If you need clean edges on the top surface of your wood then use a down spiral wood router bit. This sends the chips down into the cutting channel and hence leaves a clean top edge with no breakout. An upcut spiral bit will through the chips up so feed rates can often go up but the top edge will feather. Upcut spirals require firm work holding as they try to lift the part (just like an endmill). Down cut spirals can cause compaction of the chips at the bottom of the cut which reduces performance. Get round this by creating an ofset of your part and then stepping in for a finish cut, you should get a very clean cut that way. The geometry of end mills and spiral wood router bits are different, but I do use carbide end mills occasionally for cutting wood without too much problem. Straight fluted wood bits are ok when new but a spiral bit is far superior as the cutting edge is constantly in contact with the part, and the shear cutting action eliminates tearing out and bruising on end grain.  |