Riving Knife, A Scribed Line on the

dusty · Post by **dusty** » Wed Apr 02, 2008 7:10 pm

I am pleased when I hear that someone seldom experiences kickback. But I believe that to be an indication of a greater than average skill or a greater than normal attention to safety related details.

If you take that sawguard off your tablesaw, I don't believe you will be able to say that for long.

Also, a significant contributor - we keep our units calibrated (aligned). Rip a hundred board feet with the table malaligned and some form of kickback or binding is extremely likely.

If you go back in this forum and read a few of my posts that were made right after I got back into my shop (after my long bout with infection), you'll see that I had nothing but trouble. The SS was bouging down, heating up, binding, stalling; all signs of problems above the table top.

Once I got back up to speed (had the SS fine tuned, cleaned and lubricated) those problems all went away. I have cut up a lot of wood in the last 6-8 months and the Shopsmith has performed without a glitch. There have been "no repairs" made to the Shopsmith; just good maintenance practices again. A couple resharpened blades improved performance a lot.

Stay safe, use all of your safety gear and keep that puppy fine tuned.

Nick · Post by **Nick** » Wed Apr 02, 2008 8:28 pm

An intresting consideration if you're thinking of working without your upper saw guard: At 4000 rpm, the tips of a 10-inch saw blade are moving at 119 miles per hour. If the blade gets ahold of the wood, it will pitch it at you at this same speed. That's a good 25 to 30 miles per hour faster than a major league fastball and the wood has square corners. Don't think it won't hurt.

With all good wishes,

charlese · Post by **charlese** » Wed Apr 02, 2008 11:37 pm

Thanks Dusty! I saw my scribed line today! No late April fool's! I was really poised for someone to put in an AF post, and I just knew, with your sense of humor, you did it. Scribed line? Who had ever heard of that?

Now, can't help but wonder what other little secrets are hiding around our mark Vs.

Thanks, Nick for pointing out it's use. For some reason, way back in the secrets of my little brain, I think I did read about that line a long time ago. Is it in PTWFE?

Ed in Tampa · Post by **Ed in Tampa** » Thu Apr 03, 2008 1:39 am

Nick wrote:An intresting consideration if you're thinking of working without your upper saw guard: At 4000 rpm, the tips of a 10-inch saw blade are moving at 119 miles per hour. If the blade gets ahold of the wood, it will pitch it at you at this same speed. That's a good 25 to 30 miles per hour faster than a major league fastball and the wood has square corners. Don't think it won't hurt.

With all good wishes,

Nick
Educate me here. I would never operate a table saw without a splitter/riving knife. However I do remove the clear plastic blade guard, only on non through cuts or something really really critical that I need to see the blade wood relationship.
I thought kickback was caused when the wood pinched the blade either by closing the kerf (which a splitter/riving knife would prevent) or by having the wood trapped between the fence and the blade (usually operator error twisting the wood).
Is those assumptions not true?
Am I being unsafe depending on my splitter/riving knife to protect me from Kick back?
Like I said in my earlier post I really don't understand the function of the antikick back pawls. To me it seems the splitter to which they are mounted would prevent the kick back.
I would really like to understand this.
Ed

Nick · Post by **Nick** » Thu Apr 03, 2008 11:17 am

Pinching is only one of the circumstances that may cause a kickback. It is much more common for a piece of wood to shift sideways, the saw teeth catch it, and the machine pitches it at you. Let me tell you about the scariest moment I ever had as a craftsman/instructor.

I was teaching Wood Technology at the School of Engineering, University Cincinnati. One of my students was ripping some leg stock on our 5 hp 14" Tannewietz table saw -- it had a detached overhead saw guard but no riving knife or anti-kickback pawls. The outfeed surface on this saw is massive, so my student was letting cut piece rest on the table, then pushing it clear of the saw with the next cut. The wood was properly cured and shop-dried; it was clear walnut, and there was no "reaction wood" that was pinching the blade. In fact, the cuts were going smoothly and that might have put my student off his guard. At some point, he finished a cut with the wooden part between the blade and the fence and must have knocked it sideways as he removed the rest of the stock. In the blink of an eye, the Tannewietz grabbed the leg stock and launched it like a missile. The wood glanced off the student's shoulder, and then went through a concrete block wall. If it had caught him square in the chest, it would have skewered him. As it was, he got off lightly with his entire upper right arm and the right side of his chest one massive bruise.

I installed an anti-kickback device within the week. And I left the hole in the wall as a reminder to use it.

With all good wishes,

scottss · Post by **scottss** » Thu Apr 03, 2008 11:38 am

Many years ago in my construction days I was ripping some cedar tongue and groove on a old skil benchtop table saw. I cut a piece that left a 1/2" piece that launched like an arrow into my belly. It was fortune it that at the time I had abbs of steel

and it only slightly pierced my belly:eek: . I learnd then and there where to stand and to use safety guards and splitter/anti-kick back in place if all possible.

a1gutterman · Post by **a1gutterman** » Thu Apr 03, 2008 8:57 pm

The best lessons learned are those from ones own experience. Of those, the best ones are those learned with little or zero damage.

Nick · Post by **Nick** » Thu Apr 03, 2008 10:35 pm

Listened to a guy on NPR who had grown up in NYC and moved to Alaska with the ambition of being completely self-sufficient. He described his trials as he taught himself the necessary skills. Towards the end of the interview, he struck a happy note: "I must be doing something right. The times when I almost kill myself are getting fewer and farther in between..."

With all good wishes,

keakap · Post by **keakap** » Fri Oct 09, 2009 8:33 pm

Ed in Tampa wrote:Nick
Educate me here. I would never operate a table saw without a splitter/riving knife.
Ed

Am getting really confused here. Unless you are not including the Shopsmith table saw. Wouldn't it be awfully complicated using a splitter/riving knife on a SS when milling a groove or dado in a workpiece? Like how do you adjust it for different width dadoes and different groove depths? Is kickback even possible with those operations? How about stopped grooves?

Man, I feel like the dummy-o-the-day here, but I just can't picture this scenario. Maybe what I need is a good kickback up-side the haid!

Ed in Tampa · Post by **Ed in Tampa** » Sat Oct 10, 2009 12:34 am

keakap wrote:Am getting really confused here. Unless you are not including the Shopsmith table saw. Wouldn't it be awfully complicated using a splitter/riving knife on a SS when milling a groove or dado in a workpiece? Like how do you adjust it for different width dadoes and different groove depths? Is kickback even possible with those operations? How about stopped grooves?

Man, I feel like the dummy-o-the-day here, but I just can't picture this scenario. Maybe what I need is a good kickback up-side the haid!

Actually I never cut dadoes on my SS. I learned a long time ago that was a very dangerous operation, and in fact you can't sell a saw in Europe that a dado blade can be mounted to.
I use my router to cut Dadoes. Much simpler, much higher quality cut, must safer.

Incidently kickback and actual wood exploding is possible when cutting dadoes. Much like a jointer tension in the wood can be such that as you cut it the wood literally blows apart. Many people have found their hands in the path of a Dado blade as the wood disintegrated before their eyes.