View Full Version : Speeds and feeds question
10-09-2001, 12:32 PM
Can anyone tell me how to figure out speeds and feeds. Are there any books out there that explain in layman's terms how to figure them out easily ??? Thanks to all who respond to my question
10-09-2001, 12:57 PM
I've never bothered with the formulas, with experience you just get a feel for where to run the machines. Then again, there are times where I should go to the trouble.
Anyhow, I'm pretty sure one of Guy Lautard's bedside readers has the formulas. If you don't already have them, get all three, they are my absolute favorite machining references.
10-09-2001, 09:39 PM
As Paul says we just go by feel and experience however, using end mills has always been critical for me so I tried to find a chart and got noware. So I developed my own chart which is somewhat limited but does serve the purpose. I will e-mail it to you Timmer. It's on excel so you can see my formula.
If anyone else wants it, let me know.
10-10-2001, 12:14 AM
Komet of America, Inc.
2050 Mitchell Blvd.
Schaumburg, IL 60193-4544
Has a Speed & Feed Calculator that they give away at tool shows - Metric and Inch both!
It covers tool tooth count from 1 to 30.
hope this helps
10-10-2001, 08:40 AM
Thanks Guys, for your quick responses to my question. Jim,I look forward to recieving your email.
10-10-2001, 10:05 AM
I'll pop in here and give you an old rule of thumb, actually 2.
SFPM X 4 divided by diameter = RPM
SFPM is surface speed per minute in feet this is the speed your cutter is cutting at, whether it is a milling cutter or a lathe bit contacting the revolving work, or a shaper bit, or planer, or a grinding wheel.
Feed rates are termed in inches per minute.
One rule I go by with High Speed Steel is 50 sfpm to start with, and then work up, especially with mystery material. Easy to figure also, 200rpm for 1.00 dia. so 2"=100rpm 1/2=400rpm 1/8=1600rpm. Staring at this low surface speed saves drill bits, I have seen people burn up big bits, this formula is easy to figure in your head and avoids problems.
Feed rates, now thats another one, think about the thickness of the chip and the power of the machine. How good a surface finish do you need. I see some people using some feed rates that are so low it is rediculous.
Lathe work on med. sized machines I use from .003 to .010 feed rates, just depends. On milling cutters put the math to it and determine the chip loading per tooth.
Good luck, watch your chips, they tell the story.