SawStop/ Riving Knife Questions

[Dan Lautner]

1. Has any Sawtop user been saved by the break? If so could you describe the accident.

2. How could you have a kickback with a riving knife installed?

I'm 99% sold on the Sawstop. The only thing I care about is preventing a TS accident, I don't care about the politics of the saw. I recently bought the new Bosch TS with the riving knife for job-site use and love it. I don't understand why anyone would buy a TS without one.

Thanks, Dan

[James Phillips]

1- Not on my sawstop, but before I got it I knicked my thumb in my old contractors saw

2- You can still have kickback if the saw is not set up properly (binding between the blade and fence) or trying to crosscut narrow pieces with the fence (bad idea anyway)

[Per Swenson]

Hi Dan,

I have tons of African Mahogany stock that has not

been exorcised of the Congo spirit.

Sometimes running this stuff through the saw is akin to

witnessing a Las Vegas Illusionist's act.

In theses cases no riving knife will save you/me.

In order to not bind with the fence, I install a aux fence at least

3 inchs wide, ending one third of the way into the blade.

I cut this stuff bright eyed and busy tailed and well to the side of the saw

with my leg right on the panic button.

I own a saw stop, but nothing beats operator awareness.

Per

[Kevin Groenke]

Dan,

We've had 2 SawStops in a collegiate student shop since 2004. Wednesday night we had our first significant "save" (we've had one insignificant one as well... we think the blade had actually come to a stop). I was not in the shop and haven't spoken to the student yet, but from the information I've been able to gather so far, the student was clearing small off-cuts (3/4x1/2x1) near the blade while it was coasting down(yeah I know, duh). His thumb hit the blade and whammo, the blade disappeared. I don't know if it was because of the shock of the blade disappearing or the fact that he could have been sliced pretty good, but apparently the guy nearly passed out.

You've probably done your research, so I'll spare you the proselytizing, but yes it works.

The riving will not prevent kickback, but it does significantly reduce the potential. It is simply difficult to not push material straight, because the riving knife makes it go straight (as Per pointed out, it doesn't address tension in solid wood). The beauty is that the knife does this without ever getting in your way, which is important in our shop where we're frequently cutting 1/8"x1/8" stock.

Of course the interchangeability of the riving knife with the splitter/anti-kickback/bladeguard is not to be overlooked. It's a 15 second swap.

-kg

[Steven Wilson]

The riving will not prevent kickback, but it does significantly reduce the potential. It is simply difficult to not push material straight, because the riving knife makes it go straight (as Per pointed out, it doesn't address tension in solid wood). The beauty is that the knife does this without ever getting in your way, which is important in our shop where we're frequently cutting 1/8"x1/8" stock.

I'll have to disagree. Kickback occurs when wood climbs up the back of the blade and is thrown back. If you have a true riving knife that is properly adjusted (3mm in back of the blade) you will not give the wood a chance to be engaged by the back of the saw blade even if it's pinched. Of course having your fence adjusted to be as short as practicle (I set mine so it intersects a 45D line running back from the arbor) helps eliminate jamming from wood expansion. If you have your riving knife set up correctly you can freehand cut on the tablesaw without a fence and you won't have kickback (try it with hard foam sometime).

[Per Swenson]

I hate controversy.

Steve, you said, " I have to disagree"

No you don't.

2nd sentence, "Of course having your fence adjusted to be as short as practicle (I set mine so it intersects a 45D line running back from the arbor) helps eliminate jamming from wood expansion."

And this little tidbit,

"If you have your riving knife set up correctly you can freehand cut on the tablesaw without a fence and you won't have kickback (try it with hard foam sometime)."

Is just plain irresponsible. Besides nuts.

Per

[Kevin Groenke]

Steve,

I made some freehand cuts like you suggested. It didn't work too good, the cut's weren't straight and the foam whizzed past me and broke a window.

A riving knife must be no thicker than the kerf to be able to push material past it. The riving knifes on our saws are .100" to accommodate sawblades of various thickness, so if we're running a .120" thick blade, there is .020" difference between the kerf and the knife. That is certainly enough "pinch" to engage the blade and cause kickback. It is certainly possible to rotate the stock somewhat causing binding and possibly kickback. Of course not all riving knives are created equal, our saws have "shark fin" shaped riving knives, a deeper riving knife would more effectively guide stock in a straight line.

Again, a riving knife makes it easier to push stock straight, but certainly isn't a substitute for a fence/guide. I would never even consider freehand cutting on a tablesaw, it is the one thing that people get chastised for attempting (well, thinking of attempting) in our shop.

-kg

[Jim Becker]

2nd sentence, "Of course having your fence adjusted to be as short as practicle (I set mine so it intersects a 45D line running back from the arbor) helps eliminate jamming from wood expansion."

...~snip~....

Is just plain irresponsible. Besides nuts.

Per, this is standard operating procedure with Euro fences and the UniFence which is of similar design. It's one of the reasons that the fence face can be slid back on these particular fence styles.

I do agree that the freehand cutting situation mentioned by the other poster is a no-no!

[Steven Wilson]

Per, then you need to see Kelly Mehler's demonstration on kickback. It was amazing to see him jam foam board every which way at a MiniMax tablesaw and not have it kickback. Remove the riving knife and BAM! kickback.

I didn't want to suggest that freehand cutting on the tablesaw was a good idea but if you have a well setup riving knife then you will probably not have kickback.

As for the fence, moving the fence forward works well and is a standard method of work in some circles. I was a bit skeptical at first but I've come to appreciate it. It makes certain operations safer and easier.

[Todd Bin]

I own a saw stop and aside from it being a great saw I liked the idea that I would not cut my finger off in a moment of stupidity. But then how to deal with the other table saw problem (Kick back). I use the riving knife all the time but as some pointed out earlier this is not a 100% guarentee. So I set my fence .001 out of parallel to allow just maybe that little extra on the outfeed side. But the final nail is the installation of board buddies. These little rollers will basically prevent kickback forever. see the link below. Can't beat 'em for $50. The picture shows them mounted to a Bies fence but I have mine mounted to an Incra fence (no problem).

http://www.rockler.com/ecom7/product...rings_id=11262

But, with all that there is no substiture for awareness and planning.

[Simon Dupay]

The saw stop saved my left thumb. I was cutting some white oak for an order at work I was pushing the offcut past the blade, had my hand too close, and BOOM!!! Didn't even bleed, bearly even a nick.

[Alan Schwabacher]

According to www.sawstop.com , finger save #156 took place in March 2007. If you click on it, it describes several.

[Per Swenson]

Steven,

With all due respect, I own a Sawstop and use it daily and professionally.

Riving knife, brake technology,kickback demonstration....whatever,

I approach each and every tool I own with its potential to remove digits

or just plain ruin my day each and every time I power anything up.

To suggest on a internet forum that freehand cuts,

Oh nevermind.

P.

[Rod Sheridan]

[quote=Todd Bin;679441]But the final nail is the installation of board buddies. These little rollers will basically prevent kickback forever. see the link below. Can't beat 'em for $50. The picture shows them mounted to a Bies fence but I have mine mounted to an Incra fence (no problem).

quote]

I think that claiming that a Board Buddy will prevent kickback forever is an not accurate.

Kickback can easily overwhelm the coefficient of friction of the rollers or the spring pressure. The Board Buddies will help by holding material down and against the fence, however they cannot overcome the forces of the saw motor or inertia of the rotating masses.

I've seen great kickbacks with gang rip saws where the wood is literally sandwiched between metal caterpillar tracks and has anti kick back fingers. Some of the pieces do make it backwards out of the saw on occasion, that's why the operator doesn't stand in that area.

I do use Board Buddies on my TS for some operations, however they aren't an all inclusive solution.

Regards, Rod.

[Todd Bin]

I think that claiming that a Board Buddy will prevent kickback forever is an not accurate.

Agreed, perhaps my wording of 'forever' is a little stong. But having board buddies is a LOT better than not having them.