dust collection

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Forum topic by secretgarden posted 02-12-2014 05:58 PM 829 views 0 times favorited 2 replies Add to Favorites Watch
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18 posts in 1015 days

02-12-2014 05:58 PM

I have a Jet 1200 2 hp dc hooked up with a wok baffle, Super Dust Deputy (SSD) and a 5 ft run of 5 inch duct. I measured the velocity at this juncture at 5447 fpm/1089 cfm. At this point, I’m a happy camper. I then ran 8 ft of 5 inch flex to my Jet 10in cabinet tablesaw and measured 4375 fpm/875 cfm. Still happy. I changed the 4 in port on the tablesaw to a 4 in x 10 in metal HAVC floor vent with a 6 in intake port. I had to add a 5 in to 6 in tapered reducer in order to hook up to the floor vent, thank you SSD for the 5 inch port. I measured the suction from the inside of my tablesaw cabinet at the 4 in x 10 in opening with a shocking drop down to 1560 fpm/310 cfm.

I’m doing all this work to buy time till next year when I plan to purchase a Clear View cyclone and sell the Jet.

Is this a normal drop from 4375 fpm/875cfm down to 1560 fpm/310 cfm due to the size of 4 in x 10 in adapted tablesaw hood or was my thinking on this wrong ie… bigger duct, shorter runs would produce better dust collection using the 2 hp dc? I will add that the velocity measured at the throat plate was 550 fpm and felt a lot stronger than I have ever had.

2 replies so far

View MJCD's profile


483 posts in 1792 days

#1 posted 02-13-2014 01:51 AM

The motor is rated at 8amps 230V, which is a full 2HP (at 100% efficiency) – just to get that out of the way.

Going to a 4” port will starve the impeller: a 5” will provide approximately 56% more CFM, going to a 6” provides 125% more (more than double) the CFM, relative to a 4”: these stats are for round diameters, not rectangular, so the numbers will change. The importance is that going to a 4”-anything will significantly decrease the CFM. The 875 CFM to 310 CFM (182% increment – 872/310 – is in-line with the numbers above, though this is a broad SWAG).

My guess is that you’re stuck with the port on TS, as I am with my Delta: I just installed the Clearvue CV1800 – all 6” lines, but it is coupled to my Delta 4” x 10” dust port. The CV1800 has a 5hp motor, so I get a bit more through the 4” port: the extra hp struggling against a corresponding increase in Static Pressure through the 4” orifice.


-- Lead By Example; Make a Difference

View jmos's profile


716 posts in 1790 days

#2 posted 02-13-2014 01:58 PM

If you are able to change the port on your tablesaw, I’d take it up to at least 6” round. My Jet tablesaw had a plastic cover with a 4” port molded into it. I made a new plywood cover, that used the same fasteners as the stock one, with a 6” hole and stuck my DC pipe into it. Worked great with no flex required. Even if you had to cut some sheet metal to do it, it would help. Some tools it’s just not possible to modify, like my band saw, and you just have to do what you can.

As MJCD said, any 4” will provide a choke point and drop your flow and create a pressure drop. Likewise, minimize the amount of flex hose; the interior of the flex hose is much rougher than any sort of pipe, and will have a much higher pressure drop per foot. Use the shortest length you can get away with. Hard pipe is much better than flex from a pressure drop standpoint. Likewise, avoid sharp angled turns; an abrupt 90deg turn creates a lot more turbulence and pressure drop than a gradual 90deg turn.

-- John

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