Enlarging dust port on table saw?

[Len Rosenberg]

I'm upgrading my dust collection from 4" to 6" duct work and 5 or 6 " hose. All the ports on my machines are 4". Rather than choke the collector at the source, I plan to use larger ports. The first will be on a Powermatic 66 table saw. What is the best way to cut a 6" diameter hole in the metal cabinet? And what is a good source for a fitting to connect the saw to the hose?

Many thanks!

Len

[Ole Anderson]

I used a saber saw with a fine metal cutting blade and then used a bell mouth adaptor from Penn State for the connection to my 5" bottom hose. I had to work the cast aluminum blast gate spigot with a drum sander to get it to fit the bell mouth. Grizz 1023.

[James Baker SD]

I did it with a 6" hole saw and a portable drill. I definitely recommend trying almost any other method first. I got through, but almost vibrated my shoulders into the ER and almost ruined the hand drill. I connected with a 6" angle flange adapter from Nordfab. A bell mouth probably would have been better however.

[Len Rosenberg]

Thanks for the replies and the photos. Ole, looks like you enlarged the opening in an access plate. I'd be cutting an entirely new opening into the back of my metal cabinet.

Len

[Peter Aeschliman]

potentially controversial question:

Why does this matter? I understand that a 6" port is generally better in most cases because it moves more volume, etc, but if your table saw cabinet doesn't have tons of gaps, I would imagine that a 4" duct does a good enough job creating negative pressure inside the cabinet so that fine dust will not escape. Right? In my experience, above table dust collection is the biggest problem to solve with the TS...

[Kent A Bathurst]

........ if your table saw cabinet doesn't have tons of gaps......

Important point, Peter.

I don't know what or how the PM66 does for dust management and pickup, but my experience is this:

My 15 year old Uni had "dust collection" as a marketing throw-away phrase.

Attacked it: Duct tape all the holes in the cabinet. Expanding foam all around the top of the cabinet/under the table [this is a HUGE thing - wide open gaps on all 4 sides], weatherstripping on the inside of the cabinet door, magnetic sheet over the big slot where the depth handle travels when I crank the bevel. Then - used drill and jig saw to cut strategically-placed slots for air to enter - through the door to clean and cool the motor; through back of the cabinet to send air directly across the sloped floor toward the pickup. Adjust these inlets with duct tape as needed.

I have never, ever, had to open the cab door for cleanout since I did this. I only open the cabinet door to retrieve the arbor nut and/or washer when I drop them.

If the saw is designed for 4", but the DC system is designed to provide 6" at the pickup, then the DC wins, IMO. You just need to be sure you are supplying the correct volume of make-up air into the cabinet - don't want to starve it, because your velocity won't be up to speed and you risk heavier particles dropping out of suspension and building up in the pipe.

The performance at the saw itself won't suffer by going from 4" to 6" if you do it correctly.

The moral of the story: Like Goldilocks, you don't want your inlet make-up air volume to be too small nor too large - you want "just right", as defined by accumulation [or lack thereof] in the cabinet. And - you want to be the guy that determines the location of the inlet make-up air. Don't assume the PM guys had it correct, for your specific DC setup.

[Len Rosenberg]

4" is not enough to capture the fine dust and not so fine dust thrown off by the saw. I have an older 3" Excalibur over arm collector and am also running 4" hose to the bottom of the cabinet, and I still end up coughing.
After doing extensive research on dust collection, I've learned that 6" ducting has more than twice the volume of 4", and makes a HUGE difference in the amount of dust collected. The newer Excalibur (now Exaktor) over arm collectors now have a 4" main tube rather than three.
I'm thinking of upgrading that too, but I'll go one step at a time and see how it goes.

Regards,

Len

[Len Rosenberg]

Kent, those are great points. I was planning to use the existing 4" port as the "make up" air inlet.

And I've done the duct tape all gaps thing. Still not satisfactory.

The biggest variable in this scenario is that I'm changing from a 1 hp to a 3 hp collector, in addition to using 5 or 6 " ducting/hose instead of 4".

Thanks,

Len

[mike mcilroy]

I had to cut an opening in the opposite side of my Jet xacta saw to make a better run for the duct. Used a 6" furnace take off. Drilled four 3/8" holes representing the corners of the take off and connected the dots with a jig saw with the proper rated metal blade. Blades cost me $8 for a 5 pack. Cutting took 5 to 10 mins. I put self adhesive weather stripping around the take off, self tapping screws to secure it, foil tape around the outside for my peace of mind. On the inside bent all the tabs over and alittle more tape for smoother edges. I did all of this while crawling under the extension table. There's a couple of different metal blades but the package should tell you how thick the metal the blade can cut. You could do the same thing with the round fittings from the big box stores, I can't remember whether they call them take offs or something different but same theory. Just trace the ftting size drill,cut attach and seal. The right blade makes it very easy.

[Len Rosenberg]

Thanks Mike. That sounds exactly like what I'll have to do.

Len

[Dennis Aspö]

I have a related question, what if you collect from two points, like a table saw with DC in the overhead guard too? I would split the tubes so one goes into the housing and one into the guard, but into what size? My gut tells me the size should be equivalent of the main trunk (6" or 150mm). Perhaps a little over would be ok?

[James Baker SD]

Len:

I agree about the make up air. I left the PM's original 4" port intact and just taped in shut. My new hole was cut opposite side to the motor cover. I drilled multiple holes in the underside of the plastic motor cover with forstner bits for the make up air to try to get a straight flow just under the blade. I also had an excalibur overhead guard, but replaced the actual guard with a Shark with 4" port. I mounted the shark in place of the PM's OEM guard and run 4" flex from the shark to the outer tube of the excalibur. The 3" inner tube of the excalibur was put into storage. My DC had 7" mains which just about equaled the area of the combined 6" and 4" ports. Overall I was pretty happy with the results, much less dust escaped into the air.

[Chris Parks]

Important point, Peter.

I don't know what or how the PM66 does for dust management and pickup, but my experience is this:

My 15 year old Uni had "dust collection" as a marketing throw-away phrase.

Attacked it: Duct tape all the holes in the cabinet. Expanding foam all around the top of the cabinet/under the table [this is a HUGE thing - wide open gaps on all 4 sides], weatherstripping on the inside of the cabinet door, magnetic sheet over the big slot where the depth handle travels when I crank the bevel. Then - used drill and jig saw to cut strategically-placed slots for air to enter - through the door to clean and cool the motor; through back of the cabinet to send air directly across the sloped floor toward the pickup. Adjust these inlets with duct tape as needed.

I have never, ever, had to open the cab door for cleanout since I did this. I only open the cabinet door to retrieve the arbor nut and/or washer when I drop them.

If the saw is designed for 4", but the DC system is designed to provide 6" at the pickup, then the DC wins, IMO. You just need to be sure you are supplying the correct volume of make-up air into the cabinet - don't want to starve it, because your velocity won't be up to speed and you risk heavier particles dropping out of suspension and building up in the pipe.

The performance at the saw itself won't suffer by going from 4" to 6" if you do it correctly.

The moral of the story: Like Goldilocks, you don't want your inlet make-up air volume to be too small nor too large - you want "just right", as defined by accumulation [or lack thereof] in the cabinet. And - you want to be the guy that determines the location of the inlet make-up air. Don't assume the PM guys had it correct, for your specific DC setup.

And that ladies and gentlemen is a profound lesson in how to do it properly. It should be a sticky in a separate DE sub forum.

[Jim Andrew]

My 10 year old uni has a sloped floor down to the 4" fitting dust hookup. I took the plastic 4" off, cut a piece of wood the full size of the hole, and bent a piece of 6" pipe to fit the shape. Improved the collection, it used to plug up. I also have a 4" hose and shark guard, which works well, but since I got the Hammer saw, found it works just as well above the blade with a 2" hose, so I would go smaller on the above the table collection, and as big as possible on the cabinet. If you don't have the sloped floor, would consider adding it.

[Kent A Bathurst]

I have a related question, what if you collect from two points, like a table saw with DC in the overhead guard too? I would split the tubes so one goes into the housing and one into the guard, but into what size? My gut tells me the size should be equivalent of the main trunk (6" or 150mm). Perhaps a little over would be ok?

You want the cross-section area of pipes to remain roughly constant.

pi x radius squared

6": 3.14 x (3 x 3) = 28.3 sq inches

2 @ 4": 3.14 x (2 x 2) = 12.6 sq inches per pipe, or 25.2 sq inches for 2 @ 4" pipes feeding into one 6" main.

Or, one @3" + one @ 5" = [3.14 x (1.5 x 1.5)] + [3.14 x (2.5 x 2.5)] = 7.1 + 19.6 = 26.7 sq inches

The point is this: Assuming that your DC is correctly sized to run a 6" main, with appropriate CFM and velocity at the machines, then you want to keep the volume of air flowing through the pipes to remain relatively constant as diameters change down-stream [upstream?].