Unisaw starts with a jerk

[Kevin Hartnett]

Hi all,

I have a new 10" unisaw I picked up last December. I'm happy with the saw in most respects, but I do have one issue. When I got the saw the three belts were a little bit loose. While running, I would occasionally get some vibration which came from the loose belts vibrating a little.

Well, I tightened up the belts according to the user's manual and now the vibration is gone but when I press the start button the whole saw jerks on its stand very hard, almost enough to move the saw. I loosened the belts slightly, but the startup jerk is still present. I'm afraid, over time, that this hard starting will cause excessive arbor wear and throw the blade out of whack.

Does anyone have a solution to this belt problem: too loose, I get vibration; too tight the saw jerks on startup. Would link belts help? What's a good source for link belts? Should I throw out the Delta belts and try a better brand? Which one?

OK, now you can start with the comments about the jerk running the saw!!!

Thanks for any help.

Kevin H.

[Mike Henderson]

My guess, without seeing your saw, is that what you're seeing is normal. Induction motors (both single phase and three phase) start up pretty quick, especially with no load on them. When you put the belts on loose they're probably slipping on startup. When you put the belts on tight, you see the rapid startup as a jerk. The motor is starting "normally" (that is, starting up quickly). My guess is that the saw was designed to tolerate the rapid startup and it won't cause any problems. The Unisaw has been in use for many years and gets good reviews.

Mike

[I use table saws at school that are 5Hp, three phase, and they come up to speed almost immediately. Press the button and "bang", they're running.]

[Brad Townsend]

My Uni jerks too. Not all of the time, but often. There have been other posts on this in the past. I have accepted it as "normal" and don't even think about it.

[John Thompson]

Unless the belts are loose and slipping.. Uni-saw's jerk from torque on start-up from the day they were invented back in 1937... Well.. maybe not as they had smaller motors then.

Go cut some wood and expect it to jerk. If you want to hear a bigger thump when you start up.. upgrade to 5 HP and your wishes will come true.

BTW.. some will reduce the intial start up jerk with those link belts but.. not necessary in reality as the jerk won't hurt a thing.

Sarge..

[Ray Dockrey]

You can check this too. You said it jerks but this may still apply:

My saw 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!

[Rod Sheridan]

"Unisaw starts with a jerk"

Well, get someone else to push the start button

Seriously, it's normal operation for a tablesaw with a motor that large........Rod.

[Chip Lindley]

That's Lots of Power (3hp or 5hp) going from Zero to 60 in less than 1 second! It's normal but startling! IMO, THE reason Unisaws have Three Belts instead of one...to absorb all that sudden torque that may break a single belt!

Sudden Torque is also the reason routers are made with a *soft-start* feature. I have an old Rockwell 3hp router that will literally jump out of my hands unless I Hold On Tightly!! (old 38-Special song too)

There are *soft-start* magnetic motor starters made by Baldor and others. As the Divorce Attorney told his prospective lady client,...."You can get rid of your JERK for a PRICE!!"

[Mike Goetzke]

My Uni jerks too. Not all of the time, but often. There have been other posts on this in the past. I have accepted it as "normal" and don't even think about it.

I have a newer Uni and I'm a +1 on the jerk at start up but what bothers me is mine is like Brad - it doesn't do it all of the time (most - but not all).

I have also wondered being a hobbyist if the belts always retain a "set" and if this happens to have something to do with the clunk. My saw is almost two years old now and when I go to c/o the blade I can tell there is still a "set" in the belts because there are angular positions where the blade turns easy and other places where it has resistance and will snap back to it's original position if you let go.

[Matt Armstrong]

Hi all,

I have a new 10" unisaw I picked up last December. I'm happy with the saw in most respects, but I do have one issue. When I got the saw the three belts were a little bit loose. While running, I would occasionally get some vibration which came from the loose belts vibrating a little.

Well, I tightened up the belts according to the user's manual and now the vibration is gone but when I press the start button the whole saw jerks on its stand very hard, almost enough to move the saw. I loosened the belts slightly, but the startup jerk is still present. I'm afraid, over time, that this hard starting will cause excessive arbor wear and throw the blade out of whack.

Does anyone have a solution to this belt problem: too loose, I get vibration; too tight the saw jerks on startup. Would link belts help? What's a good source for link belts? Should I throw out the Delta belts and try a better brand? Which one?

OK, now you can start with the comments about the jerk running the saw!!!

Thanks for any help.

Kevin H.

You could use a heavier blade

[Bill Huber]

I didn't read all the replies but I am still trying to figure who is a jerk for getting a Unisaw.......

[Philip Johnson]

Trade it in on a powermatic no jerk

[Travis Porter]

My suggestion is to loosen up the motor and offset the belts. They get a memory and sometimes offsetting them will eliminate the "jerk".

PS - I had jerk on my PM-66 when I turned it off until I replaced the belts.

[george wilson]

Never noticed our Unisaw jerking. It would come up to speed quickly,but didn't jerk. ours had the old round bell motor.

[Kevin Hartnett]

Wow, some great replies. I gather from most of the responses that the jerk is normal for the Unisaw (and some others.) I am thinking I'll try to replace the belts with some high quality ones. Time to do an Internet search for v-belts. Does anyone have any recommendations for top-o-the-line belts?

Thank you all for responding, I feel better knowing it's not abnormal and won't damage my saw.

I don't feel like such a jerk anymore.

This is a great forum!

Kevin H.

[Larry Edgerton]

My ex claims all of my saws start with a jerk.....