Flycutter tool bits...??

[krems]

I need to get a bit to use on a flycutter for facing off 2024 aluminum. I have an R8 shanked flycutter that takes a 5/16" inch bit. Can you buy these specific for the job or do you need to grind these yourself. I've never used a flycutter before. Any specific brand that you've had good luck with?

What kind of material ....HSS / Carbide...coated or uncoated?? and any suggestions on RPM's to run these at. 2" square aluminum blocks will be used.

Thanks in advance.............Krems

[dp]

They're extremely easy to make:

http://homepage3.nifty.com/amigos/flycutter/flycutter-e.htm

And just about any piece of HSS can be ground to work. I built several different versions in a couple days of experimenting and they all work fine.

They're also pretty cheap to buy at Grizzly or Enco, etc.

[Mcgyver]

krems, grind your own, just pay attention to where you're putting rake and clearance....its NOT the same as a lathe knife tool. as for speed, same as always, speed = 4*cutting speed/dia. cutting speed for for Al & hss = 400 fpm. remember, calculated speeds are a theoretical maximum before the slope of the tool wear curve changes - its perfectly acceptable and easier on everthing to run slow

[oldtiffie]

Fly cutting

I need to get a bit to use on a flycutter for facing off 2024 aluminum. I have an R8 shanked flycutter that takes a 5/16" inch bit. Can you buy these specific for the job or do you need to grind these yourself. I've never used a flycutter before. Any specific brand that you've had good luck with?

What kind of material ....HSS / Carbide...coated or uncoated?? and any suggestions on RPM's to run these at. 2" square aluminum blocks will be used.

Thanks in advance.............Krems

Hi Krems.

dp's advice is right on.

You can weld (braze/silver-solder) any HSS tool bit to a bit of round stock that will fit the collets of your mill - I use 20mm as it is my larger ER-32 collet. If you are careful, you can MIG/TIG or "stick" weld it as well - but be careful!! as HSS is fairly "forgiving" - but there are limits.

Keep it as balanced as you can but it is not too important as a fly-cutter is pretty well inherently "out of balance" in dynamic state. The only 2 really important things are the shape and sharpness of the cutting edge and the cleanliness and fir of the "shank" in your collet/s.

HSS will do it - easily. Plenty of rake and clearances. Speed? Almost as fast as you like - until either the job shows too much heat or more importantly until you can feel the "out-of-balance" of the fly-cutter affecting the quill of your mill - then back the speed off until you cannot "feel it" - then another speed/stop "down". No point in flogging your mill - especially as its new and there is little or no "cost/time pressures" as in a commercial shop.

I tend to keep notes of set-ups, speeds and feeds etc. if I think they will be useful.

Speed rate - again as fast as you like - within limits.

Coolant/lubricant? Kerosene (paraffin?) WD40 or a few others as in a thread that was current up to a couple of days ago. Lane and Evan are right on top of all these items so I suggest to contact them by PM.

I keep my fly-cutters to about 30>40mm cutting width as I can "up" the feed rates - same "cut per tooth" tho'. I do have them up to about 50>130mm as well but rarely use them.

For smaller stuff, I use an old end-mill and grind back all teeth but one and then sharpen that tooth (by hand on a pedestal grinder) and hone or lap is to best edge with a small hand stone or medium and then fine diamond lap ("stick").

I don't worry at all about the "over-lap" at the intersections of cuts. But having a good "tram" is a real benefit.

Aluminium is great stuff to machine and very "forgiving".

I am sure that you will get lots of very good advice on this matter on this thread.

There are a lot of us really "pulling" for you on your mill. Keep us posted - and pics!! lotsa pics??

Best of luck.

[BadDog]

There are several differences when grinding for a fly cutter. First, you generally (not always) start with something roughly like a left hand facing bit, though sometimes more like a rougher. But the end of the tool is the cutting edge, so your rake is different than what you do on most lathe bits which cut from the side. And what would normally be end relief will be on the lower (cutting edge of a left hand bit ) side. Then cutting/clearance relief will be below the cutting edge on the end. HOWEVER, that clearance relief is much bigger than on a lathe bit because the fly cutter is swinging it describing the ID of a circle rather than an OD or face cut. So, you grind relief on the end sorta like you would on the side of a boring bit.

[krems]

Thanks for the pictures and suggestions. I get the idea now. I got some old HSS / Carbide blanks that I think I'll grind a bit out of. Should be a good experiment anyway.

Krems