blast gate issues - Router Forums
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post #1 of 13 (permalink) Old 11-10-2015, 10:06 AM Thread Starter
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Default blast gate issues

Just as I was making good progress in my sawdust production schedule today I realised my vacuum wasnt picking up as much as it usually does.
Got down and dirty with the system and discovered two of the five blast gates werent closing properly, robbing the suction from where needed. One was a quarter open, the other about an eighth.

These are black plastic gates, on 2 1/2" inch clear piping. I had to make a bent pin scraper and clear out all the slots to allow them to close properly. being plastic, I cant dismantle them
Anyone else had this?
got a cure?
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post #2 of 13 (permalink) Old 11-10-2015, 10:20 AM
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You could try turningg them upside down but you would need something to hold them closed then. I haven't had that problem with mine. I wonder if you are getting enough air movement. Theoretically that should keep them clean. I've never had that issue with mine and I have about 6 of them.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #3 of 13 (permalink) Old 11-10-2015, 10:50 AM
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The only problem I have had is they leak, but I have enough suction that it doesn't hurt to have a little make-up air when I use just a 4" port. When I use the 6" gate from Clearview, they are designed with a small hole in the back of the slide to draw air in and clear out the sawdust so that they close.

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post #4 of 13 (permalink) Old 11-10-2015, 12:01 PM Thread Starter
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There should be ample air movement, the vacuum is a purpose shop vac with 4" inlet. because the entire run is only 12 feet, I'm using 2 1/2" cyclone, pipe and gates. the vac works extremely well (except when the gates leak). I vaguely recall reading a post about this but cant find where it was.
i cant rotate them without major upheaval. But direction has no effect on this, as i have 3 with the hole vertical, 1 pointing down, and 1 horizontal, and the blocked ones bear no relation to orientation, or even to usage.
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post #5 of 13 (permalink) Old 11-11-2015, 01:37 AM Thread Starter
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I cant believe how bad these gates are. After fully cleaning all of them yesterday, i made a marker line on the slide, so its just hidden when the gate is closed. That way, when the gate doesnt go all the way home, the blue line shows up on the black plastic.
Today, I saw a blue line appear! after only a half hours routing and operating the gate no more than three times, the thing is starting to block.

Strangely, the router table is the worst offender. The belt sander (which i would have expected to be the worst) has stayed clear throughout.

I'm wondering about slicing off the back edge to allow self cleaning, but think I might lose too much air.

Havent seen any other types in 62mm (2 1/2") so i dont know where to go from here, other than make my own.
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post #6 of 13 (permalink) Old 11-11-2015, 03:58 AM
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make your own...
google will produce a bazillion hits...
Attached Files
File Type: pdf DIY BLAST GATES.pdf (136.3 KB, 161 views)
File Type: pdf Blast gates.pdf (157.8 KB, 240 views)
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post #7 of 13 (permalink) Old 11-11-2015, 08:38 AM
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Bob you said you had a 4" intake but you are only using 2 1/2" runs. What that means is that you have higher velocity but lower total volume. I'm wondering if this might be part of the problem. A lot of people think by squeezing the opening down they will get more vacuum but that is usually not true. Generally you should match everything to the inlet size. You may not have enough air volume to keep everything suspended. Is the opening at the router table the full 2 1/2"? The particles from the sander have low mass because of the small size whereas some or most of the particles coming off the router are much larger and harder to keep suspended.

Or it could be a poorly designed gate.
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Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #8 of 13 (permalink) Old 11-11-2015, 08:59 AM Thread Starter
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Charles. The cost of 4" trunking and gates was the deciding factor in going for the 62mm, as well as the fact that my work area is so small, the big 4" just pushes everything too far off the wall.
I cant run it above because of all the shelves. It does all work well (when the gates are closed properly).

I have a domestic vacuum cleaner tube and head on one of the gates, and it can take up an amazing amount of dust and chips from from my router sled table.

The router pipe is split after the gate with a home made Y joint (nobody makes one), to get suction to the fence as well as the router cabinet, so the total area upstream of the gate is much greater than downstream.
Its not ideal, but I have to juggle space and money, and in all other respects its a good system for my needs.

I've searched and found I am not alone with this problem on plastic gates. I was thinking of slicing off the rear section so the vacuum pulls the blockage free, but am worried that will just give increased air losses when its opened. I can just about swap the router gate around so that the plate hangs down rather than horizontal. I'll do that and see if theres an improvement. The gate is very stiff, so it should stay closed when pushed home. If that doesnt work,I will have to get drastic with home made.
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post #9 of 13 (permalink) Old 11-11-2015, 09:42 AM
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I think I would try slicing off the back edge. I have metal gates that are open on the back edge. Because of this they are self cleaning. When you close the gate the gate pushes any collected saw dust out the back. In the closed position the suction of the dust collection system pulls the gate up tight to the gate body and loss of suction is minimal.

Buck
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post #10 of 13 (permalink) Old 11-11-2015, 10:48 AM
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I was going to suggest what Buck said. I've read several reviews that stated the same problem and many of them said that they cut the bottom portion or the area where the gate slides into off until it was open. This makes them basically self cleaning, when you push the gate closed the saw dust is pushed through the bottom.
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