Kickback

[cabinetman]

In adding to what's already been said, I believe that injuries will be minimized by the proportionate attention to operating the tool or doing a procedure. I've seen very bad cuts done with a simple utility knife, or that beautiful chisel, slipping out of a phillips head with a cordless and plunging the bit into the other hand. I could go on, but in reality, shop dangers are where and when we let them happen. Sure, kickbacks are dangerous.

This all goes back to my statement that I've made in different posts, goes something like this: Before doing a procedure, to ask yourself "How is what I'm doing going to hurt me?"

Lack of concentration, distraction, and rushing, I feel contribute along with whatever deficiencies the tools have. I've been cut by dull knives and chisels more than sharp ones.



A THING OF BEAUTY IS A JOY FOREVER - John Keats

[Ed62]

It's agreed that the article did not mention a lot of things that should not be overlooked. But what the article did very well, is that it caused you to think. The part about blade height gave me reason to re-think that part of it. What he said made a lot of sense, and it made me think about my preference concerning blade height. I'm still not 100% sold on having the blade 1" -1 1/2" higher than the stock. I'll have to give that more thought.

Thanks, Niki, for the link.

Ed

[lcm1947]

I got several things out of it like blade height. I see no problem with 1- 1/1/2" if the guard is on?

[Stytooner]

I agree in theory. Today's blades are designed differently than they used to be. When the blade maker's themselves recommend from a half tooth exposed to the gullet exposed, I take that recommendation to be the optimal cutting zone. They have designed the blades to cut best at that tooth angle on the stock.
There is a greater chance for kickback and a more severe kickback with the blade raised so high, should something go wrong. It's more blade in the stock and as such is more susceptible to the change of angle. Flexing of the blade is more likely to occur as well.

The mention of a guard or any safety device in the article would have went farther than to simply recommend such a cutting height. I am not saying that you shouldn't cut with your blade that high. Thats up to the guy doing the cutting. I'm saying that it's been my experience that it is more dangerous than following the manufacturer's suggestions. It's only dangerous though when something goes wrong.

I didn't mean to sound like I was dissing Niki, but something was lost in translation. That was certainly not my intent. My apologies if I scratched any fenders. I get asked questions to some of these same issues almost daily. I'll never recommend things that I have done and nearly got hurt doing. The high blade is just such an instance. I have become passionate about the accuracy of safety info because there is alot of false and incomplete info lurking about.
Niki, I enjoy your posts and the information and projects you share. Don't take my negativity toward this article as anything but that. Thanks for posting it.

[niki]

Hi Lee

On the contrary, I have to thank YOU for bringing to my attention to Ray's article and what you call "my negativity" is only a part of civilised dialog and of course not everybody has to agree with the other side, otherwise, it's not a dialog and not exchange of views and nothing will be learnt from the discussion.

As long as it's not a personal attack (and this discussion is far away from any personal attack), I see it as a building and learning discussion.

Now, about the blade height;
I don't know what kind of blade guard everyone is using (or not), but when I put my blade guard on the riving knife, it covers about 1"~1½" of the blade, so if I set the blade to minimum height for the board thickness, it's actually around 1"~1½" above the board.

I attached 2 pics from other post,
On the first picture, you can see the blade guard just above the board.
On the 2nd pic, I removed the guard, to take the next picture (but did not change the blade height).
The board in the pic is 3/4" melamine so you can judge what is the blade height.

Normally, I work with the blade guard installed, and because I don't see the blade, my eyes are automatically diverted to the fence to watch for any deviation of the board from the fence.

In the very few cases that I work with the guard removed, I noticed that my eyes are concentrated on the blade, and I know that it's not correct and I have to watch the fence instead, but the blade is more scary so I'm looking at it...

I would like to advise to work with the blade guard installed and than, the eyes will look wher they have to look, at the fence.

Looking at the blade will not tell nothing about impending kickback...

niki

[Ed62]

There is a greater chance for kickback and a more severe kickback with the blade raised so high, should something go wrong. It's more blade in the stock and as such is more susceptible to the change of angle. Flexing of the blade is more likely to occur as well.

That's exactly the way I see it. But the explanation about where the teeth are coming in contact with the workpiece, and the direction of the force into it gives me something else to consider. But when all is said and done, I think the high blade cons outweigh the pros. I'm sure others will disagree.

Ed

[drumpriest]

Ed, the increased number of teeth involved in the cut is exactly what the Freud rep claims to want. Basically you are getting a smaller amount of material being cut by each tooth at the same feed rate.

[niki]

Hi Keith

I really cannot understand the Freud recommendation on the blade height.

If the recommendation is for "no guard", it looks like Frued is telling us not to install blade guard (which I don't believe)

If it's with Overhead guard or alike, they have to declare that "this blade is designed for use with overhead guard only".

But for blade guard like I have, that covers the blade 1½", there is no other choice but to set the blade 1½" or so above the work.

niki

[drumpriest]

Niki, at no point did I state "no guard". In fact, in the USA most saws do not have riving knives, and it is Very possible to set your blade height to just over the cut height without it interfering at all with the blade guard. Also, on the saws here that do have riving knives, the ones I've seen don't have a limitation like that one you describe.

I did find that with my shark guard, I had to set the blade slightly higher than the recommendation by the Freud rep, but only by about 1/8" or so, to allow for clearance of the back end of teh shark guard. On the PM2000 the guard doesn't force this type of limitation. (it is another riving knife saw)

The height recommendation from Freud involved the cut angle and mechanics of the teeth of the blade. There are some variations depending upon which blade you buy, specifically for laminate blades I think.

I've not actually seen a saw here that limits you to having to have the blade an inch or more above the cut to allow for the guard. I find it odd that yours would require that.

[niki]

Thank you Keith

Now I understand it all

If you go to page 2 of this thread, on the last reply you will see 2 pics of my guard that is probably different design than the US ones

Thanks
niki

[drumpriest]

No problem Niki, I saw the picture, hard to tell how much is covered from that angle, but from your description I can envision it. Definately different from what we see here in the states most of the time. Most of the table saws here have nearly identical guard setups. After having a BT, I knew that I wanted to have a riving knife on my saw. There arn't that many available in the US market.

[drumpriest]

Here are a couple of images of some American style guards. The left one is from a delta contractor saw, this is the typical guard found on table saws available in America. There are variations on this theme, but you can get a general idea. The one on the right is the PM2000's guard, which is a riving knife system, much like the BT3x00 series guards.

[niki]

Thank you for taking the time Keith

Yes, it's different method.
If I understand correctly, you have to remove the riving knife for "non-through" cuts (like dado).

I added 3 pics of my TS, as you can see, the minimum blade height is about 1"+ (the 1st pic just shows the blade and riving knife at full height)

niki

[Stytooner]

Niki, I don't know if you are using this correctly or according to the maker. It may be that different makers say different things about how to use these type RK's. Just the other day, I was working on a conversion for a 12" Laguna TS. These have a RK very similar to yours.
The owner of this saw stated that Laguna recommends against lowering the knife so that it is below the teeth. This is how we all like to use a RK and therefore there is less of a fiddle factor involved with it.

I feel the sole reason they suggest this is because of the location of the guard when feeding stock with the knife set so low. If you raise the knife up when attaching the guard like Laguna recommends, then you would not have as much blade exposed when making a cut.

Your manual may be different, but this is the cause of you not being able to lower your blade more. Your knife is too low when the guard is in place.

The Shark is designed with the barest minimum distance from the top of the knife to the bottom of the clamp that holds the guard. The guards bottom is in the same plane with the bottom of the clamp. When set right, there is no more than about 3/8" blade exposed when making a cut. It appears as though your guard and Laguna's as well uses a lot more Real Estate from the top of the knife for mounting it.

[wassaw998]

So - the linked article's premise that a blade height of ~1" above the surface of the wood being cut reduces the chance of kickback is not correct? His premise makes sense to me considering the forces produced by the blade / direction , although I had as a standard of practice always set the blade much lower, my primary reason being to have as little exposed blade as needed in case of an accident.