Learned the Power of my Tablesaw today!

[James Cubby Culbertson]

Hiya, It's just a Jet 1.5 horse contractor's saw. I was cutting the ends off of a 2 in thick slab of cherry and maple (cutting board season). Normally not a big deal. I was using my homemade crosscutting box with my 1/4" lexan guard (similar design to Kelly Mehler's). Anyway, I didn't notice but the cutoff (roughly 1/4" x 2"W x 11"L) had not fallen by the wayside but instead ended up riding on top of the blade. Before I could power down, the blade caught and threw this seemingly miniscule piece. Well, that little piece of wood shattered my lexan guard (the front piece that sits at 90 to the blade...see Kelly's design) and there were splinters of wood and lexan flying all over the place. Fortunately for me, I always wear a face shield so I survived just fine. Checked out the saw blade, no missing teeth. I almost shudder to think what a 3hp saw could do!!

So my question, is 1/4" lexan enough? After today, I don't think so. I was looking at purchasing an Exaktor or Excalibur but from what I saw today, I think I'll build my own that acts similarly to the Brett guard (ie. guard does not ride up and over the workpiece...it actually will hold the workpiece down). Not sure if I should go with 1/4" or thicker on the lexan.

Cheers, cc

[Bob S.]

Glad to hear your weren't hurt. You say that was 1/4" lexan and it shattered? Sure doesn't sound like lexan to me, more like Plexiglas. I have 1/8" thick lexan in the windows I built for my shed and I've clobbered them with ends of wood while stacking and with garden tool handles and never cracked them.

I won't say lexan can't break under the right conditions but a 1/4" piece is some very tough material to break and as I recall, it isn't supposed to shatter.

Bob S.

[James Cubby Culbertson]

Yup. It was lexan for sure. Peeled the clear protective coating off of it myself. I've been looking at the guard a little more. Appears that the lexan came apart right where the glue joint was. I didn't see it, but I suspect the wood put pressure on the piece and it came loose and flew into the saw blade at which time it was shattered. So I suppose it really wasn't the lexan that failed, but the glue joint. Cheers, cc

[Charlie Self]

CC responds:

I've had Lexan shatter myself. I was using it as a zero clearance insert, making a new one in fact, probably 15 years ago. Brought the saw blade up into it too fast and had Lexan all over the shop. Knocked my glasses off, generally startled the daylights out of me.

Also made me glad I was no longer riding motorcycles, where I had for years used Lexan helmets.

All it takes is a slight glitch anywhere in the process, and weaknesses are cast in, I guess.

Charlie Self

"I have as much authority as the Pope, I just don't have as many people who believe it." George Carlin

[Rick]

LEXAN is polycarbonate, and can be formed cold like sheet metal. Local fab shop routinely bends 1/4" material to make machinery guards. It is succeptable to scratching. Mills nicely with a router, especially when you use end mills designed to cut polycarbonate.

Plexiglas is methyl acrylic, and is brittle. It WILL shatter if you overstress it, but it is much harder to scratch than LEXAN. Haven't milled any Plexiglas in quite a while.

You may well have had Plexiglas Charlie ... at least from the symptoms. Sure don't want to experience ballistic plastic in any form.

Regards,

Rick

"Charlie Self" wrote >

...

[Ian Dodd]

Like Bob S., I wonder if you've got genuine Lexan. I work as a cameraman in film/TV. Whenever we need to set up a safety for explosions and gunfire in front of the camera, we always use 1/4" Lex. I've had some pretty scary pieces of shrapnel propelled my way over the years, but nothing more than a small scratch on the Lex ever resulted.

Ian

[Jay Windley]

The Apollo-era "fishbowl" space helmets and visors are 1/4" Lexan too. It's normally *very* impact resistant, which makes me wonder if the machine guard in question had a manufacturing defect, as you suggest. Or perhaps the glue chemically compromised it in some way.

--Jay

[Andy Dingley]

Lexan is prone to chemical damage that then makes it brittle.

I once saw a spectacular accident when an 8' x 4' Lexan window around a CNC machining centre let go after a fairly small impact. It turned out to be the detergents in a water soluble cutting oil.

-- Die Gotterspammerung - Junkmail of the Gods

[CW]

If it was Lexan, it wouldn't have shatered. Sounds like Plexiglass.

[Wayne K.]