A while back I bought a second hand Jet JPT-260 planner thicknesser from Aximinster. I didn’t get much chance to use the machine for a while after I’d bought it but recently I’ve been putting it to good use squaring up some oak stock for a log store cabinet for the living room. Unfortunately four boards into the project it decided to breakdown, I thought at first it was my fault for feeding it a bit of stock it couldn’t cope with but I now believe it was more likely just waiting to fail.
I was just starting thicknessing step and measured one end of the first piece to go through at 24mm. I set the table to 23.5mm and started feeding the piece in. I was greeted by the P/T’s usual happy wood munching sounds right up to the point where the wood stopped moving. I immediately spotted the problem, hit the power button and lowered the table to recover my now slightly mangled piece of wood. I’m sure you’ve already spotted my trainee level mistake – the wood got thicker towards the bottom end and had jammed against the kick back fingers.
I set the machine up again to a sensible cutting depth and started working again. Everything was going fine for about another half an hour when all of a sudden the machine started making a terrible banging noise. One of my fears with the planner thicknesser is that a blade will come lose and I thought at first that had happened. The fact that I was still alive however made me reconsider that idea and I immediately switched the machine off and unplug it.
With some trepidation I lowered the thicknessing table and lifted back the chip extraction hood. Slowly spinning the cutter block by hand showed all three blades still in their proper place. I breathed a sigh of relief then promptly punched myself in the face as the machine let out another bang. I realize that sounds crazy but I was bending over and touching the cutter block at the time and I pulled my hand away very quickly.
So, if it wasn’t the cutter block letting go it must be something internal wrong. I whipped the back off and had a look. At first glance there wasn’t anything obviously wrong so I tried turning the feed roller pulley by hand. It turned a little bit but then stopped. It was at that point I found what I thought was the problem. There is a large white plastic sprocket that makes up part of the drive train for the feed rollers. About a dozen teeth on that sprocket had sheared off and the banging was the smaller driving cog jumping on the broken teeth.
What I assumed had happened was when the wood jammed the feed rollers kept going and sufficient force was placed on the plastic sprocket to deform the teeth. Then, a little while later, they just gave up. Since it was late anyway I gave up on the machine to the day.