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Miter Saw kickback

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No injuries or gore here, other than a couple bruised knuckles. 

 

Last night I was using my miter saw and I had a kickback.  This has never happened to me before, and the only reason I'm posting this thread is because I'm wondering "Why???" 

 

I was cutting a glued up piece of hard maple and cherry, about a 2.5"x2.5"x9" piece.  I was doing a 90 degree cut and trimming a 1/2" off of the end of the work piece.    The piece was flat on the table and I was holding it against the fence.    About a quarter of the way through - BAM!! and the piece goes flying.  It either hit my knuckles, or my knuckles hit the bed of the miter saw, not sure which.  I consider myself extremely fortunate as I could have been injured pretty badly.    I was not doing anything different than I have done a thousand times before.   What cause can cause this to happen?

 

The only thing I can think of is while doing the previous cut I was thinking the blade might be getting a little dull.  I was not trying to force the blade through on the kickback cut. 

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Glad you are ok! Was it the off cut that flew? 1/2" will fit through the slot in the fence on a lot of saws. For this size trim some guys screw a zero clearance board to the fence.

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A 2 1/2" long piece of stock is pretty short to be cutting on a miter saw, in my experience.  Generally I don't like to cut anything smaller than my hand, it can be real hard to hold down a piece with just your fingers (and for safety's sake I don't like my hand within 3 inches or so of the balde).  I went a long time without a table saw so made all kinds of cuts on my miter saw so learned what does and doesn't work.  As the blade pass through your stock it will try to lift it off the table.  If you don't have much to hold on to it will win.  All it takes is the stock moving just a little big and getting pinched and you will get that kickback.  for shorter pieces of stock like that I clamp it down instead of holding it down.   

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Let me clarify, the piece was approximately 2.5"x2.5"x9".  I was taking about 1/2" off of the length. 

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There was obviously something there that was unstable.  I've and this happen to me when there is a warp in the piece and it ends up pinching the plade.

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Assuming right hand saw operation and left hand holding the good piece to the left of the blade? Are you on a slider or a pivoting chop? How were you holding the piece that it hit your knuckles? I am struggling to envision this and the direction of travel. The only pieces I have ever seen kicked were smaller than 9".

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A 2 1/2" long piece of stock is pretty short to be cutting on a miter saw, in my experience.  Generally I don't like to cut anything smaller than my hand, it can be real hard to hold down a piece with just your fingers (and for safety's sake I don't like my hand within 3 inches or so of the balde).  I went a long time without a table saw so made all kinds of cuts on my miter saw so learned what does and doesn't work.  As the blade pass through your stock it will try to lift it off the table.  If you don't have much to hold on to it will win.  All it takes is the stock moving just a little big and getting pinched and you will get that kickback.  for shorter pieces of stock like that I clamp it down instead of holding it down.   

 Nevermind, I misread your first post.  Your workpiece was 9" long  so really hard for me to say what went wrong.

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Assuming right hand saw operation and left hand holding the good piece to the left of the blade? Are you on a slider or a pivoting chop? How were you holding the piece that it hit your knuckles? I am struggling to envision this and the direction of travel. The only pieces I have ever seen kicked were smaller than 9".

 

Yes right hand operating the saw, left hand holding the workpiece left of the blade.  Using a pivoting chop. Non sliding saw.  

 

I had my hand on top of the piece with the heel of my palm pressing down and towards the fence.  I cant recall where my fingers were exactly, though I ALWAYS make sure they are clear of the blade.  My fingers were probably over the top of the fence.     I think the flying workpiece is what hit my fingers but I'm really not certain.  From the marks on the piece It pulled it to the right very hard, but it end up flying back to the left.   Rotating like a frisbee.   

 

When it happened it sounded like I took a baseball bat and hit the top of my workbench as hard as I could with it.

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 Nevermind, I misread your first post.  Your workpiece was 9" long  so really hard for me to say what went wrong.

 

I updated it for clarity.  I was pretty vague before.

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My miter saw caught a piece of trim that I was cutting last night. It was 1/4" thick, and I was taking about 3 inches off the end of a 35" piece. The offcut got jambed between the blade guard and blade and flew off somewhere in the shop. I think a new ZCI would be the solution in my case.

Mot sure what happened in your situation.

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Is it possible the workpiece lifted a bit mid-cut?  It had to move in some direction in order to catch the blade...a kickback on a 2.5" wide piece (mid-cut) is pretty much impossible otherwise.  The only time I've had a kickback on the SCMS is when a small off-cut gets caught between the blade and the fence.  And that's why I use a ZC sacrificial fence now...always.

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Just got home and I'm looking at the saw. The right side fence was knocked out of alignment about a half inch from the kickback. I started thinking that maybe the off cut may have wedged between the blade and the fence, but then I remembered there was no off cut yet.

I'm going to switch out the blade, Make some ZCIs, and look everything over real good.

Certainly scared the crap out of me. Knowing the direction the piece traveled I consider myself very fortunate to have all my fingers today.

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==> Is it possible the workpiece lifted a bit mid-cut? 

 

That's my bet or the stock was under tension and released during the cut...  Those are the only two things that have caused a chop saw kickback around my shop...

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Any chance you did have an "off cut" as in the top quarter on the waste side fractured off?

 

Its possible I guess.

 

Any chance there was a nail in the work piece?

 

No nails.

 

Is it possible the workpiece lifted a bit mid-cut?

 

That is a possibility.  Probably the most likely. 

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I having a hard time with the theory that trimming an inch and a half only one quarter of the way through released tension in the keeper side. I would have trouble saying this of a board cut completely through (same inch and a half) unless you put a board on the table with a concavity down. I would even say a substantial concavity. As I think more about your setup, I have two thoughts. First, even with a ten inch chop, your small work piece would have been contacting the upward sweep of the blade with the initial portion of the cut. Second, if you could rest your fingers over the fence, I question the security of your hold. If the board naturally bound on the blade, the whole workpiece could have had a twisting force introduced with the fence ward face elevated and the opposite pushed to the fence. This would seem far more likely a scenario with a small square shape than with a wide board. I am not sure how you'd verify any of that.

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==> I having a hard time with the theory that trimming an inch and a half only one quarter of the way through released tension in the keeper side.

 

I hear that, but I did a staircase project and unfortunately got some badly case hardened stock.  It was a bear to process... No matter what we did, we got binding -- stalling a chop saw was a pain, but fairly easy to deal with.  Stalling a 7.5HP table saw is another deal altogether -- and quite exciting.  At one point, we just gave-up processed the sticks with jigsaws...  We got it done, but we had to get more stock... It was a rite mess...

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Just got home and I'm looking at the saw. The right side fence was knocked out of alignment about a half inch from the kickback. I started thinking that maybe the off cut may have wedged between the blade and the fence, but then I remembered there was no off cut yet.

I wonder if the fence was loose and that caused the kickback.


Steve

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==> I wonder if the fence was loose and that caused the kickback. 

 

If the fence shifts during the cut, and the stock follows suit...  could happen...

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you say it was cherry and maple? so it was a lamination? could be you cut through one of the laminations and it went flying off caused a chain reaction?

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you say it was cherry and maple? so it was a lamination? could be you cut through one of the laminations and it went flying off caused a chain reaction?

That was my thought too. Many times a glued up blank has a slight gap at the end due to snipe or lack of clamp pressure. This could have lead to the offcut wedgeing between the blade and fence.

I have a clamp on my miter saw to hold the stock down and use it frequently, but I would have probably hand held a block the size you have described. Every time I make a cut an emergency plan runs through my head " if the saw grabs the part I am letting go and heading away from the danger zone". No piece of wood is worth an injury, safety is a state of mind to me.

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I'm in the camp with those who think some part of the workpiece moved.  Either the small bit of the off cut or the main piece shifted, jammed the blade and caused a catch.  ZCI would prevent one part of the problem.  Using a hold down or clamp would prevent the other.  My saw has a built in clamp and I'm religious about using it for pretty much the same reason.

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