Why is my rip cut burning?

[Tom Jones III]

I'm using a PM66 with a Freud glue line rip, full 1/8" kerf, recently sharpened and fairly clean. The fence is toed out just a hair. The blade is as parallel to the miter slot as my dial indicator can measure. Runout is minimal. The wood in the pictures is african mahogany 1 5/8" tall, but the same type of burning happens on walnut, oak and maple. Blade height on this cut is 1/2 a tooth higher than the wood, and the same burning happens when the blade height is 1/2 the gullet.

This seems like it has to be operator error, but I'm not sure what it is. Possibly inconsistent feed rate?

FYI, the piece with the burn on the right/top is the piece I want, the wood on the left/bottom is waste and has no burning.

[Jim Becker]

Is your splitter aligned properly? Are you sure that the fence is toed out? Burn on the right (between the fence and the blade) suggests pinching as the material exits the back of the blade. Does it happen with every piece of wood, or just this one? (internal stress could be bowing the board back into the blade) Etc.

[Doug Jones]

Possible solution, realign your fence and blade to the miter slot.

[Mark Singer]

Try a medium feed rate ....not to fast and not to slow....and as constant as possible...

[Kent Parker]

Check your belt tension

[Steven Wilson]

I would check the splitter alignment. Don't just check the alignment at the table but also a bit off the table as well. If the splitter is off at all it can cause burning. I would also check the fence face, is it square to the table? How flat is the fence face? You may need to shim the fence face to even it out.

[Bob Powers]

I have a Freud LM74 30 tooth rip blade that burns most everything. I complained to Freud about it and they replaced the original, but I have the same problem with the replacement. I have checked all the adjustments that might cause this but have no answer. I have a number of other blades, including a combination blade from Freud, and don't have the problem with any of them. It's not that I never have a burn, such as in cherry, but I can always attribute it to improper feed rate with blades other than the LM74.

[Lee Schierer]

The fence is toed out just a hair. The blade is as parallel to the miter slot as my dial indicator can measure. Runout is minimal. The wood in the pictures is african mahogany 1 5/8" tall, but the same type of

I am assuming the ticker piece was against the fence.

I would recheck the alignment. I found that having the fence exactly parallel to the miter gage slot worked best. Make sure your miter gage fits snugly without slop in the miter slot.

Since you have a dial indicator, you can use the method I used for alignment. Mount a block of wood to the face of the miter gage. Attach the dial indicator to this block so it can reach the blade. Raise the blade to full height and back off one full turn of the handle. This insures that you are not binding the saw carriage against the structure of the saw. Select a tooth and mark it with a magic marker. Place the tip of the dial indicator agains the saw blade metal, not the carbide tip on that tooth at the front of the throat opening. Take a reading. Rotate that tooth to the back of the throat opening and take a second reading. Adjust the carriage until the reading is as close to the exact same reading as you can get it. After you tighten everything up take a second set of readings to insure nothing moved.

Then lower your blade, slide the fence over so the tip of the dial indicator rests on the side of the fence near the front edge of the table. (Do this using the same miter slot, as some miter slots are not parallel to each other) Then lock your fence in place. Slowly slide the miter gage across the table watching the dial indicator. If the reading varies more than .001 either way adjust your fence. Watch for any variations between the front and back edge of the table. These can cause burning. It may be necessary to adjust the face boards on your fence with shims to get them truly flat.

Once you are satisfied with your fence alignment to the miter gage, unlock the fence move it a fraction of an inch and recheck the alignment.

One last thing. Your sharpening service may have made the teeth too narrow if they sharpened the sides. If the teeth are not a bit wider than the saw disk then burning will occur. The teeth should over hang about the same amount on each side of the blade.

[Bill Simmeth]

My vote is for inproper feed rate/angle. Looking at your picture, there are three primary burn points. The first is at the start of the cut. The piece may have been slightly askew, or you were feeding very slowly to get the piece aligned correctly (understandable given its length). The second point looks to me to be right about where the blade was when the piece met the router table you used for the outfeed. This probably caused some shift in the feed angle (and you may have been a bit distracted in feeding). The third area is toward the end. Given the narrowness of the piece, I'm guessing (hoping) you were swtiching to a push stick and that again altered the feed rate.

If you don't usually have burn problems with smaller workpieces, I think this would be the explanation...

[Charles McCracken]

I have a Freud LM74 30 tooth rip blade that burns most everything. I complained to Freud about it and they replaced the original, but I have the same problem with the replacement. I have checked all the adjustments that might cause this but have no answer. I have a number of other blades, including a combination blade from Freud, and don't have the problem with any of them. It's not that I never have a burn, such as in cherry, but I can always attribute it to improper feed rate with blades other than the LM74.


The LM74 GLR is unusual in that it has very low side relief angles so it can burnish as it cuts. The drawback to this is that it is not as forgiving to the setup as the LM72 rip or the combo blades. If the original and replacement blades both burn the wood then I am pretty confident that realignment will solve it.

Charles M
Freud America, Inc.

[Scott Coffelt]

Make sure you have a full tank of gas and the oil has been changed lately. Why, dunno, but everyone else's answers seemed good, so I had nothing to add.

Oh, try another blade to be sure the one you have is actually sharpened right, it does happen from time to time.

[Frank Chaffee]

The LM74 GLR is unusual in that it has very low side relief angles so it can burnish as it cuts. The drawback to this is that it is not as forgiving to the setup as the LM72 rip or the combo blades. If the original and replacement blades both burn the wood then I am pretty confident that realignment will solve it.

Charles M
Freud America, Inc.

Charles,
Will you please be more explicit as to optimum alignment?

Thanks, Frank

[CPeter James]

I use an oak splitter .130" in width with my .125" blades. This is centered on the blade and the fence is parallel to the blade. This gives a little "push" into the fence and keeps the wood from dragging on the blade. I use almost exclusively oak and pine and don't have a burning problem. I use a Forrest WWII, a Ridge Carbide TS2000, and a Freud glue line rip blade, all with good results.

CPeter

[Tim Sproul]

I don't know about anyone else.....but I've NEVER rip sawn a plank in half and NOT had it move on me. Especially such a long stick like that. Granted, I've probably only worked a couple thousand board feet of lumber so my experience is quite limited.

The temp at which wood will show burn marks depends on the wood....perhaps african mahogany is more easily burnt than other species. I have little experience with it.

Blade cleanliness is also important for burning. The more crud and gunk that is already burned onto the teeth, the more easily burned is the plank being rip sawn.

[Charles McCracken]

Frank,

The ideal alignment for ripping would have the fence exactly parallel to the blade and a splitter/riving knife that is only a few thousandths narrower than the kerf width. Since it is impossible for the fence to be "exactly" parallel it is best to err on the side of caution and toe out very slightly to avoid pinching.

The OPs's pics appear to show a problem with feed rather than alignment. IMO, the feather board is a little closer to the blade than I would place it and hold down(s) would be beneficial.

Charles M
Freud America, Inc.

[Tom Jones III]

Thanks for the suggestions. I double checked the splitter, it was not quite straight but very close. The rest of the settings are as accurate as possible with the given tools and material. The fence material is not very flat, I am going to have to consider working on that, however, at no point does the fence get closer to the blade than at the beginning of the cut.

I thought that a feather board should end just before the blade begins. Where do you put your feather board?

Initially I was suspicious of operator error and I am more confident of that now. I think Sherlock Simmeth was exactly correct with the exception that the middle burn may have been when I readjusted my hands after pushing the initial length through. Yes, the last burn must have been when I grabbed the push stick to finish the cut.

About ripping the mahogany, it just does not seem to move. Of all the different woods I've ever used, mahogany has got to be the most stable. I milled up a bunch of pieces leaving them all a little over sized. I let them sit for a while and checked them carefully. They had not moved at all.

[Travis Porter]

I like working with Mahogany and to your point it is very stable, but I have burned the fool out of it as well. My issue was the fence too far in and since them, the issues have been operator error.

[glenn bradley]

I've got the opposite problem. My Freud cuts fine, switch to my WWII and I burn (granted were talking red oak here). You swapped your blade and the problem persists so I'm not sure whether to contact Forrest or not. All Frueds and Amana's work fine, WWII burns ;-(

I'm thinkin' the blade got whacked during shipping or something. Too many respected members here sing the WWII's praises. As in most of my problem situations, I never rule out the most probable answer . . . its ME!

[Bill Esposito]

Charles, for 1-5/8" thick wood wouldn't the correct blade to use be the LM72? Or have you changed the recommended wood thickness for the LM74?

I posted a similar response in the "Need RIP Blade TODAY!" post regarding the same blade and thick stock.

[Charles McCracken]

Bill,

1-5/8" is about the top end of the range suited for the LM74. In the case of this thread the blade was only burning one side of the material so it showed that it can cut the material without burning and therefore it technically wasn't a matter of the blade being incorrect. However, the characteristics of that blade may have amplified the results and had he been using the LM72 there may have been little or no burning evident.

[Maurice Ungaro]

I've found that even with proper alignment, etc., I can get burning when the blade is not cleaned & sharpened. Try some CMT Blade & Bit cleaner. After that, have the blade professionally sharpened.

[Tom Jones III]

Just to clear things up about the original problem with this thread, even though I was ripping a very long board and thicker than the blade was intended for the cause of the burn was operator error and bad setup on the saw.

Since the board was so long I had a hard time getting the rip started cleanly so I burned it when I bobbled the board to get the cut started. The next burn was when I had to move my hand back to push more of the board through. The final burn was when I paused to pick up the push stick to finish the cut. Every burn was due to my poor technique.

Finally, I went back and checked out the setup again. The fence was angled in towards the blade a tiny amount. The only reason why it worked at all was the splitter kept it from kicking back.

I still recommend the Freud rip blades because despite my poor technique and bad saw setup most of my cuts went fine. Even this problem cut worked fine, I just had to do more sanding than I would have liked.

[Rick Christopherson]

I have observed that woodworkers get far too hung up on blade alignment as the primary cause of burning that they don't look much further.

Your blade-to-fence alignment can be off by a pretty significant amount without burning. The difference between the width of the teeth and the plate of the blade is large enough that you will get rough cuts, but not so much with burning.

The thing that everyone overlooked was your blade height. I could see from the radius of the burn marks that your blade was just barely over the top of the workpiece. This is the number one reason why you are burning, especially with such a thick rip. African Mahogany cuts fairly nicely, at least compared to other species such as cherry. When you raise your blade you will find that the wood does not burn, and it will be easier to feed the stock.

[Jesse Cloud]

I hate cutting long boards on a tablesaw. I would cut this guy 1/32 proud on a bandsaw and then joint it smooth in one pass.

[Nissim Avrahami]

Hi Tom

I’m only a small amateur, but maybe you can get better results if you make the roller feather board as in this post
http://www.sawmillcreek.org/showthread.php?t=40713

You can make it to fit your miter slot.
It has a big holding span and pushes the work to the fence and down to the table so the first feeding into the blade is more stable.

Just one note; the aft roller should not extend beyond the beginning of your fence.

I'm adding the first pic of the post.

Regards
niki

http://i50.photobucket.com/albums/f321/avrahami/Roller%20new/RN01A.jpg

[Rob Diz]

I had the same problem with my Uni, a high end Lietz blade, and cherry. Just couldn't figure it out. Spent a ton of time and money on measuring devices and beating my head on the wall.

For me, it was a two part issue. First, human error. I needed to make sure my pressure was even and in the right places. Second, when I was removing the factory splitter to install the snap in splitter I noted that the splitter was worn on the inside edge. I have alligned the new splitter properly, and no uneven wear patterns have been noted.

HTH.

[Howard Acheson]

>> Freud glue line rip, full 1/8" kerf, recently sharpened and fairly clean.

Is that the 30 tooth or the 24 tooth blade?

The 30 tooth should not be used for more than 1". The 24 tooth is good up to about 2 1/2" or so.

Are you sure it was sharpened well? Does it cut other thick woods cleanly?

It seems from the pictures that a run through your planer should clean the boards up.

[Tom Jones III]

I think it was the 24 tooth but I'm not certain since I'm not at home. I am certain that the burning was due to 2 causes, the fence was certainly angled towards the back of the blade and I certainly used poor technique. After adjusting the fence properly the very same blade does not burn anything all the way up to max cutting depth.

[Chris Padilla]

Tom,

Not trying to beat a dead horse here but assuming alignments and everything are reasonable, blade is sharp and clean, any burning problems I've had was due to too slow of a feed rate. The blade spins too much in one spot and heats up the wood.

At all the points of burning, your feed rate is different (i.e. slower) that at all the other points of non-burning.

You may not have the space, money, or interest in a bandsaw but I've found new life in using my bandsaw to rip wood instead of the TS. Plus, the BS is much less scarier than the TS IMO! :)