rpm you'll be turning it at?

02-02-2008, 09:46 PM
how many screws are holding the toolbit?
If it is just one may i suggest adding at least one more.

Michael Moore
02-02-2008, 09:47 PM

That's a 6" rule on it. The extra flywheel mass keeps it moving smoothly when it reenters the cut.


02-03-2008, 01:10 AM
Thanks for the input, I plan to try it out on an old scrap head lying around and Michael that cutter makes mine look like a toy. Testing will have to wait till next week due to the game tomarrow but we'll see how it goes.
-Robert Comer

02-03-2008, 01:12 AM
The extra flywheel mass keeps it moving smoothly when it reenters the cut.

Dat sum bia*tch ain't stoppin' for nobody!



02-03-2008, 02:34 PM
Robert, are you related to Marty?

02-03-2008, 02:39 PM
He's my father.

02-03-2008, 06:58 PM
I work for one of his municipal customers.
He does EXCELLENT work from what I've seen.
Top notch.