Sawstop CNS1.75-AU 240v - Significant Motor Jerking on Start

Hello everyone,


As a long-time listener and watcher of the forum, I've always appreciated the wealth of knowledge and insights shared by the community. However, this time I find myself in need of assistance and advice regarding a recent purchase.


Recently, I made the transition to the Sawstop CNS1.75-AU (240v) with the 36" Fence Assembly, upgrading from my previous Dwarlt and Makita jobsite saws.


Upon completing the assembly of the unit and fence, I encountered an issue when I started the saw. There was a noticeable motor jerk and significant wobbling of the entire table during startup, which lasts for about 1 second before subsiding. However, the saw appeared to stabilize afterward, although there was a slight vibration that I could feel when I touched the cast iron surface. Since I'm not accustomed to contractor saws, I'm unsure if this behavior is normal.


To provide a clearer understanding of this behavior, I have included a link to a video demonstrating the saw's startup.
https://youtube.com/shorts/4z5KgZzPD7I?feature=share


Your expertise and advice on this matter would be greatly appreciated

I should probably just leave this to the owners of your make/model of your saw but I have a 2HP Taiwanese contractor's saw and the motor does jump on startup although yours looks little more severe. However, given the Sawstop's extra safety stuff it could be understandable - more weight to get turning. Mine also jumps a lesser amount when turned off.
The motor is literally suspended by the belt and the weight of the motor tensions it so it isn't surprising that it has more movement than a motor that is rigidly fixed. The motor likely wants to climb up the belt when started until the blade mechanism gets moving.
I'm pretty sure you'll get some good replies from owners but if you don't or aren't happy, contact Sawstop.

I don't have that model of saw, but it looks to me like the motor mount or belt tensioning is loose, allowing the motor to kick back when it starts up. Once the belt tension has been set is there a bolt that you need to tighten?

I have a SawStop PCS. The few times that I have needed help or information, the customer support has been excellent.
I would call them and describe your problem.
In the past they have been more than willing to help you troubleshoot, find the problem and assist with coming up with the best solution

My issue that I reside in the Middle East and procured the saw from the sole authorized dealer of Sawstop in another country, then having it shipped to me at considerable expense (shipping about $1000). Safety is paramount for me, especially now with my kids showing an interest in woodworking, hence my investment in the SawStop.

However, my attempts to reach out to SawStop directly, even for basic inquiries, were unexpectedly redirected to contact the dealer, SawStop's reputed customer service!!. This came as a surprise and disappointment! Despite explaining the logistical challenges of accessing the dealer due to a lengthy drive and border crossings, I was unable to get the assistance I sought from Sawstop, even by just simply reading my eamil and try to provide just basic information... they know their saws better than anybody! Very disappointing.

I enndup contacting the dealer. I am not going to deny, they genuinely tried to help, and as some of you suggested, their technician suggested a solution involving adjusting the belt tension by pulling the motor out by approximately ½ cm and then tightening the screw insert. This advice seemed to contradict the manual's recommendation to push the motor rods all the way in. And I couldn't shake the feeling that the technician wasn't entirely confident in his advice. Given my lack of familiarity with these saws, I was apprehensive about potential damage to the inner mechanism.

Additionally, the technician recommended assembling the entire saw, including the 36” fence, to add more weight in an attempt to mitigate on-start wobble and significant motor kick. In my view this did not make any sense as the motor is jerking causing the table to wobble. Adding table weight will not stop the hanging motor form jerking!.

So for contractor type saws, how do you guys increase the tension? despite it not being mentioned in the manual, it would be ideal if someone has the CNS SawStop to give us his/her view.

Attachment 518819

I would guess based on your location that the saw spent considerable time in a shipping container which was probably pretty hot for much of the trip.

Your problem is most likely that the drive belt had taken a set due to the long hot transit. This used to be a problem on many table saws. The solution that was used in the past was to change out the solid belt for a link belt. That may not be necessary or possible for your saw. As you noted in your post it settles down after running for a bit. If you use your saw regularly, it probably won't take a set again. The newer brands of belts like "Gates" and some others tend to be more flexible and less like to take a set. If your saw sees very or infrequent use the starting vibration will likely continue.

At last, I've received a satisfactory response from SawStop. It seems that after sending them several persistent emails, they took notice and felt sorry for me.


Upon reviewing the video I provided, they suggested that I need to replace the centrifugal switch on the motor.


Interestingly, I haven't even made a single cut on the table yet… ☹

I agree with Lee, let the saw run for about five minutes then shut it off for a minute or however long it takes for the blade to come to a complete stop. Then restart the saw.
I also agree with the dealer and would adjust the belt tighter until there is about 1/2"-3/4" deflection in the middle of the belt, do this by moving the rods out.
I would try another new belt, preferably a link belt.
ONLY after the above would I change the centrifugal switch in the motor.
I do not have the Saw Stop contractor Saw, I do have an ICS 5hp.
I did own a Delta Contractor saw bought new in 1988. I had to change both pulleys and install a link belt to get it to calm down. Common enough at the time that you could buy a kit with the two machined steel pulleys and proper length belt.
Good luck
Ron

The motor is labeled for 240 volt 50hz, is that what you are providing to it?

I used to have a delta unisaw x5 series that jerked hard almost every start. I tried adjusting everything I could. I finally accepted it as a trait of a single phase capacitor start motor.
I eventually sold that saw but my powermatic planer has the same traits sometimes it bangs sometimes it doesn’t. Cap start single phase.
Good Luck

Quote:

---

Originally Posted by John Lanciani

The motor is labeled for 240 volt 50hz, is that what you are providing to it?

---

Yes. 240v 50hz AU version

I ran it for 5 mins few times shut it for 1 min in between .Same issue..

I have sent additional infromation to Sawstop and they advised once agina; replacing the centrifugal switch for the motor will reslove the issue. Well, they know their saw better than anyone, hope this will resolve the issue. I guess I won't know until i repalce the centrifugal switch.

I'm not sure what replacing the centrifugal switch would accomplish but as you say, Sawstop should know the saw best. The common failure mode of a centrifugal switch is that the motor won't start without a 'push' which would be 'exciting' on a circular saw. A bit of a bounce on startup may just be the nature of the beast. The only contractor style saw I've had experience with is a Craftsman and that was years ago. As I recall it had a spring between the plate where the motor was attached and where the rods attach. That may have helped to lessen the bounce.