Why did I get kickback?

[GreenCheck]

I experienced some kickback while making a simple crosscut of a 2x4 with my TS 55. I don't understand what I did wrong, which is the scariest part about it.

I've tried attached a couple pictures of my setup but the post won't go through with them attached (edit: picture now attached). I have a 2x4 that I was cutting on an MFT table. It is resting against some dog stops (on the "entrance" side of the cut) and a stop on the end for repeatable cuts. The festool rail is attached to a couple dogs via clips and was supported on both the front and the back with spare 2x4s. When I experienced the kickback, the 2x4 I was cutting was not clamped down to the MFT.

After the kickback occurred I thought the kickback was a result of the offcut drifting back into the blade, so I then tried a single cut with the 2x4 clamped down on both sides (i.e. on both the cut side and the offcut side). However, after making this second cut, I thought about it a bit more and I got to thinking clamping the offcut side could force the offcut back into the blade rather than allowing it the freedom to fall away to the side. At this point I don't know what I did wrong and don't want to touch my saw again until I realize my mistake.

As you can tell, I'm quite confused and this was a stark reminder that I have a lot to learn. Frankly, I'm embarrassed that I managed to get kickback on what should be the simplest of cuts but I value my digits more than my ego so I'm turning to you good souls for advice.

 

[ChuckM]

Reduce the size of your photos (to under 1 MB per image), and you should be able to load your photos.

 

[GreenCheck]

Reduce the size of your photos (to under 1 MB per image), and you should be able to load your photos.

Thank you Chuck, that worked.

 

[Vtshopdog]

My guess is that with no clamps and your dogs on entry side of the cut instead of exit side your stock moved under the saw and bound up to your blade.

Could be something else tho….

 

[smorgasbord]

It is resting against some dog stops (on the "entrance" side of the cut) and a stop on the end for repeatable cuts.

I bolded the relevant part. The stops you have do nothing to prevent the saw from moving the stock away from you, which is the way the saw is trying to move the stock. You have a clamp in the photo, but you said that clamp wasn't there before.

And that's why it moved and kicked back.

Clamping both sides is fine - if nothing can move nothing will kick back. Make sure the clamps really will hold it - one clamp alone usually isn't enough, so you need an additional clamp or at least another stop on the far side of the board.

 

[makpacman]

Not sure why it happened the second time if everything was solidly clamped but the first kickback may is fairly straight forward.

The dogs need to be behind the piece you are cutting(exit side) and preferably only behind the piece under the track. The reason is once the 2x4 is 75% cut it will start to bind and the extra thickness of the 2x4 on the full depth of the blade means that it will bind well, causing kickback.

That won't happen if the piece being cut can't move forward in any manner. Once the cut is complete, the offcut has no forces against it so it will simply stay put on the table.

 

[GreenCheck]

Thank you all. Putting the dogs on the exit side is an obvious step, and after my cut I even thought "well that made no sense" and planned to move them to the exit side, but for whatever reason I was only.thinking about alignment issues and didn't connect it to the kickback.

With that out of the way, I would like to follow up on the below quote:

Once the cut is complete, the offcut has no forces against it so it will simply stay put on the table.

This was basically my reasoning in thinking that clamping the offcut is a bad idea. Optimally a clamp will only exert vertical forces pinning the offcut to the table, but in reality you might overtighten the clamp (or have a poor quality clamp or whatever) such that it starts to exhibit some horizontal forces that could push the offcut into the blade. Does this make sense or am I totally off base?

Anyway, thank you again everybody for your help. Feeling confident that I know what I did wrong. Such an obvious thing, but when you're starting out there are so many things to keep track of that you can really do some foolish stuff.

 

[Michael Kellough]

Did you get kickback twice or just the first time?

Was the “end stop” to the right or left of the blade?
It should be used on the left side as the that piece of stock is trapped under the rail and won’t move when cut.

A stop on the right will not let the offcut move away from the blade and might cause it to pivot and pinch the back of blade causing kickback.

Another possibility is that the stock is not flat. If there is a gap between the bottom of the stock and the worktable in the vicinity of the blade, when the cut is nearly complete the stock will fall and might pinch the blade.

When the stock is not flat you should put the concave side up so there is no gap under the stock.

 

[ChuckM]

From the photo, I noticed that the track was anchored to the dogs via wire hooks or the like. Make sure when you push the track saw, you're pushing the saw forward and not away from the dogs that could so lightly move the track.

 

[GreenCheck]

Did you get kickback twice or just the first time?

Was the “end stop” to the right or left of the blade?
It should be used on the left side as the that piece of stock is trapped under the rail and won’t move when cut.

A stop on the right will not let the offcut move away from the blade and might cause it to pivot and pinch the back of blade causing kickback.

Another possibility is that the stock is not flat. If there is a gap between the bottom of the stock and the worktable in the vicinity of the blade, when the cut is nearly complete the stock will fall and might pinch the blade.

When the stock is not flat you should put the concave side up so there is no gap under the stock.

Only the first time. Sorry that was not clear.

End stop was to the left of the saw, for reasons you.mentioned.

Excellent tip about putting the concave side up!

 

[GreenCheck]

From the photo, I noticed that the track was anchored to the dogs via wire hooks or the like. Make sure when you push the track saw, you're pushing the saw forward and not away from the dogs that could so lightly move the track.

That's a good point. I will add it to the list of reasons I hate those clips, haha. But yes, especially when stretching I can see how you might be pulling the track away from the dogs ever so slightly if you're not careful.

 

[makpacman]

The UJK rail clips work well for many of us but simply put, there's a lot more technique in using a tracksaw than is readily apparent to new users.

And to be honest, it never becomes automatic. Just like a tablesaw, you always need to be mindful of good technique and consider the likely physics involved in each cut. After a while, you become quicker at assessing the situation, but you're still running through a checklist in your mind before every cut. It's the only way to be safe.

 

[JeromeM]

The setup from the picture shows one that has a high probability of causing problems.

Dogs on the exit side on the cut are almost always the correct position, yours are in front.

However clamping the one of the sections and constraining the other end while cutting with a stop may also create a kickback.

It is not clear if that is what is being done, but if so then as the saw almost cuts through the unclamped end that is constrained by the stop can, and probably will, move, this can only push the cut section into the blade clamping onto it so causing kickback.

If both sections are clamped, though I wouldn’t usually bother clamping either, and the end stop is moved before cutting a kickback is probably not going to happen.

TLDR dogs on the wrong side of the cut, stop block restraining the board = probable kickback

To get a better idea as to why kickback happens look at American saw kickback videos, they have long rip guides so the work piece, or off cut, is between the saw blade and the fence at the end of the cut. This means that any movement of the piece sandwiched between the blade and the cut has a reasonable chance becoming a 200mpg projectile.

Look at European saws

[attachimg=1]

this example is probably older than both you and I and though I have used it for 50 years and knew little about the subject when I got it, it has never produced a kickback. This is because the guide can not sandwich the workpiece between it and the blade.

It is also a planer and that has been the cause of a stupid injury because of lack of knowledge but the saw has never bitten.

 

[bobtskutter]

[member=82497]GreenCheck[/member] good call on stopping and asking "what just happened".
As others have said kickback is caused by the blade getting trapped by the workpiece.

I've attached a marked up photo of your workbench, is it flat?  it looks like there are gaps under the 2x4's that suggest the workbench has a high spot in the middle, this could make the timber unstable and cause the rail to move.

Bob.

 

[ChuckM]

The rule of thumb for crosscutting is to let the offcut end cut loose.

That means on the tablesaw, the sawfence must not be used as a stop, and on the miter saw, the stop should be placed on the side where the workpiece is clamped down.

I've seen some Youtubers doing the exact opposite on their miter saws. One day, Murphy's Law will hit them or their unsuspecting viewers without warning.

The tablesaw crosscut sleds should be treated similarly.

Yeah, it was a good call on the part of OP to pause and ask why. We all can learn to be safer.

 

[Packard]

I’ve experienced kick-back on my table saw (scary), and a variation, kick-up (which sent me to the emergency room), but not kick-back on the track saw.

What does kick-back on the track saw look or feel like.  What are the typical causes?  I did not even know it was a possibility until this thread.

Thanks.

 

[JeromeM]

[member=82497]GreenCheck[/member] good call on stopping and asking "what just happened".
As others have said kickback is caused by the blade getting trapped by the workpiece.

I've attached a marked up photo of your workbench, is it flat?  it looks like there are gaps under the 2x4's that suggest the workbench has a high spot in the middle, this could make the timber unstable and cause the rail to move.

Bob.

While the workbench may have a high spot in the middle, I don’t know, the pieces are construction 2x4s that are probably not flat in any orientation the front and back supports with the rail positioning clips are unlikely to move much if at all and even if they do they are probably irrelevant and won’t have any effect, the gap shown one the centre piece that is clamped on the right is rather different as the piece when cut could spring up and that could pinch the blade. This seems to be the off cut piece and as such I can’t see any reason for it to be clamped any many for it to be free

[member=82497]GreenCheck[/member] it would be helpful if you would confirm which are the important pieces.
It is usual to have those to the right of the saw, it seems you may have reversed this.
There are a few occasions when the important pieces are under the rail but this is not the way that most people use the saw.

 

[JeromeM]

The rule of thumb for crosscutting is to let the offcut end cut loose.

That means on the tablesaw, the sawfence must not be used as a stop, and on the miter saw, the stop should be placed on the side where the workpiece is clamped down.

I've seen some Youtubers doing the exact opposite on their miter saws. One day, Murphy's Law will hit them or their unsuspecting viewers without warning.

The tablesaw crosscut sleds should be treated similarly.

A table saw cross cut fence is a rather different case as both pieces of the cut workpiece are being supported past the point at which the saw blade exits the cut.
I have never heard of a case of kickback (I don’t think that it is even a possibility) with anyone using a sled. You would have to be extremely inventive (not to say idiotic ) to manage to get the blade to catch and even then since there is a fence immediately behind the 2 pieces I’m not at all sure that a kickback can happen.
I would be very interested in anyone who can explain a case where kickback is a possibility

I understand that virtually nothing is foolproof as if you have something that is, there will be some bigger fool to prove you wrong. So I would be delighted for a scenario that proves me wrong and a way for kickbacks on a sled to happen.

 

[GreenCheck]

Appreciate the continued dialogue. I am not responding to each post individually because I do not want to clutter up the thread, but will try to address the various questions/comments in this post.

First, yes the top is flat, but the boards are not. See the attached pic. One lesson from this thread is to pay more attention to compensating for deficiencies in the stock.

I have attached a pic of my updated setup. Green dots represent boards that are only there to support the rail (yes I need a more permanent solution). Purple dot is the work piece. Dogs are now on the exit side, and workpiece is clamped down on the left side where the stop block is. Offcut side is not clamped. When cutting, make sure I'm pushing the saw forward and not pushing the track away from the clips. Think through how the particular work piece might behave given its shape.

I think those are the themes - anything I'm missing or misunderstanding?

 

[GreenCheck]

[member=82497]GreenCheck[/member] it would be helpful if you would confirm which are the important pieces.
It is usual to have those to the right of the saw, it seems you may have reversed this.
There are a few occasions when the important pieces are under the rail but this is not the way that most people use the saw.

Sorry, forgot to respond to this part above - hopefully my picture helps clarify where the important piece is. Regarding your comment that it is usual to have the "important" piece to the right of the saw - why is this? I admit to not putting a whole lot of thought into it, but my thought process as far as it went was that I want the rail fully supported by the work piece. If I am only taking a sliver off the end and my work piece is set up to the right of the rail, this means the work piece barely extends under the rail and is thus not supporting it. With the piece to the left of the rail, it will always be fully supported as long as the work piece is as long as the track's width. Setting it up to the left also seems to ensure there are no forces from the rail acting on the cutoff. If this is wrong, I am of course interested in knowing why.