Hmm, Table Saw is Burning

[Michael Peet]

Guys, I need your help. I have a fairly new table saw and I took the blade (WWII) off over the weekend for the first time so I could use a dado set. While I had it off, I cleaned it. After I re-installed it, I quickly double-checked the blade-to-miter-slot parallelism and it is still about .001" at random points all around the outside of the blade. Good to go, so I thought.

My first cut following the blade re-installation was a short piece of 4/4 ash, and the cut was horrible - saw marks and burning all along the cut. It had never done this before. So I spent all of this evening checking and tweaking everything I could think of:


I realigned the fence to the blade, I think, so it kicks out about .003" at the back of the saw.
The riving knife had never been completely aligned with the blade, so I took it all apart (I will never do that again) and shimmed it with some tape. Now I believe the knife is entirely within the saw kerf.
I inspected all 4 sides of every tooth, and scraped away any remaining gunk with a small piece of scrap wood.

After all this, my cuts are still looking like this:

147318147319

Most of the saw marks are gone, but it's still burning. At no point did I stop moving the board through the blade; I used as consistent a feed rate as I could manage. I can't imagine that it needs sharpening already - it has cut probably less than 200 feet of wood so far, mostly less than 4/4.

Any other suggestions are greatly appreciated. I have to make the Big Cut down the middle of my crosscut sled and I do not want to attempt it with this issue. I'm at the end of my wits and ideas. :confused:

Thanks!

Mike

[scott spencer]

Hi Mike (neighbor!) - Grabbing at straws....have you tried cutting anything besides the ash? How did you clean the blade? Be sure the throat insert stiff and not flexing. Double check that the riving knife is in line with the right side of the blade. You might try raising the blade height just a little more.

[Joe Chritz]

My first thought is reaction wood. Try cutting a piece of MDF (or two 3/4" pieces laminated to 1.5) and see if you get any marks or burns. It doesn't take much for the wood to pinch and get bad marks and burns.

If the MDF does it also I would clean the arbor flange and corresponding area on the blade. Make sure no gunk is there. Then start eliminating things one at a time.

Joe

[James Combs]

When I was putting the Flying Grizzly back together I had a similar problem but was seeing it in measurements. After trying a third blade I happened to notice a discoloration on the outside flange. Closer examination should it to be a partial blade of grass:eek:. I removed it and everything straightened up. Perhaps Joe is on to something. Make sure the flanges were not contaminated with something when you had them off.


My first thought is reaction wood. Try cutting a piece of MDF (or two 3/4" pieces laminated to 1.5) and see if you get any marks or burns. It doesn't take much for the wood to pinch and get bad marks and burns.

If the MDF does it also I would clean the arbor flange and corresponding area on the blade. Make sure no gunk is there. Then start eliminating things one at a time.

Joe

[Rick Markham]

James, I know you tried to chop a tree down with your tablesaw, but cutting the lawn with it too? :eek::D

You didn't happen to set the WWII down on your cast iron table did you? (I doubt ya did, but that's all I could think of for the rough cut) those little carbide tips are pretty easy to break off accidentally and very difficult (if not impossible) to discern with the naked eye. Just a thought. This thread reminds me it is time to clean my WWII ;)

[Glenn Vaughn]

Are you making the cut too slow? I have that problem with with cutting Coffetree - if I go too slow it burns. My tendency is to cut slower on harder wood and if I am not careful I get burn marks. I checked my fence alignment and it is with in .001" to the blade.

[Rick Moyer]

Just trying the obvious: You didn't put the blade on backwards did you?

[Michael Peet]

Thanks for all the ideas. In response to some of the questions -

Scott, nice to see another Rochestarian around these parts. I was trying some 1/2" poplar as I was checking things and had saw marks but not the burning.

I cleaned the blade with Boeshield Blade and Bit Cleaner. Sprayed it on, let it sit for a few minutes, then scrubbed each tooth with a rag. Maybe I wasn't doing that right. It took a long time.

I will double-check the riving knife alignment. When you say make sure it is in line with the right side of the blade, are you talking about the blade face or should it be in line with the outer edge of the teeth? I usually raise the blade so the top surface of the wood comes about halfway between the bottom of the gullets and the tips of the teeth. Should it be higher?

Joe, I don't have any MDF around; will 3/4" BB ply work for this test?

James, I was actually thinking of you while I was doing this. I thought man, if he can put that saw back together, surely I can get this thing to cut straight! I will take the blade off and check the flange. My assumption was that if the flange were contaminated it would show up as the blade being out of kilter with the miter slot. But I will double-check it.

Rick, nope, I didn't set the blade down on anything harder than the masonite surface of a nearby work table. Can that damage the teeth? I think I had read about a case here where a guy set his down on the saw top and chipped the tips off some of the teeth.

Glenn, I may be cutting too slow, it definitely seems slower than before. However, feeding any faster feels like I am forcing it and it also makes the teeth marks a lot worse.

Rick, the blade is on forwards :). It was the first thing I checked.

What do you folks think about a new blade? Am I correct in assuming that if a new blade cuts well it would rule out any setup issues with the saw and kind of point the finger at the old blade? Or does a new blade allow you to get away with more?

Thanks for the thoughts guys.

Mike

[scott spencer]

It doesn't sound like your cleaning method should've harmed anything...a stiff steel brush might be too aggressive, but brass, nylon, and cloth should all be fine.

[Rick Markham]

I don't think setting it down on masonite would break the tips of the teeth off, I always set mine down on a piece of cardboard to be safe. If you always set it down on the same side (I do just out of habit) it should be easy to tell only that side of the cut would be rough, while the other side would still be smooth. I suppose if you didn't set it down gently that there is a possiblity of some of the tips being damaged. Not sure if it would cause burning, but I suppose it would increase the coefficient of friction on that side.

Just a thought. is it burning on rip cuts or crosscuts, or both? If it is doing it on rip cuts, has the back of your fence come out of alignment binding that side slightly with that side of the blade? Which side is it burning? Is it both sides? I am grasping at straws but the location of the burn, the correlation of the "rough" cut, and whether you are ripping or crosscutting are all clues to what might be out of alignment or the "suspect" of the cause.

I hope you get it figured out, I am sure your frustrated, I would be.:(

[Michael MacDonald]

how straight is the cut? see my prior thread... I ended up getting a new blade... the original was somehow damaged. Could that be the problem? I used a 2x2 scrap to check the cut... flipped the cutoff to see how straight the cut was.

http://lumberjocks.com/topics/13985#reply-144976

don't know if it is kosher to post a LJ link here... probably some friendly rivalry, I would think. Note that I have contributed to SMC... not really posting on LJ anymore.

I also found that the pics are no longer available... didn't know that they downloaded each time from photobucket... I thought they were permanently put on the LJ site.

[Wayne Hendrix]

I usually raise the blade so the top surface of the wood comes about halfway between the bottom of the gullets and the tips of the teeth. Should it be higher?

I like to have the bottoms of the gullets just above the surface of the wood. I think it clears the chips more effectively and helps to eliminate friction between the wood and the blade.

[Jim Rimmer]

I'm not sure what the effect would be but I've read more than one thread here where people solved TS issues when they found the blade washer on backwards.

[Don Jarvie]

Take the riviting knife off and see what happens. If you have no burn marks, etc it may need to be setup again.

Also, make sure the blade is 90 degrees to the table. The wood may be getting jammed on the riviting knife if the blade is out.

[Chip Lindley]

Too-Slow feed rate in hard ash could well be the cause. Ash is prone to burn if you hesitate even a bit. Same with hard maple. Your burn marks appear at the end of the board where you may have hesitated momentarily. A 40T blade should stand a fairly rapid feed, so ramp it up a bit and see if results don't improve.

But it's a tradeoff. Increased feed rate may cause more noticable saw marks. I never expect a rip cut to be a finished edge, but your *bad* results are pretty close. A touch with a card scraper and the burn would be gone. OR, as-is, you still have a very acceptable glue-line joint.

In my experience, a dull blade is noticed not by burning, but by extra force needed to feed stock through it. Burnt-on resin is the biggest cause for burning, other than too-slow feed rate.

[Floyd Mah]

How about checking to see if the fence is straight and not slightly curved? I bought and installed the Delta fence for my contractor's saw many years ago when I discovered that the front bar that the fence was clamped to was curved. A curved fence would start out well until it directs the wood into the rear of the blade.

[Lee Schierer]

Okay, here's my shot at your problem. The saw worked fine before the dado cuts right. You checked the alignment at various points on the blade.

Here's what I would suggest. First take off the blade and make sure your arbor flange, sides of the blade and washer are clean, then check the belt tension. Dado blades are a lot of metal to swing and your belt may have worked in a little so it is now slightly loose. If the saw is bogging down you will get the burn marks. Tension the belt(s) Do a test cut.

If you still get burning, recheck your alignment of the blade to the miter slot with your dial indicator. Mark one spot on the blade with a magic marker (not on a tooth, but near the edge of the blade). Then raise your blade as high as it will go. Check the distance at the front of the blade and the back of the blade using the dot you placed on the blade. They should be exactly the same. If not adjust the alignment.

Personally I keep my fence exactly parallel to the miter slots and blade.

Finally, you may not want to hear this. Get a 24 tooth rip blade. Combination blades are a compromise when it comes to ripping and they don't cut as clean or as fast as dedicated rip blade will.

[Dave Hasson]

Finally, you may not want to hear this. Get a 24 tooth rip blade. Combination blades are a compromise when it comes to ripping and they don't cut as clean or as fast as dedicated rip blade will.

Let me second this comment by Lee. I had a 50 tooth Infinity Super General blade and kept getting the burning even though all my measurements were good. I bought a Freud glue line rip blade and the difference was night and day. No more burning and I didn't feel like I had to muscle the wood thru the blade.

[Brian Kincaid]

James, I know you tried to chop a tree down with your tablesaw, but cutting the lawn with it too?
Coffee into keyboard funny!

Are you running the thin kerf or full kerf? I always felt like the full kerf gave me the best cut, I even used a blade stabilizer on it though it probably was not needed.

You mentioned that the blade was fairly new, but I think I should mention a dull blade will burn wood (slow feed) or scratch (fast feed) no matter how well set up.

How many teeth did you check with your miter slot alignment? To do this right you have to measure from a single tooth in the front, then the same tooth in the back. Do several teeth this way to evaluate if the sawblade is flat.
Can you tell if pitch / burn marks are building up around a certain section of your saw blade?
These would indicate a warped saw blade.

-Brian

[mark mcconachie]

Maybe too obvious, but I wonder how many teeth you blade has?

For a short time, I thought 'more was better' but found that to only work with ... well, we'll let that one go. Anyway, if you are running a blade with too many teeth you could end up with lots of burn marks too.