Don't Try This Experiment in the Shop - Router Forums
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post #1 of 21 (permalink) Old 01-24-2019, 05:04 PM Thread Starter
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Default Don't Try This Experiment in the Shop

Any kind of flame or igniter in a wood shop could be hazardous so be prepared when attempting experiments like I discuss below. With that disclaimer, I will get to the meat of this post.

It has been suggested on routerfourms.com that since a router in a table only produces chips above the table, there should be no need to have "under the table" dust collection. I have conducted an experiment using a 1/4" radius roundover bit in a table mounted router to visualize the air flow induced by the spinning router bit. A base line test was first conducted using an incense stick (WalMart) with the router bit not spinning; the smoke clearly rises to confirm that the laws of physics are obeyed in my shop. In the next photo, the router motor was turned on and clearly the direction of the smoke flow is reversed. The router bit acts like an impeller on a blower and induces its own air flow. This explains to me why you will get chips beneath the router table.
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post #2 of 21 (permalink) Old 01-24-2019, 07:21 PM
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Cool! Just remember, some routers like hitachi suck from the other end. Your results may be different.
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post #3 of 21 (permalink) Old 01-24-2019, 09:13 PM
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Long discussions on dust collection with routers. Stick nailed one aspect by suggesting setting up a "snorkly" to feed clean air into the bottom of the router, then both below the table and behind the fence DC to get the majority of all dust produced. A tight fitting insert can only help keep the dust above the table.

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post #4 of 21 (permalink) Old 01-24-2019, 09:15 PM
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Quote:
Originally Posted by bfblack View Post
It has been suggested on routerfourms.com that since a router in a table only produces chips above the table, there should be no need to have "under the table" dust collection
Never read anything like that, but for a few years now I've had to do most of my work sitting, because of my back. I use my router in my table, and I "always" end up with a lap full of sawdust. But I have opened my router several times, just to check, and each time it has been totally sawdust free inside.
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post #5 of 21 (permalink) Old 01-24-2019, 11:33 PM
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The router bit would be "slinging" air outward as it spins, much like the centrifugal pump on a washing machine works. That would create a vacuum both above and below the bit as air rushes in to replace the air the bit is pushing outward.
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post #6 of 21 (permalink) Old 01-25-2019, 01:47 AM
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@ Joat.A lap full of sawdust,I know what you're saying.I also sit while working for the same reason.& as my legs fit under the table I cover them with the same old bed sheet I use for the rt cover. My new table will have better sawdust control with my new shop vac. James.
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post #7 of 21 (permalink) Old 01-25-2019, 05:56 AM
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Quote:
It has been suggested on routerfourms.com that since a router in a table only produces chips above the table, there should be no need to have "under the table" dust collection.
except when doing ploughs, groves, mortises, veining, some edge dressing and rabbets...
the saw dust has no other place to go but under the table...
UTDC is a must but not at the expense of the motor...
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post #8 of 21 (permalink) Old 01-25-2019, 07:31 AM
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It has been suggested on routerfourms.com that since a router in a table only produces chips above the table, there should be no need to have "under the table" dust collection.

I don't recall "routerforum.com" ever stating anything so categorically. Can you provide references and links...?
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post #9 of 21 (permalink) Old 01-25-2019, 10:40 AM
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I believe that the statements were that it didn't make much sense to try and suck all the sawdust down through a narrow hole in the table. There are many setups that try and do just that usually by enclosing the router in a box which can lead to other problems. Some members say they have solved all those problems but not every one has, probably because they don't understand all the processes going on when they do. Certainly above the table DC is the best bang for the buck, because as I stated before, 100% is getting created there. And it's the simplest and kindest to your router. Some debris makes it's way under the table but I'm pretty sure it's being slung down there, not sucked down there. The vacuum at the bit isn't strong enough to overcome the one at the bit created by a DC pickup. You need more force than that to get those particles to go downward. Having some dust control under the table to catch them is good, you just have to be careful how you go about it.

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 #10 of 21 (permalink) Old 01-25-2019, 11:16 AM
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First, my Freud came with dust collection. However, it's ONLY about a 2-1/2" line and throttling a 3hp, four bag collector to that doesn't sound like a good shop practice.

Second, even with that kind of collection backing the table, the shelf under the router always caught a lot of dust and chips. After all, chips deflect, when they hit something, and can go everywhere, except into the trashcan across the shop.

The solution was to box the router in, which poses a risk of interrupting the cooling processes. The air for the motor has to come from somewhere, so it'd pull from the area of the router bit. As such, I ran a second line to the box.

In the end, after several long runs, I end up with, maybe, a tablespoon of sawdust on the table top.

I suppose, if the "ain't now sawdust under the router" thing were true, the ideal would be a four inch hose on top and a two inch at the box, along with a small intake, so the lower hose was less likely to pull from the area of the bit.

SIDE NOTE: I have a sanding table, on which I installed sides, a back and a top. Before doing that, it was barely worth using. After, it's one of my most treasured tools in the shop. Since the upper sides, back and top are nylon, I can stick long things out the sides or back, if need be. Otherwise, it'll handle things a couple feet wide.

When I sand, you can see sawdust flowing off an item and being drawn into the table. Even sanding exotic woods that you can, easily, smell, don't. As such, I also use for carving and grinding too. When it's clear of acting as a horizontal storage area, it's my go to place for free-hand routing. ALL the fines are captured and, depending on how I handle a piece (control the direction the router is tossing stuff), only a small percent of what the bit kicks off makes it to the shop floor. Still, there is enough that I vacuum (4" hose and tube) when I'm done.

Clearly, even good collection can't stop every bazillion mile an hour chip from escaping.
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Last edited by Dejure; 01-25-2019 at 11:31 AM.
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