# Phase 1 Recap: Feeds and Speeds

A project log for Rocking the Horses

Learn how to operate your new CNC router by making a rocking horse, then learn a lot more by setting up for mass production.

Josh 05/19/2016 at 16:130 Comments

(edited to bring more accurate feed/speed guidance)

It seems that there are quite a few different ways to calculate feeds and speeds, but I'll give you my take.

Feeds - How fast you cut (how fast tool travels when cutting), in units/minute.

Speeds - Rate at which a rotating tool spins

Chip Load - the size of the "bite" that the tool takes on every cut.

I tried to do some research to find out some other people's ideal settings for cutting wood, but I never found any and I just decided to give it a go.

## My Experience

My tool starting out is a 1/4" diameter, 2-flute straight cutter. This means it has 2 cutting surfaces and no spiral. I didn't choose it for any reason other than I had it in a box that I kept when I sold the lathe and it was still packed new in wax. I started out just setting my spindle to the max speed (25,000 rpm) and cutting slowly (20 in/min). This worked just fine, but I didn't get wood chips, I got wood dust. As I cut parts, I slowly increased the speed.

What I found was that somewhere around 70 in/min the dust started to transition into fine chips of wood. Chips would be an over statement, as they were more like delicate shavings. This makes sense, because the calculations really aren't that hard. Chip size = Feed/(speed*flutes). So my chip size is 70/(25,000*2) = 0.0014". This is about 1/3 the thickness of a sheet of printer paper.

I eventually pushed the machine up to 100 inch/min and it had no problems cutting through at a depth of 1/4". Redoing the chip calculation, I should be getting 100/(25,000*2) = 0.002" thick chips. These were nice chips that the vacuum easily removed and there was little dust formed in the process. I decided that I will target a 0.002" chip thickness for this tool moving forward.