Riving knife?

[Mike Tempel]

I have been reading the somewhat spirited threads on the SawStop and a couple of times I ran across the term 'riving knife'. Now to show my ignorance I have to ask just what is a riving knife? I am sure it is something that I have heard of before or maybe even used on a regular basis but maybe my terminology is different than this. Anyway, try not to pound my ignorance too hard and thanks in advance for the responses.

Thanks again, Mike

[Jim Becker]

A riving knife is pretty much a splitter that follows the up/down motion of the blade so it can stay on the saw even during a non-through cut. These are "standard" on Euro machines, both stationary and the Festool hand-held ATF saws. While the splitters that come with US-style saws generally tilt with the blade, they are always at a "fixed" height and need to be removed for many cuts. Same goes for the add-ons, such as the Bisemeyer snap-in splitter.

[Mike Tempel]

Thanks Jim, is it mounted to the motor/arbor somehow so it follows the blade height?

[Ian Barley]

Thanks Jim, is it mounted to the motor/arbor somehow so it follows the blade height?

It is usually mounted on the carriage assembly that holds the motor so that, as you say, it follows the blade height. It is usually shaped to follow the circumference of the blade so that regardless of the blade height it fills the kerf within a few millimetres of the blade creating the kerf. As Jim says it will be standard on all machines which carry the CE mark that enables them to be sold in the European Union.

[Frank Pellow]

I might add that I really like the riving knife on my Festool circular saw. When I buy a new table saw to replace my now defunct Craftsman (RIP), I would realy really like to be able to obtain one with a riving knife. That is much more important to me the gizmos that detect wieners and the like in the proximity of the blade.

[Jim Becker]

Save your pennies, Frank! You'll need to go upscale in order to get the riving knife...MM, Felder, etc.

[Frank Pellow]

Save your pennies, Frank! You'll need to go upscale in order to get the riving knife...MM, Felder, etc.

I can't see me ever justifying the price of one of those combination machines and, as far as I know, they do not sell "stripped down" table saws. I know that is what I tell folks when they say that they can't afford Festool tools, but we are talking an order of magnitude difference here.

[Jim Becker]

Actually, both companies do sell a basic sliding saw...more expensive than the more common US-designs, but available, nonetheless. For example, Mini Max offers the SC3 W, but it's just under five grand...a bit more than a PM66 or even the SawStop thingie.

[Bob Smalser]

Splitters are more common on US commercial tablesaws larger than the 10-inchers most hobbyists own. The big saws have much more power and the consequences of the thrown work piece are greater.

I'd argue you don't really need one on your small TS if you follow established guidelines for blade height. Why? You are generally cutting premium wood. Cutting 4X4 and larger utility-grade stock more likely to warp using a 3ph, 14" saw is where the splitter earns its keep.

So if you are cutting low grade wood likely to bind...and you don't have a splitter....simply insure your sawblade doesn't protrude significantly above the stock thickness, recruit an offbearer for that run of stock to control the far end of the workpiece, and a problem will be unlikely.

[Ian Barley]

I'd argue you don't really need one on your small TS if you follow established guidelines for blade height. Why? You are generally cutting premium wood. Cutting 4X4 and larger utility-grade stock more likely to warp using a 3ph, 14" saw is where the splitter earns its keep.

So if you are cutting low grade wood likely to bind...and you don't have a splitter....simply insure your sawblade doesn't protrude significantly above the stock thickness, recruit an offbearer for that run of stock to control the far end of the workpiece, and a problem will be unlikely.

Bob

There is much truth in what you say - but - "premium" wood also misbehaves. I use lots of tropical hardwood and many times my rip cut finds stresses in the timber that would have it clamping tight on the blade if the riving knife wasn't there. Your points are a great way to mitigate the risks if no splitter or riving knife is present but I don't believe that they are a replacement in the long run.

[Ian Barley]

Actually, both companies do sell a basic sliding saw...more expensive than the more common US-designs, but available, nonetheless. For example, Mini Max offers the SC3 W, but it's just under five grand...a bit more than a PM66 or even the SawStop thingie.

Jim

Don't know if it has or will make its way over to you but they also do an (SC2W). About 80% of the SC3W price over here.

Its nice to be on the right side of a transatlantic price difference for a change!

[Jim Becker]

Did you forget to go to sleep tonight, Ian??? Or you just up extra early??

[Dave Brandt]

Besides MM, Felder (and Hammer), Rojek also sells stand-alone tablesaws. I can't remember exactly how much, but I do remember that they're no more expensive than an "American-style" saw with comparable equipment. They come with a riving knife, sliding table, over-blade guard with dust collection, 12" blade (5/8" arbor), and are heavy! I've been looking at the Euro saws this past year and when I move, will be replacing my old Grizzly. You can check out the specs at http://www.tech-mark.com/oldhtms/pt300.htm.

[Bob Smalser]

Splitters are more common on US commercial tablesaws larger than the 10-inchers most hobbyists own. The big saws have much more power and the consequences of the thrown work piece are greater.

I'd argue you don't really need one on your small TS if you follow established guidelines for blade height. Why? You are generally cutting premium wood. Cutting 4X4 and larger utility-grade stock more likely to warp using a 3Ph, 14" saw is where the splitter earns its keep.

So if you are cutting low grade wood likely to bind...and you don't have a splitter....simply insure your sawblade doesn't protrude significantly above the stock thickness, recruit an offbearer for that run of stock to control the far end of the workpiece, and a problem will be unlikely.

Forgot a couple things....

...modern, thin-kerf blades are less likely to throw work pieces as they deflect much more easily.

...your push stick should look like the one laying on the saw, not like the notched one I see Norm using occasionally:



That design allows you to push downward on the work piece and into the fence, preventing even a dull blade and a bound kerf from lifting the board back at you.

Sure....case hardened and other improperly seasoned wood will bind a rip kerf occasionally, but with a sharp, thin-kerf blade set at the right height using a triangular push stick, even the worst bind in thick stock can be controlled at least until you can shut the saw off.

It's larger sawblades in this kind of wood where a splitter is absolutely mandatory:

[Steve Cox]

Bob,

Not sure what you mean by "quality wood". I was ripping some 8/4 mahogany one time and it bound enough to stop a PM 66. Scared the hell out of me. Trying to salvage some of that very expensive wood I ran a much smaller piece through again to make some window stops and the two pieces curved apart behind the blade and then curved back and crossed over themselves. I didn't use any of that plank again. Point is, reaction wood is everywhere and you can't predict it. Splitters are nice, a riving knife would be nicer, neither are a replacement for proper technique.