Dust collector pipe sizing

[William C Rogers]

I have read some previous post regarding dust pipe size. Just for information consider 5" cost twice what 4" SD pipe would cost. For my table saw I have a dedicated Jet 1100 with the vortex cone, Wynn filter. So piping will be short with one lead to the saw and the other to my Excalibur over arm guard. My second dc is a Jet 1900 3hp with Wynn filters. This one will be hooked up to a cyclone. This dc will service my PM 90 lathe, miter saw, band saw, belt sander, spindle sander as stationary locations. The run to the lathe will be about 30 feet and the other tools 20-30 feet. I plan to run overhead my 12' ceiling. I also have a Mini Max FS 35 J/P, Dewalt 735 planer, and a Supermax 19-38 drum sander. These are mobile and will be used within 10 feet of the cyclone. They all have 4" ports, so would 6" reduced down to 4" be much benefit for these? I plan to use 6" between the dc and cyclone. What would I gain running 5" to the lathe and other tools? The lathe of course has no dust port and would build some kind of box mainly to collect sanding dust. The other stationary tools have 2 1/2" or less dust ports. There won't be any future expansion. Is there some major benefit I am missing?

[Jim Andrew]

I have increased the openings on some of my machines, where it needed help. The edge sander had a 4" connection, and it collected about half the dust. I found a short piece of the proper size of pipe, just used my jigsaw to cut the hole a tiny bit smaller than the pipe and used my harbor freight wire welder to weld it on. Came out real nice, and now the 6" gets nearly all the dust. My thickness sander had a 5" round flange over a 5" square hole, so I cut the flange off with a dremel tool, then jigsawed the hole square to match the duct underneath, and used sheetmetal to make a 5" square to 6" round adapter. Nearly the same square inches, but I could not find a ready made adapter. Really helped the sander. My Hammer saw has a shroud on the blade, with a 4" hose, and then a 2" over the blade collector, and it works surprisingly well. Only trouble I have had with it, is the tiny strips you sometimes cut off wind up stuck in the hose where it curves. Wasn't picking up dust well, so I looked in there and found several sticks plugging up the hose. Much better now.

[Anthony Whitesell]

You need to look at what you are trying to collect and how the system will go about doing that. Each diameter pipe has a maximum flow rate, regardless of the horsepower, impeller diameter, and everything else.

For the lathe, you need to move a lot of air to capture the particles you list. Using 4" diameter pipe is very limiting in its CFM and is the minimum even considered for an enclosed tool (such as your table saw). Additionally, you cannot achieve decent collection if the area of the openings outsize the area of the pipe. For example, if you have a 4" diameter pipe that splits to a 4" port on the bottom of the table saw and a 1 1/2" opening at the over arm guard then the openings are larger than the pipe and neither will collect properly. This will be important as you design the collector for the lathe. A sanding box design is more effective than the "big gulp" design available retail.

[Michael W. Clark]

For the tools with 2-1/2" ports (and smaller), I would be tempted to upsize them to 3" or exhaust them with a shop-vac.

If you start branching ductwork, try to conserve the duct areas. For example, a 6" can split into two 4" ducts or into a 5" and 3". When you split, you may have to consider the balance and adjust your blast gates to get the performance you want. Just because the areas are equal, it doesn't mean you will pull the correct flow in each branch.

You have a minimum flow in ductwork to maintain enough velocity to keep the dust entrained and prevent it from dropping out in the ductwork. Higher velocities are not a problem except you can get abrasion and HP requirements go up significantly with an increase in air speed.

Look at metal duct, the cost difference between 3,4,5,6,7,8 is not as bad as with plastic. Odd sizes in plastic are expensive if available at all.

[Russ D Wood]

My piping is all 4 inch but I think the main issue with DC is the total CFM of the DC. I know that others talk about leaks and good blast gates, but I have a pretty good system that even keeps up with my 24 inch planer. It is from Woodmaster. Russ

http://www.woodmastertools.com/NS/accessdetail.cfm?PID=88

[Ole Anderson]

For a 3 hp cyclone hoping to pull 800 cfm, 7" is the sweet spot for your main run. Fairly economical if you use 26 gauge snap lock. As Michael said, if you go with steel, you aren't limited to even inch sizes. I used a lot of 5" and 7" in my collection system.

[Dennis Aspö]

I've been looking at round aluminum ventilation ducts, 160mm or 6,3" aren't very expensive here and are commonly used for making DC systems. I am going with a good sized piping myself so I won't be limited. Also got an attic space to put the bulk of the machinery so it won't actually be in my shop, I'll just have ducting in the roof.

[William C Rogers]

I agree with all the comments. 6" is optimum if you can utilize it. I have looked at all the equipment dust ports and really the only one that could support a 6" port easily is the Mini Max jointer/planer I have and this is more for chips rather than dust. I could add a second 4" port to my drum sander, but it was working very well with the current 4" port. For my table saw both the saw and my Excalibur over arm both have 4" ports. I will use my Jet 1100 dedicated to that set up. I don't think I can improve on this setup. For my lathe I am really more concerned about dust rather than chips. I don't think there is a really good way to collect chips on a lathe. I am only going to run a 4" line to the lathe. This will be for chip collection behind the lathe. I am going to build a dust hood above the lathe using a furnace blower blowing out through a filter. Since I have 12 foot ceilings and the lathe is against the wall it would not be that hard. This should give me 800+cfm for dust extraction. I will need some type of screen to prevent chips from damaging the blower. I will also look at connecting the DC 4" port between the exhaust and filter, but will need to verify my DC amps do not go high as this will be a somewhat positive pressure area. I can also incorporate some LED spots into the hood for extra lighting above the lathe. My bench sanders pose a different problem. They have small ports that can't be increased. I can't put an over head hood here but I can make the table a down draft using a second blower I have. I am also thinking of adding a DC port to this if amps are not a problem. I know this will help, but I don't know the efficiency. Feel free to comment if you think I am out in left field. What I think I will buy is a Zylos meter to see how well all this is doing.

[Anthony Whitesell]

What type of "hood" are you thinking about for the lathe?

[William C Rogers]

Anthony, I haven't given it a whole lot of thought at this point. My lathe is a PM90. Something that is overhead with backs and sides. Maybe some hinged wings for sanding. I would have inlet above and in the back. I am thinking of installing a couple of can lights that I can put LED spot light in for added light. I would have a DC port behind the lathe and also have a way to hook up a floor sweep. The blower would be in the overhead "box" exhausting through a filter and possibly hooking up a DC port between the exhaust and filter area. That will depend on DC amps, but should be fine with a 4" run. This is a new shop and I am still setting up things. In my previous shop I tried a Big Gulp, but only marginal for dust and much less for chips. Once I get time to do this I will post the results. I have a brand new SawStop I bought in April that I still haven't plugged in yet. I should do that this week. Then I need to install the Wynn filters on my Jet DC 1900 and start running the ducts for the tools. Once I make the hood I will post the results. I know it will help, but not sure how much.

[Anthony Whitesell]

The big gulp hood does nothing to spread out the suction. It isn't much better than laying the hose directly on the table, and saving your money. Something needs to be done to cause the suction to spread out across the entire face of the hood. The 'sanding box' design (such as http://www.rockler.com/downdraft-table-panels, or home made version using 1/4" perf board) allows for the suction to be spread out over a larger area. Each 1/4" diameter hole has and area of 0.0156" where as the 4" diameter duct has 12.5" sq in. Dividing one by the other gives 800 1/4" holes, or 30 sq in of 1/4" perf board. Simply placing a piece of 1/4" perf board in front of the big gulp hood would increase the effective collection area. The catch is the velocity will be limited at each hole as is the ability to catch dust flying by at high speed. Everything has a pro and a con.

Increasing to 6" duct, providing your DC has that option, increases the area to 42 sq inches or provide small improvement to the 30 sq in above.

[Jim Andrew]

For sanding at your bench, either using a shop vac with a hose attached to your sander, if it has that option, or using a down draft table is the way to get that fine dust. Using 6" versus 4" for your main system moves 2 times the air, of course if your machines can not use 6", that is another thing. I find some of my machines are designed well for dust collection, and 4" would be adequate, but others could benefit from 6", especially sanders.

[Lee Schierer]

I've been looking at round aluminum ventilation ducts, 160mm or 6,3" aren't very expensive here and are commonly used for making DC systems. I am going with a good sized piping myself so I won't be limited. Also got an attic space to put the bulk of the machinery so it won't actually be in my shop, I'll just have ducting in the roof.

Depending upon your system, you could suffer a duct collapse if you run the collector with all the ports shut and pull negative pressure (vacuum) in the duct work.

[Ole Anderson]

I was thinking the same thing, it would have to be fairly heavy gauge aluminum to match the strength of steel. Under pressure, no problem, but under a vacuum is a different case.

[Michael W. Clark]

The big gulp hood does nothing to spread out the suction. It isn't much better than laying the hose directly on the table, and saving your money. Something needs to be done to cause the suction to spread out across the entire face of the hood. The 'sanding box' design (such as http://www.rockler.com/downdraft-table-panels, or home made version using 1/4" perf board) allows for the suction to be spread out over a larger area. Each 1/4" diameter hole has and area of 0.0156" where as the 4" diameter duct has 12.5" sq in. Dividing one by the other gives 800 1/4" holes, or 30 sq in of 1/4" perf board. Simply placing a piece of 1/4" perf board in front of the big gulp hood would increase the effective collection area. The catch is the velocity will be limited at each hole as is the ability to catch dust flying by at high speed. Everything has a pro and a con.

Increasing to 6" duct, providing your DC has that option, increases the area to 42 sq inches or provide small improvement to the 30 sq in above.

You really want more hole (or slot) area than this. For woodworking, you want to run about 4000 FPM in the duct. If you try to run the slots at this velocity (same area as the duct), the hood loss will be too high and you will not get the flow you need. Behind the slots, you need a plenum to get distribution, the plenum velocity should be about half the slot velocity. A slot velocity of 2000 FPM is a good rule of thumb for capture vs energy requirements.
Mike

[Dennis Aspö]

The ducts I plan to use are these:
http://www.luftbutiken.se/163-thickbox/spiroror-stl-160-langd-3-m.jpg

They've been used by plenty others to build their own DC systems so I think it should be alright.

[Jim Andrew]

Dennis, I have spiral pipe in my shop as well. Only downside I can see, is you have to use couplings that fit inside the pipe to attach your fittings and joints. With snaplock pipe, the ends of the pipes are crimped and fit inside the pipe it joins to. You can orient the crimps so the air flows through the crimp toward your dust collector, and no edges face into the flow. Can't help that with the couplings. Have never had a plug as a result.

[Michael W. Clark]

The ducts I plan to use are these:
http://www.luftbutiken.se/163-thickbox/spiroror-stl-160-langd-3-m.jpg

They've been used by plenty others to build their own DC systems so I think it should be alright.

Dennis, most of the spiral duct I have seen is galvanized steel. It seems like aluminum would be more expensive? It is used mostly for HVAC, so an HVAC installer should be able to get all the fittings you need.
Mike

[Dennis Aspö]

My fault, I for some reason thought they where aluminum, but they are galvanized steel.