Best location for blastgate?

[Rick Hubbard]

I've decided to run my 6 inch metal ductwork on the wall about 60 inches from the floor to the top of the pipe. My question now is whether it would be best to use 6 inch blastgates ahead of the reducer or 4 inch after the reducer. Something makes me think the 6 inch would be a better way to go, but on the other hand I have several metal 4 inch gates on hand. some thoughts?blastgates.jpg

Any thoughts?

[Rick Potter]

Depends on what it is connected to. If it is a router table, 4" is fine.... jointer, I'd use the 6". My general rule is if I neck it down, I do it as close as possible to the machine.

Rick Potter

[Rick Hubbard]

If it is a router table, 4" is fine.... jointer, I'd use the 6". Rick Potter

Which brings up a whole other kettle of fish. I just bought a (used) 16 inch Jet Planer and I was eyeing the 4 inch DC port on the unit and wondering if I could modify it to 6 inches. We shall see!

[Bruce Wrenn]

Before spending the time to enlarge outlet port on planner, try the 4", increasing to 6" hose as quick as possible. My Delta 15" has a 5" port, which I connect to 4" flex. My 1.0 HP cyclone (Wood Magazine) with Thien baffle on a 30 gallon can, has no trouble keeping up with the chips

[Peter Aeschliman]

From what I understand, the 6" connections are most important for machines that make fine dust, and less important for those that produce mostly chips.

For example, jointers and planers make big chips and very little fine dust. So I wouldn't worry about enlarging the port. But an oscillating spindle sander or a drum sander make fine powder. Miter saws need tons of air movement behind the saw to pull in the fine dust, so a 6" port (or a 6" port divided into smaller ports around the back of the saw) works best.

I've also read of people cutting into their cabinet saws to increase the port under the table to 6", only to find that it made almost no difference.

Here are the hookups I went with for my machines, for better or worse:

Table saw (Sawstop): small port on the blade guard (like 1.5") and 4" under the table (would much prefer 4" on top as well)
Jointer/Planer: factory 4" port (almost no fine dust in the air afterwards because it produces chips, not fine dust)
Bandsaw: 2 4" ports, one right under the table, the other in bottom door
Slot mortiser: 6" port with a shroud around the cutting area (full disclosure- I'm still designing this)
Oscillating spindle sander: 6" connection above the table
16/32 Drum sander: 6" port (almost no dust escapes this sucker!)
Router table: 4" on top, 4" on bottom.

As for where to put the blast gates, I really don't think it matters. If you have a 4" hookup to a machine, save some money and us a 4" blast gate, placing it in a convenient location.

[Ole Anderson]

Rick, just out of curiosity, what will you be using as the dust collector, a bag or cyclone system, and which one? Reason I am asking is that a 7" main really hits the sweet spot for air flow vs resistance if you are at 2 or 3 hp on your collector and can pump 800 cfm at 6 to 10" of suction, and with metal duct, 7" pipe is no problem.

[Rick Potter]

Hey Peter,

When you are done with that shroud around your slot mortiser, I would like to see it.

Rick Potter

[Rick Hubbard]

Rick, just out of curiosity, what will you be using as the dust collector, a bag or cyclone system, and which one? .

Well, it seems like nothing is ever straight forward with me!

I’ve actually decided to use 2 bag-type collectors (since I now own 2). One will have a 20 foot run the other, about 30 feet, both with 6 inch mains.. The shorter run will accommodate my two planers, a jointer and a router table. The longer run will collect from a band saw, spindle sander, drum sander and a belt/disk sander. My table saw and miter saw are still problems, but since Grizzly has their portable 1 HP collectors on sale for $169, I’m seriously thinking about running up to their store in Muncie and buying a couple of them to tuck under the TS outfeed table and miter saw bench . That’s far from an ideal set-up, I know, but this is leased shop-space and I hope to buy my own building next year, so I don’t want to devote more time (and money) than necessary on DC plumbing in this one.

BTW, has anybody had experience with these little portable DC units?

[Jim Andrew]

The Jet planer will probably work fine with the 4" pipe, as the 15" Grizzly does. They are probably the same planer. Someone did a great design of the 15" planer dust collection. Wish they did as good a job on sanders.

[glenn bradley]

I position my blast gates to exclude any flex from the system when closed. That is, between pipe and hose. This lets me keep the unused runs strictly rigid.

[David Kumm]

Keep in mind that a 4" gate really has an opening more like 3.5" so take that into account when determining cfm. Dave

[Jim Neeley]

One advantage of going 6" all of the way is because the pressure drop in 4" is much higher than 6". To maintain the 4000fpm normally targeted in a DC piping system, you'd need about 8,000 fpm in the 4" to get to 4000 fpm in the 6". The pressure drop at 8000fpm is astronomical.