I cut out a cribbage board this past weekend. Happy with everything except there is a slight “anomaly” on the finishing pass where the tabs are. I cant for the life of me figure out why that would have happened.
Also still getting tool marks on the edge/side grain. Wood is maple. I’ve had constinet issues with this cutting maple. Is it a material thing? Should I slow down or speed up, or is this just part of machining maple?
Maple tends to get tear out because the grain runs in a lot of directions on some pieces. Your second picture looks like classic tear out due to the grain changing direction. Maple is a very nice wood to work with but because of its structures is always subject to tear out. You can see the grain takes an up sweep where the tear out is. Changing grain will tear out because the wood fibers become unsupported. It is like petting a cat. If you pet from head to tail the fur lays down and the cat likes it. If you pet from the tail to the head the fur goes everywhere because it is unsupported and the cat does not like it. the Maple is very much like petting the cat. There are many hidden features inside all wood but maple is notorious for tear out.
Take this advice with a grain of salt: I have never used a CNC machine (although I do have a 5 Pro on order), and I have yet to learn what these machines are capable of. If you could set up a final pass around the board that takes a very shallow cut, and does a climb cut (cutter moves right to left, or clockwise around your cribbage board, for a clockwise-rotating bit), that might help. Experiment with scrap.
Someone feel free to jump in if I am entirely off the mark here.
Bret, good suggestion. I expect the first issue is because on the final pass the cutter stops, lifts over the tab, and then cuts across the tab with no resistance because that material is already gone.
The finish above the tab is indicative of the finish you would get with the small finish pass you suggested.
Either offset the vector to create a rough path, or program with a slightly oversized tool, then use the nominal sized tool on the machine. i.e. if using a 1/4" tool, program with a 0.260 tool. This will leave 0.005" for finishing.
To get the climb cut finish path, offset the vector to the outside by the cutter diameter. Then contour that vector on the inside. It will conventional cut the offset vector, resulting in a climb cut on the part.
Looking at the file, you have already followed a rough / finish strategy, but left 0.0625" for finishing. With maple I think that’s way too much. Try 0.005 - 0.010"
Picture #1, if that was a TAB, it looks like an artifact due to the bit retracting to leave the TAB. As the machine is cutting the contour it lifts at every TAB. may be it’s due to that.
