greitz wroteI was practicing scroll sawing straight lines using some oak pallet wood scraps. The piece of wood was ca. 4" wide, 1/2" thick, with ca. 1/8 " cup. I had the two edges flat on the table, and was sawing with the grain. Everything was working fine until the last 1/4" of cut, when the saw blade just grabbed the wood and started slamming it up and down on the table ...
So, my questions:
1. Is it a big no-no to use a scroll saw on cupped wood? I should have jointed it flat first, but I figured it wasn't necessary for "just practicing".
2. Would it have been better if I had the wood's curved middle on the table, so that the two pieces "fell away" from the blade at the end of the cut?
3. Would it have helped if I had slowed the blade speed near the end of the cut?
4. I was using a #5 blade. Would a different blade be better for ripping 1/2" oak?
Thanks for the advice!
Gary
Gary - This is a safety issue!!!!!
Your experience is pretty easy to explain - As the cupped wood reached the end of the rip, it could no longer hold it's cup and the high area fell enough to pinch the blade. From there the wood was pinching the sides of the blade and the teeth could no longer cut.
To answer your questions the best I can -
1) It is always a good practice for safety to only saw flat wood.
2) Yes! But this can still be risky - Probably not as much as using a table saw or band saw.
3) I don't think the blade type mattered much here.
That said, I have ripped cupped wood at times. Only when I needed the piece that was not cut off. (in order to joint it) In these limited cases, the high side of the cup was always on the table. This kind of operation is risky because you are not sure where the cutoff will go when released. It is not a good practice, and you have to be aware of the risks prior to cutting.
As said in an earlier post, I have successfully planed a thicker (5/4) piece of wood by very gently removing the top of the cup. In this case I put the concave side (only two edges) down and took VERY light cuts so not to let the planer press the board flat before cutting. Even this way such an operation is not recommended and may not work.
Finally - All cupped wood should be flattened prior to any sawing, regardless of the type of saw.