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6/6/2007

Combination Saw Blades


Combination Saw Blades
1/1/1996

(Note: This tool review was published in ShopNotes No. 25, January 1996.)

We have several speciality blades for the table saw in our shop. But the one that gets used day in day out isn't a specialty blade at all -- it's a combination saw blade.

Basically, it's designed to make a number of different kinds of cuts without changing blades. So you can rip a board one minute, crosscut (or miter it) the next, and still get good results.

TEETH. What makes this work is the design of the teeth. Not so much in how they're arranged (in groups of five), but the shape of the teeth in each group.

For ripping, each group has one flat-topped tooth (raker) with a deep gullet in front for removing chips quickly. And to make smooth crosscuts, the four other teeth in the group are angled (beveled) across the top in alternating directions.

Okay, so it does a good job of ripping and crosscutting. But which combination blade does the best job of both?

TEST. To find out, we tested six 10" industrial quality blades, see table below. When selecting blades to test, we also noticed several "general purpose" blades as well (the teeth are evenly spaced, and there are no raker teeth). So we decided to test two of them as well.

CMT 110-500 $62.90 800-531-5559
Delta 35-617 $49.95 800-223-7278
Freud LU 84-10 $49.95 800-334-4107
Oldham C3470 $44.95 800-828-9000
Sears 932035 $69.99 800-290-1245
SystiMatic $59.95 800-426-0000
General Purpose Blades
DeWalt 3213 $45.00 800-433-9258
Forrest Woodworker II $119.95 800-733-7111

TEAM. As with our other tool reviews, we rounded up our team of three woodworkers to test the blades. Once again, to provide a wide range of viewpoints, each person has a different level of woodworking experience.

So the best blade for a professional cabinetmaker like Ken may not be the one that Cary, a beginning woodworker, chooses. And an advanced woodworker like Steve may pick a different blade altogether.

PROCEDURES. While the final selections may vary, the test procedures were identical. The same contractor-style table saw was used throughout the test. (Using a dial gauge, we measured the runout of the saw at .0005".) And the same type and number of cuts were made in hardwood, plywood, and particleboard.

Q: Before making a single cut, you had a good chance to check out the blades. What do you look for in a quality blade?

Ken: As a rule, the thicker the carbide, the more resharpenings I'm going to get. Of the blades we tested, I liked the hefty carbide tips on the Freud and SystiMatic.

Steve: Another thing I check is how securely the carbide tips are attached. After all, with a blade whirling around at 100 mph and carbide tips slamming into a chunks of hardwood, something's going to give. Hopefully, it's the wood -- not the carbide tips.

To make sure they stay put, they're brazed into "pockets" machined in the teeth. What I look for is a smooth, even bead without any pinholes.

Q: Anything else about these blades that jumped out at you?

Cary: The outer rim of the blades appeared to be etched. At first I thought I thought it was to help keep the blade from getting gunked up with pitch and resin. But I called a technician at one of the companies and learned that it's more cosmetic than anything else.

The same is true for the "ring" on the body of the SystiMatic and Freud blades. The ring is what's left behind when the blade is tensioned to ensure that it stays flat.

Q: So why doesn't the ring show up on the other blades?

Cary: It depends on what stage of the manufacturing process the tensioning is done. On the blades where you can't see the ring, the final grinding of the body is done after the tensioning. And this grinding removes the ring.

Performance
Q: I'd expect all these saw blades to perform pretty well right out of the box. So how did you go about finding the one that was best?

Steve: By making all different types of cuts in all kinds of materials. After all, a blade that produces a smooth edge when ripping might cause chipout when cross cutting.

Cary: Especially in plywood. And since many projects combine hardwood and plywood, I was curious to see how using different materials affected the quality of the cut.

Ken: A blade should stay sharp, too -- even if you occasionally cut abrasive material. So we cut up a sheet of particle board with each blade and ran the test again.

Q: Was there any single type of cut (or material) where these blades just didn't measure up?

Cary: Crosscutting plywood -- especially oak which tends to chip anyway. While the top side was almost perfect with no chipout, the bottom splintered like I'd cut it with a chain saw.

Ken: I'd say the problem isn't so much the blades as the blade height. With the height adjusted correctly, I got smooth cuts with each blade. (Note: To get a smooth cut (top and bottom) raise the blade only 1/8" above the plywood. This way, the teeth make a shearing cut and don't chipout the bottom.) But the one blade that made a slightly smoother cut was the CMT. Probably because the raker teeth are chamfered, so they're not as likely to to chip out fragile veneer when crosscutting.

Q: What type of results did you get when crosscutting hardwoods?

Cary: That's where I noticed a big difference. When I crosscut a board, all the blades except one left saw marks on the end. But the Forrest blade practically burnished the end smooth.

Ken: Two other blades that impressed me were the SystiMatic and the Freud. Although the cuts weren't as polished, the ends were quite smooth. And the quality of cut didn't deteriorate after cutting the particleboard like it did with the Delta blade.

Q: How do the rest of the blades stack up when crosscutting?

Steve: The Sears, CMT, and Oldham blades all made consistently good cuts. In fact, even when I used a magnifying glass, it was hard to find any significant differences.

Q: What did you find when cutting miters and compound miters?

Ken: I expected problems here. Especially since I was working with cherry which tends to burn. But all down the line, I got the same results as when crosscutting.

Q: How about ripping?

Cary: What surprised me was that all the blades except one left ridges on the edge when ripping. But with the Forrest, I got a smooth enough edge to use as a glue joint.

Ken: Don't forget. These blades are designed to do a good job with all types of cuts -- not necessarily to excel at one. I can live with a few ridges. I'd just rip the board a hair wider and run the edge across a jointer.

Q: One thing I'm curious about is the different look of the Freud and CMT blades. What gives?

Steve: You mean the tall shoulder that sits behind each set of teeth? That shoulder or hump is there to limit kickback by making the blade take a smaller bite.

That's a nice safety feature if you get kickback caused by feeding the workpiece too fast. But I wouldn't count on it if the fence isn't adjusted right and the workpiece gets pinched between it and the blade.

Q: And what about the slots cut in the body of the CMT blade?

Ken: They're supposed to absorb vibration and make the blade run quieter. And if you go by the "thunk" you hear when you flick the blade with your finger, it should work.

To find out, I borrowed a meter that's used to measure sound. I found the CMT was quieter than the other blades when ripping 1½"-thick maple. But at 99 decibels, it's still too loud to cut without hearing protection.

Recommendations
Ken:

To be honest, I'd be satisfied with any of these saw blades. But I pick the SystiMatic as the best.

Whether crosscutting or ripping, it gave me a slightly cleaner cut than any other blade except the Forrest. Yet it costs half as much.

A second choice? Probably the Freud. It's a good quality blade for a little less money.

Steve:

Eliminating three blades is easy. The Forrest is too expensive. And the Delta and DeWalt don't give me as smooth a cut as I want.

Then things get tough. I can make a perfectly good joint with either the CMT, Sears or Oldham. But the SystiMatic and Freud have a slight "edge" in price and quality, so I chose them instead.

Cary:

The way I look at it, buying a saw blade isn't all that different from buying any other tool. Quality means more than price.

So I picked the Forrest blade because of the quality of cut. Polished ends when crosscutting. And when ripping, it leaves edges smooth enough to glue up. That's nice since I don't have a jointer.

(c) 2002, August Home Publishing Company. All Rights Reserved.

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