Blast Gates

[Bill Pentz]

Although a few nice looking blast gates were recently shared, I wish folks would quit following this approach because it has problems.

First, the sliding part of the gate does not go all the way through. This causes the gates to build up sawdust that you pack in tighter and tighter every time you close your gate. Eventually this causes the gate to not shut fully, will cause it to jam, and can even cause your blast gate to split in two if you push it closed too hard. This approach leaves regular a big cleanup messes. Even when mounted with the slide opening downward, over time they still plug. A far better design makes a longer slide that goes all the way through. One half of the slide has a hole to match the gate. This keeps the chips from building.

http://cnets.net/~eclectic/woodworking/ducting/BlastGate.gif

Second, the use of the metal flanges is pretty, but can easily increase the cost of each gate near the cost of a commercial gate and the flanges don't work all that well. They seal fine to the gate sides, but often are difficult to seal to your metal or S&D 2729 PVC ducting. These flanges have razor sharp edges that can easily draw blood when handled or bumped. It is far safer and less expensive plus you get a better seal by cutting a PVC coupling in half and using it on both sides. The couplings let you connect directly and tightly to your ducting without another fitting. It also makes it easier for you to mount your gates up high next to the mains where they go instead of down next to your machines as many keep doing. Putting them low lets blocks and such build up in the pipe when the gate is closed. Opening the gate slams that junk right through your separator or cyclone into your impeller then filter, potentially ruining motor bearings, breaking impellers, punching holes in the cartridge filters, and greatly reducing filter life from the need to do far more frequent cleaning.

The site I recommend and shared for properly building blast gates when I engineered and designed the dust collection systems that so many on this forum have built is Phil Bumbalough's Building a Blast Gate (http://www.benchmark.20m.com/articles/BlastGate/blastgatebuilding.html).

bill

[Chris Padilla]

Thanks, Bill. A good lesson and everything makes sense once I thought about it a little bit.

Phil's gates look good to me...I'll follow his approach when I finally, someday, put your kit together.

[Stan Smith]

Thanks Bill. That's mighty nice of you the share your expertise with us. I have yet to set up a central dc system. I'm currently using a Jet 1100 with the retrofit cannister and using a 10' hose to hook up directly to each machine. Since I have so much invested in the Jet dc, I really haven't given much thought to putting in a central system with blast gates. In fact, I don't have any idea of even how to go about it. I have an Jet air filter unit almost in the middle of my ceiling. Do you think that I could or should change my existing system to one with ducts and gates? Thanks.

Stan

[Donnie Raines]

Thanks Bill. That's mighty nice of you the share your expertise with us. I have yet to set up a central dc system. I'm currently using a Jet 1100 with the retrofit cannister and using a 10' hose to hook up directly to each machine. Since I have so much invested in the Jet dc, I really haven't given much thought to putting in a central system with blast gates. In fact, I don't have any idea of even how to go about it. I have an Jet air filter unit almost in the middle of my ceiling. Do you think that I could or should change my existing system to one with ducts and gates? Thanks.

Stan
I own the same collector as you. I have a number of runs via 4 inch PVC and all machines have blast gates at the unit it's self. This made the system much easier to use(simply close a gate...then open gate) and your off to the races. I would suggest(without giving you all the techincal mumbo jumbo) that you consider installing runs with blast gates at each unit.

DonnieR

[Jack Diemer]

I was working on a through blast gate design (made of wood), but someone brought to my attention that going all the way through may cause a "whistle" effect if everything isn't real snug.

Do you have any experience with this "whistle" effect.

My design is basically like Terry's except I break up the one section shaped like a U (sandwiched in the middle) into three pieces. Two running rails, and a triangle. Using the triangle, the dust should get pushed through the bottom while still lining everything up tight. I have yet to build and test this design, but it should work. (just don't want it to whistle)

Any thoughts would be appreciated.

[John Weber]

I had some clogging with the black plastic blast gates, but switched to the diecast frames with metal gates and I have yet to have any clogging or bleeding. They seal very well and Rockler often has them on sale. If I needed larger gates I guess I might need to build them - but I've seen several designs that looks promising. As for mounting them, I think a person needs to do what makes the most sense. If a gate is away from the machine, it's easier to say "just one cut, I'll leave it closed".

John

[Lee Schierer]

I made my own blast gates from two pieces of wood, with holes cut to fit the O.D. of the pvc pipe I use. Sandwiched between these is a piece of 1/4" lexan with a "U" cut in it that is 1/4" per side larger than the ID of the pipe. The center part of the U fits in nicely once the parts are sandwiched together. A sheet metal screw keeps the tounge from being pulled all the way out of the U. I seal the pipes in place with some silicone caulk. I have yet to have one jam or accumulate debris.

[Chris Padilla]

I was working on a through blast gate design (made of wood), but someone brought to my attention that going all the way through may cause a "whistle" effect if everything isn't real snug.

Do you have any experience with this "whistle" effect.

My design is basically like Terry's except I break up the one section shaped like a U (sandwiched in the middle) into three pieces. Two running rails, and a triangle. Using the triangle, the dust should get pushed through the bottom while still lining everything up tight. I have yet to build and test this design, but it should work. (just don't want it to whistle)

Any thoughts would be appreciated.
Jack,

I would hazard a guess that any leakage of air through a small orfice/slot could be noisy (i.e. whistle effect). If you don't build the blast gate pretty flat or use good flat stock or the wood moves/warps/twists, I would surmise this could be an issue whether the sliding gate is snug or slightly loose (as Bill points out it should be). Assuming good flat surfaces, I like the slightly loose gate idea and using the vacuum to seal itself.

As far as the clogging issue of a U-shape versus a | |-shape, it may not manifest itself right away...but over time, I could see it happening. Is it a big deal? Dunno...time will tell. It could be that a shot of compressed air will clean it right out. Perhaps a tapered design (/ \-shape) could be considered? :)

Edit: Ah, I see what you are saying. When the gate is open, you could be drawing air through the open-end of the blast gate and since it would be a small area of opening, it could whistle. Hmmm....

[John Weber]

The way you tell they are clogging is they don't close. With the old plastic gates I would just take them out of the system abd use a little air and a little screwdriver to clean them - maybe a 5 minute process. The dicast gates were cheap enough (about half price) at Rockler, I decided to upgade. I think they don't clog, because the slots are for thin steel vs 1/8" plastic.

John

[Robert Ducharme]

Bill,

I am using the gates purchased from Oneida (do not know where they get them from). Unfortunately, I need to put them low (main duct runs 16 feet from the floor). How do I know I have no buildup behind the gate? Could I open the gate with the DC off and see if stuff drops down into the clear flex plastic pipe? Or are you writing about something else?

[Donnie Raines]

Every person I have every seen that had issues with their blast gates sticking,thus, not closeing all the way, was due to the fact they had the gate with the lift in the "to be pulled up" or the " to be pulled down" postion. If you install the gate so that you need to open the gate to the side dust will not get lodge into the seam and you will have solved your gate closing issue.


DonnieR

[Stan Smith]

I own the same collector as you. I have a number of runs via 4 inch PVC and all machines have blast gates at the unit it's self. This made the system much easier to use(simply close a gate...then open gate) and your off to the races. I would suggest(without giving you all the techincal mumbo jumbo) that you consider installing runs with blast gates at each unit.

DonnieR

If only my brain would have been working at the time, I would have had the "runs" put in before the concrete floor was poured..Sad to say that my advance planning is less than exemplary. The machines that I use the dc for are TS, router, drum sander,bandsaw, jointer, and planer. I hardly have to move the dc at all except for the jointer and planer. Not sure how I could do a run without a bunch of elbows or Y's. I heard that's not a good way to do it, but really don't know anything.

Stan

[Jim Becker]

If only my brain would have been working at the time, I would have had the "runs" put in before the concrete floor was poured..

Actually, Stan, you're probably better off that you didn't put them in the concrete unless you did channels with removable panels. The major problem with putting duct work permanently in the floor, aside from any possible deterioration issues, is that you are committed to one arrangement "forever". My present shop has been in use for a little more than four years and I have made many changes to tool placement over that period of time...some requiring relocation of DC accomodations. Although overhead is sometimes less attractive, it's at least more flexible when it comes to changes. You can also usually get a more optimal routing of the duct when it's "up there"...allowing you to keep runs shorter and putting the drops right where you need them. IMHO, of course!

[Bill Pentz]

Jack,

If you take your design and extend the length of the slide so it always is in the slot, then there is no whistle. The whistle comes from not making the slide long enough to fill the slots when open or closed. Make one half of your gate slide plain and the oher with the hole.

bill

[Bill Pentz]

Every person I have every seen that had issues with their blast gates sticking,thus, not closeing all the way, was due to the fact they had the gate with the lift in the "to be pulled up" or the " to be pulled down" postion. If you install the gate so that you need to open the gate to the side dust will not get lodge into the seam and you will have solved your gate closing issue.


DonnieR

Donnie,

Admitted that installing the gate with the slide mounted vertical and pointing down will reduce the cleaning problem, it does not eliminate it. It just takes longer before the problem appears.

bill

[Bill Pentz]

Bill,

I am using the gates purchased from Oneida (do not know where they get them from). Unfortunately, I need to put them low (main duct runs 16 feet from the floor). How do I know I have no buildup behind the gate? Could I open the gate with the DC off and see if stuff drops down into the clear flex plastic pipe? Or are you writing about something else?

Robert,

Just leave your DC off and open the gate. If you have a buildup of material, then you need to make repair. Sadly, what often builds up will be big chips and chunks that when you open your gate can go slamming into your cyclone then directly into the impeller. Those with plastic and aluminum impellers are having trouble with broken and chipped impellers from either having the gates too low or using small down drops that do not provide enough FPM to keep the mains from building up piles of chips, blocks, and other debris.

bill

[Bill Pentz]

Thanks Bill. That's mighty nice of you the share your expertise with us. I have yet to set up a central dc system. I'm currently using a Jet 1100 with the retrofit cannister and using a 10' hose to hook up directly to each machine. Since I have so much invested in the Jet dc, I really haven't given much thought to putting in a central system with blast gates. In fact, I don't have any idea of even how to go about it. I have an Jet air filter unit almost in the middle of my ceiling. Do you think that I could or should change my existing system to one with ducts and gates? Thanks.

Stan

Stan,

You have an excellent unit, in fact the same as I chose for myself except I use my own cartridge filter setup. If it works for you as is, I'd say enjoy. I found with my own that changing to 6" ports with better hoods on my tools and using a 6" hose in place of the wye on that dust collector made a huge difference. I went from about 450 CFM with the 4" to close to 1000 CFM with the 10' of 6" duct.

Changing that DC-1100 impeller to a DC-1200 impeller is enough that you can power a cyclone for a small shop as well.

bill

[Stan Smith]

Stan,

You have an excellent unit, in fact the same as I chose for myself except I use my own cartridge filter setup. If it works for you as is, I'd say enjoy. I found with my own that changing to 6" ports with better hoods on my tools and using a 6" hose in place of the wye on that dust collector made a huge difference. I went from about 450 CFM with the 4" to close to 1000 CFM with the 10' of 6" duct.

Changing that DC-1100 impeller to a DC-1200 impeller is enough that you can power a cyclone for a small shop as well.

bill
Thanks for the info Bill. I would have never though of changing the impeller. I had read in a Canadian woodworking mag about a drop box. I built one and tried it but didn't think that it worked too well. I don't think that I got the door sealed good enough. Sounds like a cyclone would be better but am unclear what and how to use with the dc-1100.

Stan

[Chris Padilla]

Stan,

I assume you have Bill's site linked?

http://cnets.net/~eclectic/woodworking/cyclone/index.cfm

You'll find lots of answers there though it takes some time to read...well worth it.

[Bill Pentz]

... Sounds like a cyclone would be better but am unclear what and how to use with the dc-1100.

Stan

Stan,

A 20" diameter cyclone and Jet DC-1200 impeller with all 6" ducting and you would be in business for a shop sized up to a one-car garage. You could push it further, but the extra ducting my add enough resistance that you could begin to have airflow problems. If you located all the high CFM machines close to the cyclone, you would be in good shape.

bill

[Stan Smith]

Stan,

A 20" diameter cyclone and Jet DC-1200 impeller with all 6" ducting and you would be in business for a shop sized up to a one-car garage. You could push it further, but the extra ducting my add enough resistance that you could begin to have airflow problems. If you located all the high CFM machines close to the cyclone, you would be in good shape.

bill

Well, thanks again, Bill. Do I buy the 20" cyclone or make my own. My shop is 24'x20'- a garage kit from Meeks Lumber. I have been on Pentz Road, near Oroville, a number of times. Any relation?

Stan

[Bill Pentz]

Well, thanks again, Bill. Do I buy the 20" cyclone or make my own. My shop is 24'x20'- a garage kit from Meeks Lumber. I have been on Pentz Road, near Oroville, a number of times. Any relation?

Stan

Stan,

The available snap together kits are all 18" cyclones, so you are going to have to either build your own, or trade blowers.

Bob Meeks (Meeks' Lumber) is a very close friend of one of my buddies that moved out of the area about 17 years ago. We lost touch, but I often heard that Bob was quite a character. And yes, my parents checked out Pentz road near Oroville and turns out it was named for a second cousin to my father. I was getting up that way a few times a year for my son's soccer tournaments at Chico. Can't believe how quiet my life is now wtihout five soccer practices a week and games on almost every weekend from January through December. Had one day off last year and was so stunned did not know what to do.

bill

[Stan Smith]

Stan,

The available snap together kits are all 18" cyclones, so you are going to have to either build your own, or trade blowers.

Bob Meeks (Meeks' Lumber) is a very close friend of one of my buddies that moved out of the area about 17 years ago. We lost touch, but I often heard that Bob was quite a character. And yes, my parents checked out Pentz road near Oroville and turns out it was named for a second cousin to my father. I was getting up that way a few times a year for my son's soccer tournaments at Chico. Can't believe how quiet my life is now wtihout five soccer practices a week and games on almost every weekend from January through December. Had one day off last year and was so stunned did not know what to do.

bill

My, my it's a small world. I'm using those faslock fittings that come from Woodworker's Supply. I was using a press-fitting but it came off sometimes. The faslock's never do and they are even easier to attach than the other one was. Although I would eventually like to build a little shed and put the DC outside, I guess I'm not really ready for a duct system until I can get the whole plan thought through. Have you ever heard of anyone having success with a drop box?

Stan

[Scott Coffelt]

Well, in the 10 years it will take to completely fill the area on the design I used, Thanks T.H., I don't see any problems. Anyways, in the rare event and I mean rare event that the my blast gates start to stick or get clogged, I will take a coat hanger and scrape clean. No big deal. It will have to clogg with a good inch before that is needed and besides, I drew a line on my gates when they were new to watch for that. Amazing after several bin fulls of saw dust. Each and every one is still even with the line.... Ummmmmmmmm. :p

Oh well, good luck with spending all that money buying fancy metal gates. I'll stick with my gates that cost me less then $7 to build and function as good.