Originally Posted by Fastskiguy
Am I doing something wrong here? I'm making boxes, I'm leaving some overhang then coming back with a flush cut bit. Bearing on the first bit crapped out, bearing on the second bit flew off and gouged my edge.
Now...at the risk of asking a stupid question....am I doing it wrong? I have an old router that spins super fast, I'm not putting a ton of pressure on the bearing, and I'm letting the big cut. Still, two busted bits and the second one bought the farm after maybe 8' of cutting MDF.
Or are these just crappy bits? (They cost 15-20$ each if that matters)
Finally...how the heck do I fix that gouged edge?
Hard to tell, if these are 1/4" shank bits or not. That said, a 1/2" diameter shank is 8 times stiffer in deflection, and less prone to vibration or chatter, which can elevate the chances of breaking a bit.
Possibly no threadlocker on the screw to retain the bearing, vibration loosened it, and it flew off. If you have Loctite or equivalent threadlocker, you can remove the screw and apply some before using a bit for insurance it will not fly off.
For the bearing that went for a dump.... that is a junk bearing. In no way should it fail after a few revolutions other than a lack of lubricant.
I would lighten the load on the router some by carefully trimming the excess down closer to the box before attempting another pass.
A gouged edge can be repaired with 2 component polyester resin autobody filler. Mix a small amount of filler with the hardener, and apply to the gouge, then sand flat after curing. ( usually 20 minutes or so ) Start with P80 grit on a block, and finish in P180 before priming.
Depending on your skill in application and sanding, you may need a second coat of body filler before the repair is seamless. A long block with sandpaper wrapped around it will enable you to get that flat without creating a depression.