Kickback

[Connor Aston]

[todd]

A riving knife adjusts its position as the blade height is changed. It is curved to fit the shape of the blade and maintains a consistent distance from the blade, as opposed to a splitter. It's also set up so that the height of the riving knife is slightly less than the blade height at any time, permitting non-through cuts.

todd

[Warren Weber]

(snip) Know all about that plywood. Had a 12 x 12 inch piece of 3/8 ply peel the top of my left fore finger down to the tendon. On the way home from ER I decided it was time for a good hold down. Purchased one with two spring loaded adjustable rollers. This works great.

[Peter Huebner]

MDF (and ply) suggestion: don't use a table saw :-) yes, I really do mean that. When I want to cut mdf panels I have two tables/workbenches of equal height that I arrange so the cut falls in the gap after I place the work on them. I then securely clamp an aluminium fence to the work, and I run my DeWalt circular saw, fitted with an aluminium cutting blade, over the top of the work. I get superclean cuts, dead accurate to 1/2mm and I don't have to lug the sheet over the saw which is never all that accurate unless you have a really good carriage. Only truly safe way to do that is to have a specially equipped panel- saw, in my opinion. If the work is smaller than 18" I use the radial arm saw.

I've never, ever had a problem, other than making sure the fence doesn't ski on the superslick mdf dust. I now use a nonslip latex matting between fence and work to prevent that :)

-P.

[Bugs]

Your posts all make a good argument for building a saw sled like David Marks uses on his DIY programs. He typically opens the program by cutting a small piece of wood on the sled while holding it with a pencil eraser. A very safe and stable method everyone should use. Bugs

[mew]

I haven't looked at hold downs. That is a good idea. To address the circular saw post... I have tried that but I can never get a really good cut. Must be my technique.

[charlie b]

Second illustration shows the difference between a splitter and a riving knife. Notice that th distance between the exposed rear of the blade and the splitter INCREASES as the depth of cut decreases while with the riving knife the distance between the rear of the blade and the knife remains constant - AND CLOSE.

charlie b

[charlie b]

By "good cut" do you mean the cut line is straight but you're getting splintering on the edge? or the cut line is not straight because you let the saw wander?

The former problem can be somewhat mitigated by prescribing the cut line with a utility knife, using the right saw blade, set to the minimum "height" AND with the "good face" down (splintering and tear out with a circular saw is on the side side of the stock whereas with a table saw, it's on the bottom of the stock on the table)

If wandering is a problem - they do make a stragith edge clamp and saw holder that fits in a groove on the straight edge. No more wandering Clamp 'N Guide makes this type of thing. Of course, if you've got deep pockets, FESTOOL has a plunge saw and straight edge guide . . .

charlie b

[charlie b]

Trying to cut up a full sheet of ply or MDF on a table saw - by yourself - is a recipe for a bad back and often - bad cuts you have to do over again. Half sheets pretty much the same thing. When you get down to quarter sheets the problem becomes keeping the edge against the fence - throughout the cut. If you don't, things can start flying in very unpredicatable directions - all at high velocity.

SLIDING TABLE - NO RIP FENCE!

It's still a mystery to me why US table saws don't have a sliding table option. Two miter slots - but no sliding table? A sled with guides riding in the slots on each side of the blade is great for narrow cross cuts. But when you want to work with half or quarter sheets they're essentially useless.

And what the hell are you doing to do with a 52" capacity rip fence system"

Rather than changing the name and/or color of the table saw (Delta's "X" models, "Platinum Limited Edition" "75th Anniversary Model") why aren't American brands actually improving the machines they make (or spec and farm out the actual manufacturing)? OK - so there's a LEFT TILT - but come on - there's not bee much innovation by US machine sellers. Of course, we did come up with SawStop - oh boy!

rant off

charlie b

[todd]

Thanks for reinforcing my point with a pic.

todd

[Enoch Root]

They're busy racing to the bottom.

er

[TheNewGuy]

What caused the mdf panel to sail? Since it's pretty much the most stable material to work with (i.e. it shouldn't have "pinched" the back of the blade), do you know the mechanism that caused it? (Yes, I realize it happened in microseconds).

Thanks, Chris

[B A R R Y]

Because it's cheaper to simply say it's better than to actually make it better.

Barry

[mew]

Well, what really caused it to sail was stupidity. Not using a sled but the fence in combination with sneezing at the wrong moment that caused my hand to twist which caused the piece to twist back into the blade as I was almost all the way through the cut. The stupidity part was not using a splitter or blade guard as I had removed them to use the dado blade and not reinserted them when I changed blades. The factory ones are a real pain to take off and put back. That is why I am looking at an overhead guard with an easily removed splitter. As well as building a sled for this kind of stuff.

[CW]

It's cheaper not to.

[Tom Banes]

Mike:

I went two ways after a couple of "interesting" kick backs. The Bies splitter went into my Jet cabinet saw like it was made for it (it was, of course). Later I added a Delta overhead blade guard. Works like a dream. I bought an extra splitter blade for the Bies and cut it down and removed the pawls, so I can split a board held on its edge. Resawing w/o a bandsaw if you like. Bandsaw is next on my list as splitting a 6" 5/4 board (2 cuts) is a bit spooky even with a fence mounted sled. It works, but it is a bit scary.

Regards

Tom