Face mill speeds and feeds

[aallen]

I usually machine aluminum and teflon. I need to face mill a small plate of steel. I have a 2.5", 6 flute, face mill with carbide inserts. I have all kinds of numbers, but wanted input from machinists who deal with steel all the time.

Thanks,

A

[Heinz Putz]

300 SFM is a really safe number to figure RPM for Mild Steel.
Here is a simplified method to get to RPM.
SFM times a constant of 4, divided by the tool diameter.
So that comes to about 450 RPM.
The really safe feedrate is about .005 per tooth, so its .03 per rev or 450 RPM. Take the 450 times .03 to get the feed in inches per minute that the mill uses.
F13.5 is a real safe number.
Now for cycle improvement:
Listen to the cut, look at the finish and make small improvements by editing speed and feed.
Do not get carrid away.
All this is in great detail on my CNC DVD called "Prep for CNC" on my website.
Good luck: Heinz, www.doccnc.com

[superchev76]

I run my 3 in 5 flute at 900 rpm and 20 ipm @.050 a pass, but the ipm will depend on the bite you take, and the inserts you use

[aallen]

I appreciate the input. I'll give it a shot.

[Strat]

RPM X Chip load X number of flutes = IPM

[MMMMM]

SPEEDS and FEEDS - basics;

Think of SFM (Surface Feet / Minute) as a constant rate like, MPH (Miles per Hour) or KPH.
The RPM of the wheel is based on the diameter of the tire required to spin to maintain this rate. The smaller the tire, the faster it must spin. The larger the tire, the slower it needs to rotate.

To convert; Take the (distance/time) rate and divide it by the distance traveled in one revolution.
One revolution of a tire of diameter X = pi*diam. (circumference formula)
Then, take the distance needed to travel in the time being measured and divide it by the circumference. This gives you Revolutions per TIME.

Most cutters are specified in Feet per Minute. However, they are usually measured in Inches.
To get an RPM (revs per MINUTE) either divide the diameter by 12 to get FEET or divide pi by 12. Either way gets the same answer.
(3.1416/12 = .2618) ... this is the magic number to memorize

To get your RPM; SFM/(diam*.2618)


FEED is a little simpler.
Feedrates are usually defined as Feed per Tooth for any cutter.

Feed per Tooth times the amount of Teeth on your cutter gives you Feed Per Rev.
FPT*teeth=FPR

Once you have Feed per Revolution, simply multiply this by your RPM to get your feedrate.

FPR*RPM=Feed/Minute


Drills are usually considered as "single effective" cutting tools. Meaning, that the feed rates reflect that this tool only has ONE tooth.

[MMMMM]

BTW - this wasn't intended to "dummy down" anyone here, it was something I had written before to add to a good thread for others to read if they searched Speeds and Feeds.