Tag Archives: trunnion

Shop Tip: A Problem with the Powermatic PM66

A Problem with the Powermatic PM66

I have owned my Powermatic Model 66 for 10+ years. It’s a great saw and I have no plans to change it out for a Powermatic 2000, SawStop, Delta Unisaw, or any other “new kid on the block.” A few winters ago I noticed the blade elevation wheel was near impossible to turn. I was not excited about tackling the problem, but knew it had to be done. I did all the research I could, contacted Eastside Saw in Bellevue Washington, and they put me in touch with a mobile tool repairman. He was expensive, but was willing to work with me and told me that he’d save me money by waiting until I had the cast iron top off the saw. He’d then diagnose and fix the problem, and let me reassemble. This was going to be an all-day job.

After removing all fences, rails, and the table top (which I recommend you get help with), I cleaned the dust out of the cabinet and called him.

He confirmed that the elevation wheel was tough to move, and originally thought it was that the elevation worm was out of alignment. About 30 minutes into the work it was clear that we had other problems. He spent the next half hour explaining how the saw operated, and we concentrated on how the blade elevated and how to take the saw apart even further. After a crash course he left so he wouldn’t miss the last Ferry home to celebrate his granny’s 94th birthday.

And there I was with a pile of iron and a big job ahead of me. We had a theory that the main saw pivot arm shaft was not moving freely in the trunnion. There was only one way to find out if that was the problem, I had to remove everything piece by piece. The PM 66 was stripped to almost nothing, the motor was laying on the floor, the elevation wheel and worm screw on the workbench. I was more than a little freaked out. Through a process of elimination I determined that we were correct – the main saw arm pivot shaft had to come out of the trunnion.

The shaft is held in place with retaining rings and retention nuts, which were easy enough to remove, but the shaft wouldn’t budge. The only way to get it out was to put on leather gloves, and pound it free with a piece of steel and a short handled sledge. I was very nervous to pound that shaft out of there but after 45 minutes and a few dozen cusswords the shaft was free of the trunnion.

I then cleaned and polished the shaft and the holes in the trunnion. I wanted the shaft to fit tight in the trunnion but not too tight, so I would polish a little bit, test fit the shaft, and repeat until things seemed right. After reassembly the wheel is easy to turn and glides with ease when being raised or lowered.

You can see the Saw Pivot Arm Shaft below, it’s #45 in the center of the schematic.

PM66 Trunnion

Read the next post to see what problems I caused when reassembling the saw.