Ply blade and problems

Used a De Walt 3326 140T blade in a circular saw as I wanted a clean cut and the blade was new. Was I EVER wrong! Got about 3" into a cut in 3/4" multiply slab and the blade bound. Extracted the blade and second through fourth were equally exciting. Let the smoke clear and double checked alignment of blade with guide as blade was drifting away from the guide while smoking, not sure what it was using but it smoked! Next cut I just slowed down feed rate but no resolve. Could NOT extract the blade and saw from ply. Dismounted the saw from the blade, wedged the saw kerf and got the blade out with difficulty. Switched to the old 24T blade and made clean cuts.
I do NOT understand what was going wrong but obviously something was out of whack! Guess I'll reserve that blade for thin ply cuts only. Observations welcomed.
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snipped-for-privacy@vcoms.net wrote:

That blade appears to be hollow ground. If so you probably had it set too low and the fatter part near the arbor was binding in the kerf. Hollow ground blades especially need to be set so that the teeth just protrude through the material being cut.
Let us know.
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Thanks for the comments/observations! Teeth were barely exiting the ply. Labeled for ply. Had to use pliers to handle so it's dust, burned dust at that. The 24T Piranha finished the job nicely and will continue to be used. Using the Penn State Panel Cutting jig as guide.

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snipped-for-privacy@vcoms.net wrote:

I have the Piranaha in my saw and rarely take it out. Cuts surprisingly well and is cheap. I have no reason to try any other blade.
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Ray has hit on a possibility. Additionally most likely your 24 tooth blade is a carbide tipped blade. If this is true, a carbide blade leaves a kerf that is wider than the body of the blade. Most plywood blades have no carbide tips and the teeth have little to no set. The teeth cut little if no wider than the body of the blade. When the body of the blade comes in contact with the wood you get the results that you are having.
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I was gonna mention, and I'm sure this ain't the right place, that I set my 200 tooth ply blade backward to cut acrylic light shield, and immediately breezed through 2" ABS with perfect joints!
-
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snipped-for-privacy@vcoms.net wrote:

A couple of things I would suspect off the bat. First, cutting plywood with a steel blade that has 140 teeth. If you are not great (not just good) at cutting a straight line with a circular saw, this blade will be your undoing in 3/4" material. There is not enough clearance on the set of the teeth to allow for any wobble at all. You must use a long, straight guide of some sort for your rips, or you will do what you have done, and that is burn the blade. When you correct a tiny bit (just a tiny bit with a 140 tooth blade) to get back on your line, you throw the blade out of alignment, which causes the blade to rub instead of cut, making heat. Heat causes the blade to distort, making more rubbing action, and then finally a literal burning of wood. Since you are using a steel blade and you got it that hot, you have probably ruined that blade.
So you can guess the second. IMO, the 140T isn't a good choice in a circular saw. Too many teeth in contact at once with the material making it very unforgiving when sawing. They are OK at best for 1/4" ply, but no more. And with the resin glues that are used in today's plywoods, all those teeth making all that heat is a recipe for disaster.
OTOH, my experience with DeWalt blades hasn't been good either. They get the "close but no cigar" nod from me. Also, I am taking for granted that you are using a saw that has plenty of power for ripping.
When set up on a job that I need to knock out a quick cabinet, shelves, or anything that requires ripping sheet goods with my circ saw + guide, this is what is in my saw:
http://tinyurl.com/y8we3q
Been using these blades for years and have changed all of mine over to them for finish work. >When I use a guide<, I have seen cuts as smooth as most table saws. Now all my 16 - 24 tooth consumable blades that I buy on sale I use for framing, demo, etc.
Robert
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snipped-for-privacy@vcoms.net wrote:

Those 140T hollow-ground blades are better used for plastics or really thin materials. For 3/4" wood, I'd use a 40T carbide-tipped finish blade, like the Freud D0740X (available at Home Depot, if I remember right):
http://www.freud-tools.com/freuddiabfin.html
Also, using a saw guide is an immense help to get straight cuts with circular saws: http://benchnotes.com/Skillsaw%20Guide/skillsaw_cutting_guide_boa.htm or http://www.woodzone.com/tips/saw_guide.htm
Regards,
Mark
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On Mon, 08 Jan 2007 08:18:14 -0500, snipped-for-privacy@vcoms.net wrote:

Am I reading this right, 140 tooth?
That's an awful lot of teeth on a circular saw... The only time I've used a blade like that was for cutting wood panelling- which is very thin.
Freud makes a 40 tooth blade for fine cutting that works really nice on plywood, especially if you add a "zero clearance" hardboard foot to the bottom of the saw to prevent chipping.
But 140 teeth can't have much of a gullet at all- my guess would be that instead of tossing the sawdust out effectively, it is clogging and burning before it gets through that 3/4" plywood. Save that blade for panelling or cutting things like plexiglass.
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Prometheus wrote:

I might try that out ... what would be a good way to attach the hardboard to the saw's shoe?
Thanks in advance,
Mark
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redbelly wrote:

Double sided carpet tape always works for me. If you like it, you can make all permanenent with countersunk flat head machine screws.
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Polyu glue also works but difficult to reverse. Like double sided tape idea, thanks.
wrote:

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snipped-for-privacy@vcoms.net wrote:

All wood shops should have a roll on hand at all times. <G>
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B A R R Y wrote:

Barry, thanks. -- Mark
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In my case, I countersunk the holes in the hardboard and drilled and tapped a few holes in the shoe. If you don't want to go to that amount of trouble before you try it out, double-sided tape might work in a pinch, especially if you have a smooth shoe, and not one with the sawdust grooves in it.
Make sure that if you go with the drill and tap method, you make those countersinks deep enough that you don't scratch up the wood with the bolt heads.
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Prometheus wrote:

Thanks. I THINK I have a 10-32 tap in my set, if not then I'd probably go with 8-32.
At this point it's a low priority "something to try one of these days" item, but thank you for replying.
Mark
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