How to sharpen a fly cuter bit

[Deny1950]

Hi just wondering how to sharpen a fly cuter ,and at what rpm to run it on a Bridgeport? about 2 1/2 circle

 

[DMS]

I have had good results with this method, but there are lots of ways to do it. I'm going to assume a HSS cutter here. Grind it like you would a left hand turning bit; give it a pretty generous tip radius (1/8-1/4"). Couple strokes with a diamond hand lap, arkansas stone, or india stone. Remember you don't want to take deep cuts, less than 10 thou. The formula for calculating RPM is

RPM = 4*SFM/TOOL_DIAMETER

SFM is material dependent and cutter dependent. For Aluminum with HSS, figure 500-600 SFM (you can always go slower). If your cutter is a 2.5" diam, that gives you

4*400/2.5=640 RPM

For mild steel, SFM is 125-215, so

4*125/2.5=200 RPM.

 

[Bill C.]

Hi just wondering how to sharpen a fly cuter ,and at what rpm to run it on a Bridgeport? about 2 1/2 circle

When using your fly cutter if the surface doesn't show a complete circle then the head needs to re-indicated.
When I used one I would have to double check the machine I was using.