How Many Flutes

[joe]

Some how, I've ended up with a half dozen or so router bit with three flutes and I haven't been able to find a guide recommendation as to what they are used for.

Is this type of bit for ferrious cutting?

[gerald_d]

3 flutes are not the most common for metal cutting, but not unheard of either. Even numbers of flutes are popular, but I don't see a problem with 3 flutes for metal or wood. Be more concerned about the material from which they are made - solid carbide is good, HSS is short life.

[Brady Watson]

Joe,
These may be what they call spot mills...is it hollow in the center? Some of them have coolant channels in them.

In theory, you can use any type of end mill...try testing with moderate speeds and calculate chipload just like you would any other bit.

-Brady

[joe]

Thanks Brady & Gerald,

These are 1/2" solid carbide spiral compression bits. Four flutes insted of three.

My best success for plexiglass and aluminum are single flute, spirals by Belin. It would appear that a single flute allows for removal of waste cutting, reducing aluminum gaulding or plex melting. So it would seem that the more flutes would encourage heat. Am of completely off base?

You guys probably know, I'm cutting mainly HDU, Extira, Cedar and Trupan most of the time.

Joe

[Brady Watson]

Joe,
You are completely correct. For a given RPM, 4 flute tools rub the part 2X more than 2 flute tools. Theoretically, if you ran the part with a 2 flute at 16,000 RPM, you would have the same chipload as if you ran the 4-flute at 8,000. Remember that chipload is calculated by the # of flutes...The 4-flute tool would generate smaller chips, more heat and less tool life. Typically, unless you are milling foam, you should never really use a 4-flute tool on a CNC router...UNLESS you really start pushing the tool at move speeds that are at the upper limit of what a Shopbot can move.

-Brady