Maximum tool stick out on a fly cutter

Seems like you could make a disc type fly cutter with minimal tool stick out. It would probably run smooth enough at your slowest speed. If it is a bit out of balance just add weights until it smooths out. That is a lot of swing for that little mill! I'd go for multiple passes. The setup time is probably less than all the fooling around with giant fly cutters.
 
tomw said:
This reply may not be necessary, but:

If the flycutter radius was, say, 4", at an rpm of 800, then the tip of the tool is moving approximately 20 mph. If things go **** up, you have a small but surprising problem that will be OK if you are wearing safety glasses. At an 8" radius, the tip would be moving at 38 mph. If the piece that is flying around has enough mass (say 100 grams), your safety glasses are probably in trouble.

Assuming my math is correct....
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A tool at 8" diameter at 800 RPMs would be cutting at 1600+ FPM, this is well beyond what a high speed steel tool will do in ideal cutting conditions.
If the conditions are not ideal all bets are off, I would not exceed 200 FPM for such work in aluminum with HSS tooling.

However the OP may get away with dusting it off at that speed, say a .001" cut for a finish pass, you will not know until you try it. The worst that can happen is that you have to make another, stock aluminum shapes are cheap and easily sourced.

I will run aluminum parts in a lathe at 1200 SFM with carbide tooling in ideal cutting conditions, a large flycutter with HSS tooling is Not Ideal.
 
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"250 rpm (lowest my mill would go)"
250*Pi*12"/12=785.39816339744830961566084581988'/min. For a 12" dia. cut.
 
Larry42 said:
"250 rpm (lowest my mill would go)"
250*Pi*12"/12=785.39816339744830961566084581988'/min. For a 12" dia. cut.
Click to expand...
Way to fast for such a tool, In order to make this work I would use less then 40 RPMs, as I mentioned you may be able to dust it off and have a satisfactory surface with a very shallow finish pass, this will work in some aluminum alloys but not all.

As many would ask, What Is The Proper Way To Do This job, the short answer is rough mill to around .005" per side big and grind it to finished size.
The long answer is try a whacking great flycutter and see if it works, if not you have only lost a cheap piece of stock material, if it is still within the range of thickness required THEN grind it.
We did a job 2 years ago, 1 1/2" aluminum round bar cut 1 1/2"+long, all the blanks were cut in a bandsaw using a 1/16" wide blade.
12,000 parts, do the math and figure out how much stock went into the saw (-:

The purchasing agent came out into the shop and said that we were short 60' of stock and I told her that I knew exactly where it was, funny stuff
 
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Thanks a bunch gentlemen! I think I'm gonna roll with Downunder Bob here. After watching everything Chris from Clickspring posted on YouTube a have a lot of faith in Australian machinists:)) in all seriousness I happen to have some 1 1/2 square steel stock which would do OK I believe with 7/8 welded shank and 3/8 boring bar with carbide inserts. People were asking why I don't want to do two passes : my table is 6x26, the stock will be 12" x 30" x 1 3/4" aluminum that will be bolted to the ways so repositioning it accurately would be straight PITA !! I'm gonna use some strategic shimming and check to make sure that I'm not twisting the slab by bolting it. The table extension will allow me to pretend it's a big boy mill and hold down large stock. Once I get to it I'll either post a beautifully machined piece, or my shop mates will post a picture of my disfigured body as a lesson for everyone!
 
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