Cutting Cedar Without Splintering on a CNC Router

Pros recommend climb-cutting for the first pass, and add other tips. December 6, 2006

I'm cutting the perimeter of canoe and kayak paddles made from western cedar and having split out problems. The curved cut starts across grain, then turns to parallel, and then curves to cross grain and out. I'm having splitting problems with the parallel to the grain segment of the cut. I've been using 1/2" straight cutters and have a 1-1/4" cut depth in 3 passes. What type of cutter would work better? Spiral, up or down cuts? The depth of cut appears to limit me to 1/2" diameter. My normal feed rate is about 80 ipm.

Forum Responses
(CNC Forum)
From contributor A:
Have you tried to do a back cut (or reverse cut), leaving 1/32"? Then come back and do a cleanup cut in normal direction?

From the original questioner:
I've just been doing a 3 or 4 pass cut through the stock. The splintering takes place on the first or second pass.

From contributor B:
Contributor A is right... you need to do a first pass climb cut. Also, if you have adequate hold down pressure, there is no reason you can't cut full depth in one pass. If the straight cut bits don't have enough cutting length, go to a down cut spiral. Also, you don't need carbide. We run our mouldings with HSS 3/8" down cut spiral bits and they last as long as carbide does in that situation. The reason for this is that holding irregularly shaped parts calls for slower feed rates (as you have apparently discovered) while retaining the more typical 18k rpm rates. This causes higher heat buildup in the bit, and HSS stands up to that better than carbide. Hence, we get about 40 mouldings out of either HSS or carbide.

From contributor D:
I would use a 2 flute down spiral and climb cut every pass. Cedar is a bear to cut without splinters, and climb cutting is the best fix - that and slowing feed rate to around 600 ipm.

From contributor S:
Solid wood should use 4 flute spiral, or diamond bit.

From the original questioner:
I talked to Onsrud yesterday and they recommended a carbide tipped opposite shear #13-54, so I'm going to start there and increase the feed rate to about 150ipm. Thanks for the help.