improved table saw dust collection.

[keith ouellette]

One ting that has been lacking on dust collection in my shop was the jet 3hp table saw. I had always thought it had to do with the size of the cabinet and the fact that a lot of the dust blew up from the blade. Then I noticed that air gets pulled in to the cabinet from multiple locations. Vents on the door and the area around the height adj. wheel just to name two. I taped up both of these areas and the suction through the table at the blade more than doubled.

[Brian Kent]

Keith,

I never taped mine up, but that always seemed logical. I just assumed that it had something to do with air flow being as important as suction, or something like that.

Since yours is working, what kind of insert are you using - factory insert or a zero clearance insert?

It seems like another good invention would be a rubbery flap that closes the gap in front, and that keeps the hole covered as the blade angle changes.

[Mike Goetzke]

Then I noticed that air gets pulled in to the cabinet from multiple locations. Vents on the door and the area around the height adj. wheel just to name two. I taped up both of these areas and the suction through the table at the blade more than doubled.

I did a similar thing to my Unisaw a while back and then read this is not the thing to do if you are using a dust collection system. A DC removes dust by moving lots of air. If you restrict the air to flow only around the blade the DC will become less efficient due to the restriction. I would recommend adding an overhead DC device. I personally have a SharkGuard.


Mike

[keith ouellette]

Keith,

Since yours is working, what kind of insert are you using - factory insert or a zero clearance insert?

It seems like another good invention would be a rubbery flap that closes the gap in front, and that keeps the hole covered as the blade angle changes.

I have the stock insert and i love the rubber flap idea.

[keith ouellette]

I did a similar thing to my Unisaw a while back and then read this is not the thing to do if you are using a dust collection system. A DC removes dust by moving lots of air. If you restrict the air to flow only around the blade the DC will become less efficient due to the restriction. I would recommend adding an overhead DC device. I personally have a SharkGuard.


Mike

I can say for certain that it isn't true. It may hurt if to much air flow is restricted but the two spots I am talking about helped a great deal. There is still the entire space between the table and the cabinet that is open. I am going to block that space with some styrofoam for a test. I can see the difference at the blade opening (as dust goes in) and feel it (when the blade is off of course).

[Jeffrey Makiel]

I taped up both of these areas and the suction through the table at the blade more than doubled.

Keith...although the local velocity increased thru the throatplate, the overall flow through your tablesaw has significantly reduced. Air must be let into your saw in order for it to leave your saw. Therefore, in the end, you will discover a greater build up of sawdust within the saw's cabinet.

For your type of cabinet saw, an overarm hood is the easiest retrofit. But overarm hoods often need to be removed for some operations and thus limiting their benefit.

-Jeff :)

[Steven Wilson]

Overarm blade guard will give you the most bang for the buck. You could also build a shield around your blade and extend a hose from the cabinet up towards your saw blade.

[Jim Becker]

Keith, sealing of "excess" air source is fine, but you need at least the same area open as you have for your port in order to have the best results. Dust collection is about moving air, not suction. In order to move the air, you have to have the air to move!

[keith ouellette]

Keith...although the local velocity increased thru the throatplate, the overall flow through your tablesaw has significantly reduced. Air must be let into your saw in order for it to leave your saw. Therefore, in the end, you will discover a greater build up of sawdust within the saw's cabinet.

For your type of cabinet saw, an overarm hood is the easiest retrofit. But overarm hoods often need to be removed for some operations and thus limiting their benefit.

-Jeff :)

The total flow through the table saw cabinet may have reduced but the flow through the blade opening has definitely ( and i mean definite) increased.
Jim: If I understand what you are saying if I have four inch dia. flowing out i need at least a total of four in. to pull from or maybe double that. I am pretty sure the space between the cabinet and the table as well as the throat plate should have that covered. What do you think?

[Jim Becker]

Keith you have it correct. You effectively want the equivalent area of your 4" port and keep in mind that a ZCI will cut flow from directly around the blade. (One of the reasons that an overarm collection point works so nicely for the "up top stuff"--because it can)

[Mike Goetzke]

I can say for certain that it isn't true. It may hurt if to much air flow is restricted but the two spots I am talking about helped a great deal. There is still the entire space between the table and the cabinet that is open. I am going to block that space with some styrofoam for a test. I can see the difference at the blade opening (as dust goes in) and feel it (when the blade is off of course).

Keith - I know you don't like my suggestion to keep the gaps open. I agree you will definitely get more flow around the blade applying blockage elsewhere. But, most of the saw dust is deposited in the saws cabinet below the table and to get rid of it you need the full CFM your DC can produce (I assume you are you using a dust collector?). As Jim B. suggests you need at least 12 sq.in. to provide adequate air flow.

I found this by chance but you should try this experiment. I had put adapters on my DC to reduce the dia. to about 1" for my P-C plate jointer. There wasn't hardly and flow or vacuum at all. I ended up using a shop vac for this application.

Also, if you look at Norm's router table design, that many Creeker's have built, if you don't provide air inlet holes at the bottom of the door the cabinet will quickly fill with dust - since there is not adequate air flow to remove the dust.

Good Luck,

Mike

[John Thompson]

The total flow through the table saw cabinet may have reduced but the flow through the blade opening has definitely ( and i mean definite) increased.
Jim: If I understand what you are saying if I have four inch dia. flowing out i need at least a total of four in. to pull from or maybe double that. I am pretty sure the space between the cabinet and the table as well as the throat plate should have that covered. What do you think?

Keith... I can pretty much asure you the space between the cabinet and throat plate will give you all you need if your Jet's base is similar to my Uni-saw. When I first got the saw and hooked up the 4" DC.. saw-dust spitted and spewed from every one of those opening leaving my front side caked in dust.

Whoa... what's the point of a DC to collect dust if chips and dust spew out every opening on the saw into the surrounding shop? What do I do to avoid the dust spewing and still collect the chips and fine dust? Had to think about that for a bit and came up with the final solution in my case.

I sat and watched where the saw-dust omitted the saw as I had my son rip some stock... and then went to work to modify it using my theory. My theory works for me with the set-up I have.

Plugged the areas between the table and base with self adhering campers tape. Plugged every hole on the saw with the exception of the "throat plate" with campers tape. All holes plugged except throat plate which still spewed out the front on my lower body and floor.

Cut a piece of blank sheet metal and replace the cover around the "tilt" slot (which is large to allow the crank shaft to move from 90 degrees to 45. Attached with sheet metal screws but..... first cut a piece of plastic type table place mat (wife's still looking for it.. he...) and placed that between the sheet metal cover and the saw cab frame. I cut a narrow slot in it to duplicate the movement of the tilt shaft.

When I use the tilt slot.. the slot opens and basically closes behind itself and still allows air entry. I will take air but pretty much keeps the chips from spewing out. As the rubber gasket you guys mentioned and wished some offered. They don't.. so I made my own.

I use a zero clearance throat plate (Lee-craft) but.... once the blade has cut it's own slot when raised, I trim off an additional 1-2 mm on each side as that blade will deflect in certain hard-wood and you have to calculate arbor run-out. Listen to the blade scrape the Zero clearance when that happens. I want it wider as I feel it doesn't sacrafice much and adds a lot as you don't destroy the teeth on blades from rubbing.. over-heat them and add to general dulling sooner than they should.

But.. I also added two additional holes in the zero plate and have room to add more if it were necessary. It's not as I have a 2 1/2 HP cyclone that directly connects to each machine. I opened the port from 4" to 6" and added a 6" plastic port. The 6" pipe from cyclone hooks directly to the 6" port so there is no down-size on a short 15' run.

I built my own crown guard and shield (much like the shark guard) and added a 2 1/2" ducting pipe from over-head to that shield running off a dedicated 6 HP shop vac beside the TS.

I removed enough campers tape from low spots on the sides and rear of saw to get the open area that has been mentioned. But none in front of the saw and none high on the saw. Let the extra air come from the bottom.

At this point... saw-dust basically doesn't exist on my Uni-saw when using it. I have added a pic of the over-head... throat plate with grommet to view. Don't mention to my wife where her dinner place mat went. ;)

Hope something here helps and good luck with yours....

Sarge..

[Jeremy Parkins]

I also saw somewhere were magnetic "sign" material was used to cover the openings around the wheels. just peel them off and adjust.

I really like the rubber flap idea.

[Jake Helmboldt]

The total flow through the table saw cabinet may have reduced but the flow through the blade opening has definitely ( and i mean definite) increased.
Jim: If I understand what you are saying if I have four inch dia. flowing out i need at least a total of four in. to pull from or maybe double that. I am pretty sure the space between the cabinet and the table as well as the throat plate should have that covered. What do you think?

Actually you need 12.5 sq inches in, not 4 (in order to equal the flow out).

[keith ouellette]

Keith - I know you don't like my suggestion to keep the gaps open. I agree you will definitely get more flow around the blade applying blockage elsewhere. But, most of the saw dust is deposited in the saws cabinet below the table and to get rid of it you need the full CFM your DC can produce (I assume you are you using a dust collector?). As Jim B. suggests you need at least 12 sq.in. to provide adequate air

Mike

I already had what little dust that was pulled into the cabinet collecting in the cabinet. I understand your point but what I am trying to say is if you are pulling enough air through a 4" hole to move say 800 cfm's but the rest of the cabinet has enough holes and gaps to allow 2400cfm's then hardly any air at all will flow by the turbulence of the blade. I do agree with you to a point that if I close to much of the cabinet up and don't have the proper inlet for the air to be pulled out of like jim becker describes you won't pull the maximum amount but if you have to many openings you won't be pulling air though where it counts.

Thank you John Thompson. I would have gotten to your system eventually but it would have taken a very long time to figure all that out. I printed what you wrote so I can move in that direction more easily.

[Jim Becker]

Keith, you effectively cannot pull enough air through that 4" port to get anywhere close to 800 CFM...max is more like about 350 CFM, give or take for a 4" port at the typical velocities generated by dust collection systems. You can't physically fit that much air in the pipe. This is the major reason why you'll often see recommendations about increasing the size of the cabinet port if you want to totally clear it...for close to 800 CFM, you'll need a 6" port and a DC that can perform at that level. It's pretty much a physics problem...

[keith ouellette]

Keith, you effectively cannot pull enough air through that 4" port to get anywhere close to 800 CFM...max is more like about 350 CFM, give or take for a 4" port at the typical velocities generated by dust collection systems. You can't physically fit that much air in the pipe. This is the major reason why you'll often see recommendations about increasing the size of the cabinet port if you want to totally clear it...for close to 800 CFM, you'll need a 6" port and a DC that can perform at that level. It's pretty much a physics problem...

I kinda figured something like that Jim from reading your other posts on this subject but didn't have the numbers. I just used 800 and 2400 as examples. some day I hope to get some 6" pvc and expand my ports. That and a lot of other things i need to do.

[Jim Becker]

I have that kind of list, too, Keith...the "someday" list... LOL! Someday when I get to spend time in the shop, that is...business travel really has cut into that in a major way this year. And 2008 is looking about the same.

[Chuck Lenz]

One ting that has been lacking on dust collection in my shop was the jet 3hp table saw. I had always thought it had to do with the size of the cabinet and the fact that a lot of the dust blew up from the blade. Then I noticed that air gets pulled in to the cabinet from multiple locations. Vents on the door and the area around the height adj. wheel just to name two. I taped up both of these areas and the suction through the table at the blade more than doubled.
Keith you won't be geting much air around the blade insert when you are cuting, the wood will be over the plate. I have been working on dust collection for my Contractors table saw with the open back. For my situation it makes more sense to seal alot of stuff up and let the back of the saw cabinet bring in all the fresh air in. I have blocked the back off some, not alot, put closed cell foam between the top and the cabinet, blocked off the degree slot in the front of the cabinet with a piece of magnetic sign material and it all works great. With your cabinet tablesaw I think I'd leave well enough alone, you should have good airflow. Like others have said, for dust above the table a over the table dust hood would be the answer.

[Mike Goetzke]

Actually the best dust collection I've had on three different TS's was on my Ryobi BT3000. It had an aluminum casting and metal plate encapsulating the blade:

http://img.photobucket.com/albums/v212/mbg/Saw%20Skirt/th_100_0014_2_1.jpg (http://img.photobucket.com/albums/v212/mbg/Saw%20Skirt/100_0014_2_1.jpg)


With the stock setup a 2-1/4" ported vac left the top almost dustless. But, it bugged me that dust would accumulate in the bottom of the cabinet. So I added a "saw-curtain" to direct the flow of the air over the motor (yes the motor needs air to keep cool) and out the dust port:

http://img.photobucket.com/albums/v212/mbg/Saw%20Skirt/th_100_0010_1_1.jpg (http://img.photobucket.com/albums/v212/mbg/Saw%20Skirt/100_0010_1_1.jpg)


It was on my Ryobi that I discovered it wasn't best to block all but the throat plate flow areas.

Mike