Shopsmith Forums

What causes the key to fall out of the upper pulley on my ProPlaner?
This has happened the last three times I've used it. I loosen the motor to remove belt tension, pull the pulley off, reposition it, insert the key, replace the set screw, tighten up the motor mounts.
I use a straight edge to verify pulley alignment.
The planer seems to work well but when I go to put it away, the key is on the floor and the pulley has shifted up to 45 degrees on the shaft.
I'm the original owner (since '78) but don't use the planer that much.

Even if the alignment is slightly off the key and setscrew should hold the pulley in place. Just as a sanity check, the pulley should be just barely outboard of the cover and the belt cover should not be scraped by the pulley or belt.

There are three potential causes of the problem:
1) The shaft is worn so that the pulley will not ride evenly on it. I little play is OK.
2) The key is not setting properly or is worn or the keyway on the pulley or shaft is damaged. Get a new key and try it out; make sure you have the right key! Major hardware stores should have what you're looking for. The key should fit tight in the shaft and the pulley should go on over it with moderate to slight force. If not the pulley keyway or the shaft keyway may be worn or damaged.
3) The setscrew may be damaged or the threading may be damaged. Check to see that you have a nice flat bottomed (may not be all the way across) set screw. It should not wiggle in when it's inserted.

Let us know how it goes and what you find.

Adding to what gpmark's advice, check the pulley itself to see if the bore is true. It may be out of round and wobbling on the shaft and causing your problem. I had a problem with one and picked up a new pulley at Tractor Supply.

A few years ago I had problems with the key falling out of the lower (motor) pulley. My solution to this problem was to replace the original steel pulleys with new cast iron pulleys, and new key stock, from Motion Industries. I've had no problems since then.

I just had the key fall out of my Pro Planner today as I was planning. I've been using it for a while. No problems, no vibrations, runs smooth and then the boards stopped moving and the motors bogged down. I quickly turned it off to prevent any more problems. Smelled burning rubber as well. Upper pulley shifted about 45 or more degrees. The key was on the floor.

...sorry I never got back to this post.
I had already replaced both the pulley and the key.
I'll have to check the set screw for flat bottom.
I won't be back to PA and my SS unitl the end of April.

wgander wrote:...sorry I never got back to this post.
I had already replaced both the pulley and the key.
I'll have to check the set screw for flat bottom.
I won't be back to PA and my SS unitl the end of April.

I do not think this is a good place to use a 'flat' bottomed set screw. A cup or serrated cup is indicated for 'permanent'(as opposed to ss quill) attachment.