Table Saw Kickback

[Frank Pratt]

All of these things are important together. WITH the splitter and guard, I still had some kicks before I aligned the saw. Misalignment probably starts the problem, the others are still important. I've never cut without the splitter, and almost never without the guard.

Glad you clarified that Carlos.

[Doug Garson]

I’ve always viewed kickback as having a singular cause - when the workpiece contacts the rear of the saw blade, which then causes it to climb up the blade. This is explained and demonstrated very well by Roland Johnson in a video by Fine Woodworking: https://www.finewoodworking.com/2008...a-riving-knife

Preventing kickback should be very simple - just do not allow the workpiece touch the back of the blade. A riving knife should do this. However, in practice there are other factors to consider. For example, one cannot use a riving knife when sawing blind cuts, such as grooves.

I generally keep the blade high for two reasons. The first is that this ensures that the riving knife is always high enough - a low blade has a yet lower riving knife, and the workpiece can move over it into the blade. The second reason is that the angle of the teeth is more vertical, and this does not allow the workpiece to climb over the blade and shoot forward, as it can with a low blade.

All is not safe yet. I have a Hammer K3 (slider). Kickback is highly unlikely (in my understanding/experience here) when ripping on the slider, where the workpiece is fixed and the off-cut runs parallel to the cut. Kickback is more a feature of ripping against a rip fence, where the workpiece may be forced into the blade.

When using the rip fence, I have noted how a workpiece may be lifted and ejected. I have been puzzling why this occurs, and the reason I have come up with is that the blade cuts a fine kerf, and that the ejection is a milder version of kickback - that is, the teeth at the rear of the blade can lift the workpiece. This is controlled when ripping on the slider as the workpiece is secured at the front and rear. But I use the rip fence as well (mine is a shorter, 49” slider). I added a finger board to the fence, and this has stopped any lifting ...



As a result if this thread, I revisited my thoughts on the dynamics of ripping and recognised that the rip fence can do more. There is the obvious issue of a fence that is poorly aligned with the blade and will push the workpiece across and into it. That is not my concern. Instead, what I wanted was to ensure that the side of the workpiece stayed tightly to the rip fence and did not wander off it, which is largely down to operator error (how we push, and from what angle we do so). The finger board does not control this. All it does is hold down the workpiece.

In my surfing the Net, I again came across the JessEm Clear cut Saw Guides, and now understood them better. These not only hold the work down and prevent it from moving backwards, but importantly also force the workpiece into the side of the rip fence.



Expensive, but I caught a discounted special, and ordered a set. It is on its way, so not feedback as yet. At the least, I expect cleaner cut when using the rip fence. Plus it should make blind cuts much safer.

Regards from

Derek

Well said, I agree with all you said except why do you say you cannot use a riving knife with "blind cuts AKA non thru cuts? Doesn't a riving knife move up and down with the blade so it is always below the top of the blade and thus can be used with non thru cuts? Did you mean to say splitter which has a fixed height?

[Derek Cohen]

Well said, I agree with all you said except why do you say you cannot use a riving knife with "blind cuts AKA non thru cuts? Doesn't a riving knife move up and down with the blade so it is always below the top of the blade and thus can be used with non thru cuts? Did you mean to say splitter which has a fixed height?

Doug, the riving knife does move with the blade. However, it is generally set a little below the top of the blade. It cannot be set above the blade for blind cuts, of course. Some like to set it low enough to wind down the blade and have enough free above the riving knife to make blind cuts. With a blind cut, setting it lower effectively removes the riving knife and enables the workpiece to contact the back of the blade. Setting it level with the top of the blade should prevent this. I wonder how many table saws allow this. Many I have seen make it difficult owing to the design of the riving knife - consequently, the riving knife is either low or high. Some report removing the riving knife owing to the latter.

Regards from Perth

Derek

[Mark e Kessler]

I have never had or seen one set above the blade, the main purpose of the riving knife is to prevent the wood from pinching on the back of the blade and ejecting

Riving Knives and splitters cannot be used on non-through cuts either as they stick up higher than the top of the teeth.

[Mark e Kessler]

The other thing I never see mentioned (well probably mentioned at some point somewhere...) here when a kickback/blade height discussion occurs is how sharp the blade is, I have noticed that responses that state something like “i set the blade high” , “1” taller than work piece” ect will almost always be individuals that have worked in commercial shops where the blade in the saw is more likely to be on the dull side than the sharp side, a dull blade is a dangerous one, if to low can lift a board up ( swear never happened to me) i just don’t like a blade too low super dangerous in my opinion, too low being 1 tooth or whatever the magazines/books recommend...

[johnny means]

Hmmm, I wouldn't have imagined a discussion about blade height setting without a single mention of cut quality or tearout/chipout. That's the only real factor, as far as I'm concerned.

[Brian Holcombe]

We can never make it past safety. Safety is interesting to an extent, but it’s well covered here. I generally raise the blade up but rely upon blade choice to make a high quality cut.

[Patrick Walsh]

Another valid instance that creates or lends itself to kickback Mr. Kessler

There really are many tbh.

I think what matters most in regard to kickback is not precautions but awareness and the hands on experience and capacity for one to recognize something going sideways as it is going sideways and the experience to react appropriately.

Sure if you swim with sharks chances are sooner or later you get bitten but a in depth understanding of your environment and the subject goes a long way towards avoiding gettin bitten.

Sharks aren’t bad nor are tablesaw shapers yada yada.

You just gotta take it slow be honest and develop a relationship with your machinery.

That’s takes time, hours upon hours behind these machines experimenting with different approaches used for similar and different tasks.

Like anything in life you will succeed and fail. Hopefully when u fail u don’t loose a extremity but if you do I get you learn something you didn’t know prior. Hopefully your smart enough to recognize what does not work before there is a consequence but you know somethings can only be learnt i the physical form.

Nothing in life is without risk. It’s just some risk “our bs minds or ignorance” or what I like to think of as conditioned minds rationalize better than others. That imop is the most dangerous.

I’ll take shop risks or the risks presented in nature “say the mountains” over those out in the populated world counting on the masses to make good decisions.

You know like driving..

Sorry I typed that in a Whole Foods parking lot in my phone so the typos where even worse than worse lol.. as if they could be hahahah


https://www.youtube.com/watch?v=2UFc1pr2yUU

[Mark Hennebury]

Well put Patrick, 100%

Another valid instance that creates or lends itself to kickback.

There really are many tbh.

I think what matters most in regard to kickback is not precautions but awareness and the hands in experience snd capacity to recognize something going sideways as it is going sideways and the experience to react appropriately.

Sure if you swim with sharks chances are sooner or later you get bitten but a in depth understanding of your environment and subject goes a long way towards avoiding gettin bitten.

Sharks aren’t bad nor are tank saws shapers yada yada.

You just gotta take it slow be honest and develop a relationship with your machinery.

That’s takes time hours upon hours behind them experimenting with different approaches used to similar and different tasks.

Like anything in life you will succeed and fail. Hopefully when u fail u dint loose a extremity but if you do I get you learn something you didn’t know prior.

Nothing in life is without risk. It’s just some risk our bs it ignorant or what I like to think conditioned minds rationalize better than others.

I’ll take shop risks or the risks presented in nature “say the mountains” over those out in the populated world counting in the masses to make good decisions.

You know like driving..

[Bill Space]

Doug, the riving knife does move with the blade. However, it is generally set a little below the top of the blade. It cannot be set above the blade for blind cuts, of course. Some like to set it low enough to wind down the blade and have enough free above the riving knife to make blind cuts. With a blind cut, setting it lower effectively removes the riving knife and enables the workpiece to contact the back of the blade. Setting it level with the top of the blade should prevent this. I wonder how many table saws allow this. Many I have seen make it difficult owing to the design of the riving knife - consequently, the riving knife is either low or high. Some report removing the riving knife owing to the latter.

Regards from Perth

Derek

I am missing something here. My riving knife is set very slightly below the apex of the blade, but not by much. Never measured it. Could be several thousandths or perhaps a little more.

It always maintains this position with respect to the blade regardless of blade height setting. Seems like the action of the riving knife is the same whether making a through cut or a blind cut...

[Doug Garson]

I am missing something here. My riving knife is set very slightly below the apex of the blade, but not by much. Never measured it. Could be several thousandths or perhaps a little more.

It always maintains this position with respect to the blade regardless of blade height setting. Seems like the action of the riving knife is the same whether making a through cut or a blind cut...

Don't have a riving knife on my saw but that is my understanding of how they are supposed to work and thus my original comment.

[Derek Cohen]

I am missing something here. ...

It always maintains this position with respect to the blade regardless of blade height setting. Seems like the action of the riving knife is the same whether making a through cut or a blind cut...

Bill, in my reasoning, there are two actions, not one.

In a through cut, the blade and riving knife may be set high ... much higher than the workpiece. The riving knife will ensure that the workpiece does not touch the blade.

In a blind cut, with a lowered riving knife, the workpiece must touch the top of the blade to cut (naturally). It is this lower cutting angle that is more likely to propel it forward, and if conditions are tight for kickback, it can occur. Blinding in the cut is one condition.

Regards from Perth

Derek

[J.R. Rutter]

Hmmm, I wouldn't have imagined a discussion about blade height setting without a single mention of cut quality or tearout/chipout. That's the only real factor, as far as I'm concerned.

I just set blade height low initially and as the zero clearance insert wears, it gets raised so that it is cutting fresh at the tip of the carbide teeth. Riving knife and overarm blade guard though...

That's kinda what I was getting at.

[Dan Jansen]

Don't stand behind the blade.

Sometimes it takes a shot in belly to learn this lesson. It was an odd place to have a bruise. I once dented a steel door 20 feet away. Fortunately, I already learned to not stand behind the blade (the hard way of course).

I have a hunch most kickbacks come from a fence pinching the material because the fence isn’t parallel to the blade.

Learning a feel for when to not push it helps too but takes time. I recently had a bad SYP 2x8 that actually pinched the miter saw blade so tight I had to remove the blade from the saw to get enough leverage to free the blade. I safely ripped it after that but was very alert.

[Patrick Walsh]

https://www.youtube.com/watch?v=3KBGv-LCKeg