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Jet cabinet saw re-hab #17: bummin about humming

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Blog entry by Mainiac Matt posted 03-29-2013 06:06 PM 2811 reads 0 times favorited 5 comments Add to Favorites Watch
« Part 16: Time to think about the extension table Part 17 of Jet cabinet saw re-hab series Part 18: Wings mounted... ready for takeoff »

So the saw is making a weird vibration/humming noise, but when I take off the belts and run just the motor it’s amazingly smooth and quiet… even the starting surge is barely perceptible.

I also noticed that one of the bearings on the arbor is running warm. So I yanked the arbor again and attempted to loosen up the bearing. But since the bearing is press fit, both into the arbor bracket casting and onto the arbor shaft, this isn’t as easy as simply loosening a nut.

After loosening the retaining nut, I gave the arbor a couple taps with a mallet, in an effort to relieve some pressure on the bearing. It seemed to spin just a tad more freely, but who knows…. may have done nothing at all.

Upon reassembly, I realize that the noise is actually more likely coming from the link belts….. (which are supposed to reduce vibration, not cause it). I had been uncertain about which way to mount the green link belts, as they don’t have an arrow on them, like the red ones are reported to have…. but I had found this graphic on the web… and decided to follow it.

But now I realize that this makes the drive pulley tend to push the tabs over backwards…. and though it looks like it would produce a better grip this way, I started wondering if it will run more quietly the other way. And come to think of it, when I put this same HF link belt on my jointer years ago, I now recall that I put it on one way, and then the other, and simply went with the way that was more quite. So I check the jointer…. and yup, it’s the other way.

So I reversed the belts and put it all back together.

Now to get my arbor bracket off, I have to push the roll pin that secures the worm gear on the crank shaft, so I can pivot the bracket further to the rear and clear the ways. When re-installing the roll pin, the little monster went in 3/4 of the way, b4 I realize that the hole is not drilled plum, that I’m going in the out, and the exit hole in the worm gear doesn’t line up…. AND…. that roll pin is not coming back out with vise grips :^(

Dremmel to the rescue…. I cut the last 1/8” of the pin flush and called it good, figuring that it was bound up in there so tight that the worm gear would never slip.

Bad news…. taking this apart again is going to be a major PITA

Good news…. between reversing the belts and playing with the arbor bearing, the vibration is gone.

-- Pine is fine, but Oak's no joke!



5 comments so far

View Mainiac Matt 's profile

Mainiac Matt

3998 posts in 985 days


#1 posted 03-29-2013 06:13 PM

this pic shows where the offending roll pin is located

the belts are shown mounted in the “quiet” direction… which is how I first had them on, b4 I consulted the inter web :^(

-- Pine is fine, but Oak's no joke!

View Mainiac Matt 's profile

Mainiac Matt

3998 posts in 985 days


#2 posted 03-29-2013 06:30 PM

I’m pretty embarrassed about bunging up the roll pin.

When I put this all back together the first time, I chocked the motor out with some scrap wood until the holes in the worm gear and the shaft were lined up perfectly, and checked the alignment with a nail b4 tapping the roll pin back into place.

I think I was tired and in a hurry this second time around….

I won’t be able to pull the arbor bracket again, without pulling the entire yoke and way assembly.

-- Pine is fine, but Oak's no joke!

View NormG's profile

NormG

4181 posts in 1660 days


#3 posted 03-29-2013 10:38 PM

I am not sure, but I believe your issue maybe the result of not having match belts. Links even though they have the same number in each are not matched in length and thus will not have the same pressure applied on the pulleys. One maybe slipping as the other maybe tighter

-- Norman

View DIYaholic's profile (online now)

DIYaholic

13565 posts in 1331 days


#4 posted 03-30-2013 02:27 AM

I hope it all works out.
You’ve got a lot of work into this & I wanna see saw dust!!! ;^)
But don’t rush on my account!!!

-- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procratination a bad thing?

View doyoulikegumwood's profile

doyoulikegumwood

384 posts in 2649 days


#5 posted 03-30-2013 02:33 AM

i agree with norm i rebuilt my unisaw and had the same issue with the twist belts went out and bought a set of matched belt and it ran smooth as a brand new Mercedes.

-- I buy tools so i can make more money,so ican buy more tools so I can work more, to make more money, so I can buy more tool, so I can work more

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