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Saw Start Up Has A Large Jolt

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Forum topic by rkruz posted 02-17-2020 05:43 PM 483 views 0 times favorited 16 replies Add to Favorites Watch
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rkruz

49 posts in 55 days


02-17-2020 05:43 PM

Topic tags/keywords: tablesaw

I just got a used Unisaw. The newer versions with cranks on the front. 2012 mfr I think.
5hp single phase and prior owner put a big Powertech magnetic switch on it (just saying in case its the reason for the jolt)
When I start it up with a blade installed it makes a loud jolting sound for a fraction of second then a nice smooth whir.
I dont know what this saw should sound like but the jolt doesn’t sound right to me. Here is a video of it if it works….
https://photos.app.goo.gl/b7wePa5ohk1hNWmq5

Without a blade installed, at start up no jolting sound and just nice smooth whir.
I adjusted the belts per manual and when watching them with a blade in at start up, they expand out coincident with the jolt.
Without a blade the belts just hug the pullys, no expansion or flyout.
Do you think its just the belts need replacing or do I did I get a bummer used saw?
If its the belts would the link belts be better to use then the stock Delta part?

ANy experience here?
Appreciate any help
Thanks!


16 replies so far

View MrUnix's profile

MrUnix

7809 posts in 2870 days


#1 posted 02-17-2020 06:37 PM

Sounds pretty normal to me.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Fred Hargis's profile

Fred Hargis

6041 posts in 3164 days


#2 posted 02-17-2020 06:45 PM

Yeah, I didn’t hear anything to worry about either.

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

View tvrgeek's profile

tvrgeek

547 posts in 2320 days


#3 posted 02-17-2020 07:35 PM

Is the belt tension correct? 5HP is a lot pf power to put to a blade that has a lot of inertia. A soft start is expensive.
Personally, I have never been let down with Gates belts for anything. Their are higher tech poly belts with steel wires, kevlar cords etc.

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Woodmaster1

1353 posts in 3258 days


#4 posted 02-17-2020 08:09 PM

I have that same saw with a 5hp motor on it nothing to worry about. It is the nature of the saw with that much power. I love mine works great. I bought it 8 years ago.

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rkruz

49 posts in 55 days


#5 posted 02-17-2020 08:24 PM


Sounds pretty normal to me.

Cheers,
Brad

- MrUnix



Yeah, I didn t hear anything to worry about either.

- Fred Hargis


Is the belt tension correct? Personally, I have never been let down with Gates belts for anything. Their are higher tech poly belts with steel wires, kevlar cords etc.

- tvrgeek

Thanks guys. I feel better knowing it did not sound unusual to you. But I found something. When I removed the belts I noticed that both arbor pulleys were jiggling back and forth every so slightly. The allen screw in each of them was loose and took a good quarter turn to tighten. After that the start up jolt was greatly reduced:). Still Im worried as I assume there is a key that should keep the pulley tight on the arbor on its own and single allen wont hold that in place for long if the key slot has worn causing a loose key slot.

As far as the belts go, they look in good shape and I did tighten them. One belt has about a 1/4” play but the belt closest to the blade has about a 1/2” play. Since its a new saw to me Ill look into replacinge the belts if they are not too expensive. The Delta belts are $71 apiece which seems like a lot.
How does one find the right Gates or other replacement belt?

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rkruz

49 posts in 55 days


#6 posted 02-17-2020 08:29 PM



I have that same saw with a 5hp motor on it nothing to worry about. It is the nature of the saw with that much power. I love mine works great. I bought it 8 years ago.

- Woodmaster1


Nice. you have the same saw….beauty! .thanks for that. Sounds like about the same age saw as mine. Seller said he bought in 2015 but I saw a date of 2012 on it..maybe on the motor. I did discover loose arbor pulleys and tightened the allens for better result. See prior post. Have you ever replaced the belts?

View CaptainKlutz's profile

CaptainKlutz

2622 posts in 2165 days


#7 posted 02-17-2020 09:32 PM

The jolt on start up is normal due massive HP and getting things moving.
BUT:
I hear unusual sounds?
There is subtle growling when running, a squeaking on shutdown, and several metallic clicks on start-up, when I should only hear one centrifugal switch click removing the start capacitor.
IMHO – MIGHT need to adjust the centrifugal switch on the motor and/or maybe motor bearings are running dry?

Suggest removing the belts and testing the motor.
It should be dead quiet on start/stop without belts, except for two noises:
- near silent mechanical jump when motor starts moving,
- metallic click when the centrifugal switch closes as the motor reaches speed 1/8-1/2 second after motor start.

If the squeaking or other noise in the above video is still present, suggest closer motor inspection.
- unplug machine
- check for loose pulley, tighten if needed.
Remove the fan cover and:
- check fan mounting is not loose or rubbing (spin by hand), then remove fan.
- Check contacts on centrifugal switch for burnt/missing contacts.
- connect power to saw and
- start stop the motor checking switch engagement.
(leave at least 30 seconds between off-on to discharge capacitors and reduce stress on motor starter)
The position of the switch on the motor shaft adjusts turn on time. It should be adjusted to disengage when motor goes above 15-25% of rated RPM, or 540-900 rpm for 3600rpm motor. Might sound silly, but if you don’t have tachometer to measure RPM, typically a correct adjustment is when it generates least amount of sparking when contact closes?

If the motor is still has shutdown rattle/squeak, then would assume it’s a bearing noise, and they are due for replacement soon. Can use saw for days/weeks, but the noise is due lack of bearing grease and they are going to fail eventually. Had both a TS and dust collector motor with same noise (rattle/squeak on shutdown). DC motor locked up ~1 month after i noticed the noise. Saw starting growling like hungry bear about 3 months after noise started.

If the motor squeaks during shutdown only with belts attached, it’s a sign you will need new bearings in future (weeks with daily use, months with weekend use).
If the motor squeaks during shutdown with only properly tightened belts, it also means bearing replacement is in your future – but is shows the previous owner had the belt tension to tight. Which is common issue for mechanically challenged folks. Setting proper belt tension is an acquired skill.

The other noise, growling, could be motor bearings, or could be arbor bearings. The growl is usually how failing arbor bearings are found. Saw will work for long time with small noise in arbor bearings, months/years. They eventually get so bad the cabinet shakes, then the bearings get so hot they weld together. When this happens the belts burn, and it makes a HORRIBLE noise/mess and maybe even a saw dust fire. So don’t let growling bearings run forever. BTDTGTTS

If you end up changing motor bearings, might as well change the arbor bearings too. They have working as team since they left factory, and typically last about same length of time, +/- a few months.

PS – OEM recommends matching belt lengths, that is why they are expensive.
Finding alternate belts is not hard as they are standard size, but finding a matched set, or set from same date code with same lengths is hard part?
IMHO – Best method is to find a Napa Auto Parts store, take old belt in, and ask for 3 Gates belts with same date code. Belts are sliced from master tube, and same date code means they should be nearly same length, and you avoid the odd belt being loose while others are tight. They will be < $20 each. If Napa asks for more, laugh out loud, smile and ask for ‘jobber price’ or you visit another store.

Yes, you can order belts online for ~$5 each, but it’s impossible to get all of them the same length.

Hope this helps.
As always, YMMV

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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rkruz

49 posts in 55 days


#8 posted 02-18-2020 12:28 AM


Suggest removing the belts and testing the motor.
It should be dead quiet on start/stop without belts, except for two noises:
- near silent mechanical jump when motor starts moving,
- metallic click when the centrifugal switch closes as the motor reaches speed 1/8-1/2 second after motor start.

- CaptainKlutz


Thanks so much Capt. I read all your suggestions and working through them. But I wanted to get you the video of the motor with no belts connected to get your opinion.
https://photos.app.goo.gl/qn5VW6uU1FYEQN7A6

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CaptainKlutz

2622 posts in 2165 days


#9 posted 02-18-2020 01:00 AM


Thanks so much Capt. I read all your suggestions and working through them. But I wanted to get you the video of the motor with no belts connected to get your opinion.
https://photos.app.goo.gl/qn5VW6uU1FYEQN7A6

- rkruz

Sounds normal without belts. Nice whine and single click.
I.E. The growling and squeaking on shutdown in 1st video is gone. :-)
Doubt you have a motor issue. That is why you remove belts and isolate the parts first. :-)

My new guess? Slipping belts or arbor bearings?

Check sides of belts for burn marks, or highly polished edges. Both signs of belt slipping. Clean with lacquer thinner (if you don’t have rubber rejuvenater) on a rag to remove dirt and rubber residue. Check pulleys for dirt and clean as well. Reassemble with proper tension, and check for shutdown squeak.

IME – Since the growl is not the motor, it has to be in the arbor; unless the belts were way too tight.

Check the arbor shaft for side to side movement and ‘feel’ as you turn the shaft.
Should spin when spun, but stop when not spun due heavy grease. If free spins for very long, the bearings are dry and due for change. If you feel any ‘grit’ or harsh spots turning 360° by hand, also a sign bearings are worn out.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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rkruz

49 posts in 55 days


#10 posted 02-18-2020 03:15 AM


My new guess? Slipping belts or arbor bearings?


Here is a vide of the motor alone, no fan. Very Quiet.
https://photos.app.goo.gl/FU5Z2xPTWm2PC5rDA

Here a vid all buttoned up with a blade. I tightened lose arbor pulleys and I used weight of motor plus a gentle downward pressure to set belt tension. Seems to be reasonable jolt and noise.
https://photos.app.goo.gl/dAPrkKbgVwHrHpcC6

Here is arbor free spinning. Its spins a long long time. I thought that was a good thing but you think the bearing are bad because of the free spin? I feel no play or grind at all and it spins very smoothly as seen in the vid.
https://photos.app.goo.gl/UwQgy2ogWRf7s91X9

The belts are Delta matched set. They look good, no cracks but the threads are showing on the sides. I went to Napa and Orielly and they didnt know of one to replace it. Looks like Delta parts are $71 each (ridiculous!)

Thank you again for your generous help. One last imposition. would have any idea of a belt substitiute for the expensive Delta pair?

View MrUnix's profile

MrUnix

7809 posts in 2870 days


#11 posted 02-18-2020 03:38 AM

Your belts look fine from that picture… bearings appear to be on their way out though. Good bearings should provide a little bit of resistance and should not free-spin like what you show.

As for belt tension… I prefer to tension them with the machine on so you can observe them in action. You would be surprised at just how little tension they need. Too much tension is just as bad (or worse) than too little. With the machine running, you can dial in the sweet spot easily.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View CaptainKlutz's profile

CaptainKlutz

2622 posts in 2165 days


#12 posted 02-18-2020 10:18 AM

Agree with Brad:
+1 belts look ok. Clean sides of belts and pulleys to remove any dirt, and keep using them.
+1 tension belts with motor running
+1 too much arbor free spin
= Arbor bearings are usable for awhile, but need to be replaced in future.
How long depends on amount of use/run-time?

FWIW: Grease in bearings is typically heavy weight lithium based. As grease ages, the lithium ‘soap’ stabilizers sort of ‘dry out’, and the grease turns into a waxy substance with zero lubrication. The result is ball bearings also have zero resistance to movement, which manifests as free spin, eventually with a metal on metal rubbing sound. New bearings with good grease spin easily, but stop quickly due friction of grease. A good bearing has to be almost too hot to touch for grease to have low enough viscosity to ‘free’ spin very long. As soon as you spin a new bearing, you will see the difference. :-)

The length of time for typical grease conversion from thick paste to wax solid varies based on temp and humidity? Reading backwards and seeing this tool is now 7 years old, not surprised by the arbor bearing condition. Just about every motor/arbor/cutter head, I have used needs new bearings every 7-12 years. Don’t despair about length of time between bearing maintenance? Tools with cheap Chinese bearings and cheap grease only last 2-4 years. Which is the primary reason you see folks recommending use of decent quality (USA/Japan) bearings when you rebuild tools. :-0)
Tons of references on LJ and WWW on how to change Unisaw arbor bearings.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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rkruz

49 posts in 55 days


#13 posted 02-18-2020 03:52 PM



Agree with Brad:
+1 belts look ok. Clean sides of belts and pulleys to remove any dirt, and keep using them.
+1 tension belts with motor running
+1 too much arbor free spin
= Arbor bearings are usable for awhile, but need to be replaced in future.
How long depends on amount of use/run-time?
- CaptainKlutz

Thanks Brad and Capt. Ill remove the arbor today and replace the bearings clean belts and pulleys etc and report back. Ive replaced bearings on my Powermatic recently so a doable do for me.

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rkruz

49 posts in 55 days


#14 posted 02-19-2020 02:02 AM

I damaged the arbor threads and cannot get the nut on.
Do you know what die size I would use to clean up the threads?
It model 36-L552 and nut is righty tighty.
thanks

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MrUnix

7809 posts in 2870 days


#15 posted 02-19-2020 03:04 AM

Just fix ‘em with a small needle file.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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