Miter saw kickback?

[Dave Rosner]

I was cutting a 3" tall square of laminated plywood sheets that is 5" square on my chop saw today and it went flying violently. I had bearly cut down on it but it was pretty cut up.

Wasn't a pleasant experience and if I didn't know any better it was like backwards kickback that happens on a tablesaw.

Wondering what causes this so I can make sure I don't do it again - or if my saw could be a contributor to the problem.

[Alan Lilly]

The smaller the pieces you cut on a miter saw.. the greater the chance for less support from the fence (depending on the saw). Ideally you would have a zero clearance surface and zero clearance fence when cutting anything... especially small stock. Thicker stock creates more pressure and tension and small stock is more likely to move. Any slight movement is not good. Clamping is preferred. Smaller stock gets your hands closer to the blade. Small stock is best cut on a table saw sled IMHO. What you experienced is logically the same as table saw kickback. The wood moved slightly and the blade grabbed it.. which moved it more... in an exponentially increasing loop within a microsecond. BANG!

[keith micinski]

Depending on the hook angle on your blade more then likely it's actually lifting the piece up and yanking it. Ideally you want a negative hook angle so the blade is pushing down somewhat against the piece but most mitre saws just have a regular blade with positive hook on them.

[Wayne Lomman]

Keith is spot on - all mitre saws must have a negative rake angle on the teeth. Sadly they rarely do. For the sake of keeping all your fingers etc, get one and also clamp the workpiece when it is so short. Cheers

[John TenEyck]

I had a very close call not so long ago in a similar situation as the OP described, except the workpiece was only 4/4 stock and the blade was a negative hook. I think the most important thing is having a zero clearance back rest and insert and clamping the workpiece with really short stock. I had a zci but not the other two at the time. I do now.

The kickback was so bad it ruined the blade. The blade actually jambed into what must be an arrester at the back of the blade shroud. When I stopped shaking I said a thank you prayer that I still had all my digits.

John

[Doug Hepler]

I, too, have had this experience. It was a surprise, probably because kickback on a miter saw does not get as much attention as kickback on a TS, or at least that's how it seemed to me. When you think about it, however, kickback on a miter saw it should be just as likely as on a TS.

I understand the cause to be very similar to TS kickback. The piece rotates, rocks, etc and the set of the teeth grabs it. Thicker pieces are worse because the teeth can't just cut a wider kerf. The preventive, IMO, is to fix the workpiece in place but let the cutoff be free to fall away after it is cut. The shorter and thicker the workpiece, the more important this would be. If the front of the piece can lift or can rotate, it's a matter of workshop roulette. The hold-downs on my SCMS are primitive and I have made some secondary tables with hold-downs. These are especially necessary when I am cutting small pieces. Picture shows one example357972

Best regards

Doug

[Bill Orbine]

With most saws being compound angles, the gaps in fence are crazy ridiculous. Set up a backer board in front of fence so you can have zero clearance. In addition to safely cutting small pieces.... It even prevent small cutoffs from flying out.

[glenn bradley]

Yep, backer board for small cuts. Also for cuts resulting in small off-cuts that can become projectiles.

[Edwin Santos]

I had bearly cut down on it but it was pretty cut up.



If you had barely cut into the workpiece and the kickback happened, then my theory is the workpiece was not tight against the back fence and/or the blade caused it to pivot. Likely the latter because you were cutting a relatively tall piece with a relatively small footprint and physics were not on your side. A tiny bit of motion is enough to start the wheels of kickback in motion. I would not suggest a cut like that on a miter saw unless you jigged up a method of clamping and support (see more about this below). The backer board suggested is good and will help but rotation is still possible.

The other way I see miter saw kickback happen is when the operator is in the habit of lifting the blade out of the cut while still spinning like a down and then back up karate chop. I was taught to make it down karate chop, pause, wait for the blade to stop completely, then lift out of the cut. Requires a tiny bit of patience, but it's worth it. I'm not sure this particular issue was behind your incident.

I learned a good bit from a video on YouTube by a woodworker from Georgia named Ted Baldwin who demonstrates a bunch of interesting ways to cut amazingly small pieces safely and accurately on a miter saw. I'm talking about workpieces the size of a dime.

Here are some other ideas - I've had success mounting DeStaCo type toggle clamps to the edge of offcuts which I can then clamp to the miter saw to locate a clamp where you need it. Using hot glue you can also glue a strip of wood as a temporary front fence which will also prevent rotation. The hot glue will pop off when you're done, or you can use some isopropyl or denatured alcohol to remove it. Like Ted Baldwin demonstrates, in addition to a backer fence, you can double stick tape or hot glue a piece of ply as a temporary platform on the base of your saw and then fix some sticky sandpaper to the area under the workpiece but not in the blade's path. This with some clamping pressure from above will also prevent movement in the workpiece.

[Dave Rosner]

Thanks all - I definitely didn't have that piece secure against the fence and I checked my blade and it's got a 10 degree positive hoOk too.

Im trying to stick with all Freud blades but the only negative hook they have is a thin kerf. I. He checked Forrest too and same thing. Only tenyru had one blade with enough teeth for good crosscut and negative hook. Guess I'll use my cross cut on the tsaw only and get me a negative hook.

Yud Think there would be more options and the blade manufacturers wouldn't mark many of their blades as good for miter saws...

[Ruperto Mendiones]

The forrest chopmaster blades are advertised as "negative hook" on the factory website. However they do not specify the angle. Not cheap but I'm sure you could get a great miter saw blade from Carbide Processors.

[rudy de haas]

While all the responses here make sense and together provide both good advice and a sufficient explanation, there is one more possibility. My first mitre/chop saw was a direct drive (blade on motor axle) and the mounting for the combo eventually loosened a bit. As a result it would start to cut, and then grab and throw. Not nice and something that turned a $300 (canabucks) saw into a throwaway.

[Dave Borrelli]

I do a lot of small work on the miter saw and ran into the same problem. I designed a jig that solved the problem nicely. Here is a link to the YouTube video that demonstrates the use of the jig as well as a step by step on how to build it. Hope this helps.

Dave

https://www.youtube.com/watch?v=Npnxib4v7pM

[Kevin Smira]

I cut up about 30 pcs of 10' 2x4 lumber this weekend for a shelving project in my garage. I bought the 2x last weekend and used it this past weekend. During that week long time frame, it developed a bad bow on many of the boards. Got lots of kickback on the saw this weekend. I didn't anticipate it, but it did happen. Once I realized what was causing it, I had to be more careful in how I cut it...more support, hands free, etc...