Extrapolating speed and feed rates

In plumbing designing we had a process much like calculating the feed and speed rates. We “calculated” sizes based on charts that “should” work based on “tests” utilizing ping pong balls not the real world stuff that flows down hill. We called it “extrapolating” or an educated guess or WAG (Wild A__ Guess). I feel that calculating speed and feeds is much like this since I can’t find any actual chart that lists any absolute rates. Speed and feed rates have too many variables which can not be controlled by the author of any rate chart. Because calculating a speed and feed rate seems to only work for that operator along with a YMVM. That said I am think “extrapolating” should be added to the glossary, and included in “calculating speeds and feeds” although I used it for 15 years I never verified if it is a real word. But as in scrabble, “it is a real word because I just used it in a sentence” an argument I never seem to win.

Chip load seems to be the “variable” factor in calculating speed and feed rate. Does this chart provide a reasonable “start” point to calculate using chip load as the predominant factor?? https://www.vortextool.com/images/chipLoadChart.pdf

Still trying to wrap my mind around all this myself.

There’s a bit on this on the wiki: https://shapeoko.com/wiki/index.php/Materials

I believe that we should start with the specifics:

There has been a pair of blog postings by Bob Warfield of the CNC Cookbook:

and he has a bit more at: http://www.cnccookbook.com/CCCNCMillFeedsSpeeds.htm and of course there’s the G-Wizard program which he publishes.

There’s been some useful stuff posted here as well — I’m going to look things over and try to put together a ground up discussion and hopefully we can all achieve a better understanding.


Hugh undertaking ! Chip load per tool diameter varied by number of flutes, a nominal cutting depth stated, and than the calculations required to maintain that chip load at a maximum speed and feed rate. I’d like to see a chip load chart based on Carbide3D’s cutters because that is all I own and every company’s charts are intended for their own products which include a disclosure "Even though there are formulas for calculating feed rates you will find that optimum feed rate will be determined from experience. " Our goal of a speed and feed rate chart seems to be elusive in nature. I support your efforts and best of luck, I wish my valued ignorance as a noobie had any real value to assist you other than asking questions.

Here are the Niagra charts, if someone wants to reference them.
Niagara Cutter.pdf (357.3 KB)

After trying all day to answer the chip load question, I checked out Will’s advise about G-wizard calculator. Looks like that addresses all situations and I’ll purchase a subscription. I tried to build an excel speadsheet that included everything and I learned that everything is too big for excel or maybe too big for me. Thanks Will

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I also want to note and thank Richard’s comment in the other thread that kicked me in the head: “this is how we do it”, put that to a song and maybe us noobies will catch on quicker.

Richard, please see my 2nd post in Waste board t tracks $7.95 , your advise here would be valuable to me. Thank you for providing answers. Jude