View Full Version : Fly cutting

01-18-2003, 12:18 PM
I have done some fly cutting of aluminum stock with sometimes great results and other times mediocre results. Are there specific approaches to obtaining a good finish? Would the sfm calculation of a fly cutting tool be the same as if one would be if using a standard end mill? Yu guys out there are great and I have had some very helpfull ansewers in the past. Thanks in advance.
Stephen K.

01-18-2003, 12:25 PM
When flycutting aluminum I use a carbide lathe tool in my flycutter. Take a fine diamond stone or hone and break the sharp point on the tool. A very small radius on the nose will produce remarkable results. If the tool is sharp it will what I call fur up leaving a real rough and furry finish. With a slight radius you will get a mirror finish. In my mill I run about 10 ipm and about 1500 rpm. Hope this helps you out.


Big Dipper
01-18-2003, 02:33 PM
Figure the rpm like any cutter. With light cuts that you normally take with a flytool, average SFM for AL with HSS 600+, carbide...2000 at least. What this adds up to is some really fast speeds. Be careful what your machine will handle, the cutter probably isn't balanced, you don't want it walking across the floor, or worse! Also consider the flytool Ø, easy to get in a bad situation.
Alum. alloys vary also. Some cut real nice, some are more like bubblegum! Welding also affect the finish you can get. If everything is going good you should be able to get, what I like to call a "rainbow" finish :-)

01-19-2003, 01:03 PM
lets see if I can get say this in simple terms, maybe you already have this figured out, first,it is good to know the material being worked, second, the distance traveled by the cutting portion of the carbide tool should be calculated X rpm = sfm sometimes aluminum cutting fluid helps. you know this already I am sure but I didnt see it in previous posts so I just thought I would mention it.



01-21-2003, 06:54 PM
Thanks guys for your suggestions. I'll give them a try as soon as I'm able to get back into my shop. Darn, you never know how much your disabled from some minor toe surgery. Thing are getting better now.

01-21-2003, 11:17 PM
my question was the same as Samuel's. Some aluminum alloys machine pretty well and others are rather gummy. From the scrap pile you never know.

01-21-2003, 11:54 PM
The 7xxx series are high in Silicon and very abrasive - usually the best finish is had with PCD inserts at very high speed. These are the strongest alloys - the reason they are used in aerospace.

6xxx Alloys are nice to cut, and the alloys get worse as you drop down the alloy list to pure aluminum 1xxx series.

01-22-2003, 03:11 PM
Are there any major differences in grinding a HSS cutter for flycutting and as a lathe tool? i.e. Cutting angle, rake, etc.?

Mike L
01-22-2003, 03:44 PM
I've found the Rotary Tech flycutter to give the best surface finish I've ever gotten with any flycutter.

See a disscussion on the Chaski board:


Or, see the website:


They currently have a 2" 1 insert cutter on sale for $29.95 and a 2" 3 insert cutter on sale for $59.95. See the webpage:


The cutters are unique to this product. 12 indexes per side and two sides equals 24 cutting surfaces/insert. I bought one for work a couple of years ago, and liked it so much I bought another one for home.

Mike L
Amateur machinist, self-taught. I had a poor teacher, but I was a good student.

Chris Fazio
01-22-2003, 04:29 PM
I just purchased the 3 insert cutter from rotarytech and it machines 4140 to almost a mirror finish. At the $59.95 price it's like buying 3 inserts and getting the holder free. Can't wait to try it on other metals.


Mike L
01-22-2003, 06:58 PM
One other thing - what are you using for lubricant?

Two things I've found that improve surface finishes with aluminum are:

Tap Magic for Aluminum


It's thing only thing that I've found WD-40 really good at (besides displacing water).

Mike L
Amateur machinist, self-taught. I had a poor teacher, but I was a good student.