Milling Feeds Speeds Depth and all that rot Newbie

[AndrewEvans]

So I am going to be attempting our shops first foray into really using the milling capabilities of our new (old but new to us) Bridgeport mill

It is outfitted with a Proto Trak M3 (dear lord the boot is slow on that thing)

I have an Aluminum Rod I need to put a 3/8" slot into one end of (2"ish long), it's 1 7/16" in diameter and I'll Be milling it perpendicular to the mill head.

Now according to all the lovely internet information I come up with the following:

Material - Aluminum 6061-T6 rod 1 7/16" dia
bit - 3/8" dia, 3/8 dia shank, cutting length 2 1/2" 2 flute
RPM of bit - 3200 (this may stretch the mill a bit but I think I can at least manage 3000 rpm)
Feedrate - 12.8 ipm
Depth of cut .1875 inches

Knowing full well that there will be SOME amount of tweaking this that and the other thing, rpm up feedrate down etc etc, is this actually a good beginning?

I just get very cautious when I start something completely foreign to the shops know-how & don't want to shatter bits/waste material/break my machine

Thanks in advance

~Andrew

[gus]

18 years into cnc and I have still yet to calculate a feed.

use your ears

most mid size end mills [the 1/4 to 3/4 sizish] you can start at 2000 rpm and 10 ipm and your chicken switch will keep it sane. Find a spot that sounds right


then 4000 and 20

8000 and 40

12000 and 60

most manual machinists go way too slow

[Smoked]

I would start the rpm's at 2133. That's what I came up with. What type of endmill will you be using? Basic? Coated? For just a basic I would start at 2133. If your using a coating I could see 3200 easily. Most endmills manf. should say what they can be ran at.

[AndrewEvans]

rpm and speed are easy, its realy the volume (depth) that i'm most worried about, any thoughts?

[Smoked]

The depth is okay. I would maybe decrease the feedrate some. I was machining some aluminum yesterday with a 1/4 endmill running 3200rpm at .250 depth with around a feedrate of 6.4 and it turned out great.

[AndrewEvans]

hooray, I didnt break a bit or machine on the test runs, now to see about the actual peices....