Burning Cuts

[BasementDweller]

Hi all!

My BT3100 has a habbit of burning through wood about as much as cutting through it. I notice it most on longer rips. Yesterday and today i've been doing a lot of long rips on rough 4/4 red oak. And oak veneer ply. I rechecked all my alignment and don't see anything that is off. So I put the blade gaurd back on to see if the wood was crossing the blade in the back. . . Still burning.

Then I noticed something. On a long rip the board will move away from the back of the rip fence by about 3/8 of an inch!!!! How is this possible? I have the gaurd assembly on! I honestly am confused where that 3/8" is coming from, is the fence being somehow deflected over that far? I'm kinda lost on this one. Anyway, any ideas you guys can give me on what to check would be great. Here is a shot of some of the ply I cut and the burning:

http://www.teraflax.com/BT3%20Burning/

Thanks for any tips!

[onedash]

I dont know if the BT3 can but on my craftsman you have to adjust the splitter and make sure its alligned with the right side of the blade.Do you have anything supporting the wood on the outfeed side?

[LCHIEN]

This discussion a week ago, read it.

http://www.bt3central.com/showthread.php?t=26165&page=2&highlight=burn

[RodKirby]

Unless my (old) eyes deceive me, the riving knife is way out of alignment - needs to be moved to the right - centered immediately behind the blade...

[Greg.B]

If the knife is truely sitting like that, what is happening is it is contacting the cutoff piece (left of the blade) and pulling your board off the fence. Get that bad boy directly inline with the blade.

[Tom Slick]

what blade are you using?

[BasementDweller]

RodKirby: There is nothing installed behind the blade in those pictures. I think you are seeing down in to the place where the gaurd is installed. I should have taken a profile shot!

TomSlick: I'm using the blade that came with the saw. Unfortunitly I used the blade enough to rub off all the marking before I looked to see what it was/is.

Loring: I'll read it.


Let me know if you guys have any other ideas.

[padboy]

Time to resharpen your blade or get a new one, perhaps designed for ripping.
Just my 2cs. Good luck!

[Tom Slick]

with the plywood you should be ok with the original blade since there isn't really ripping or coss-cutting. I agree that your blade may be dull. increasing feed speed may help. are the cuts coming out straight?

[LCHIEN]

Looking mroe closely at the pcitures, there are some areas with very strong burn. Did you stop and readjust your hold at that point? Usually that kind of burn happens when you shift hands and let the wood stop moving and maybe come off the fence some. You have to plan you feed for a smooth steady feed and constant pressure towards the fence, to prevent burn, Then there's also the issues of alignment, cleanliness, sharpness etc. that everyone else has mentioned.

[Anna]

Hi,

For long rips, are you using a roller to support the outfeed? If you are, and the roller is not parallel to the table's edge (or, more accurately, not perpendicular to the blade) it will affect the direction of the board as it comes off the table.

As for the burning, I've been having that problem, too. My bt3100 is about half a year old, but it was burning my wood really badly. They probably looked as bad as, if not worse, than yours. I replaced the stock blade with a Forrest 40-tooth blade, and what a difference that's made. No burn marks at all, and it cuts like a hot knife through butter. Much quieter, too.

Anna

[Pappy]

Looks to me like a combination of erratic feed rate and pitch build up on the blade.

[cgallery]

In the photo Rod linked to above, it appears that the edge of the wood that is against the fence isn't straight. It is tapering away from the fence towards the back 1/2 to 1/3, but is flush against the front of the fence. Perhaps you don't have a straight edge to start with?

I would toss a straight edge (like a good level) on each edge opposite the burn (the fence edge of the wood) and check to make certain it is straight.

The fact that the burning happened in the middle seems to me to indicate that you had a concave edge riding the fence.

[SARGE..g-47]

Good morning...

And possibly all the above... Dull or gummed up blade (which ply will do quickly especially if it is very fresh and the glue hasn't cured completely).. feed rate which is an art with ply as you are ripping and cross-cutting at the same time with alternating layers running in opposite directions so the feed rate is sensitive.. and I certainly wouldn't over-look blade aligned to fence parallel as just mentioned.

And just when you think you got it figured out.. throw in the fact that I have run into ply (and I don't use it very often) that one or more of the layers might have contained compression wood that was dying to get released and stink up your day. Not high odds on that scenario, but still a consideration that has to be accounted for as you trouble-shoot starting with the most likely causes. Ain't WW fun? ha.. ha...

Regards...

[BasementDweller]

More data

OK thanks for the great info. I'm going to stand out on a limb and blame the blade... I guess you have to replace these things?? I cleaned it about two weeks ago, but it didn't really make any noticable difference.



Also I used the method suggested of magnets on a board with a nail to check if the rip fence is parallel to the blade. From what I can tell the back of the fence was a little away from the blade, maybe 1/8 inch. My fence isn't nearly as long as the guys that posted the howto, he must have had some kind of extension? Anyway, I corrected the 1/8 to as close to dead on as I could get. At least it wasn't pinching!

I also put my gaurd back on to check if it was centered. It isn't. I have some pictures of that too:

http://www.teraflax.com/BT3%20Burning/target8.html

But it is hard to get a photo of that. Mine is on the left of the blade and I understand it should be on the right. . .

Ok, so I need a new blade (wish WWII would go on sale) and I need to adjust the gaurd.