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View Full Version : Overhead blade guard finished--Pics included



Dan Forman
12-17-2006, 10:26 PM
Well, almost anyway. All that's left to do is enclose the upper part of the vertical extension thingy, and run the 4" spiral pipe from the wye off the main, over the heating duct, then come down to the guard with 4" flexhose. With a 5" pipe going to the cabinet, that shoud give the Gorilla something to munch on.

http://i98.photobucket.com/albums/l279/T-Caster/Woodwork/P1010568.jpg

http://i98.photobucket.com/albums/l279/T-Caster/Woodwork/P1010569.jpg

http://i98.photobucket.com/albums/l279/T-Caster/Woodwork/P1010573.jpg

The heating duct running directly over the saw was both a blessing and a curse. I ended up making a u shaped piece out of 2x4 to straddle it, and screwed it to the ceiling joists. The joists were'nt in plumb, so I had to compensate for that with a few strategically placed wedges. The blessing is, that all of the adjustsments are now easily done without having to stand on anything or strecch unduly.

Most of the designing was done on the fly, as I don't seem to be able to visualize things in stages very well, which explains a few superfluous screw holes and such.

The swinging unit is two pieces of 1/2" maple, with a slot in the first and a groove in the second to accept a piece of 3/4" wide UHMW plastic, through which a 1/4" bolt passes, and is captured in the star knob, which locks the vertical arm in place. I thought I was pretty clever until I tried to lock down the knob, and realized that the head of the bolt was just spinning around in the UHMW, which was countersunk to accept the head. I ended up cutting a coulpe of small slots leading into the recess, and filling in those along with the space left around the hexhead with epoxy putty, which then locked it in.

The outside of the telescoping upright was a scrap of cherry, which was grooved with the dado blade to accept the nearly 1x1 purpleheart inner piece. The twin star knobs have pieces of 1/4 x20 threaded rod epoxied into them, and screw into brass threaded inserts embedded in the cherry. There is a piece of the cherry that was trimmed off that will be glued back on to enclose that part of the upright, but I wanted to wait and see if everything was going to work ok before doing that.

The upright has about 9" of horizontal travel, about the same amount of vertical travel, and the whole thing can swing 180* to get out of the way altogether if need be, or in dire circumstances, be removed altogether, though that would involve disconnecting the flexhose.

I had thought that the draw clasp on the right would keep everything tight when in the closed position, but it doesn't, so I ended up drilling a couple more holes, and just using short screws to lock it up tight. I don't know how often I will need to swing it out of the way, but the inconvenience of having to unscrew it is outwieghed by having it snugged up tight when it is in use.

Since the sliding vertical is only supported by the one bolt, it could swing like a pendulum, so I glued and screwed a short cross piece against the bottom, parallell to the solt, to keep it upright and perpendicular to the saw table.

The guard itself I pretty much copied from Jeffrey Makiel, it's made of 1/4" polycarbonate, with a 1/2 baltic birch plywood top. It took most of a 12x24" sheet of polycarb. . The sides were cut and screwed to the top, then the front and back were cut to fit, and glued to the sides. the short nose piece was done last, and it to was glued on. The glue ( I think more like a solvent really) is very liquid, and a bit got away from me which marred the front a little bit in one place. I then screwed the front and back in place, and figured while I was at it, I might as well reinforce the whole thing. So after trying it first on a scrap, I went to the drill press and drilled some holes for screws to secure the plastic parts to each other. Using a 7/64" bit, and 3/4" #4 squarehead screws (these have no taper), it was not necessary to tap the holes first, saving considerable time. This last step was probably unnecessary (can you say "anal?") but not being familiar with this plasic or it's glue, I didn't want to take any chances with it coming apart in action, and having any more plastic than need be flying about th room in case of any sort of mishap. Like jeff's, my guard will soon be sporting a "mustache".

The port I picked up at local woodworking shop, it's a piece designed to connect 2 pieces of 4" pipe together. I looked around at the Borgs for something first, but couldn't find anything with a 4" outer diameter, then ran across this, and it fits the bill perfectly.

Material wise, most of this was made of stuff I had on hand, scraps that were laying around. I bought the polycarbonate (about $14), the hinge, clasp, dust port, brackets to mount the guard to the upright, various knobs, threaded rod, that's about it, maybe $40 total.

As I said at the beginning, this was a trial and error process, with lots of each. It would be easier and maybe a bit more stable to use a couple of pieces of T Track for the sliding arm to run on, and if doing this again, I might try a beefier telescoping unit, but I think this one will be sufficiently strong.

I spent some time looking at various blade guard threads to see how others went about this, borrowed bits and pieces from them, and came up with this. My thanks go out to all of those who have posted their solutions to their particular conditions. I'll update this when I get a chance to use it, hopefully can get it hooked up tomorrow, need a few transitional pieces from my duct supplier.

Dan

Jim Becker
12-17-2006, 10:32 PM
Nice job on that project, Dan!

Jim O'Dell
12-17-2006, 10:50 PM
Great write up Dan! I will want to build one myself in a few months. I have a 4" pipe over the TS already waiting on me to do so. Capped off right now. How hard is it to cut the polycarb? Did you give any thought to using it for the top as well? I've got some plastic pieces in the shop that were left by the previous owner. I may play with that before I actually purchase something. Thanks again for the report! Jim.

Dan Forman
12-18-2006, 12:00 AM
Thanks Jim and Jim.

The polycarb cuts well on the table saw with a carbide blade, leave the protective sheeting on it until there is a need to remove it. It will protect the surface from sctaches during the rest of the construction. One thing I tried which I thought helped while cutting is to keep a little more blade exposed than usuall. The polycarb tends to want to rise up in the cut, so having the blade higher works against that, seemed like the edges were a little smoother that way. I also used rubberized jointer paddles to push the material through, making sure I put good downward pressure on the material near the blade.

Polycarb will melt with some cutting tools, when drilling the holes to fasten the material to itself, (into the edge rather than the flat face), I would push in and retreat a few times to prevent it from melting inside. Even then, it still formed to the bit a few times, but didn't really stick to it.

I think the plywood is easier for the top than polycarb would be. With the front end slanted at 45*, you lose very little of visability, given that the dust port will block out most of the rest of the view anyway. I wondered whether it would block out too much light, but that doesn't seem to be a problem. I'm sure it would be fine either way, but I just felt more comfortable with the wood.

You might want to identify the type of plastic pieces you have before starting, as my understanding is that polycarbonate is more suited for this application than acrylic (plexiglass) and some others might be. You won't be able to find 1/4" stock at the Borgs either, I had to locate a local plastic supplier to get mine.

Dan

Jeffrey Makiel
12-18-2006, 7:09 AM
Nice job! I like your swing gizmo. Very creative, and functional too.

I found the glue to be very strong for both plexiglass and lexan (polycarbonate). I believe this same stuff is used to glue large display aquariums together and is really an MEK solvent.

As far as cutting acrylic, I agree with your description of how it 'rises up' during cutting. It's very un-nerving for me. I understand the tablesaw blades that specialize in acrylic work well. But I don't do enough projects to warrant this specialized blade.

Again, nice job.

cheers, Jeff

Tom Hamilton
12-18-2006, 8:34 AM
Nice, Dan. I've seen several overarm guards/dustcollectors, and made one for my shop, but never with the swing-out feature. I like that. Hope your patent is in place and air-tight! :D

Merry Christmas, Tom, in Houston, off to the Borg to buy a hinge.

Jim Becker
12-18-2006, 8:45 AM
Dan, my local 'borg does carry 1/4" Lexan. What I had to go to the plastics supplier for was the solvent...that stuff wasn't at the 'borg or any other local retailer. (My first guard was a UniGuard and I built a replacement head to accomodate dust collection...I didn't want to do screws, so I welded it together using the solvent. MEK based and nasty, but it did the job!)

Tyler Howell
12-18-2006, 9:19 AM
Nice one Dan,
Shop is really shaping up.
TJH

Jeffrey Makiel
12-18-2006, 8:46 PM
Jim,
Go to any decent hobby shop and buy Ambroid glue. It's a clear MEK based solvent adhesive that comes in a bottle with a brush. It's applied using capillary action to suck the thin solvent into the butted joint of many plastics including polycarbonate and plexiglass.

-Jeff :)

Jim Becker
12-18-2006, 9:21 PM
Jeff, MEK is what the plastics supplier, umm...supplied...and they are closer than the closest "decent" hobby shop! When I built the guard I described, I dry assembled it on a jig I quickly made with some scrap MDF...and then used a small syringe to do the capillary action thing. Rock solid in just a few minutes.

Dan Forman
12-18-2006, 9:54 PM
Not sure what MEK is , the stuff my supplier gave me is called Weld-On 3.
Methylene chloride, trichlorethylene, and methyl methacrylate. Warning says "This product is intended for use by skilled individuals at their own risk". Hopefully if it's that dangerous it ought to be good.:eek:

Just got the rig hooked up, and it really sucks!. Another pic to follow.

Dan

Noah Katz
12-19-2006, 1:01 AM
MEK = methyl ethyl ketone

Dan Forman
12-19-2006, 2:43 PM
My stuff has a lot of methyl ethyl type stuff, but doesn't mention ketone.

Here is a pic of the plumbing and all. It will take a little while to get used to, as I have not been using a guard before. Sure does take care of the dust though. The mustache is a worthwhile addition, it does catch and redirect most of the few fine chips that would otherwise be propelled out onto the table surface. For those who don't remember Jeffs post, it's just a piece of brush made for the bottom of a door.

http://i98.photobucket.com/albums/l279/T-Caster/Woodwork/P1010576.jpg

Dan

JIm McMullen
12-20-2006, 8:34 PM
Dan-
I believe MEK=methyl ethyl ketone