Fixing plastic blast gates

Blast gates is necessary to block outlets and/or sections of the dust collector ducts. These cheap plastic ones are good, except when they clog up with dust so they can’t be closed. Let’s fix the problem!

Do you sometimes have a eureka moment so bad that if you were to slap yourself in the face you’d get a concussion? I got one of those while browsing one of the woodworking Facebook groups. A fellow named Lars showed me a solution to the blocked gate problem that was so obvious I nearly got mad; it was so stupidly simple! Within half an hour I solved a BIG problem with my duct work! But since I got your attention, let me elaborate…

All the images expand if you click on them.

An image tells the story better than a thousand words. I have several of these plastic blast gates in my dust collector duct system (be sure to check that article out), and they work great – except after a while, when the damper can’t be closed due to buildup of dust inside the housing. Which resulted in this:

This blast gate is an extra outlet where I connect my router table or any other large diameter dust hose. Since it would not close all the way, false air is drawn in and reduces the effectivity of my dust collector. Even when the gate for my big band saw is fully opened, I could feel a good draft going through this partially open gate. NOT good!

It is the topmost gate in the image above.

I had already purchased metal blast gates to solve this problem, as they do not have this issue. They are open at the back, so any dust is just pushed out – or I could easily remove any debris with a bent wire or something:

Here’s another image of the type I got:

Now, even though I found a fix for my plastic gates I am still going to swap those out for the metal ones. In the long run I have more confidence in metal. And since I already got them…

But back to the plastic ones. They are, for now, installed in my duct work, so I thought I could try to fix the problem – Lars style.

I removed the blast gate shown earlier (the first image) and clamped it in my vise. A ryoba pull saw is excellent for choppin’ plastic, and with a couple dozen swiffa-swoffa I removed two of the corners.

See that yellowish square? That’s the buildup of dust! I poked a fine screw driver through and cleaned the inside of the blast gate. There was quite a lot of debris in there!

I thought the small corner hole would probably not be sufficient to keep the blast gate free of debris over time, so I opened up the housing a little in the corner of the raised portion on one side.

On the image to the right you can see the corner of the damper. This shows how tight it is in there.

This solved the problem for that blast gate, but I could spot a few problems right away. First, chopping off the corner compromises the integrity of the blast gate. They are glued together, so removing the corners will weaken them and give a starting point for a crack in the glue seam. Secondly – what to do with the blast gates that are already mounted? It isn’t much space behind the ducts, so it would be a pain to do this modification in situ.

The enlarged hole shown above would not be possible to do without disassembling a lot of the duct work. And then it hit me again: just drill a hole!

And there you have it! A 10mm hole using a wood drill bit, easily done even in that cramped space. I opened the blast gate and zapped a hole at each corner. Finito! I then poked the screw driver inside and cleaned the clogged debris while the dust collector was running.


If I close the blast gates now, vacuum builds up in the ducts to the point where it makes a loud BANG if I yank open the damper!

Lately, I have experienced issues where the dust collection on my band saw has become worse and worse. I have also had problems using the floor dust port – it would not pick up dust and shavings as good anymore. That problem is gone now!

If you have blast gates similar to mine, go grab a 10mm drill bit (the ones with the spur in the middle) and zap holes like I did. Remember to open the blast gate fully first. Poke a screw driver or a piece of wire and clean out any debris. Your problems should now be gone for good.

Thank you, Lars! This worked so well it is stupid! Why did I not think of this myself..?

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