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Half-baked tablesaw dust collection idea

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Forum topic by JeffP posted 02-19-2016 12:33 PM 505 views 0 times favorited 4 replies Add to Favorites Watch
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JeffP

573 posts in 856 days


02-19-2016 12:33 PM

Topic tags/keywords: question

Like many of you, I’m disappointed with the performance of my “under the table” dust collection on my saw.

It is a sawstop pcs saw, and it seems they built a sort of “shroud” around the blade area to attempt to create better suction…in reality, all it does is greatly reduce the airflow.

That said, a big part of the problem with under the saw collection on a TS just has to do with the basic geometry of what’s usually going on during use. Only some fraction of the waste and fine dust winds up anywhere near the hole in the insert where it could get sucked in.

Obviously, there are those above the table guard/DC-shroud things that are the intended solution for this. Somehow, those land squarely in my “just too much in the way to put up with it” zone.

So here’s the idea I had. As stated in the title, it is only partially baked:

It amounts to combining a blower and a sucker to move all the stuff away from above the table.

The “blower” would be compressed air being shot in the general direction of the blade from near the front of the fence and pointing towards the back of the saw. Could be a typical flexible coiled air hose coming from behind the table and mounted along the length of the fence with an air gun mounted near the front of the fence pointing backwards.

The “sucker” would be just an open “cowling” back behind the saw hooked to a DC. Not sure if this could work effectively with the cowling below the surface of the table and just creating a “suction zone” in that vicinity to suck down the debris and dust as it passes by.

My intent would be for this to be in addition to the (weak) under the table collection, not a replacement for it.

Ok, flame suit on. Help me bake the idea, or tell me why I should take it out of the oven and toss the remnants in the can.

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.


4 replies so far

View Fred Hargis's profile

Fred Hargis

3942 posts in 1958 days


#1 posted 02-19-2016 12:57 PM

No flaming, just a suggestion. I’ve read others have tried the compressed air idea, and no one reported to was effective…most guessed the speed of the blade is just too fast. But here’s what will work: more DC (I think, not knowing what exactly you have) and the seemingly dismissed overblade pick up. Believe me, the biggest complaint I have about the SS saws (I have an ICS) is that puny 4” dust pickup they use. The shroud is less of an issue (to me) than the inability to get enough air flow through the port. Even so, I can pull about 550 CFM through the port (large DC) and I put an Excalibur over the blade (from my previous saw). This set up gets probably 95+% of the dust, below and over the table.There is some chips (very little dust) on the bottom of the cabinet, mostly from when I forget to close that shroud “door” on blade changes. The thing about trying to invent something else is that it’s probably already been tried. I don’t think the idea is half baked at all, otherwise others wouldn’t have already tried it.

-- Our village hasn't lost it's idiot, he was elected to congress.

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ChrisK

1809 posts in 2546 days


#2 posted 02-19-2016 12:58 PM

Look at he nozzles offered by http://www.exair.com/en-US/Primary%20Navigation/Products/Air%20nozzles/Pages/Air%20Nozzles%20and%20Jets%20Home.aspx.

The key to dust collection is air movement. The sucker behind the blade needs to be able to pull enough to air to collect the dust coming from the blade. An air nozzle blowing air to the sucker will help. It needs to be more of a wide fan than a narrow jet.

-- Chris K

View bigblockyeti's profile

bigblockyeti

3668 posts in 1185 days


#3 posted 02-19-2016 01:59 PM

I’ve thought about using an air jet of some sort to drive the dust down into the cabinet where it will be sucked up. I find the biggest issue is when trimming up a piece where less than a full kerf is being cut, the exposed side of the blade tends to throw more sawdust at me than down into the cabinet. If I mounted a blow gun nozzle above the work piece and close to the blade I could drive the dust down but only if the air flow was substantial and the air speed was greater than the tangential speed of the blade trying to throw the dust at me. Ultimately this concept has the ability to get very complicated very quickly, for the time being I just rest in the fact that I have a bit of sweeping up to do after spending some time in the shop and that’s ok with me. Have you tried removing the dust shield from around the blade on your SS?

View clin's profile

clin

514 posts in 460 days


#4 posted 02-19-2016 06:14 PM



Like many of you, I m disappointed with the performance of my “under the table” dust collection on my saw.

It is a sawstop pcs saw, and it seems they built a sort of “shroud” around the blade area to attempt to create better suction…in reality, all it does is greatly reduce the airflow.

- JeffP

I disagree. The shroud ensures the fastest air speeds near where the dust is actually created to optimize dust collection.


Only some fraction of the waste and fine dust winds up anywhere near the hole in the insert where it could get sucked in.
- JeffP

I’m not sure this is true. The dust comes from the cut. The cut is at the front right where the blade goes down under the table top. So I think the best opportunity is to get the dust from underneath.

While I don’t know this to be true, I suspect that the dust that comes out the top is actually dust trapped in the teeth and going under and around with the spinning blade until some of it then gets flung of the top.

Regardless of the whys, obviously, there can be significant dust on top. But I don’t think expecting dust to be sucked paste the blade through a zero clearance insert is ever going to work well.

Again, I don’t know this to be the case, and I’d love to see some high speed video of exactly what does happen.


Obviously, there are those above the table guard/DC-shroud things that are the intended solution for this. Somehow, those land squarely in my “just too much in the way to put up with it” zone.
- JeffP

I also have a SS PCS and find the overarm dust collection to work extremely well. And I only have a shop vac connected to the whole saw. I can barely feel any air movement in the overarm hose, but in combination wioth the gaurd it works well. I also find that the SS guard is so easy to take on and off, and controls dust so well, I use it any chance I can.

Note: I do find that when the cutoff is thin (< 1/2” or so), then the guard doesn’t fit against the stock and then I get some significant dust out the top.

Regardless of how well a guard can work, there are always cuts where you just can’t use the guard.


So here s the idea I had. As stated in the title, it is only partially baked:

It amounts to combining a blower and a sucker to move all the stuff away from above the table.

- JeffP

Sounds plausible that it could work. But I think the compressed air would create a very turbulent airflow. More likely to scatter the dust than drive it. I think you’d need to get a rather wide column of air movement so that edges of the column (where there would be the most turbulence), would be away from where the dust is.

Maybe if you could blow a sheet of air along the top of the table. I think you’d have to experiment and see what helps.

In general, the problem with vacuums, is that the air gets sucked into the inlet from all directions. So as you move away form the inlet, the air speeds drop dramatically. That’s where shrouds come in. They help to control the airflow.

Blowing air does have the advantage that due to the momentum of the air, it tends to stay in a column. That’s why you can blow papers off a table from across the room with a fan, but can’t suck them in from across the room.

I’d look at the blowing air as a way to guide the dust. I’m not sure the theory behind it, but blowing air is used in some doorways to provide some sort of way to keep the inside air in and the outside air out. Like a wall of moving air. Maybe blowing air could work more to contain the dust than to actually propel it toward the vacuum.

-- Clin

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