Homemade Riving knife setup

[James Cowart]

Hello, I recently cut my own riving knife out of stainless steel for my Bosch 4000 tablesaw. I used a template I got online for my saw. So far it fits well except for the very top of the knife is not parallel with the tabletop. The front of the knife is about a quarter inch below the top of the blade and the rear of the knife is about an 1/8" below the top of the blade. It angles up as you move back away from the blade. Will this be a problem? So my question is what is the standard setup in regards to height of the knife above the blade. And should the top of the knife be parallel with the tabletop, slope towards the blade, or slope away from the blade. If I remachine the top edge more level, the entire height of the knife will be about a 1/4" below the top of the blade. Is that too much? Or just not ideal? Thanks

[Keith Weber]

Did you mean homemade splitter? A riving knife usually raises and lowers with the blade as you adjust the blade height. They are very complex to retrofit into a table saw without a riving knife. A splitter doesn't move up and down automatically as you adjust blade height.

I also wonder if you didn't mean that the blade was not perpendicular (90 degrees) to the table top, not parallel. I can't see how a riving knife would be parallel to a horizontal surface.

While a riving knife can be higher than the top of the blade, I like to see mine about 2-3mm lower, so that you can do a non-through cut through a board without it stopping when the board hits the knife.

If your riving knife isn't resting behind the blade, then there's a chance it could laterally put pressure on the wood and possible move it away from the rip fence and cause burning in the wood from rubbing on the side of the blade.

Distance from the blade to the riving knife isn't overly critical. It's basically preventing tension in the wood from pinching the back of the blade behind the cut. You'd have to have some pretty serious tension built up in a board to pinch before it reaches your riving knife/splitter.

[johnny means]

It doesn't matter that your riving knife is not parallel to the table top. They come in all sorts of shapes. My saws have ones that come to a point, one is flat on top with holes to m mount a guard. The important thing is that it prevents kickback. As far as the height goes, it is nice if the riving knife sits a bit lower than the blade for making none through cuts.

How about some pics?

[James Cowart]

Thanks guys. I continued to search the internet for some of the measurements I was looking for. About the only variable I saw stated was that the gap between the blade and guard should be about 5mm. And then the top should be somewhere just below the top of the blade. Mine is about a 1/4" below the top of the blade, but I would rather have it more like 1/8" to protect a little more of the back of the blade. After a LOT of tuning and fanagling I got it parallel with the blade vertically and in line with the blade. So now I have another piece of stainless for my full 1/8" kerf blades and I hope I can machine it closer to where I want it to be. 283638

[Keith Weber]

OK, I've got the whole parallel reference now. I was picturing one that came to a blunt point, and not one with a flat top. That extra material that you got there to make the knife flat on top doesn't really need to be there, nor does it create any problems being there, so to answer your question... The top of your knife does not need to be parallel to your tabletop.

I don't know the inner workings of your saw, and I cant tell by the picture. Does that knife go up and down as you raise and lower the blade, or is it fixed in position?

One thing that is important is the thickness of the knife. It should be of a thickness that is thicker than the main blade body thickness, but thinner than the cut width of the teeth.

[Sam Murdoch]

Though you have already done the modification to your saw - here is an article that might add to this discussion. I used this mod on my Bosch TS -http://www.garymkatz.com/ToolReviews/riving_knife.html My saw is currently at a job site so I don't dare try to answer your questions specifically.