I challenge you to fix my Unisaw problem

[Jameel Abraham]

Everytime I start up my 2002 Delta Unisaw, I get this loud metal-on-metal thunk that drives me crazy. It even causes the blade to jump to the side momentarily, albeit minutely.

I took a peek at the motor itself while starting the saw and I'm pretty sure I've tracked it down to the height adjustment screw and it's engagement with the rack that's mounted to the motor mount. There's just enough play in the gear teeth that when the motor is started the torque bangs the rack teeth against the screw teeth and the thunk happens. I've tried turning the height adjustment wheel so I end on both raising and lowering, and tightening down the nut at the center of the handle. No luck with that.

I further tested my theory by removing the cabinet cover and holding the motor rigidly (effectively removing the slop in the worm gear) by either pushing on the motor or pulling on the motor while I started the saw. This eliminated the thunk. I further tested this by completely raisng the blade, which also removes any slop in the worm gear since the arbor bracket seats tightly to the worm gear when the blade is completely raised. This also eliminated the thunk.

The manual does not mention any adjustments to this mechanism. And I can't see any way to eliminate it. I've been living with this for about 4 years now and am getting really sick of it.

I hope somebody here can shed some light.

[Ray Dockrey]

There are all kinds of info on this on the net. I turned this up doing a Google search. I suggest doing some searching. Also a common issue is belt set. Here is one I turned up :

Q. My Unisaw makes a "clunk" when it starts. What could cause this?

A. On the elevating shaft, inside the saw toward the back, there is a round stop collar with a locking set screw. First crank the blade down, and then up just a few turns, enough to tension the elevating shaft. Now check to make sure that the stop collar is seated all the way back against the rear trunnion assembly. If it is not, loosen the set screw and tap the collar toward the back of the saw, and then re-tighten. If this collar is allowed to move forward, the whole elevating shaft will move back and forth, allowing the blade arbor to jump when the saw starts. This causes the "clunk" on start up. Another source of this noise could be a loose arbor pulley. There are two set screws in the grooves of the arbor pulley. They can be accessed from underneath the saw if you rotate the arbor until they are uncovered by the drive belts. Make sure you unplug the machine before attempting this!

[Bruce Page]

Jameel, most often it is just loose belts but as Ray points out, it can be other things.
Thank God that my Uni has never had a clunk problem. (Knocking on wood…)