Yet more thoughts on TS duct collection

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Forum topic by tvrgeek posted 01-25-2021 11:39 AM 488 views 0 times favorited 10 replies Add to Favorites Watch
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1430 posts in 2659 days

01-25-2021 11:39 AM

Topic tags/keywords: tablesaw

As my new ductwork slowly approaches the tools, I was visualizing.

Old cabinet saws just had a 4 inch port in the bottom of the box. Big low pressure box, lots of dust falls out. Not very effective.

My contractor saw has a blade shroud with about a 1 3/4 port on the back. Connected to a 4 inch line, it could get about half the dust. Much fell below, much out the top and airborne. So I enclosed the saw, 2 1/2 from the shroud and 4 inch from the bottom of the box into a Y and it does much better but still so much is carried by the gullets back up through the table.

I have seen pictures of newer cabinets that seem to have a shroud and run the duct back to share the main cabinet port. So very much like my current setup.

Now to me, none of these will inherently work. If I have too much airflow from the cabinet, then I am just pulling dust away from the blade at the entry, but fighting the shroud port as the gap from shroud is much larger. Basically making actual flow across the gullets nil, so it carries more dust back up and out.

So, maybe things are backwards.

Maybe if I run the shroud port to the outside and take opposite side shroud cover off, so the full effect of the dust collector is across the blade into the cabinet. Clearance on that side can be a ramp up to a pretty tight clearance. This wil make the saw blade sort of an axial fan blowing the dust sideways.

If there is space, I can fabricate a new side to the shroud to connect a full 4 inch duct to it apposing the opposite side ramp. Then the existing 2 inch port I run to the outside as an clean air intake, just below the ramp. This will provide a higher velocity across the blade clearing the gullets. Then instead of the big port in the bottom of the box, it gets just a cleanout tray or maybe a 2 1/2 into the trunk.

The other idea is to leave ductwork as is, but get a high pressure blower to blow a focused small jet right at the gullets as they pass the shroud port. Not sure where to get one. Not a compressor, but not a single stage fan either.

I was considering a dangling hood high enough to not be in the way, but not sure there would be the velocity to pull dust up and away as it seems to really want to throw it to you. Getting it out of the gullets seems like the best approach.

Enough thinking. Coffee is ready. I found out last night how screwed up my plumbing waste lines are, no where near code on slope and not enough cleanouts. Yet another big project in a tight crawlspace. ( 1/8 minimum, 1/4 preferred)

10 replies so far

View Fred Hargis's profile

Fred Hargis

6834 posts in 3503 days

#1 posted 01-25-2021 12:06 PM

The newer saws I’ve seen have that blade shroud duct being the only exit from the cabinet (my SS is that way). It’s a 4” duct to the shroud, connecting to the 4” port on the back of the saw. IMHO it’s a disservice to an otherwise fine saw. The port could have just as easily been 5” or larger….but this all a digression. In any case, my port is connected to a 6” duct which also has a 4” split going to the overblade guard. This setup works fairly well, the missed chips that pile up in the cabinet are not much more than nuisance level. This same setup also worked well on my previous saw, a circa 2000 Uni. It had no blade shroud, but did have a catch pan in the bottom of the cabinet that was slanted toward the port which was 6” with my modifications. The key (IME) is to have a great deal of airflow. BTW, you have my sympathy on the waste line projects…..that really sucks, and not in a good way.

One other thing, the high pressure jet idea has come up several times in the past. I have never seen anyone post back saying it was a success. One woodworker went through the physics of the saw blade speed and other factor saying it was wasted air. Just an observation.

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

View Robert's profile


4447 posts in 2490 days

#2 posted 01-25-2021 12:49 PM

IME I wouldn’t put much effort in cabinet collection. It requires substantial CFM’s & a lot of saw just aren’t designed well for it.

About once every month or so I open the gate and clear it out.

I think over the blade collection is what really matters and I’m committed to doing that + a Clear Vue collector.

-- Everything is a prototype thats why its one of a kind!!

View tvrgeek's profile


1430 posts in 2659 days

#3 posted 01-25-2021 01:09 PM

I wondered about how much force would be needed to jet clear the gullets. Just not much time. Yet they do a pretty good job once the blade comes out the top of the work. Just thought of a test. Set up a leaf blower on the top, then do some rips and see if any dust fills my pockets, or if it all gets blown to the side.

I will have a full 6 inch from collector, a 1 3/4 Jet, but may go to 3 HP as that is all the electrical power I have. I tend to believe Mr. Pentz that 5 is better, but I just can’t. So bought the small Clear View cyclone for my Fein vac. It should get here soon.

I am at a toss up if to drop with 6 inch or drop with a 5 or 4. Overheads are just always in the way. I have looked at some of the DIY floating designs. One was integrated with a nice shelf that looks quite handy.

As so much dust gets released as soon as the blade exits the work, makes me wonder if my idea of a internal zero clearance “blade” would cause a low pressure zone and let more dust fall out into the cabinet.

I wonder how much dust would get picked up if I just had a 6 inch hose dangling a foot above the table and then just a cleanout box under the table?

View clagwell's profile


363 posts in 802 days

#4 posted 01-25-2021 03:09 PM

Try your shop vac on the 1-3/4” shroud port. The high pressure will be a better match for that port size. Keep the DC connected to the cabinet.

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View tvrgeek's profile


1430 posts in 2659 days

#5 posted 01-25-2021 04:14 PM

Try your shop vac on the 1-3/4” shroud port. The high pressure will be a better match for that port size. Keep the DC connected to the cabinet.

- clagwell

I will when I get the ClearView. Otherwise, a couple cuts wil fill up an $11 bag!

View cut50's profile


20 posts in 4038 days

#6 posted 01-29-2021 01:05 AM

I am at a toss up if to drop with 6 inch or drop with a 5 or 4. Overheads are just always in the way. I have looked at some of the DIY floating designs. One was integrated with a nice shelf that looks quite handy.
- tvrgeek

It`s a tough call as what to do sometimes with dust collection, I`ve found that every set up is a little different.
I have a 3hp with an older designed cyclone with a dust bag in a small room added to the shop, at times was painful because it would pull the smoke right out of the stove, not fun. Just upgraded to a filter, so far very nice. Have 6” for table saw, planer and miter saw, use 4” flex on drum sander and router table.
The 2.5” on the table saw blade cover, works just fine , not getting any blade spray, made it so swings out of the way, for blade changes and such. I did have a 4” on the table saw but it was not big enough, 6” is the king there.
So far that old cyclone is keeping the fine dust in the barrel where it belongs, also added an Ivac Fill Level Meter
for the dust bin, big help, the little plexiglass window did not work well for me.

As much as photo tell alot they can also be deceiving, it`s not as busy as it looks.

View 2Goober's profile


23 posts in 612 days

#7 posted 01-29-2021 01:33 AM

Here what I have done to my 2004 10” Jet TS and it works great. I ran the 6” trunk line all the way to the cabinet, (had to modify the TS cabinet). It has a aftermarket Shark blade guard with a old whole house vac connected with 2” PVC and a blast gate. It works better than anything I’ve ever used. I found the whole house vac on facebook marketplace for less than I could buy a shop vac for. I also ran it to the BS and miter saw. The high pressure-low volume vac works great for these tools also. To keep from having too many things to turn on, everything is on automatic contactors so all I have to do is turn the appropriate tool on and everything switches on with time delayed relays (to keep the electrical surge under control).

View Aaron312's profile


46 posts in 409 days

#8 posted 01-29-2021 04:27 AM

I had a Ridgid TS3650 contractor saw with a nice shroud around the blade with a 2.5” dust port that I connected to a shop vac. I built a box to collect what fell out.Then I got a Unisaw with a 4” port at the bottom which I connect to a 1.5 HP D.C. thru 6 ft of flex hose.

Before selling the Ridgid, I made a equal number of cuts on the same board with each saw. The Ridgid with the full blade shroud and shop vac left less dust on the table than the Unisaw. Disappointing. That blade shroud was fairly effective. I think I am going to get a shark gaurd and try that.

View tvrgeek's profile


1430 posts in 2659 days

#9 posted 01-29-2021 11:26 AM

I have the 3660. Port is less than 2 inches, not 2 1/2. I tried a shop vac on it years ago and it was not very effective.
My setup before this round was a 2 1/2 reducer to the shroud, semi-enclosed cabinet and a 4 inch to the slopped tray. Better, but not good enough. So it will be a 6 inch all the way to the DC.

As I got a clear view for my vac yesterday, I can try that again while making the base/cart for it.

I am still thinking about several baffle/port ideas to get the dust to fall out of the gullets. It seems so willing after it cones back through the table, why can’t we get it to fall out below? One idea is a wedge shaped ramp to the left of the blade in the shroud. it would then let the blade act as the fan to push the dust out.

Anyway, 6 inch duct should get here today so I can get it connected and see if it helps. There are so few operations where the overhead would not be in the way. One idea is a to integrate one into a sled. That may solve a lot of “normal” crosscuts. Seems a lot of what I do is rip thin pieces where it would be in the way of the push sticks, or using some sort of fence jig for rabbits, beveled doors or something on edge.

I have a plan to duct the full 6 inch to the miter saw and build a large shroud. Hooking to it’s built in port is darn near useless.

I have also thought maybe we have two problems and need two solutions. Big ports for chip collection and ambient cloud. Easy. But small focused high velocity ports for dust collection. It takes a different kind of blower for that.

Another thought was something like a kitchen hood. The big sawdust is just messy, the health concern is the fines. Could just a hood work well enough to pull suspended fines up before they get back to you? Traditional DC to a hood, high pressure vac to the shroud, and just a collection tray for what falls out?

View tvrgeek's profile


1430 posts in 2659 days

#10 posted 01-30-2021 12:10 AM

Hours of searching, I did find a reference to someone using a compressed air jet right at the blade where it first drops through. No data on how big a compressor was used, just mentioned a 1/6 inch tube, but said zero dust came up to the table.

It may not have enough force, but I still can envision a ramp on the right side basically forcing the attached flow through the gullets carrying the dust with it. Vac port on the right side right before the end of the ramp.

I also keep thinking about an outside port feeding a slot on one side, and the DC hose to a matching slot on the other side. The critical factor is to be close enough to the blade the flow is across the teeth, not down the side of the blade. Even thinking about a bristle brush sweep.

These ideas are a lot of stuff dangling around and may not clear on full tilt or height. The air jet is much smaller and could actually be attached to the insert.

For a cheek cut, a magnetic base to hold the above table hose close to the blade should work well. It would not be in the way as ll the work is to the right of the blade.

It is making more and more sense to me, below the table is is about velocity, not CFM. Above the table for a hood or shield, it is about CFM. Not how much airflow, but where.

Thought experiments while waiting in my ducts delayed in shipping. Built the cart that holds my new ClearVIew small cyclone feeding my Fein. Seems to work exceedingly well. Watched a video that did objective testing of miter saw dust collection through factory port. Surprised, DeWalt and Ridgid did best, Makita and Bosch were terrible.

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