I used a 1/4 inch plywood template to outline a shape on 1 1/4" thick wood. I then cut out the 1 1/4" thick shape on the badsaw. I attached the plywood template to the 1 1/4" thick shape. THere was a <1/16th inch overlap. I tried to use a flush trim trim bit to clean up the 1 1/4’ shape. I was using a 1/2 diameter compression spiral flush trimbit. The trim bit ripped a chunk out of my shape, very violently.
Was this possibly because the rotational speed o the router bit was too great. We used to have a controller on the router table that allowed adjustment to the optimal speed for larger diameter bits. Or was there some other cause that the flush trim bit broke the wood piece?
Any insights /advice welcomed!
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You can still control the speed of the router, via a dial on the router itself. It is rather awkward and has to be done by feel, but it is adjustable. Once you find the dial, you set it by going to one extreme or the other, then counting steps; the detents are fairly clear by feel. The speed steps are listed on a label I printed and put on the dust collector door used to access the router. (That onboard speed control means an external speed control will not function correctly and could damage the router.)
However, for a 1/2” diameter bit, the max speed is appropriate. You could maybe step down one step for a hard wood, but no more. You will actually generally get much worse results at slower speeds.
What happened to cause the problem? Taking too large a cut could, but if I understand your setup correctly, you would’ve only been cutting 1/16”, which should be fine. Another cause would be making a climb cut, moving the piece in the same direction as the cutting edge of the bit. That mistake is a very common cause of violent jumps on the router table. A sharp feature can be an issue with trim bits. Finally, there might just have been an imperfection in the wood, like a knot or an existing crack.
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Agree with Ethan without a photo is hard to disect what happened. I also say an existing stress fracture on the material. A telltale sign looking at the tear-out is shiny parallel fibers initially then vertical fuzzy fibers of the pre-existing micro gap. If you have shiny parallel fibers throughout the edge of the torn edge is technique or going against the grain on very brittle lumber (purple heart, poplar, some times, some pine species, alder, etc.). Another monkey you can throw into the circus is your feed speed and how you held the stock against the bearing. Too fast, the bit doesnt have time to cut or evac the waste and tears out the fibers. If you were repositioning your hands and came off full contact with the bearing the ammount of torque will take it from you, you would have heard a hard “tock” ensued by the fibers tearing or the stock being thrown as a projectile (either against the fence, in your direction, or airborne until it meets resistance). When something wrong happens on the router due to the velocity the bit is spinning or torque, everything is violent. Im glad nobody got hurt. One thing not mentioned about the router is that it has a “soft start.” It will start slow and increase to the right speed as you put a load on the motor.
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Thank you so much Ehan and Jose. I really apprecaite your insights!
Ethan.