Delta table saw blade flexing

[Brent Romero]

I have an older Delta table saw and while ripping some #2 pine 2x4s the other day I noticed the blade actually flexed and yielded a curved cut.

Any insight as to what is going on there?

Many thanks in advance for the suggestions and comments.

[Van Huskey]

I have an older Delta table saw and while ripping some #2 pine 2x4s the other day I noticed the blade actually flexed and yielded a curved cut.

Any insight as to what is going on there?

Many thanks in advance for the suggestions and comments.

Was it actually curved or just angled across the wood? If it is curved describe the curve, if it is angled it is probably the fence.

[Jerrimy Snook]

What type of blade is it? Is it sharp? If the material is pushed harder than the blade, belt, and machine can handle then the machine RPM can slow down which may make the blade "wobble' some. Pushing the material may also produce a "curved" cut. The best blade for this scenario would be a 24 or 30 tooth rip blade.

Jerrimy

[glenn bradley]

Dull blade is my first guess since this is an emergent behavior. Even thin kerf blades work admirably on a well aligned saw if they are a sharp quality blade. Sounds like a good excuse to head to the sharpeners ;-)

[Brent Romero]

Thanks for the insight. Tough to describe, but the blade really flexed more than anything and was not really just angled. The flexing had a lot of curvature I guess I would say.

I am not sure of the blade type or age. It is a ripping blade I do recall that much. Is it sharp...well, probably not the sharpest as it has been in use for a while now.

Just learning here....sorry for the lack of info on my part.

Thanks

[Van Huskey]

Is the blade tight on the arbor? Do you have the ability to measure the runout of the arbor?

I for one am having a difficult time "seeing" exactly what you mean. Maybe try to describe the entire issue like you would to a blind person. Could you see the blade flexing as the saw ran, what do the cuts in the wood look like.

[Brent Romero]

With the table saw running and without any wood being cut, the blade appears to the naked eye to run "true"....meaning it does not wobble or flex. Once I began running the 2x4 through the saw, I observed the blade and it seemed to continue to run "true"....suddenly the blade flexed in a curved fashion but not a symetrical curve...very ashpherical if you will. The cut at that point in the board has a curve in it...so the two edges of the board are not parallel.

[Van Huskey]

How high above the board was the saw blade raised? You still need to figure out the root cause but try cutting with the blade raised so the gullet of the blade is just above the top of the wood, which depending on the blade would be around 1/4" to 3/4" inches, given it is a rip blade it will have deeper gullets so closer to 3/4".

[Brent Romero]

The height above the lumber was ~1/8". Sounds like I may need to raise it a bit to explose the gullet....makes sense as I am assuming the purpose of the gullet is to get the cut lumber out and reduce heat, etc.

Will try that. The blade cuts fine in other apps. I also probably need to invest in a good quality blade...which I probably did not do with the purchase of the existing blade. Any suggestions on blade Mfg?

Thanks

[Don Jarvie]

The best thing to do is dig out the manual and follow the instructions for setting up the saw. Next would be to buy a high quality blade and see what happens. The saw just may need to be set up.

[Van Huskey]

The height above the lumber was ~1/8". Sounds like I may need to raise it a bit to explose the gullet....makes sense as I am assuming the purpose of the gullet is to get the cut lumber out and reduce heat, etc.

Will try that. The blade cuts fine in other apps. I also probably need to invest in a good quality blade...which I probably did not do with the purchase of the existing blade. Any suggestions on blade Mfg?

Thanks

You are correct about the gullet.

I only use the Industrial line from Freud or Forrest blades but there are many other blades both more expensive and cheaper that are fine. Scott Spencer posts a lot of information here especially about blades that are "bargains".

Since it is not a fence issue I would bet it is either the blade or your arbor bearings. I would either have the blade sharpened or get a new one. If you want a lot of good answers as to what blades to buy you may want to start a new thread, you will get lots of opinions, include a budget since it will help focus the replies.

[Brent Romero]

Thanks a bunch for the help....greatly appreciated.

Geaux Tigers....a true fan never strays.

[J.R. Rutter]

Once I began running the 2x4 through the saw

Ah. Probably the wood more than the blade - or that the blade did not stand up to the tension in the wood. 2x4s are a mess of uneven moisture and internal stresses.

[Tom Walz]

Saw blades have critical speeds. At the first critical speed the saw blade wobbles. At the second critical speed it wobbles two ways and this is often called “potato chipping”.

You sometimes see a saw blade go through a period of wobbling as it slows down.

Each saw blade has its own natural harmonic. If you hit them they all ring (or thump) with their own individual tone. Critical speeds are a multiplier of the natural frequency. If you remember science or physics class where you shook a rope and it formed a single arch then you have the idea. As you put more energy into it, it formed a double arch. And so on.

Saw blades are designed, built and tensioned to make them run straight and true at the recommended speeds.

Saw mill blades are often run between the second and third critical speeds. If your blade wobbles once as it slows down then you are cutting between the first and second critical speeds. If it has two wobbling cycles then you are between the second and third critical speeds.

The steel in saw blades loses its tension as it is used. After a while mill saws can no longer be retensioned. The same thing happens to all saws.

I would listen to the advice above before I go too excited about this but it could be the cause. Mostly it is just on my mind. I just solved a problem in this area. The mount a series of 24” and 30” saw blades under helicopters and use them to cut brush along power lines, roadways, etc. If the saws stay at a critical speed too long the whole machine can oscillate wildly.

[Jeff Duncan]

JR beat me to it.....I also think that the blade is flexing under load. As your cut releases the tension in the wood, the board is pushing itself away from the fence and into the blade. Try cutting some plywood, mdf, or particleboard and see if the saw still displays the same behavior....I'm guessing not.

If this is the case there's not much you can do to 'fix' it outside of not cutting unstable wood. Some blade stiffeners should help a little though.

good luck,
JeffD

[Van Huskey]

Tom, I will say it again I always love your posts.

Is it possible to bog the average 10" TS to the point of introducing harmonic oscillation? I would guess blade manufacturers would shoot for a harmonic not too far above the fastest 10" TS speed of what 4,400 rpm, to keep the next lower harmonic as far below the slowest 10" saws speed (maybe 3,800 rpm) as possible so that when slower saws begain to bog you would have as much headroom as possible above the harmonic frequency as possible?

[glenn bradley]

With the table saw running and without any wood being cut, the blade appears to the naked eye to run "true"....meaning it does not wobble or flex. Once I began running the 2x4 through the saw,

Ah, this may be a contributing factor. Many a story of kickback can be backtrailed to running a non-jointed face against the tablesaw and capturing the 'sure to wobble' material with the fence. If your 2x4's surface that you are resting on the table is bowed, curved, crooked, etc. it will not follow a consistent path. While the board wobbles in an attempt to keep the face to the table, many interesting things might happen. Bad cuts at best and kickback at worst. Let's be careful out there.

[Brent Romero]

Ah, this may be a contributing factor. Many a story of kickback can be backtrailed to running a non-jointed face against the tablesaw and capturing the 'sure to wobble' material with the fence. If your 2x4's surface that you are resting on the table is bowed, curved, crooked, etc. it will not follow a consistent path. While the board wobbles in an attempt to keep the face to the table, many interesting things might happen. Bad cuts at best and kickback at worst. Let's be careful out there.

Very good point. I am not sure about the rest of the country, but in my neck of the woods, not many 2x4s are straight these days. Could very well be the issue.

Thanks

[steven c newman]

Maybe also a little operator pressure causing the curve? Trying to rip too fast, op. places too much strain on the blade. If one can, push straight through. I can get an older, full kerf one to "wobble" by pressing the board as I try to "bull" through a cut. Either into the fence, or I'm back near the end, showing through, trying to keep against the fence. It's at a point just a bit short of kickback.

Try push through the cut by allowing the blade to do the cut, do not force things through.

[glenn bradley]

Very good point. I am not sure about the rest of the country, but in my neck of the woods, not many 2x4s are straight these days. Could very well be the issue.

Thanks

The perfect job for a bandsaw ;-)

[Bill Orbine]

Ah. Probably the wood more than the blade - or that the blade did not stand up to the tension in the wood. 2x4s are a mess of uneven moisture and internal stresses.

I'm inclined to agree with JR. I've experienced the blade flex with ripping 2x4 lumber materials.

[Chris Rosenberger]

I have an older Delta table saw and while ripping some #2 pine 2x4s the other day I noticed the blade actually flexed and yielded a curved cut.

Any insight as to what is going on there?

Many thanks in advance for the suggestions and comments.

I have had this happen in the past with some lower cost blades & it does cut a curved line. It is caused by the blade over heating. As soon as the blade cools it goes back to to running true.

[Tom Walz]

It could be but it seems unlikely. The problem is that we don't know anything about the blade.

My focus is on industrial problem solving and we just don't see many low, end 10" blades. In addtion we don't know much about the condition of this blade.

I think of the wobble problem as more of a high speed issue when the blade is in the material but that is based on big, thin saws in sawmills. You sometimes see low speed wobble when a 10" blade is slowing down after the motor has been shut off.

Jerrimy Snook, who posted above, is much more of an application expert than I am. I am materials and theory, especially carbide and brazing. He designs and builds saw blades. In my opinion he is one of the very best in the country. His is one of the very few shops we trust to build our custom blades with our advanced materials. Jerrimy built that "flat bottom groover blade" for Glenn Bradley that he likes so much. I know Glenn has Jerrimy working on another design for him as well.

Sorry, I got off track. There are some real experts here and I like to acknowledge them when I can. Besides, maybe I can embarass him into offering an opinion.


Tom

[Brent Romero]

Update:

They say the first step is admitting it....so, here it is:

I did a little maintenance on my saw this weekend and found that I had a contractor grade, stamped, 24 tooth blade....Geez, I am so embarrased. New Onsrud blades come in this week.