Unisaw belt issue

[Bob Rufener]

I bought a used model 36-816 Unisaw last year and I really like the saw. The saw had been sitting unused for several years when I purchased it. I noticed some excessive vibration when I got the saw home but I assumed it was due to a "memory" problem with the belts having set for so long in one position. The vibration got better with use and is not a major issue. Tonight, I decided it might be time to check the belt tension and was surprised to find that the tension on the three belts varied a great deal. I am wondering if it might be time to change the belts as there doesn't appear to be any individual belt adjustment. If so, is it recommended to buy Delta belts that are recommended for the saw or to go with the "chain link" style belts that some people feel are superior. Any help is appreciated.

[Paul Stroik]

Bob, I would first check the belts out for wear and damage. If they are still good I would tighten'em up (if that's possible) and see if that resolves the problem. If the problem still persists (or you can't tighten up) then it would be time for the link belts. Personally, I would not bother with replacing the v-belt with another v-belt. Since I started using the links anytime a belt is the problem I replace with a link belt.

[David Christopher]

Bob, I got my belts at the auto parts store, their the same as delta sells. I think their A-26 IIRC.but just take one with you so you can get three of the same

[Chip Lindley]

Hi Bob! If your set of belts is still in ok condition, try loosening the bolt on the motor mount that adjusts the belt tension and let the weight of the motor hang on the belts 24 hours. the shorter belts will stretch to match the longer belts. After a day, tighten the bolt as is. You should have a *matching* set now!

If replacement is needed, the Fenner PowerTwist link-style belts will be the last set you will probably ever need. Unisaw belts are 21" *long* (not dia.!!....MyBad!) so you will need 6 feet of belting. Grizzly offers a more economical link-type belt, but not sure how they hold up compared to Fenner.

[CPeter James]

Rather than the Fenner Power Twist (The correct name for the "link" belts), try the AX series of belts. The are a premium quality belt that is cogged and has machined sides and they are made to very close tolerances so that any of a given size will work as a matched set. I used the Fenner Power Twist for many years an almost all my machines, but have switched to the AX series of "V" belts as they are smoother and much quieter. Also, the power twist MAY and I say may cause premature wear on die cast pulleys as they are made form a very hard composite.

The AX series of belts are available from McMaster Carr and others and only cost a dollar or two more that a standard "V" belt from the hardware store.

CPeter

[Pete Bradley]

It's likely time for new belts. I haven't found a Unisaw to be particular as long as they're good quality. A matched set of solids from McMaster should be fine, as should AX. What you can get from a hardware store depends a lot on the hardware store. They may be selling good quality machine belts or lumpy cheapo belts made somewhere far away. McMaster sells Gates, which is a top quality brand.

Link belts on a Uni are pointless in my book, but you won't do any harm with them. They do ride a little taller which may result in the belt being able to touch the table at the max height setting.

Pete

[M Toupin]

Link belts on a Uni are pointless in my book, but you won't do any harm with them.

I agree, a good set of premium AX belts is a better choice.

Link belts can do some harm. They are much harder than normal belts and can wear the sheaves much quicker than normal, especially on cheap cast aluminum or pot metal sheaves. Probably not a problem in a hobby shop, but if you run your machines for long periods it can be a problem.

The other issue with link belts is the reduced power transmission. If you run your machines at or close to full load link belts will slip long before a quality belt. Again, maybe not a problem in a hobby shop depending on your uses.

Mike

[Dwayne Watt]

the belts on your saw may have been unmatched hardware store variety if not originals. Buy a set of matched belts as mentioned by others and make sure the motor is parallel with the arbor when you tighten the belts during installation (ie, the belts are equal tension when installed). Don't try to buy 3 belts of the "same size" and think you have matched belts. The same result as present will likely occur. Matched belts will have equal tension and share the power transmission equally. The saw will run smooth after new belts are installed. Good luck

[CPeter James]

Gates AX series belts meet the matched set specifications. They are the OEM for the last of the PM66s.

CPeter

[Pete Bradley]

Link belts can do some harm. They are much harder than normal belts ...
That's a good point. Uni sheaves are pretty soft and with wear they get knife edges. I believe I could cut paper with the ones on my 1940 Uni.

Pete

[Richard M. Wolfe]

Just replaced the belts on a 1940. If you go with regular belts from an auto parts store check to see that they are the same size.....believe it or not. Same brand, same # and there was close to a quarter inch difference in the first ones tried. Obviously quality control is lax on something like that since a single is used for nearly all applications and tensioning takes care of length.

[Frederick Rowe]

I bought my Unisaw brand new and the vibration was terrible. The belts had taken a set so firm that I could rotate the blade by hand 120 degrees and the belts would pull it back into it's native position.

Swapped out with Fenner Power Twist V-Belts and huge immediate improvement. Passed the nickel test.

As for the material wearing away the sheaves of the pulley, no evidence of that in three years of operation - but that doesn't mean it won't happen over time. However, Pete reports wear on a 1940 Unisaw which most likely spent most of it's life with traditional belts. There'll probably be wear regardless of what you use.

Many SMC users of Fenner belts report greatly diminished vibration. Not cheap, but you'll never buy the wrong size (length, that is).

[Pete Bradley]

[quote=Frederick Rowe;1079460]I bought my Unisaw brand new and the vibration was terrible. The belts had taken a set so firm that I could rotate the blade by hand 120 degrees and the belts would pull it back into it's native position.

Swapped out with Fenner Power Twist V-Belts and huge immediate improvement. ...

Many SMC users of Fenner belts report greatly diminished vibration...

Not specific to this post, but if your belts are shot any good quality belt will make a "huge immediate improvement" and "greatly diminished vibration". 90% of the Fenner testimonials l see on sites like this are comparing apples to rotten oranges. I suspect there's be no discernable difference if comparing new to new on a Uni.

Pete

[Chip Lindley]

Concerning Fenner Power Twist belts, it is 99.999% doubtful that a 3-belt saw like the Unisaw will *lose any power* regardless of belts used. Reduced vibration is the BIG DRAW of Fenner by woodworkers. They work wonders on many machines that were virtually unusable. Vibration issue aside, they simply offer convenience of making up a belt of specific length to fit the application.

To those who still have the original 1940 zinc/aluminum arbor pulley on a Unisaw, soft metal is not guaranteed to wear evenly. It is one thing to keep a saw *original* and quite another to keep it *usable*! I would venture to say that a new steel pulley would solve problems that no brand of belt can??

[Frederick Rowe]

Not specific to this post, but if your belts are shot any good quality belt will make a "huge immediate improvement" and "greatly diminished vibration". 90% of the Fenner testimonials l see on sites like this are comparing apples to rotten oranges. I suspect there's be no discernable difference if comparing new to new on a Uni.Noted that this was not specific to my post, but in my case my Unisaw was new and the belts were new - albeit mildly out of round. Certainly, comparing poor quality, worn, or in my case defective belts against a set of good quality non-defective belts is a faulty comparison.

To refine my point, besides that the Fenner belts work great and make a good alternative to traditional belts, is that new belts don't necessarily equal quality or that they don't have a set. Either of which would create vibration or noise under load. New saw owners who experience these symptoms should not assume that simply because their belts are new that they are not the cause of noise/vibration. The out of round condition of my Unisaw's factory belts were visually mild, but firm. I could see how one might deduce that the weight of the motor would easily remove the mild set and eliminate it as a possible cause of the noise/vibration.

The Gates brand belts which were factory installed on my saw took a set in the short time they were installed on my Unisaw. I carefully inspected them and found no visible signs of wear or other defect other than their oval shape. I carefully marked the apex of the set and rotated the three belts 120 degrees from each other to equalize the oval shape, and while this reduced the vibration and noise; it remained unacceptably high.

I'm sure had I replaced the factory belts with new Gates belts, not out of round, the saw would run fine - as Pete points out. I do believe that, given the design difference between traditional belts and the link belt, that the link belts are less susceptible to taking a set.

So, if you suspect your belt driven tool should be running more smoothly, look at the belts. Don't assume that just because they aren't horribly out of round, or that they don't have loose threads everywhere - that they aren't the problem. As for what you replace them with - there are choices, just don't try to solve it on the cheap.

[Pete Bradley]

To those who still have the original 1940 zinc/aluminum arbor pulley on a Unisaw, soft metal is not guaranteed to wear evenly. It is one thing to keep a saw *original* and quite another to keep it *usable*! I would venture to say that a new steel pulley would solve problems that no brand of belt can??

Happily even with almost 70 years of use my Uni passes the dime test with solid belts and the original pulleys. That's the beauty of the Uni - all that mass and a solid design soak up potential vibration that would make a modern contractors saw dance.

When I rebuilt it, I considered swapping the arbor pulley, but it's matched to its old school 1725 RPM motor pulley, and not buying it saves me money that can go into other machines (like my "new" 1952 HD shaper).:D

Pete

[Mike De Luca]

Rather than the Fenner Power Twist (The correct name for the "link" belts), try the AX series of belts. The are a premium quality belt that is cogged and has machined sides and they are made to very close tolerances so that any of a given size will work as a matched set. I used the Fenner Power Twist for many years an almost all my machines, but have switched to the AX series of "V" belts as they are smoother and much quieter. Also, the power twist MAY and I say may cause premature wear on die cast pulleys as they are made form a very hard composite.

The AX series of belts are available from McMaster Carr and others and only cost a dollar or two more that a standard "V" belt from the hardware store.

CPeter

Which size AX for the Unisaw...?

I think it is time to replace these 25 year old belts... helluva vibration after having set idle for over a year (long distance move). I let it run for awhile; it didn't improve...

Thanks...

[ken carroll]

Gates AX series belts meet the matched set specifications. They are the OEM for the last of the PM66s.

CPeter

Peter,
I think 3vx belts were used on the last of the PM-66s

However, I replaced the three wimpy 4L belts on mine with TWO AX belts.
As you mentioned (and as you recommended) the AX belts are far superior. BTW, my pm-66 is a 5hp unit and the belts don't slip under heavy load!

[Josiah Bartlett]

Noted that this was not specific to my post, but in my case my Unisaw was new and the belts were new - albeit mildly out of round. Certainly, comparing poor quality, worn, or in my case defective belts against a set of good quality non-defective belts is a faulty comparison.

To refine my point, besides that the Fenner belts work great and make a good alternative to traditional belts, is that new belts don't necessarily equal quality or that they don't have a set. Either of which would create vibration or noise under load. New saw owners who experience these symptoms should not assume that simply because their belts are new that they are not the cause of noise/vibration. The out of round condition of my Unisaw's factory belts were visually mild, but firm. I could see how one might deduce that the weight of the motor would easily remove the mild set and eliminate it as a possible cause of the noise/vibration.

The Gates brand belts which were factory installed on my saw took a set in the short time they were installed on my Unisaw. I carefully inspected them and found no visible signs of wear or other defect other than their oval shape. I carefully marked the apex of the set and rotated the three belts 120 degrees from each other to equalize the oval shape, and while this reduced the vibration and noise; it remained unacceptably high.

I'm sure had I replaced the factory belts with new Gates belts, not out of round, the saw would run fine - as Pete points out. I do believe that, given the design difference between traditional belts and the link belt, that the link belts are less susceptible to taking a set.

So, if you suspect your belt driven tool should be running more smoothly, look at the belts. Don't assume that just because they aren't horribly out of round, or that they don't have loose threads everywhere - that they aren't the problem. As for what you replace them with - there are choices, just don't try to solve it on the cheap.

I had the same problem with a brand new set of belts from Delta on my 70's Unisaw- I installed them, it ran smooth. I went away for two weeks and it shook like an overloaded Huey. The belts took a set.

The other thing to watch out for is that your pulleys aren't loose on the shaft and that your bearings are ok.

[Jeff Duncan]

My inclination would be to snug up your belts just a bit and see how that goes. Assuming your not running your saw hours every day you can probably get by for quite a while with the old belts unless there is still too much vibration.
As for what kind of belts, my personal opinion is it doesn't make a darned bit of difference. I had link belts on my 54' Uni for a good ten years in almost daily use and didn't notice any premature wear. I only used 2 belts and never had any of the slippage or stretching problems some complain about.
My other 70's era Uni has v-belts on it that may very well be original? It also runs fine and as old as the belts are they don't give me any problems.
This is one of those topics that generates a lot of hard opinions, but is really not all that big a deal. Either choice will get the job done. Oh and one other thing....don't tighten the belts too much! It's not like a car alternator where it has to be tight to run. You just want them snug enough to not slip. If you tighten them too much you'll just end up wearing the bearings out quicker.
good luck,
JeffD

[Scott Schwake]

I recently ordered AX27 replacement belts from McMaster-Carr for my Unisaw. Two of the three were matched, the third was quite a bit longer than the matched ones, and was way too loose when the other two were tensioned properly. I'm not sure how to get a matched set of three belts unless you go pick them out yourself.

[Dean Ousterhout]

What does it mean to "take a set"?

[David Christopher]

What does it mean to "take a set"?


it means it gets stiff where it goes around the pulleys...then when you turn it on it viberates

[Mike Cruz]

I put the powertwists on my Uni and they work great. You also know that they are all the same length this way. If you decide not to go with the linkbelsts, I wouldn't bother buying them from Delta...way too expensive. Just get the right ones somewhere else that offers "sets" of them. These are belts that were cut sequentially.

[Ron Bontz]

Not to hijack this thread . But what is the average life expectancy of the uni belts. Mine are now 10 years old. Don't have any excessive vibration but now you have me wondering.:)