Feed Rate and RPM for Bamboo on the CNC

Struggling to eliminate chatter when cutting bamboo, a CNC operator gets advice on tooling and settings, as well as on specifying tool paths. April 17, 2009

I can't get the chatter down using downshear spirals, compressions, anything. I can't tell if it's the RPM's or just the chip isn't getting out. Does anyone have experience with bamboo sheetstock?

Forum Responses
(CNC Forum)
From contributor G:
What is your material thickness and part size? What type of machine and HP do you have?

From the original questioner:
I'm cutting screens out of 1/4" and 3/4" bamboo, with some pocketing. I'm running a Biesse Rover with a 10HP spindle.

From contributor G:
Can you provide us with the diameter and cut length of the tool?

From the original questioner:
I'm either using a 6.23mm diameter two-flute down with a 24mm cut length or a 12.61mm two-flute down with a 31mm cut length. I also have a 12.55mm two-flute compression.

From contributor G:
Based on Courmatt's tools, the following would apply:
The 6.23 OD feed speed should be 600IPM @ 18K
The 12.61 OD feed speed should be @ 900IPM @ 18K.

If you reduce your feed speeds, reduce your RPMs. If you still are getting some chatter (it seems the tools have serviced) try a new tool and change your collet.

From contributor M:
Something else to keep in mind is that bamboo is not wood. Though it shares many characteristics of wood, it is still actually a member of the grass family.

From contributor J:
In what way should he compensate for that?

From contributor M:
Unfortunately I don't have that answer, as I have never had to work with bamboo. What prompted my first response was remembering an article I read in Wood & Wood Products somewhere around two years ago. The article talked about some of the differences, and specifically stated that it is not actually wood. If I remember correctly it did have some basic info on tooling as well as feeds and speeds.

From contributor I:
I've had quite a bit of experience cutting bamboo. Feed rates are less of a concern than your approach to actually cutting the material. It has a tendency to split if you enter and exit the cut at the corner, especially in the solid (vs multi/cross layered) variety. My best results were always when starting the cut in the middle of a straight stretch. I would favor a 1/2 inch compression bit for 3/4 inch material and a 1/4 inch down spiral bit for the 1/4 inch material. I recall that the 3 flute 1/4 inch down spiral from Vortex worked quite well for 1/4 inch material. If you are using similar feed rates and still getting chatter, I'd try a new collet or bit as contributor G suggested, though I think the feed rates he listed are a bit fast. I run bamboo at 400 ipm (at 18k) for 1/4 inch cutter in 1/4 inch material, and 600 ipm (at 18k) for 1/2 inch cutter in 3/4 inch material. Other than splitting, I haven't found bamboo to be a demanding material to work with and it is somewhat similar to Baltic birch.