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post #1 of 18 (permalink) Old 10-18-2016, 03:44 PM Thread Starter
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Default Router Table Build

I am in the process of starting to build a new router table. I want to enclose the router and lift in a box so I can use dust collection for what falls through from the router. It occurred to me that if I build the box then the router will be sucking in a lot of dust into the motor because of the box. Am I just over thinking this or is this a problem I need to address in the build? I will be using a 4" pipe for dust collection located in the back and bottom of the box with a slanted board inside the box to feed the dust down to the connection. How did you keep the dust out of the motor intake? Thanks guys.

Chuck
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post #2 of 18 (permalink) Old 10-18-2016, 04:24 PM
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I would think the dust collection would have more suction that the router motor, or at least I hope it does.



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post #3 of 18 (permalink) Old 10-18-2016, 07:02 PM
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Dunno, but I sit to rout, and have a fairly large hole for the bit, so lots of sawdust goes thru the hole. I know this because most of it seems to end up in my lap. I was told by an 'expert' that my router would pack in a lot of sawdust, and fail sooner than it should. Well, I opened up my router to check, and lo and behold, not a speck of sawdust in there. Apparently the fan inside the router is more than enough to keep it clear of sawdust. Can't say what would happen in your case tho, as my router just sits in the open, not in a box.

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post #4 of 18 (permalink) Old 10-18-2016, 07:03 PM
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Different schools of thought here Chuck. Mine is enclosed on 3 sides and yes, it makes a mess but it works for me. Certainly NOT the only way of course.

If you enclose it, you will have to leave enough openings to allow the dust collection to work. If you close it tight, your dust collection will not work properly because it can't draw enough air to move the dust. And, it's been discussed here in the past, your router might overheat due to the enclosure. Use the search function to find it, and lots of other hints and tips on dust collection for the router table.

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post #5 of 18 (permalink) Old 10-18-2016, 08:11 PM
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Hi chuck, you are the first one I have seen concerned about this. There are two things involved in this, one is makeup air for the dust collector and running dust and chips through the router, not good. here are some pictures of how I solved the problem.

Cut a hole in the bottom of the box larger than the lift to allow air to flow into the box and the router motor to extend down below so it breathes fresh air.

Also a good idea to wye off the DC hose to the top back of the fence.

I also incorporated an adjustable opening in the side of the box to adjust air flow to keep the box clean.
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post #6 of 18 (permalink) Old 10-18-2016, 11:07 PM
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Unlike Herb and others I am deeply concerned about the effects of trying to draw air against the direction that the router wants to pull it. The router is trying to draw air from it's bottom and push it past the bit. The motor in the router and the bit are both generating quite a bit of heat so I don't want to add the heat from the bit to the heat of the motor plus defeating the draft through the router. The suction in the box lowers the possible flow through the router since it is going contra to it and the air flow going past where the air is supposed to exit the router causes turbulence as the two air flows try to pass each other which doesn't do either one of them any good.

In my opinion the best arrangement is to keep the area around the router open and try to gather the dust at the bit or just above and around it. Some of the manufacturers have incorporated dust collection in the area between the router and the bit as part of the base and this actually enhances the flow of cooling air. Air moves from areas of high pressure to areas of low pressure (the principle in physics is that energy always moves from higher potential to lower potential regardless of what type of energy we are talking about.) Any time a fan starts pushing air it will build a high pressure in front of it. This principle is what allows a helicopter to hover. So if you remove the air as the router fan pushes it the more air will flow through.

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post #7 of 18 (permalink) Old 10-19-2016, 12:46 AM
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I feel that sucking dust into the router is not good. I solved it on my enclosed table by making two seperate systems in the same box. The 4" dust collection hole is at the back of the machine enclosure, with infeed air holes on the front panel (4 x 2"), allowing the air to be drawn across the bottom to the exit. Then I used a piece of flexible hose big enough to fit over the bottom of the router (in my case that was 4" ducting hose), and cut a similar sized hole in the floor of the box. The router then has its own air tunnel sucking clean air through it.
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post #8 of 18 (permalink) Old 10-19-2016, 01:13 AM
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It would need to be well below the air intake for the router Bob otherwise you have a Venturi Effect across the intake opening which still pulls air the wrong way. This is a pretty good explanation of what is happening by Matthias Wandell who I would not have expected to be that knowledgeable about physics.
Air blowing across the opening of the router causes a pressure drop. Since the air at the other end is at full atmospheric pressure and the fact that energy always travels from higher potential to lower potential that means the air at the other end wants to move backwards against the flow. The fan in the router should be capable of still moving air in the intended direction but the potentials have to be added together for the net result and since one is positive and one is negative you have a deduction from full flow. A vacuum at the other end by the bit has the opposite effect. Since both potentials are in the same direction the net result is increased flow.
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post #9 of 18 (permalink) Old 10-19-2016, 02:13 AM Thread Starter
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Chuck thank you for the tutorial that made things very clear for me. It raises the question that Herb addressed by using the air suction to pass his router to the collection hose thus allowing the router to blow air into its motor. Are you saying by the Venturi Effect that the router motor would fail to blow enough air into the motor to cool it? Since it is grabbing air from the same source (the hole around the router) wouldn't the air flow not be affected by the dust? Herb's idea looks promising I just want to know why you disagree.
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post #10 of 18 (permalink) Old 10-19-2016, 05:34 AM
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You lost me Chuck, all I know is that it was designed by an engineer and it works great. This is not a system that Bench Dog has, which to me describes exactly what you are talking about. The system I use draws air from around the router housing at the hole in the bottom of the box and through the air vent in the side of the box for the DC, not from the end of the motor sticking through the box where the router gets its air. Seems to me this would cool the router not cause it to heat up.
I have yet to see any top of the table dust collection system that works to get all of the chips.

Herb
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