Riving Knives... I'm 'Confounded"....

[Steve Sawyer]

I recently purchased a new saw, and the riving knife was the one "must have" feature. I was willing to compromise on just about every other issue, including horsepower and configuration (contractor vs. cabinet vs. hybrid). I tried to get the new Grizzly G0661, but had I committed to that model, I'd still be waiting another two months to get it. As it is, I had to wait six weeks for the Jet I ended up buying.

Neither the Grizzly nor the Jet is priced exorbitantly IMO, but their scarcity tells me that there are probably other woodworkers that value this feature. If you look at how the riving knife is mounted and moves with the blade on both of these two saws (as well as the PowerMatic PM2000), you'll see the extent to which the entire trunnion needs to take the riving knife into consideration when it's designed. No, it isn't rocket science, but it's like designing a convertible vs. a sedan. You don't just cut the top off the sedan and throw a piece of canvas over the passengers. The convertible option has to be designed into the vehicle from the start. Are convertibles a lot more expensive than sedans? No, just as riving-knife-equipped saws aren't a lot more than non-RK saws. However, there are considerable design and manufacturing costs involved with introducing a new saw equipped with a riving knife, and manufacturers need to look carefully at how they spend their limited resources to introduce new models with these kinds of up-front product development costs.

[Vic Damone]

I disagree. A riving knife might be a little easier to make for a blade/trunnion that moves vertically, but one for the typical swinging trunnion would only need a pivot link to keep it at the same height as the blade, despite blade height. The link could be designed with multiple user selected settings to allow it to work with different blade diameters or not at all. We are not talking rocket science here, just a little mechanical engineering. Besides, a riving knife does not have to be some sort of heavy-duty, massive device. A riving knife is just moving splitter and can be a piece of metal or other material that will keep the saw kerf from closing behind the blade. There are little to no forces on it from any direction, except occasionally some pinching and rearward force. Look at some of the manufacturer supplied and after-market splitters out there. At least one brand is made out of plastic!!

Alan, I agree, your suggestion is possible but your looking at least two links for your mechanism. The cost of manufacturing and assembling two links with the minimum of runout needed to create the stiffness needed by the function of a riving knife might be quite high. The performance would certainly draw criticism when compared to solidly attached designs.

Poor bean counters! Get all the blame! And does anyone think they will become one penny richer for all their profitable influence over the company they draw their wages from?

Now -- just think of a good opportunity to sell a bunch of saws today. Just tell your potential customers that if they wait until tomorrow, they will have to pay $800 more because of a Government mandated requirement for a silly little riving knife that will most likely be jerked off and tossed in the trash the first time it gets in the way of some real work.

So you better buy your new saw today. I think we have just three of the old models left. Wait, lem'me check our inventory on my computer. Oops, nope, just two left. Which one do you want? I can't guarantee we'll have one for you tomorrow.

Interesting cost estimate, care to elaborate? Government mandate or simply an Underwriters Laboratory approval?


Vic

[Larry Conely]

I'm not sure I can add any more relevant information. I have an INCA 12" table saw with a riving knife. I've owned it for over 15 years. It is always perfectly positioned and I have not had a kickback in that many years of amateur use. The blade rises and falls in a straight line, not an arc. I doubt I will ever purchase another saw, but I would never own a saw without a riving knife.

[Steve Sawyer]

Loren,

Maybe I missed something. Where is the government mandated requirement for a riving knife.

Some people just like to speak in terms of hyperbolic absolutes, and if they can make a case against our government in the process, they will.

From what I understand, the situation is that as of this year (2008) UL (an independent, non-governmental testing service) will no longer certify a table saw of new design unless it's equipped with a riving knife. Existing designs are grandfathered for a few years (I've seen some quote until 2014). And it isn't costing anyone $800. The Grizzly G0661 is about $800 in total, the Jet I just bought was $1500, and the PM2000 goes for about $2200.

I think someone spoke of a cost of $800 to retrofit an existing saw with a riving knife, which means replacing the entire trunnion assembly. The point of THAT is to illustrate that it isn't practical to retrofit, that it requires a new design to do the job right.

[Ken Fitzgerald]

I couldn't understand why the existing trunions would have to be modified until Larry posted that picture of the riving knife and then it struck me ...........Most trunions tilt to raise or lower the blade.

For the riving knife to maintain it's position with respect to the postion of the blade, the trunion has to move vertically. If the trunion tilted instead of raising and lowering vertically, the knife would change and could be either higher or lower than the blade (depending on which way the trunion tilted w/respect to the riving knife) and could not only defeat it's designed purpose but actually become detrimental to the safe operation of the saw. Of course you could manufacture some type of lever action or cam action to offset this but................

In any case it would require redesigning and retooling and increased manufacturing costs.

I see the light! Fiatlux!

[Karl Brogger]

I know I ranted on this before, but riving knives give me the willies. So do blade guards. Don't put your hand in front of the blade and every thing is fine. Trust me I've ran some really stupid shit through a table saw.

In 10 years of doing woodworking at a professional level I've never worked at a shop that had a single riving knife, on a single saw. I can count the number of kickbacks I've had on my fully fingered hands. The only time we ran guards is when we got the phone call from another shop that OSHA was around town. The first table saw I bought both sat on a shelf for 3 years before I finally just pitched them in the trash. The last table saw I bought it went into the garbage as soon as I unloaded it.

Now air clamps always get me. I've gotten fingers caught in every single stupid pnuematic clamp at one place I worked at. Cope clamps, face frame tables, castle machines, and pnuematic door clamps, (Which was the worst one BTW), for some reason I have a mental block on air clamps.

Just because someone gets hurt doesn't mean we need legislative action. We've got too many laws already, and to many mindless civil servants trying to enforce them. If a-holes stop sueing everyone else everytime they do something to THEMSELVES the world would be a much shinier place.

[tim rowledge]

Same old story; "oh noes! woe is us! this will add a gazillion gold pieces to the the price of the widget!"
Seat belts in cars. Airbags. Catalytic converters. Fused plugs on appliances. Smoke alarms in houses.
Every time some feature is proposed the manufacturers scream and holler about the end of the world. I seem to recall UK car companies trying to scare customers with claims of adding a couple of thousand pounds to the cost of each car if the evil catalytic converters were mandated. Did actual prices go up? Nah. People will pay what they find acceptable and manufacturers have to live with that. Same old story.

[Steven Hardy]

I can tell you that before I boughy my steel city saw I looked at the models with and w/out riving knives. There is a considerable difference in how the saftey devices are attached to both saws. That said. The way I understand is that as of 2009 every new saw sold will be required to have a riving knife. If that is the case the change to riving knives should be a very small difference in prices. If there would be an option to buy with or w/out a riving knife. I can understand the extra cost to buy the saw with the knife(still not $800). But since it is going to be mandatory the costs will be made up soon enough because the extra $20 added to every saw would off set the cost of redesign. My brother works in a factory as an engineer he tells me the re tooling cost would be next to nothing. I think it is just the bean counters saying we have to requop the costs as soon as possible.

I think the story with most manufactureres is "Why include something and lose the opportunity to upsell the item?" I believe that: most accesories not included "in the box" are grossly overpriced (relative to manufacturing cost).

[Glen Blanchard]

I know I ranted on this before, but riving knives give me the willies. So do blade guards. Don't put your hand in front of the blade and every thing is fine.

Karl,

I would think that if it was just that simple, there would be more folks walking around with intact fingers than there are.

I'm trying to wrap my brain around why riving knives (JUST a riving knife - no blade guard) give you the willies. A properly adjusted riving knife never gets in the way. The only time I remove mine is if I change blades. Why would it cause any discontent?

[Peter Quinn]

I have the beis splitter on my PM66 and it works well for me. It is the same thickness with in thousands as my full kerf blades, set up easily. comes in and out easily, and those kick back pauls that some hate have saved my butt more than once. I have yet to cut any wood with so much tension that the difference between the 3/16" gap between to the blade that a riving knife would create and the gap my splitter creates made a hill of beans. As far as non through cuts it would be nice to have a riving knife there but thats not my highest likely hood kick back operation and iI've never felt lost without one!

As far as the previous suggestion that a ZCI helps prevent kick back, perhaps you could explain that theory again, cause us slow guys missed that the first time. It might stop small off cuts from becoming torpedos, but how does it affect a serious kick back?

I see the riving knife as a marginal improvement worth including on new models. Its not quite the emperor's new clothes, but its close. I for one would never pay to have my cabinet saw retrofitted with a riving knife. For what? More important would be some serious dust collection, now thats a retrofit I would throw down for.

[Karl Brogger]

It is just that simple though. I think the idea of a kickback has been somewhat inflated too. I've gotten hit by things catching and then whipping out of a saw, it doesn't feel nice, but its a good solid reminder of why you don't allow those things to happen. Most animals respond well to pain, including humans.

Whacking a finger off, or getting a kickback isn't an act of god. It's not lightning where it is out of your control. Its having your head elsewhere and not paying attention to the signs of the proverbial poop hitting the fan. I've been there, hung over or thinking about something else and "oops". Driving a car in poor weather, flying a plane, open heart surgery, being in the middle of a combat zone, there is all sorts of things that demand 100% attention to come out unscathed or not kill someone else unintentionally. Woodworking is no different if you want to count to ten with out removing your shoes. These things are sharp, powerful, and dangerous when not granted the proper amount of respect. I've seen alot of guys get mangled because they forgot that whatever they were doing could hurt them. Whether it was a saw, shaper, chisel, motorcycle, icy steps, whatever, life's dangerous, having your head up your butt makes it more so. I'm not saying I don't make mistakes either, but preventing such things requires more between the ears than a piece of metal or plastic.

While it can be said that a guard or a riving knife will thwart or prevent an accident I just don't like em'. I like a naked blade, I can see all the issues before they arise. It's probably more just because that is what I am used to. I'm not trying to convert anyone, but for me the hassle isn't worth it and with proper care isn't neccesary. I do everything I can to keep my digits out of harms way. I spent $800 on a clamp for the shaper for coping door rails. I worked at a place all we had was a T-square. That scared me everytime I used it.

[Steve Sawyer]

As far as non through cuts it would be nice to have a riving knife there but thats not my highest likely hood kick back

The advantage, Peter, isn't so much preventing kickbacks on non-through cuts (I agree that kickbacks are much less likely in that situation), as it is that you seldom, if ever, need to remove the riving knife. Splitters must be removed for most non-through cuts, and I know that I'd be careless enough (or lazy enough) to not put it back on afterwards. With the RK that's never an issue. I don't even need to remove it to change the blade.

I agree that the additional advantages of the RK over a good splitter (and I've heard nothing but good things about the Bies) - that gets used - makes it hard to justify the trouble and/or expense of figuring out how to retro-fit an RK.

[Peter Quinn]

The advantage, Peter, isn't so much preventing kickbacks on non-through cuts (I agree that kickbacks are much less likely in that situation), as it is that you seldom, if ever, need to remove the riving knife. Splitters must be removed for most non-through cuts, and I know that I'd be careless enough (or lazy enough) to not put it back on afterwards. With the RK that's never an issue. I don't even need to remove it to change the blade.

I agree that the additional advantages of the RK over a good splitter (and I've heard nothing but good things about the Bies) - that gets used - makes it hard to justify the trouble and/or expense of figuring out how to retro-fit an RK.

Guess that's what I'm saying Steve. I have the beis splitter. I use the bies splitter for every cut where it is applicable. It only come out when actually necessary as it takes only seconds to remove/install. That or a simple shop made version is the way to go on a traditional cabinet saw. Forget the $800 retrofit. The guard with build in splitter that came on my 66 was a joke, and I wish it had been optional. I'd love to send them back that POS for a refund.

If manufactures want to include a good riving knife or even just a splitter that is actually useable on new machines then more power to them and its about time. I sure would have bought a model that had one if they were available when I got my saw. I see the riving knife as a nice tweak that is just beginning to jump the pond, not a great leap forward or a must have. There out to be something in there keeping that kerf open when ripping off the fence. Riving knife? Splitter? Piece of frozen hot dog? Something.

I worked for years in a shop that had 4 cabinet saws (one was an SCMI that came with a riving knife) and a big slider. All had the guards/splitters removed. Every guy in there could count to ten. Long push blocks, feather boards, and power feeders were on each machine and got used all the time.

Before I'd make riving knives mandatory I'd require manufacturers tap the tables and offer a power feed bundle with each saw as well as hold regional educational seminars on safe saw use. That might prevent some accidents. Perhaps a wrench to tighten up the nut that holds the wood to the table and pushes?

[Steve Sawyer]

[quote=Peter Quinn;862395]Before I'd make riving knives mandatory/quote]

I don't think anyone (at least around here ) is suggesting making anything mandatory. UL, an independent organization, has made a decision as to the importance of a riving knife as a safety enhancement, and the insurance industry seems to be paying attention to that.

Personally I believe in the value and for me it was a "must have" when making my recent purchase, especially as it didn't add noticeably to the cost, only limiting my range of choices. Others have found other (and equally good, for them) choices as to how they want to work safely. That's as it should be.

Splitters work, as do featherboards, power feeders, paying attention and not working "under the influence" . I lost the tip of my left thumb many years ago to my tablesaw (my fault, not the saw's), so I might be just a tad more paranoid than most.