table saw makes a clunk when starting up

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Forum topic by mzimmers posted 08-16-2014 06:34 PM 4124 views 0 times favorited 9 replies Add to Favorites Watch
View mzimmers's profile


218 posts in 5198 days

08-16-2014 06:34 PM

Hi, all -

I bought a pre-owned Unisaw last weekend (detailed in another thread). Finally got around to starting it up in its new home. It makes a fairly loud “clunk” (or maybe a “bang”) when I hit the power switch. Only does it once per power-up, then the saw runs nice and quiet.

It didn’t do this when I was looking at it, so I figure maybe something happened on the ride home. Any ideas what I might look for? The previous owner said he didn’t use it much, and I believe him, so it seems unlikely that anything is worn out. Would a lose bolt somewhere inside the cabinet cause this?

Thanks for any suggestions…I may be worrying needlessly, but I figured I should ask…

-- M. Zimmers

9 replies so far

View Fred Hargis's profile

Fred Hargis

7292 posts in 3776 days

#1 posted 08-16-2014 07:12 PM

I have a Unisaw, though I haven’t had that problem (it is common). Anyway, I came across this somewhere and saved it….so it’s something you might want to check. No guarantees, just a place to start.

“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!”

-- Our village hasn't lost it's idiot, he was elected to congress.

View mzimmers's profile


218 posts in 5198 days

#2 posted 08-17-2014 12:21 AM

Hey, Fred -

Thanks for the reply. The collar was fine, and in all honesty, I couldn’t figure out how to get to the pulleys to check them, but while I was reading the manual on that subject, I noticed further down on the page that both the height and angle knobs should be locked before you start the saw. I didn’t know that…one of many, many things I don’t know.

Anyway, when they’re nice and tight, that noise is gone. I removed the fence rails and readjusted the wings…they’re not perfect, but they’re better than they were and good enough for me. Double checked the table for square against the blade…absolutely perfect. put the rails back on, tweaked the fence to get it parallel, leveled it and cleaned it up a bit. Waxed the table. Tried getting the OEM miter gauge to a good 90°, gave up and put in my Incra 1000 HD that I usually use on my router table. I do believe I’m ready to go. Only thing left to do is install my Forrest blade and wait for the splitter parts to come from Delta.

I’ve been obsessing over getting a real cabinet saw ever since I moved and got a 3-car garage. Feels good to have this taken care of. Now, to start using it…anyone need anything cut?

-- M. Zimmers

View TheFridge's profile


10863 posts in 2769 days

#3 posted 08-17-2014 01:00 AM

That incra is awesome. If there is any backlash, especially in the elevation, it can move a tad. Had the same problem.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View KE4NYV's profile


138 posts in 2744 days

#4 posted 08-17-2014 01:02 AM

My old direct drive Craftsman did this, but it did this from day one.

-- Jason R.

View bruc101's profile


1541 posts in 4824 days

#5 posted 08-17-2014 02:34 AM

One of my daughters has a 3 hp Griz in her home shop that will do that. If she just pokes the start button it does it. If she pushes the button in like any normal person should, her remark not mine, the saw doesn’t do it.

Her other remark was…if someone poked you in the stomach with a finger you wouldn’t have time to react to the poke and it would probably hurt…if someone took their finger and slowly pushed it against your stomach it wouldn’t be such a shock as getting poked with the finger…the same goes for my saw on start up.

I’ve got five of them and they’re all mouthy like that in their offices or working in our commercial shop…I always agree with them and life goes on peacefully for me in the

-- Bruce Free Plans & Calculators

View Rick  Dennington's profile

Rick Dennington

7176 posts in 4477 days

#6 posted 08-17-2014 05:13 AM

I have a 2010 Unisaw X5, and it makes a slight bumping sound when I first hit the button….It’s done it from day one, not a problem, and I fiugured it’s because it’s a 5 horse…...This thing is a beast, and will take anything you throw at it…..I don’t think you have anything to worry about…I’ve also read where they all do it, sometimes…....

-- " There's a better way.....find it"...... Thomas Edison.

View MrRon's profile


6205 posts in 4526 days

#7 posted 08-17-2014 04:02 PM

My 3 HP Jet saw does the same. It has from the day I got it, 25 years ago. I never gave it any thought and the saw cuts perfectly. I wouldn’t worry about it.

View poopiekat's profile


4991 posts in 5017 days

#8 posted 08-17-2014 04:56 PM

That’s a good thing to keep in mind, to be aware of any rise and fall of the arbor height, when making dado cuts. The depth could change with any off-on cycling.

-- Einstein: "The intuitive mind is a sacred gift, and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift." I'm Poopiekat!!

View SCOTSMAN's profile


5849 posts in 4868 days

#9 posted 08-17-2014 07:34 PM

Sounds like the saw might be a bit loose on it’s mountings by the sound of it I would switch it off and check underneath by grasping the saw unit and trying to make it move in any direction with your ordinary hand grip.I.E up ,down .side to side.etc if there is even a bit of drift or sloppiness in the unit I would tighten it up a bit.
Please though, don’t swing on a large piece of extended pipe. Just tighten normally LOL Alistair P s I hope this is your problem it is the kind of thing that happens when the motor is loose it tends to jump forwrd on switch on due to the heavy forces involved when starting.

-- excuse my typing as I have a form of parkinsons disease

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