How do I set a fly cutter to a specific radius?

[prasad]

Guys,

One of my planned projects (my new design Crayford Focuser) involves a rectangular aluminum 6061 block to mate with the OD of a 3" tube. The aluminum block is 2"x1" and its length matches the 2" length of the tube. I want the curved surface to match the tube surface as good as possible. I have a set of fly cutters that will fit in the MT3 collet of my Grizzly mini-mill but I am not sure how to set the cutter to get me the precise diameter that I want. Any helpful advice is highly appreciated. BTW I have not tried fly cutters on the mini-mill yet.

Regards
Prasad
Wynnewood PA

 

[fastback]

Since you have a mill you can center the spindle in the edge of your vice using an edge finder. You then determine the diameter you need and set the distance from the edge of the vice for the radius. For example if your looking for a 1.5 inch diameter you would be looking for a .750 radius. So back the spindle the 3/4 inch from the vice and set the cutter to the holder touching the vice, you now have a fly cutter set up to cut the proper diameter.


Hope you can understand this explanation.


Paul

 

[Bill Gruby]

The known diameter you have on a Fly-Cutter is the diameter of the body. Lets say it is 2 inches. That gives you 1 inch of the radius you are seeking. You are looking for a 3 inch diameter circle so you want a 1 1/2 inch radius. Stick the cutter out 1/2 inch and you are there. I do it that way all the time. It works fine for me.

"Billy G"