feeds and speeds for routing redwood

[mread]

Hi all-
I am new to this forum and am hoping I can get some advice from those who have been doing this for longer than I have. I am cutting out an arrowhead shape in 1 3/4" redwood. I have been using a two flute, 1/2" bit, with 2" depth of cut. I am taking .3125 in each roughing pass and a final .1875 to free the piece. I am routing with an upcut (counterclockwise) direction. 18000 RPM on the router and 125ipm feed rate. I'm getting pretty nice chips (not dust), but I am getting some major chipping out of the grain on some pieces, especially on the last pass that frees the piece. I understand the nature of redwood very well, and have been working with it for years, but mostly routing by hand. I'm fairly new to CNC routing. I know that the direction you rout is important, but I'm wondering if any of you have any advice as to a type of bit that might cut better, or if I should increase or decrease my RPM or feed rate, or maybe take a full 1/2" pass each time. Or....? Any advice is greatly appreciated!

[ger21]

A downcut will tear out less, but it's hard to keep the chips clear.

I've found that the best way to prevent tear out is to always have wood on both sides of the bit. There's nowhere for the wood to go, so it can't tear out.

I've never routed redwood, so can't really give you any more advice.
But your rpm could probably be much lower, maybe 12,000-15,000.

[mread]

Thanks for your reply. Basically, there is wood on both sides of the cuts. I'll try a slower RPM and try a downcut.

[louieatienza]

I haven't cut solid redwood but have done a couple redwood tops for electric guitars. I climb cut at about 100ipm, with the same doc, but it's only a 1.4" laminate over alder or basswood. Then again, that might be even more likely to chip. Would also try a sprial downcut bit, but I would guess you'd have to definitely lower your ipm...

[Phife]

Easiest thing to try would be a down cut bit, changing the feeds and speeds will probably have little impact on the tendency for the wood to tearout.

Also Climb cutting on the final passes helps too.

If you have a good cam program and are good at using it you should be able to approach the area that tears out in a different manner so it doesnt tear out. Either climb cut those areas, or come at if from a different angle.

Also if you have a 1/2" down cut bit, it shouldnt be too much trouble for it to clear its chips, i have a 3/8" bit and my dust collection keeps all the chips out of the cuts easily. Its when you get into the 1/4" and smaller that chip packing becomes a problem with downcuts.