Saw blade run-out

[Mark T]

I've been dialing in the table saw, and have come across an "issue".

I measured the run-out of the spindle- 1/2 a thou
I measured the run-out of the blade backing washer- about the same.
I measured the run-out of an installed blade (brand new, B&D, full kerf, plywood tooth count)- 12 thou at the outer diameter.

Essentially, the blade is warped to beat hell. New, never used.

So I put on another blade (Erwin, used, carbide, 40TPI, thin kerf). !5 thou at outside diameter.

OK, so I can see a thin kerf, used blade being a bit out of whack, but I HATE that maybe all blades in my price range might be *junk*. I cannot, or will not afford hundred dollar blades. And I don't know that they wouldn't be warped anyway.

Am I just looking for trouble here? Should I throw the dial indicator in the trash (yeah, sure)? I am not experiencing bad cuts, per se, but I'm always looking for a smoother edge... again, in my price range.

Debate away.

[brburns]

5 thou is about what I would expect with 0.0005 at the arbor. 0.0005 at the 1" out will translate to 0.005 at 10" That shouldn't cause you any issues.

the other one, you could try to rotate the blade 180 degrees in relation to the arbor and see it that helps. I would probably stay away from the B&D blades.

[sawduster]

Keep in mind that 1/128th" = .0078125". Five thousandths is miniscule and I would worry about it.

[dcarter636]

I expect high dollar blade plates to only be flat within .004" TIR @ 9" diameter. That ain't easy to do and cheaper blades will tend to be more potoato chippy. The thing is, wavier blades tend to change shape at full speed anyway so don't waste your energy worrying about them if you can't justify $40-$100 for a 10" blade. The only practical effects of wavy blades is more operating noise and a minutely wider kerf.

The reason all reliable table saw alignment rituals specify that you mark a single spot on the blade and rotate the blade to use that single spot for all alignment meassurements is to eliminate the perturbations of blade waviness from your measurements.

So really, why are you fretting about wavyness?

[Ruffnek]

I have a dial indicator but I've never measured arbor or blade runout. If I can't visibly see the blade wobble and don't experience poor cuts, I'm not concerned about it.

[sachbvn]

Are you having issues with poor cuts? If not - I wouldn't make your life difficult over a TS blade.

Zac

[Leo Voisine]

I am going to go along the lines of what Cody said.

It is really not going to matter all that much - unless of course you are getting a cut so bad that it is causing you trouble.

One thing you did not mention was side play. Does the blade move sideways?

You said you saw which about 1/64 of an inch. OK - so is it causing a bad cut?

One thing you could do -- is to push against the blade in the opposite direction - and "band" it into conformance. That's a completely legit thing to do.

There is a point where - you get what you paid for - and a point where you pay too much for too little.

I am gonna get beat up here - but back at ww.com there was a LOT of discussion about the Woodworker II blade. I am not a wwII supporter. One of the discussions was about a member that bought one and found it to run out - called the factory - returned it - and got another bent blade. It convinced me - that the wwII is no better than any other premium blade.

However, I will say, that my Freud bladea at around 50-60 make superior cuts.

I will also say - I have never put an indicator on my saw to check runout. I might tonight - just out of curiosity.

.015 "sounds like a lot - but the proof is in the cut. Irwin is an OK construction grade blade - but Freud is a lot better.

I have used a Irwin 7-1/2 blade on my table saw - because it was so thin -- I got an unbelievable great cut. But it was a premium Irwin blade.

-------------------------------------------------------------------

OK - I just measured mine
1/8 kerf
Freud Glue Line Rip
New - 1-2 weeks old
Runout = .002/.003

-------------------------------------------------------------------

So -- find the high spot and bend the blade into conformance.

[TDHofstetter]

Yeah, I think you may be getting overly excited. You can improve it, if you like, though... before you do ANYTHING ELSE, take the blade off and inspect the arbor washers. What's the runout there? CLEAN them. WELL. Put the blade on, snug it down, gauge it. If you don't like what you see, rotate it 90 degrees on the arbor & gauge it again. If that's an improvement, rotate it another 90. If not, rotate it 180. Gauge again. Every time you see it getting worse, rotate it forward or back to a better spot.

When you've found the "sweet spot" for that blade on that arbor, mark the arbor & blade together so you can repeat that position. When you change blades, find that blade's "sweet spot" and mark the blade to match the arbor mark.

Mostly, though... runout like that won't have any notable effect on the accuracy of the saw. What it MAY do is give you a slightly rougher cut than it might. I doubt I'd fret about it a lot. Heck, I've run saws with blades wobbling pretty badly & not been unhappy with the cuts I got.

Chances are very good that your technique makes more difference in the cut than that runout will.

[sawduster]

There was an article on the internet that I stumbled across some time back where a fella sent another brand of blade (Systematic, I think) off to the folks who make the WWII, along with a WWII blade, for sharpening. When he got them back, he could find no difference in the cuts the blades made. One of the things they do at Forrest when they sharpen blades is to go to a much finer final grit for the sharpening, and he was convinced that that was the difference that made the WWII make such clean cuts. I'm pretty convince of that myself since it is something that I do with my hand tool blades, take the edge to a very fine (8000 grit) stone.

The bottom line, though, is the cut you are getting with the entire set-up. Barring a bent tooth or something similar, most rough cuts translate to an alignment issue of either the rip fence or the miter gauge or, most likely, both. This is especially the case if the rip fence is aligned to the miter gauge slots, which is a common method of alignment.

I've gone over this a few times before over at the other place, but it bears repeating. There is a common misconception that the angle of the miter gauge to the blade determines the angle of cut. Fact is, the angle of the cut is determined by the angle of the face of the gauge to the bar on the gauge. Now, if your miter slot is dead on the money parallel to the blade, then setting the gauge square (or at any given angle) to the blade will give you a cut at the angle set. If the blade is set dead on parallel to the miter slot, then setting the angle to the blade will also result in the gauge face being set dead on to the bar on the gauge. But if the blade and slot are off by any amount, then the resulting cut will be at the angle of the gauge face to the bar. But, even if the blade and slot are off a bit, if you set the angle between the gauge face and the bar, then the angle of the cut will be correct. If the slot and blade are off far enough, the angle will be right, but the quality of the cut will suffer.

To demonstrate this, I did a SketchUp drawing of a table saw top and intentionally set the angle of the blade to the slot off by two degrees. I then "adjusted" the face of the miter gauge square to the blade, added a "board", and locking movement parallel to the miter slot, moved the gauge and board so that it the leading edge just touched the near edge of the blade and marked both sides of the kerf onto the board. I then continued moving the gauge/board to the point where the board was exiting the cut and again marked the edges of the kerf. By connecting those points across the board, the resulting cut was determined as in the drawing below.


The outer lines show the final cut, with the area between them being the kerf. As noted in the drawing, one side of the cut was 92 degrees to the edge of the board, while the other was 88 degrees.

Repeating the same process, but with the gauge face set to the miter bar, the below drawing shows the result.


Note that, while the kerf is still basically the same width, the cut is 90 degrees to the edge of the board.

The slot being off from the blade will manifest itself as a rough cut because the blade will be "twisted" in the cut and instead of the edges of the teeth making a smooth cut, the corners of the teeth will leave a rough edge, but the cut will be at the angle of the gauge face to the bar.

[Mark T]

This is not a tragedy for by any means, and I'm not losing sleep over it. I was just cleaning things up and, being a machinist wannabe with a bunch of cool dials and do-dads, thought I'd run the dial on it. I was just surprised that it was as much as it was.

No, I am not getting bad cuts, no burning, no binding. I really only wanted to know if a zillion dollar blade would run much, if any truer than a medium grade blade. I have no zillion dollar blades to compare the two.

I do know for a fact that the blades form some of the Chinese outlets are horrible, to the point that you can see them deform. Some of them will even almost shake the saw across the floor. I made this mistake a long time ago. Ended up making .22 caliber spinner targets from three of them (that was kinda fun). They make a wonderful ring when hit by a 22.

All is well in the shop.

Cheers,
Mark

[sawduster]

Mark,
Over the last few years I have been quite amazed at how well even some of the lower priced name brand (or secondary brand name) blades now perform. Part of it is that most are thin kerf which, under normal circumstances, work very well. In many cases, the main difference between these $30 range blades and those costing 2 or 3 times as much, is the thickness and grain size of the carbide. They can not be sharpened as many times as some more expensive blades, and the sharpening will not result in as fine a cut as you would expect from the more expensive blades, but at their initial cost, it is almost a wash as to sending them out for sharpening as it is to just buy a new one.

I've a friend who swears by the Freud Diablo blades, which are fairly inexpensive and not worth getting resharpened. Cleaning the crud off of a seemingly dull blade often brings back a very nice cutting blade, so that is my first step when ever I have a blade that starts lacking in performance.

Your initial post brought out a very interesting and informative bunch of responses, and that is always a good thing and the real reason most of us are here.

[rrich]

I've been lurking in this thread.

There are a lot of very interesting comments. Perhaps it is time for me to add my 22¢ to the discussion.

If the blade is giving a good cut, what difference does the runout make? Think of a wobbler dado. The wobbler could be said to have .750" runout.

If it were my blade and my saw, I would have never bothered to check the runout unless the cut was bad.

[Mark T]

Rich, I haver never been one to leave well enough alone. I am extremely inquisitive, and machines are my weak point- any machine. I constantly play with things to either alter their action, improve their operation, or, well, just mess around with them.

I machined several new parts for my old Walker Turner stationary belt sander, just to make the belt ride a LITTLE BIT better. There was no reason to really do so, but I did it anyway.

Just seemed like fun to dial the saw while tuning it up... and it was. I learned a lot from doing it, and I learned a lot from posting the results here.

I am a professional tinkerer. Thats all.

Cheers,
Mark

[Leo Voisine]

Jan 28, 2010 6:00:32 GMT -6 Mark T said:

Rich, I haver never been one to leave well enough alone. I am extremely inquisitive, and machines are my weak point- any machine. I constantly play with things to either alter their action, improve their operation, or, well, just mess around with them.

I machined several new parts for my old Walker Turner stationary belt sander, just to make the belt ride a LITTLE BIT better. There was no reason to really do so, but I did it anyway.

Just seemed like fun to dial the saw while tuning it up... and it was. I learned a lot from doing it, and I learned a lot from posting the results here.

I am a professional tinkerer. Thats all.

Cheers,
Mark

Ain't nuttin wrong with any of that. After all - a hobby is all about the enjoyment of that hobby. I have always said - enjoying woodworking, can be manifest itself in many ways. For some - it's collecting tools and tinkering with them - for others, it's building benches for the shop - for others it's building furniture - and others might make bird houses - yet others might just like hanging around and watching the action.

In a football game - there are the players - coaches - parking lot attendants - concession stand people - announcers - and spectators. ALL - are enjoying the game - and ALL - are needed for the game to succeed.