Fly Cutting Issues

C

Charley Davidson

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Tried fly cutting some aluminum for a pair of reversible soft jaws I'm making to hold round objects in multiple sizes. The sides turned out "OK" but noticed some wierd finish issues but they were square & parallel. When I attacked the face it wasn't so nice. It started out ok but when I got to the end and the tool holder was past the material it started digging in. The cutter it's self was hot rolled steel ground to the proper angles (I think)

Hope it's not my spindle bearings

DSC00461.JPG DSC00463.JPG
 
Charlie,
Looks like you are in pretty good tram, from what can be seen in the pic I'd be pointing the finger at a dull tool, improper relief or both.
What rpm you running?

Ken
 
The tool did get dull quick, as for speed I played a bit with that on my VFD I was in the slowest speed range but adjusted speed & feed to try & get best finish. I'm gonna stop in at where I'm laid off from and borrow a fly cutter & a face mill along with the drill that bores the stepped hole for allan bolts for jaw making. Plus they have a print for hole location.
 
Charlie,
You can and should be running cutters in aluminum at higher RPM.
The low rpm can also dull cutters quickly causing then to rub instead of cut, especially true when associated with a small depth of cut.
Fly cutters usually leave a very nice finish but I still prefer a face mill.
What's happening I suspect is the cutter being dull is springing, then returning when unloaded on the exit causing the marks.


Ken
 
Charley, I've found that a radius on the tip of my fly cutters improves the finish. The best finish that I've ever got on steel was with a large radius on the cutter. Something to experiment with. Aluminum may be totally different. Let us know what you come up with?
Phil
 
Philco said:
Charley, I've found that a radius on the tip of my fly cutters improves the finish. The best finish that I've ever got on steel was with a large radius on the cutter. Something to experiment with. Aluminum may be totally different. Let us know what you come up with?
Phil
Click to expand...

Charley,
I would agree. Here is a picture of my fly cutter and the bit that is currently in it.
IMAG0154.jpg

I tend to use carbide whenever possible. It stays shaper longer, I can run it faster etc.
The last time I use this on aluminum I was running 1750 on the spindle and feeding fast!!
Chips were flying all over the place. The end result was a mirrored finish.
Another thing to consider is the type of aluminum your using. I know that the 5000 series
alloys are really gummy. A friend of mine refers to them as trying to face bubble gum. To get
good finishes you need high speed and steep relief angles.

Good luck

Ben

IMAG0154.jpg
 
Got a piece of HSS & ground it but had bad results still, had to square up a block on the lathe for another project cause it was so out of square after fly cutting it.
 
From your pic, I'd say you have way too much radius on your tip. Especially with carbide, that'll cause the material to gall up. Tram that head first, and use a small radius on your tip. :thinking:
 
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