My vote for the riving knife!

[Rob Price]

Okay, so I'm using some wide plank, quartersawn African mahogany for some large panel doors. A friend with a huge drum sander planed up some 20" wide boards for me, I was crosscutting them on my TS with a sled when I met major resistance. I couldn't advance the board at all. Thinking my sled was catching on something I first pushed harder, but then stopped the saw. I couldn't back out either, then I realized the board was pinching on the riving knife so hard I couldn't free it. After about 10 minutes of prying, and jiggling and coaxing, I finally got the board free of the blade and riving knife (praying I hadn't bent my blade or saw). I'm a big dude, former college O-lineman, and I couldn't get this thing off the saw. The kerf completely closed at the back of the board when I finally got it off.

I tried to crosscut the same board on my miter saw (thinking I would flip it end for end) and it bogged down and stalled :eek:

Needless to say the wood had some major tension in it, but in retrospect, without the riving knife (standard blade guard doesn't work with my crosscutting sled, or any sleds for that matter) I'm pretty sure it would have been my face vs a 20" wide, 5' long plank of mahogany being tossed by my 3HP TS motor.

Just wanted to share the experience, I've never had wood bind like that on a crosscut, scary. I had to literally nibble the rest of the crosscuts, go in two inches, back out, let it close a bit, and then nibble a few more inches. Finally got the panels cut out, and they stayed flat. Rails cut from the same board stayed flat and straight, so I'm not sure what the deal was, but that board was clamped onto the riving knife like no one's business.

[Ken Fitzgerald]

Rob,

My contractor saw has a splitter on it. I was recently ripping a piece of fir for a painted shop cabinet I was building. It started to get more difficult to push during the rip and I watched the board cut and comeback together pinching the splitter in the process.

Some folks never use them. The only time I don't use the manufacturer furnished splitter on my contrator saw is when I am using my dado blades.

It's spooky isn't it?

[Anthony Whitesell]

That mahogany must have been seriously stressed if the kerf closed during a crosscut.

I found that 2x4s ripped into 2x2s are a very useful size. I recently made my now 3 year old daughter a handrail so she could reach it (half height) of 2x4x12. My wife had to support the outfeed during the rip. I hit a magic spot in the board that caused it to bow (but not pinch on the blade as my saw is too old to have a splitter or knife). It bowed so quickly and badly that before I realized what could happen and with still 18" to cut the board "exploded". The bow tore the board apart and moved the fence away from the blade over 2 inches. Neither a knife or splitter would have helped.

[David Nelson1]

That mahogany must have been seriously stressed if the kerf closed during a crosscut.

I found that 2x4s ripped into 2x2s are a very useful size. I recently made my now 3 year old daughter a handrail so she could reach it (half height) of 2x4x12. My wife had to support the outfeed during the rip. I hit a magic spot in the board that caused it to bow (but not pinch on the blade as my saw is too old to have a splitter or knife). It bowed so quickly and badly that before I realized what could happen and with still 18" to cut the board "exploded". The bow tore the board apart and moved the fence away from the blade over 2 inches. Neither a knife or splitter would have helped.


Wow thanks for sharing guys never knew that could happen.

[Brian Kincaid]

Wow thanks for sharing guys never knew that could happen.

Ripping/crosscutting construction timber will suprise you. I was cross-cutting 2x12's at a site and the kerf pinched and locked the blade on my miter saw. I was suprised by this once, then again when I was doing shallow cuts to keep from binding. The best I could do was start shallow and just keep making deeper and deeper non-thru cuts until it was through.

-Brian

[JohnT Fitzgerald]

Wow, that's quite a bit of internal stress!!!

This is something that needs to be highlighted more with 'current' generation saws. I recently upgraded from an old Delta TS, and I can honestly say that the ease with which I can use the splitter/blade guard or riving knife makes me more likely to use them. There's another thread about the stupid "fried chicken" demo on a Sawstop. I have a SS, and I really do think they are doing themselves a disservice by not doing more demos on the benefits of a riving knive or splitter. Ditto for any of the other current designs for Delta, PM, etc.

[anthony arguello]

being a beginner in actual woodworking, I think this information is very important to know. I have some construction experience, but I never really thought about what could happen when crosscutting and wood getting hung up and 'exploding'. Thanks for sharing the experience.

[Don Alexander]

The bow tore the board apart and moved the fence away from the blade over 2 inches. Neither a knife or splitter would have helped.


uhhhhh your fence moved? that needs to be fixed ASAP your fence shouldn't move period , destroy the board , bend the blade sideways , but the fence should be rock solid anything else is very unsafe and yes a splitter/riving knife would have helped alot had your fence been solid like it should be

if the fence can't be locked down solid you should not use that saw in the interests of your health

[Dave MacArthur]

Good post and interesting story, thanks!

[glenn bradley]

Good stuff Rob. I do shake my head when folks "brag" that they have never used a guard or a splitter/RK in 30 years and blah, blah, blah. I don't know what material they work with but I have had a few boards with some amazing movement while milling. I'll take the safe route, thank you very much ;-)

[Lex Boegen]

Good stuff Rob. I do shake my head when folks "brag" that they have never used a guard or a splitter/RK in 30 years and blah, blah, blah. I don't know what material they work with but I have had a few boards with some amazing movement while milling. I'll take the safe route, thank you very much ;-)

I agree with you one thousand per cent! Nobody hands out awards for doing risky techniques, and even if they did, it would be a poor substitute for still having ten fingers. A friend of mine was using a table saw and although he had just turned the saw off, the blade was still spinning. He had removed the stock splitter and guard so the blade was exposed. He reached over the spinning blade to remove the off-cut and before he realized what had happened, he had split his thumb from the tip down to the knuckle. He has an ugly scar and limited use of that thumb, which he'll never recover the use of again. I've never had an accident with tools, because I am practically paranoid about their use. I wear ear, eye, and lung protection and think each operation through before I turn the tool on. I keep reminding myself that the biggest risk factor is me becoming complacent because of familiarity with the tool. I plan on leaving this life with exactly the same number of body parts that I started it with. :D

[Philip Rodriquez]

I just had something like this happen, recently, when cutting some 6/4 Cypress. In my case, I encountered too much resistance, while feeding it. I immediately stopped the saw, waited for the blade to stop, and removed the material – it was pinching my riving knife. Cypress is soft, like pine. My TS is a 3 HP ICS SawStop and I was using a new WWII Forrest blade. I ended up resetting the fence and taking ¼” passes until I got close to the 2” part I needed. I also rejointed the edge as the board released the stress. Instead of two parts, I only got one.

I cannot stress how important it is to pay attention to everything you are doing. If the wood feels like it is taking an excessive amount of pressure to feed or control the cut, expect the worst. Stop feeding the material, turn off the machine, and wait for everything to stop before you try to remove your material. Even with a riving knife, you can still have it kick-back on you if you try to pull back your material while the blade is moving.

[Will Overton]

Glad to hear I'm not the only one that had a problem with cypress. The only way I got to salvage any of the board was to cut it down on a bandsaw.

I first tried to rip it on the ts ... no go.
I then decided to cut it into shorter pieces on the ras ... no go.

On the bandsaw, things went fairly smooth.

[Chris Friesen]

I found that 2x4s ripped into 2x2s are a very useful size. ....It bowed so quickly and badly that before I realized what could happen and with still 18" to cut the board "exploded". The bow tore the board apart and moved the fence away from the blade over 2 inches. Neither a knife or splitter would have helped.

This is why I rip construction lumber on my bandsaw.

Also, there's something wrong with your fence if this caused it to move.

[Anthony Whitesell]

There's nothing wrong with my fence. I can't push it with my hand when it is locked (I know I've tried. LOL).

As I hit a particular spot in the board, it released an extreme amount of causing the right half of the board to bow and close the kerf 9 feet from the blade. At the rate a board is feed through a table saw, by the time I saw the gap at the blade opening it was too late to try to comprehend what might happen. While the right half bowed, the left half was put under tension when the kerf was closed. When the board broke, the left side straightened suddening causing it to try to shift. It couldn't go to the right because of the blade and featherboard. So it moved the fence. I don't think I have ever found the off switch so fast.

I found it really impressive. My wife, not so much. When I finished I have a fairly straight left piece 12 feet long, the right piece was straight for about 8 feet. The last 4 ' make a really nice arc, about 18-20 in height. Impressively really.

I never even thought of the bandsaw. I think the reason is that the blades I have wander so much that I don't think to use it on long cuts that must be straight.

[Philip Rodriquez]

Nice, I didn't think about using my BS... Doh!

[Howard Acheson]

>>>> I finally got the board free of the blade and riving knife

The way we used to do it in the shop I was involved with was to put a wedge in the kerf either right after the riving knife of just before the riving knife. Sometimes a large screw driver or a chisel will work. The idea is to wedge the kerf open.

Once you free up the kerf, you can generally complete the cut but it's generally safer to get the board off and figure out some other way to cut it.

[Don Morris]

I always thought I paid too much for my Biesemyer add-on splitter for my Griz 1023SL. Around $125.00 as I remember (probably no more that $5.00 of metal). Maybe not.

[Rob Price]

>>>> I finally got the board free of the blade and riving knife

The way we used to do it in the shop I was involved with was to put a wedge in the kerf either right after the riving knife of just before the riving knife. Sometimes a large screw driver or a chisel will work. The idea is to wedge the kerf open.

Once you free up the kerf, you can generally complete the cut but it's generally safer to get the board off and figure out some other way to cut it.

Trust me, I tried. The board didn't make it past the knife to begin with, and I keep it pretty close to the saw blade and I didn't want to tear up the blade with my screwdriver. I honestly thought about taking the dremel to it right next to the knife, but I was finally able to bend the wood enough to wiggle it up and free. I only had the top of the teeth above the board so I didn't have far to go. I think I definitely made it worse by pushing harder :o