Troubleshooting Table-Saw Tearout

Blade sharpness is a bigger factor than you might think. May 10, 2005

I am using a Powermatic 66 to cut plywood and am getting more tear out than I would using a zero clearance insert and a Forrest Duraline HI-A/T blade. I am considering getting a Modulus scoring attachment. Can anyone advise how good or bad this attachment is? I do know that a slider would be a better choice, but I do not have the room or the budget for a slider at this time.

Forum Responses
From contributor J:
My first thought is before you buy anything else, revisit your setup. Sounds like either the fence, blade, or something is not set up right. Easiest thing is to check blade square to table. Next, is fence parallel to blade?

From the original questioner:
Tear out was virtually zero when the blade was new. While I have not been using the blade that long, I have done zero maintenance to it since it was new. Perhaps even a good cleaning would help. I probably need to buy a 2nd blade as well and get the first one sharpened. Forrest seems to imply that since it uses special C-4 super hard carbide, it should be sent to them for sharpening! Forrest also strongly recommends that you use their large dampener-stiffener for the smoothest cut.

But at almost $200 for a second Duraline blade and stiffener, I could spend $400 and get the Modulus for my saw instead. I am wondering if this would be a better choice. It seems likely that either the Modulus would work very well or it would be a big disappointment.

From contributor L:
Remove the blade, spray oven cleaner on it, scrub with a soft brush and rinse off. Replace the clean blade on your saw and see the results.

From contributor K:
You probably already know, but don't overlook blade height. Too low will sometimes lift a few splinters on the top, and too high will almost always mean more bottom splintering.

Also, make sure that the flanges on the arbor are clean. Sometimes I can get a little less run-out simply by loosening the blade and rotating the blade relative to the shaft and flanges until you find the sweetest spot. If you turn the saw on, then off, watch the blade as it winds down. Watch for the little side to side wobble just before it stops.

From contributor J:
Here is another thought. After you clean that blade and double check entire setup, I would buy a Freud plywood blade that is TFE coated. They are quite reasonable ($50ish). One problem I have had over the years (very seldom) is some blades are ground with very little side clearance, which gives a smooth, polished cut, which is one thing that Forrest likes to brag about. But what they don't tell you is that the blade has to rub the whole tooth, and this can tear on plywood faces. I only use Amana and Freud blades cost much less and I get great service.

From contributor M:
It seems like the topic of the Modulus comes up from time to time. You might want to check the Knowledge Base for previous comments. As best I can recall, it gets negative reviews. Along with the comments above, you might want to see if your insert is fresh. After a while, the front edge of the insert gets worn away and less effective.

From contributor R:
I checked out the Modulus years ago. I heard they're more trouble than they're worth. I'd check out your saw - it might need tuned up. As well, you can adjust the blade height. The higher the blade, the better the cut on the top, but worse on the bottom. Raise and lower till you get decent cuts top and bottom. You should also have 2-3 blades of every type.

From contributor A:
I use Forrest Duraline blades and they are very good, but you will need to sharpen them more often than you might think, especially if you are cutting composites and melamine.

From contributor I:
I use Freud blades with good results. As mentioned by others, you'd be surprised how often you need to sharpen even a good blade. One or two large projects and I have a blade resharpened. Makes a big difference.

From contributor N:
I have been using a Modulus for about five years now. There is a new and maybe improved version where the scoring unit uses shims now, so it's more adjustable. I'm basing my experience here on the first version.

When I first got it, I thought it was terrific until it came time to remove the blades to get sharpened. That's when the honeymoon ended. When I called the manufacturer, I found out that a special kit is needed to remove the scoring blade. (Plus a lot of screwing around till you figure some things out yourself.) I use it for cutting small parts on my Unisaw. I adjust the scoring blade to get a perfect no-chip cut on one side of a pass. The other side leaves a slight ridge. Honestly, I'd give the thing a C+ or B grade. It has some merit depending on your situation. I cut my large panels on a vertical saw.

From contributor E:
When I was using my Powermatic, I also used the Forrest Duraline and had very good results on melamine, but it only cuts about 20 sheets of melamine before re-sharpening. When I used it on real plywood, tear-out was virtually nil. A zero clearance insert helps a lot. You gotta spring for at least another blade, though, so you always have a good one ready. I suspect your fence isn't square to the blade, but I would also check the blade against the table first. One of those Master Plate rigs with the run-out gauge is very accurate and could be a worthwhile investment.

From the original questioner:
I really appreciate all of the responses. My saw is aligned correctly and that certainly is not the problem. As stated, I had virtually zero tear out when the blade was new.

I will purchase another Duraline and once I get it in, I will send the original to Forrest to be sharpened. Depending on turnaround time, I will buy more if needed.

Do others generally send theirs to Forrest for sharpening or have you had good luck using others?

From contributor W:
Use Forrest for the sharpening. I found out the hard way that a local sharpener is just not the same. Forrest will sharpen and tune any brand of blade. The price is not that much more. They use CNC sharpening equipment and the polishing grits run up to 1200 grit for a mirror smooth finish. It makes a huge difference when crosscutting ply or for melamine blades. For a small fee they will also do a test cut with your blade and adjust it if necessary. This is a good idea if you are making critical cuts.

From contributor A:
I have used Forrest as a sharpening service for many years with good results. I recently tried the sharpening service at Bull Sharpening and had good results. Turnaround was about the same for both companies.

From contributor G:
I too strongly recommend using Forrest to sharpen their own blades… But one thing I haven't noticed on this thread yet: is their Hi ATB blade a positive or negative hook angle? Negative hooks impressively decrease the tearout. I have a great Amana 10" blade that is negative hook. I can cross cut pre-finished maple ply on it with no tearout with a good zero clearance insert (when I cut this insert, I cut it only as high as I need for 3/4 inch panels, and every time I use it, I set the blade to that exact height - it helps a lot). But I can get about 5 kitchens worth of boxes out of that blade before re-sharpening (with plywood, not melamine).

From contributor T:
I think contributor L had it. I clean my blades often and a sure sign that I waited too long is tearout on the bottom side. Think about it. That extra glob of goo comes flying through the kerf and just pulls on that 1/10000000" thick veneer. I use oven cleaner too. Leave it for 5 minutes, run over the teeth with a brass bristle brush, wash, spray with WD40, dry with paper towel - good as new. Alignment is always good to check too, though.

From the original questioner:
I ordered a second blade and the cut is once again perfect. In fact, it is such a sharp edge that you probably could cut yourself on the cut edge! I have not cleaned the old blade as recommended, but I will send it to Forrest for sharpening and hope that they will clean it as well!

I have heard that oven cleaner is a bad choice. I believe it reacts with the carbide or something. Seems like Fine Woodworking did a article on blade cleaners not so long ago. Seems oven cleaner did not work as well as most of the other products, either. Thanks for all the replies - it really helped point me in the right direction.