Weird Fly Cutters

rwm

Robert
H-M Lifetime Diamond Member
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Mar 25, 2013
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I picked up these fly cutters at an auction:

30472698002_ca88d7d5fa_h.jpg

I am not familiar with this design. These have large heavy cylinders on smaller shanks. The large one i s about 3 x 6" with a lot of heft to it. Are these common? What is the purpose of this design?
Robert
 
They look homemade to me.
Maybe somebody made them to rough bore cylinders or deep holes.
I'll often use a fly cutter to bore larger holes when the dimension isn't critical. Just bump the tool bit out a little, and plunge away.
Obviously you need a big enough pilot hole before plunging a fly cutter.

Or they could have been made to finish cut the bottom of a deep channel, rather than making multiple passes with a long skinny (expensive) endmill.

I'd be careful with putting too much side pressure on these. Seems like that's a whole lot of leverage to be putting on that small diameter, short shank.
 
It is possible to use a dial indicator to set and adjust the cutting tool for more accurate boring work. Use light cuts and sharp tools with those cutters and they will be fine. I have some similar ones, but shorter.
 
Consider using very slow spindle speeds.
That is a lot of mass!

Daryl
MN
 
Hmm. yes, probably for boring. I agree about the leverage on the small shank. Should be longer/larger
R
 
It also looks like, depending on your mill, you could replace the whole spindle with that. I know on my G0704 some people talk about removing the spindle and putting something else in it. Then again, the others who have answered probably know better than I.
 
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