Even with a new Forrest WWII blade, I seem to get a modest amount of scorching when I mill cherry lumber to width before gluing up wider panels. The cut line feels and looks smooth, but minor scorch marks are definitely visible in places. (Does cherry scorch easily? I don’t have this problem with any other wood I’ve used so far.)
My real question, though, is this: will the scorch marks interfere with the integrity of the glue-up if I just ignore them? I’ve been removing them at the jointer, taking off about a 64th inch — but it occured to me to ask if I’m just wasting my time doing that.
Thanks!
-M.
Replies
Mark,
Cherry burns more than any other species with which I've worked. I found that it's less likely to happen if I keep the stock moving through the cutter or speeding up the feed rate if it continues to burn.
As far as your joint question, I don't know for sure but I can't imagine any reason it would weaken the joint. I've always jointed after ripping but I don't have one of those "jointer" TS blades either.
Good luck,
Kell
Packing tape on one surface will lubricate the blade and stop the burning.
Cherry does tend to be a burner. Besides feed rate, double check fence and splitter alignment. Combo blades more closely resemble cross cut blades, so there's more teeth in the kerf so there's more friction, they don't clear the chips as well when ripping so again more friction, and they require more feed pressure which makes it tougher to maintain a good feed rate. Get a good dedicated rip blade in the 24 to 40 tooth range (10"). If your saw has under 2 hp probably a thin kerf would be best, for 2hp and over a standard width tooth blade is more stable and will yield a cleaner cut. I have an FS Tools rip blade on a 3hp cabinet saw.
I suspect that burns don't glue as well because of the glazing. But as long as the burn is a small part of the overall surface in the joint it shouldn't make a difference in the finished joint.John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
I have a 3HP cabinet saw, and am using an 1/8" blade -- and you're right, it's a combo blade. I don't have a good quality dedicated ripping blade yet. I've added it to my shopping list.
Didn't occur to me that me feed rate might be too *low*. Hmm. I'll experiment with that notion.
In practical terms, taking the extra 45 seconds it takes to joint off the scorch marks on one board edge doesn't bother me at all -- I was just curious.
-M.
Oh yeah, slow is what burns! Think of those burns from router bits, they are always where you slowed down to get the surface just perfect, or you have a tricky part coming up ahead and stop and think about it!Edward
Agreed, 45 sec. for just 1 cut and trip to the jointer. But on the other hand you're burning more and more pitch on to that blade which is only making the problem worse so you get even more and more burning which is bad for the blade and makes it's crosscut performance suffer as well. I've never timed myself, but I can probably change blades in under 3 mins., unless I drop the !#$%* nut or washer.
BTW - DO NOT TRY THIS AT HOME! (Discalimer for the safety police) When I got my FS Tools rip blade I deliberately tried to stall my saw with 8/4 QSWO - I really had a tough time doing it. Also since I got a Makita LS1212 the amount of crosscutting I do on my TS has gone way down.John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
Burned wood glued to burned wood will not make a strong bond as there is no integrity to the charred surfaces. Jointing the board after you get scorch marks is definitely necessary. Cherry is high in sugar content and is prone to burning.
Mark,
You never indicated how thick your stock is and the tooth count on the blade..they have a bearing too on burn marks. I think your probably using a 40 tooth blade on 5/4 or 4/4 stock? that should be okay...but, (safety police are gonna get me for this) if you raise the blade up to 2" I'll bet that burning will disappear. Also, I think the burn marks will show up as gaps in your joint...
Dead right -- it was 4/4 stock with a 40-tooth WWII combo blade, raised to the traditional 1/4" above the stock.
I experimented on a piece of scrap in the shop tonight, using a higher feed rate than I normally use when ripping (and I also raised the blade up an inch or so more). Sure as heck -- the only scorch mark was at exactly the place I hesitated for a second to reposition my push stick. Tried it again without hesitating -- no scorch marks at all. Then I ran out of scrap to continue safe experimentation.
For me personally, I'm not completely comfortable with the feed rate I needed to keep from scorching. Even though I always use blade guard and splitter when ripping, I tend to slow down as my hands approach the blade area, just to make darn sure I know where fingers and thumbs are.
I think I'll just accept that a trip to the jointer will be needed when I rip cherry -- but it's been very useful to learn what was causing the scorching. Thanks to everybody for their comments and guidance.
-M.
Edited 10/14/2003 1:14:17 AM ET by MarkH
MarkH,
"For me personally, I'm not completely comfortable with the feed rate I needed to keep from scorching. Even though I always use blade guard and splitter when ripping, I tend to slow down as my hands approach the blade area, just to make darn sure I know where fingers and thumbs are."
FWIW, I haven't regretted a single moment spent building my various crosscut sleds and other tablesaw accessories that enable me to concentrate on things like my feed rate instead of worrying about snagging my thumb (Once 15 or so years ago was enough! Ouch!) in the blade. Properly designed and built jigs can help a great deal with safety-related issues as well as improving the quality of your work.
Invest the time today and you'll never regret it tomorrow.
Good luck,PaulWhether you think you can, or you think you can't, you're right.
I usually guage the dullness of my router bits by running a piece of cherry. If it burns, I know the bit is dull. Since sanding out burns is not my favorite thing to do, I make frequent trips to the sharpening shop.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)PlaneWood
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