Blade wobble at startup

[David Falkner]

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.

https://www.youtube.com/watch?v=T-qOOiq5M5E

[Brian Tymchak]

Interesting video. Thanks for sharing. Do you get the same behavior with a different blade? I notice a tiny bit of wobble even after the blade stabilizes. That looks like a thin kerf blade. It might be the effect of a 3hp motor whipping a thin kerf blade up to speed. Try a full kerf blade if you have one. Other than that the only thing that I can think of is that you have an arbor bearing starting to fail.

[Ken Fitzgerald]

While it could be the effect of mechanical harmonic resonance as it starts up, I wonder as Brian suggested, if every blade or a full kerf blade does it too.

[David Falkner]

Interesting video. Thanks for sharing. Do you get the same behavior with a different blade? I notice a tiny bit of wobble even after the blade stabilizes. That looks like a thin kerf blade. It might be the effect of a 3hp motor whipping a thin kerf blade up to speed. Try a full kerf blade if you have one. Other than that the only thing that I can think of is that you have an arbor bearing starting to fail.
This is the only blade I use. I think what appears to be wobble in the video may just be the ATB cut and the way it videos. Yes, it's a thin kerf blade. I restored the saw a few years back - the arbor bearings were new a that time and all is well with the alignment, matched set of belts, blade, etc. I just shot the video to demonstrate what likely happens on tons of saws but the cuts on mine are about as good as can be.

While it could be the effect of mechanical harmonic resonance as it starts up, I wonder as Brian suggested, if every blade or a full kerf blade does it too.
A full kerf blade may not do this but I don't have one. I just found it interesting to demonstrate and video; it's not a problem.

[Robert Hayward]

I have a PM200 that does the same thing with a Ridge Carbide 40 tooth blade. Does not do it with the WWll blades I use, only the Ridge Carbide. Wobbles bad enough at start up to widen a ZCI slot. Only does it at start up and then the blade cuts normal.

[David Falkner]

Wobbles bad enough at start up to widen a ZCI slot. Only does it at start up and then the blade cuts normal.
And that's precisely why I always start the saw with the blade below the table. I only did it with the sled in place to demonstrate the startup wobble. If the saw had soft start it would be a different story but this thing hit hard on startup and the thin kerf blade takes the hit as the video shows.

This was a topic on another forum and I found it interesting enough to shoot some video footage, thought I'd share it here. My guess is many saws with thin kerf blades do this exact same dance at startup but it's over in about one second so it has never affected any cuts.

[Bruce Wrenn]

Look at 0.46 mark, looks like blade is bent. Centrifical force could straighten blade as it comes up to speed, phone isn't fast enough to record wobble at speed. Lay blade on a flat surface and check for bent teeth.

[David Falkner]

Look at 0.46 mark, looks like blade is bent. Centrifical force could straighten blade as it comes up to speed, phone isn't fast enough to record wobble at speed. Lay blade on a flat surface and check for bent teeth.
That's why I shot the video at 240 fps so I'd have a better chance of seeing what's happening. It's not bent, I've checked. It's a thin kerf blade and just flexing under the startup torque so yes, as the centrifugal force builds it overcomes the flex.

[Lee Schierer]

I would switch to a full kerf blade such as the Freud LU82M010. (https://www.amazon.com/Freud-LU82M010-10-Inch-Crosscutting-Ripping/dp/B0000225UJ/ref=sr_1_17?crid=GS7K9Y7LDVYE&keywords=freud+saw+blades+10+inch&qid=1672764134&sprefix=freud+saw+blade%2Caps%2C620&sr=8-17) I use that blade on my saw regularly. The cut quality is excellent.

[David Falkner]

I would switch to a full kerf blade such as the Freud LU82M010. (https://www.amazon.com/Freud-LU82M010-10-Inch-Crosscutting-Ripping/dp/B0000225UJ/ref=sr_1_17?crid=GS7K9Y7LDVYE&keywords=freud+saw+blades+10+inch&qid=1672764134&sprefix=freud+saw+blade%2Caps%2C620&sr=8-17) I use that blade on my saw regularly. The cut quality is excellent.
Thanks, Lee, but I prefer the thin kerf blade. The one you referenced is a good blade, though.

[Ken Combs]

I guess it isn't surprising that a thin blade might flex when started really quickly. Not that I expected that, but I've seen similar behavior on my ancient Unisaw with a 1hp Repulsion/Induction motor. They make lots of torque!

Not that it is a problem that needs fixing (it get fixed in a second or so) but I have a set of blade stabilizer washers, about 5" or so in diameter that stop it at the cost of some depth of cut.
That's not the reason for having them, they were intended to prevent flex/runout/wobble with thin blades on solid surface plastics and melamine to prevent chipping. And, in that use depth of cut was not an issue..

Today's phones are impressive. I just wonder why we still can 'em phones?

[John Kananis]

I have a blade stabilizer for thin kerf blades. This one.

https://ridgecarbidetool.com/collections/accessories/products/saw-blade-stabilizer

Edit: I also have the original throat plate on a shelf or in a drawer somewhere. Looking at it, you'd see the damage done by a thin kerf blade gone astray - and we're talking about a pretty large clearance for the blade to begin with. It had to be pried out of the throat.

[David Falkner]

I guess it isn't surprising that a thin blade might flex when started really quickly. Not that I expected that, but I've seen similar behavior on my ancient Unisaw with a 1hp Repulsion/Induction motor. They make lots of torque!

Not that it is a problem that needs fixing (it get fixed in a second or so) but I have a set of blade stabilizer washers, about 5" or so in diameter that stop it at the cost of some depth of cut.
That's not the reason for having them, they were intended to prevent flex/runout/wobble with thin blades on solid surface plastics and melamine to prevent chipping. And, in that use depth of cut was not an issue..

Today's phones are impressive. I just wonder why we still can 'em phones?


I have a blade stabilizer for thin kerf blades. This one.

https://ridgecarbidetool.com/collections/accessories/products/saw-blade-stabilizer

Edit: I also have the original throat plate on a shelf or in a drawer somewhere. Looking at it, you'd see the damage done by a thin kerf blade gone astray - and we're talking about a pretty large clearance for the blade to begin with. It had to be pried out of the throat.
I've thought about getting some blade stabilizers but it's just not enough of an issue for me, plus, I often cut full depth with this saw/blade combo and wouldn't want the blade stabilizers getting in the way.

Phones? They are way more powerful than our computers from even just 10 years ago. Calling them phones is a bit of a stretch, right!?!

[Mel Fulks]

Do you have the big “stabilizer” washers on both sides ? Failure to use them is ,I think a common cause of wobble. Seen it in a commercial
shop with a dumb-bell foreman. Company had dumb-bell policy of giving the foremen extra bonus for not buying stuff needed . A used saw
might not come with the correct washers.

[Mel Fulks]

The stabilizers I’ve seen would not interfere with cuts. Can’t imagine that with modern liability laws that they would sell any that could
impede full standard range of cut.

[Lee Schierer]

Thanks, Lee, but I prefer the thin kerf blade. The one you referenced is a good blade, though.

What benefit do you think you are getting from a thin kerf blade instead of a full kerf blade?

[David Falkner]

Do you have the big “stabilizer” washers on both sides ? Failure to use them is ,I think a common cause of wobble. Seen it in a commercial
shop with a dumb-bell foreman. Company had dumb-bell policy of giving the foremen extra bonus for not buying stuff needed . A used saw
might not come with the correct washers.
I bought the saw new in 1990 and I'm still using the same 2.5" stabilizers that came with the saw.


The stabilizers I’ve seen would not interfere with cuts. Can’t imagine that with modern liability laws that they would sell any that could
impede full standard range of cut.
The ones on there now are the 2.5" that came with the saw; no, they don't interfere with the cut. I've not checked into aftermarket stabilizers.


What benefit do you think you are getting from a thin kerf blade instead of a full kerf blade?
Less wood removed in a cut. I work with a lot of exotic woods and fine domestic hardwoods and want to make as small a cut as possible. If I was just cutting Pine for crafts and such or cutting sheet goods where I may want a flat bottom for a dado I'd have a full kerf blade in a heartbeat but I rarely work with those.

[Lee Schierer]

Less wood removed in a cut. I work with a lot of exotic woods and fine domestic hardwoods and want to make as small a cut as possible. If I was just cutting Pine for crafts and such or cutting sheet goods where I may want a flat bottom for a dado I'd have a full kerf blade in a heartbeat but I rarely work with those.

I don't know what rpm the wobble you have observed occurs, but if you saw slows down to that rpm range during any cut the wobble will be there making your kerf wider.

[John Kananis]

IMHO: I don't like thin kerf blades for deep cuts (or in general really). That said, I own two thin kerf blades, the forest ply veneer blade and a Freud glue line rip that hasn't come out of the draw in many years.

[David Falkner]

I don't know what rpm the wobble you have observed occurs, but if you saw slows down to that rpm range during any cut the wobble will be there making your kerf wider.
LOL! I've never seen any cut slow this saw down! There have been a couple of times where a board closed up on the blade and I fought like crazy to hold the board down, hoping the saw would stall but it never even changed pitch.


IMHO: I don't like thin kerf blades for deep cuts (or in general really). That said, I own two thin kerf blades, the forest ply veneer blade and a Freud glue line rip that hasn't come out of the draw in many years.
I've had no issues with this one, suits my needs perfectly.

[John Kananis]

Btw, I really like your Pantagraph design.

[David Falkner]

Btw, I really like your Pantagraph design.
Thanks, John! I had forgotten there was a video on that. Thanks for checking it out!

[Mel Fulks]

I just remembered that many years ago when I worked in a mill that was opened about 1900 ,we had good on site sharpener who did all.
He said that the saws (blades) would get warped from heat . He used a thick steel machined plate to check for saw flatness, then hammered
them flat ,( I’ve forgotten the details on how). He also took in outside work. When he started the tapping he turned oven a 5 minute egg
timer , I think it was 5. If he straightened saw in the 5 minutes there was no extra charge. All the saws we used were high grade .

[David Falkner]

Pretty cool story, Mel. Probably not a lot of guys left around like that.