Progress on shop made blade guard dust collector < Its too good!

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I'm on iteration #1024 of a shop made table saw blade guard with dust collection. This whole thing got started when I sunk $529 in a jet dust collector and it practically did nothing for my table saw. I've been mocking up prototypes with 1/2" plywood and a brad gun.
My bad-boy dust generator is using a saw blade that's got lots of resin on the blade and crosscutting some old spintery wood.
In my latest test, I was elated to run the test cut and no sawdust escaped. In the midst of my split second elation, I heard a loud metallic clatter. My prototype was so good, it sucked the offcut into the dust collector.
...back to the drawing board.
Bob
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If you ever get it to work, I would sure like to see it!

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Show some pics of your progress.
Chances are someone did it already and can give you some pointers.

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I'm sure every idea I'm trying has been done at least a 100 times and I'd welcome some opinions. There's a natural reluctance to show ugly prototypes because it could be very embarrassing. But what the heck.
The main thing I'm doing that I've not seen any where else is using a 4" hose right down to the guard, instead of shop vacuum size hose. There's no way to effectively seal the dust collection on a table saw near the blade because of the wood moving through and the dust coming off a table saw is moving very fast. I decided the only hope of controlling most situations was sheer brute force. It works. Now I'm going to develop a mini-hood made of lexan on top of the guard so I can see the blade and still have an effective 4" connection.
One observation already - using a tablesaw without the dust is a positive experience.
Bob

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Put a "Cyclone" in line ,saves on filter media , and lets all the chunks of stuff fall into the drum/ can . Empty the can once in a while. A fitting for a 30 gal trash can may be purchase from Griz. Use a plastic trash can. I do a LOT of metal, hot sparks and all,so I add water and a dollop of liquid soap to settle the grit . That way it won't enter the ducts and/or dust collector.
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Another good idea. I think that's one' of the best. I think the system won't suck up all the offcuts, just the smaller ones.
Thanks, Bob

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I've posted pictures in alt.binaries.pictures.woodworking.
Bob

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Bob
Some air intake ports on the bottom edge will prevent this from happening
John
On Sun, 18 Jan 2004 21:50:43 GMT, "Bob Davis"

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The whole guard was sitting 2 inches off the table and open when this happened. It wasn't a vacuum, it was just a lot of air moving.
Bob

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Maybe put someway to throttle the total flow to prevent this. Tune it till it just doesnt' suck the insert out of the table saw???
Didn't ask, but how many cfm is the DC moving??
John
On Mon, 19 Jan 2004 02:09:22 GMT, "Bob Davis"

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My sense is that if I move to reduce the air flow, I'll lose the effect I want - pull all the high speed dust in a situation that requires the dust to make a near right angle turn.
I'm going to try putting in a very coars screen, something like hardware cloth with 1/4" or larger mesh - just small enough to block wood chunks.
There's no way for me to measure the cfm. I suppose I could estimate it using the calculated pressure drop and blower curves, but that's not very accurate.
I can tell you that I have a Jet DC1200 2 hp collector connected. One connection goes to the saw cabinet through a 3 1/2 foot 4" hose. The other connection goes to the saw guard through a 10 foot 4" hose. I'll post some pictures.
Bob

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On Mon, 19 Jan 2004 02:28:56 GMT, "Bob Davis"

watch for chunks bouncing off of this and into the blade. little wooden projectiles....
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Good advice! This is going to take more thought.
Bob
wrote:

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I've been working on the same thing. I have the framework done just haven't worked on the dust collection part much lately. The frame bolts to the floor so it don't have to be removed when you do dado cuts. It all telescopes for adjustability.
KY
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http://users.adelphia.net/~kyhighland


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Let's exchange some pics, soon. I haven't done much in the way of support and fanciness for the blade guard - focusing all my attention on dust collection. I'm sure my priorities are not going to agree with those of many woodworkers. When you focus on dust collection, you have to fight with loss of visibility of the blade and bulkiness of the guard.
Bob

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I found some links to home-built guards/dust collectors a year ago, but the links are all stored at work. However, do a search of the web and you can probably round them up pretty quickly. Seems that a few people have come up with good designs.
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Larry C in Auburn, WA

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Larry, thanks. I looked at every guard I could find on the net. I agree that there are many good designs. However, they are all based on using a 2 or 2 1/2" section of hose several feet long. In my tests, I found this approach simply did not move enough air to catch the dust "spray" generated during many cross cut situations. I played with articulating guard sides used in one design. This helped but still failed in cross cuts where the dust gets sprayed at the end off the cut when the blade emerges from the wood and the guard is still at the same height as the cut stock.
I found that, with enough air movement and placing the collection point a few inches in front of the blade, collection was reliable and complete under all situations.
Bob

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Keep working on it because I never did build a copy of any I found and I'd rather copy your better mousetrap. <g> Are you really interested in just collecting the DUST or are you interested in both the DUST and a GUARD? If just dust it might open up other options like hanging the hose further in front of the blade which might be more effective (I don't know, just thinking out loud).
Another idea: I think I read someone else's post that mentioned toning the suction down. You could easily install a $5 plastic blast gate on top of the guard and start with it closed, slowly open it until you get enough suction to grab the dust without grabbing cutoffs.
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Larry C in Auburn, WA

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My personal priorities are:
0) get rid of the factory blade guard contraption 1) dust 2) Riving knife 3) guard
All are important. The guard part is not all that interesting and pretty easy to conquer. The only decision is whether to have one that "floats" over the wood or one that locks in position (like brett guard). We all know there are some types of cuts where the guard has to be removed. For that I'm probably going to get a Gripper. I'm working with a suspension design that locks in position using a toggle clamp that's quick and easy to set or release.
That's a great idea about the blast gate throttle.
The dust collection is awesome on my prototype. Nothing escapes. I know - I overkilled. I wanted to convince myself that hurricane force suction would overcome all the other shortcomings of dust collection on the topside of the tablesaw. It does. One valiant attempt at other options is described in the Workshop book by Taunton press. There's a fixed guard with articulating sides and flexible plastic curtains front and rear. I got it all copied and working in a prototype but discovered it fails to do the job on cross cuts, right at the end off the cut, when the blade emerges from the wood.
I'm in the process of mounting the whole prototype on a counter weighted suspension system now, so I can begin using it and find out how much it gets in the way of working., if at all.
I made one prototype that worked fairly well with a 2" hose and a flexible plastic curtain at the front of the guard. But it wasn't good enough. The guard had to be well centered on the blade for it to work optimally. With 4" hose, you can shove the guard over to the left and use it for close ripping, yet it still sucks up all the dust.
My hope is that I'll get everything working, then find out that a 3" hose is just perfect. The 4" hose is not in the way, but its visually disturbing. :-)
By the way, I found one very nice advantage of the flexible plastic curtain which I may add back. It acted like a built-in featherboard, holding the stock against the table - very nice and it worked for everything from 1/4" to 3" stock. My plastic curtain was made of 1/16" thick lexan. This is a feature that could be added to any basket style blade guard that locks in place.
Bob

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Did you get the Jet info + pics I sent over about ten days ago? Not sure you did as I've not heard from you.
Rgds
Noel
noel dot hegan at virgin dot net
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