Blade wobble/flex on startup

[difalkner]

This is a topic that came up recently with some other woodworkers so I thought I'd shoot a short video to see just how much my blade wobbles at startup.  Turns out it's fairly slight and is over in about one second.  The video is less than two minutes if you're interested in watching.

 

 

[JohnG]

I didn’t watch the video, but of course there will be some wobble when it is first getting up to speed. Soft start motors will help reduce it compared to non-soft start, but any blade worth owning (and without defect) will stabilize before you begin a cut anyway.  

[treeslayer]

I’d watch the video @JohnG, I think there is something wrong here, I would suspect a bearing or 2 on the arbor shaft, I can’t argue with @difalknerabout the cut he’s getting, if not the bearings maybe some issue with the 90 to 45 degree lock or adjustment, always interested in other opinions as to what if anything is wrong 

[difalkner]

On 1/2/2023 at 5:39 PM, JohnG said:

I didn’t watch the video, but of course there will be some wobble when it is first getting up to speed. Soft start motors will help reduce it compared to non-soft start, but any blade worth owning (and without defect) will stabilize before you begin a cut anyway.  

The video is less than two minutes long.  I agree that soft start would eliminate this issue but like you say, the blade stabilizes long before I make the first cut and it cuts perfectly each and every time.

On 1/2/2023 at 6:07 PM, treeslayer said:

I’d watch the video @JohnG, I think there is something wrong here, I would suspect a bearing or 2 on the arbor shaft, I can’t argue with @difalkner about the cut he’s getting, if not the bearings maybe some issue with the 90 to 45 degree lock or adjustment, always interested in other opinions as to what if anything is wrong 

Nothing is wrong.  I restored the saw a few years ago with new arbor, bearings, matched belt set (3), and the saw cuts perfectly every time I use it, which is often.  The locks are fine, too, btw.  It was a topic on another forum and I found it interesting so I shot the video and shared it here, not to point out an issue but rather to show what happens when the saw it turned on (can't point out an issue because there isn't one).

My guess is many, if not most saw blades on tablesaws do this, especially if they're thin kerf like this one.

[treeslayer]

Thin kerf would explain a lot, your woodworking is top shelf, so it took all day but I learned something , great video BTW

[difalkner]

On 1/2/2023 at 7:00 PM, treeslayer said:

Thin kerf would explain a lot, your woodworking is top shelf, so it took all day but I learned something , great video BTW

Thank you so much!!  Glad you were able to watch that lengthy video.

[wtnhighlander]

After watching the video, it appears to me that the blade is actually flexing under the start-up torque of the motor. I have seen similar performance from industrial machines  at work, when a high-torqe is applied to a relatively light load. Once the the blade reaches speed, centrifugal force straightens it out.

Repeat the video with a heavier blade, like a dado stack, and I bet the wobble isn't detectable.

[difalkner]

On 1/2/2023 at 8:36 PM, wtnhighlander said:

Repeat the video with a heavier blade, like a dado stack, and I bet the wobble isn't detectable.

I agree.  If I had one I would do just that for testing purposes.

[Chestnut]

That's interesting. It seems like there still is some wobble but maybe it's just a trick of the slow motion and shadows.

I have some blades that wobble on slow down but they are warped. They seem to cut fine when not pushed but when feed is too fast or material is to thick they vibrate and the cut quality drops. As a result i've switched to only using full kerf blades even on a 1.75hp saw. They don't seem to suffer from the warping that thin kerf blades have and my cut quality has improved. I do change blades more often as a result and tend to match the proper blade to the task eg 24 tooth blade to rip thick hardwood, 80 tooth balde for cross cuts. I've pretty much shelved combination and utility blades as they only offer the worst of both worlds.

[difalkner]

On 1/3/2023 at 11:46 AM, Chestnut said:

That's interesting. It seems like there still is some wobble but maybe it's just a trick of the slow motion and shadows.

It could be but I really think it's more flex than anything else.  And it only lasts for about a second, has never affected a cut.  I've heard from more than a dozen people using thin kerf blades and they see the same flex at startup.  It was just interesting enough that I thought I'd shoot some video to show what's happening.

If I had a full kerf blade I would have done a comparison but oddly enough, with all the woodworking I'm doing and have done, this is the only blade I have.