Dissatisfied with Norm's router table dust collection setup

[Rick Dennington]

Hey guys;
Like a lot of you, about 4 months ago I ordered the plans and video of Norm's newest version of his router table. I built it exactly like the plans called for, including the dust collection setup with the PVC" T-Y" connections. I ran the 2 1/2" hose from the dust port to the inlet on top,sealed it off to prevent air loss, and hooked up the 4" d.c. hose with a 2 1/2 " reducer. My r.t. is about 20 ft. from the room where my d.c. sets in. This setup really"sucks"(no pun). It does o.k. at the dust port on the fence, and clears very little inside the cabinet. Frustrated, I unhooked the the 4" at the bottom, sealed it off completely, and hooked the 4" to the dust port at the fence.
How many out there(if any) has had this same problem? I think the t-y out the back is wayyyy toooo small. And of cousre, it's gluded in. It needs to be at least 3-4" for both to work properly. My d.c has 1200 cfm, so that's not the problem.
I'd like some feedback on this, and pros and cons are welcome. Rick D.

[Thomas Knapp]

I haven't seen Norm's design. I assume the router is in a chamber in the cabinet, Yes? What do you have in the way of openings in that chamber to allow airflow? The airflow around the router bit opening is not sufficient to keep the heavier sawdust moving.

[J.R. Rutter]

I'm not familiar with Norm's table, but you are right that bigger is better for DC ducting, right up until the point where you are collecting. Then when it does step down , you will get a velocity boost (which is good for capturing dust particles) but still maintain max air volume.

On my table, I bored a row of 1" holes in the door across the front of the router cabinet to wash air over the shelf below the router towards the port. This does a great job of keeping the cabinet clean.

If you want to be scientific about it, you could try to keep the total area of the openings in the fence and elsewhere the same as the area of the 4" duct (about 12.5 sq.in). Run 4" to cabinet and fence. This will give max velocity at each opening. At least that is my understanding...

[Fred Hargis]

I built his cabinet, but did not like the DC design from the beginning. Taking a Tim Taylor approach, I have a 6" drop that goes to the cabinet, and on that drop is a 4" gate/hose that goes to the fence. Overkill? Maybe, but nothing gets past it.

[glenn bradley]

I run a 4" to the lower and a 2-1/2" to the upper. No tees, just wyes. Works fine.

[Rick Dennington]

I forgot to mention in my post that I drilled 4-1" holes across the bottom of the door to take care of the"makeup air" as Norm called, only I made my door out of 1/4" plywood instead of plexy. That should not make any difference as long as the holes are there.
I can't see a way to hook up a 4" hose at the fence the way the dust port is made without reducing it like it is. And would have to tear the back off to get the T-Y connection out, as like I said, it's glued in.

[Stephen Edwards]

Have you tried it with the door open, to varying degrees? If not, if you were to try that perhaps that would tell you if you're getting enough air flow with just the holes drilled in the door.

[Rick Dennington]

No, I haven't tried it with the door open, but it sounds worthwhile just to see what happens. I have a feeling that it will not make much difference with the small inlet, but I'll give it a whip. Thanks, Stephen.

[Joe Jensen]

Hey guys;
Like a lot of you, about 4 months ago I ordered the plans and video of Norm's newest version of his router table. I built it exactly like the plans called for, including the dust collection setup with the PVC" T-Y" connections. I ran the 2 1/2" hose from the dust port to the inlet on top,sealed it off to prevent air loss, and hooked up the 4" d.c. hose with a 2 1/2 " reducer. My r.t. is about 20 ft. from the room where my d.c. sets in. This setup really"sucks"(no pun). It does o.k. at the dust port on the fence, and clears very little inside the cabinet. Frustrated, I unhooked the the 4" at the bottom, sealed it off completely, and hooked the 4" to the dust port at the fence.
How many out there(if any) has had this same problem? I think the t-y out the back is wayyyy toooo small. And of cousre, it's gluded in. It needs to be at least 3-4" for both to work properly. My d.c has 1200 cfm, so that's not the problem.
I'd like some feedback on this, and pros and cons are welcome. Rick D.

The problem is that most dust collectors can't move much air through a 2 1/2" port. 1200 CFM or 2500 CFM, if the pressure delivered to the port is the same, the CFM through the port will be the same. I'm pretty sure a Rigid shop vac will pull more CFM through a small port than a 1200 CFM dust collector. The reason is a 1200 CFM dust collector will develop a raw 12" of pressure with a clean new filter and no duct but it will deliver somethinge like a real 5" of pressure at the machine. A Shop vac with a new filter will deliver like 110 CFM, but 90" of pressure with a new filter. With a used filter, and typical losses, the shop vac will get 80" or so of pressure to that 2.5" port. Even though the shop vac can only do 110 CFM with no load, it will likely pull more air through that small port because of the higher pressure.

Try an experiment. Try the shop vac on the same 2.5" port and see what happens...joe

[Bruce Wrenn]

Joe's post are exactly my thoughts also. Your DC can't produce enough static pressure to over come the restrictions place in the router table. I would prefer to have air from fence travel into the box where router motor is to help with cooling.

[Brad Townsend]

I increased the size of the bottom hole and replaced the PVC T with one of these. It's a 4" with a 2 1/2" coming off it. They can be ordered from Woodcraft.

http://img.photobucket.com/albums/v238/btownsend/DSCN0929.jpg

[Jim Becker]

4" port on the cabinet works much, much better and has been a recommended upgrade in the online community for many years. But don't forget to calculate the necessary air intake area so that you can supply that 4" port with enough air to make it work properly. Dust collection is about moving air, NOT suction. No air. No collection.

[John McCaskill]

You're starving the 4" dust collection port for air. 1 hole at 4" diameter = about 12.6 square inches. 4 holes at 1" diameter = about 3.1 square inches. That's why it doesn't work. You need something like 16 holes if you stay at 1" diameter, or 4 holes if you enlarge them to 2" diameter. Then it works fine. Mine does.

John


I forgot to mention in my post that I drilled 4-1" holes across the bottom of the door to take care of the"makeup air" as Norm called, only I made my door out of 1/4" plywood instead of plexy. That should not make any difference as long as the holes are there.
I can't see a way to hook up a 4" hose at the fence the way the dust port is made without reducing it like it is. And would have to tear the back off to get the T-Y connection out, as like I said, it's glued in.

[Gary McKown]

I built the Nahm router cabinet from two pics rather than plans, so was not saddled with the dust collection setup. I did, however, use 2½" ports both top and bottom (figuring I could go to 4" if necessary) simply to relieve the bulk at the rear of the cabinet.

Collection in the cabinet was abysmal, as you observed. Taking a tip from the cabinet saw trade, I installed a removeable shelf (actually just a piece of foamboard) under the router, angled down toward the rear port. Shazam! Went from collecting nearly nothing to practically all of it. I still get a little buildup in the corners after hours of use, but it is mostly the coarser stuff.

I also bored holes near the TOP of the door, rather than near the bottom, figuring that clean air flowing past the router motor, rather than scooting across the floor, should be good.

[Tim Cleary]

+1 on using shop vac.

[Gary Redden]

I run a 4" to the lower and a 2-1/2" to the upper. No tees, just wyes. Works fine.

Ditto. It has so much suction with this setup that it actually broke the catch for the door over the lower section from sucking the door out of my hands closed. This is with the cyclone about 40 feet away from the router table.

I was like you and with just a 2 1/2 connection on the cabinet it did a terrible job. A 4" connection is the way to go.

Gary

[Stephen Edwards]

No, I haven't tried it with the door open, but it sounds worthwhile just to see what happens. I have a feeling that it will not make much difference with the small inlet, but I'll give it a whip. Thanks, Stephen.

Rick,

I'm doing some changes on my RT today, an experiment. I'll let you know how it turns out.

Mine has a 2 1/2" dust port on the bottom of the back of the cabinet. I'm converting that to 4". Also, I'm installing a 4" blast gate above the dust port in the back of the cabinet, per someone's suggestion in another thread a while back.

My table is functional but not yet "finished". It doesn't yet have a door on the router cabinet. I'll clamp a piece of lexan that I'm planning on using for the door over the door opening so I can see what's happening.

If it doesn't work, oh well, just another hole in the back of the cabinet to cover with a "patch" and make up some good story about how that piece is part of the structural integrity of the cabinet back. Oh yeah, I got it! I can cover it with a piece of rubber and it'll be a remote shock absorber and sound baffle!

I'll keep you posted.

[Stephen Edwards]

Rick,

OK, I made the changes on my RT today. What a difference in how it works!

I changed the cabinet port from 2 1/2" to 4". As you're facing the cabinet I installed a 4" blast gate in the upper left hand corner of the cabinet back. I cut my lexan a bit oversized and taped it over the door opening with painter's tape, completely sealing the front opening.

My table has separate blast gates for both the fence and the cabinet. Using a 1/2" spiral upcut bit I made dados and rabbets in scrap lumber. For the dados I closed the fence blast gate. For the rabbets, I tried it open and closed. Currently the insert in the plate is the bushing insert.

The best results were with the cabinet blast gate (the one that isn't attached to the DC system, just a hole to provide air flow) half open. Even with the fence DC blast gate closed while doing rabbets there was hardly any accumulation of dust on the table. It was all sucked down through the insert hole.

Next, I put an ogee bit with a bearing in the router. Most of the debris was still sucked down through the insert opening and out of the cabinet. Then, I opened the fence DC blast gate, too, and that got all of it.

My conclusion for my table: I'm not gonna have any holes in the door at all. The adjustable opening provided by the newly installed blast gate, described above, in the back of the cabinet, and increasing the cabinet port to 4" did the trick.

I did try leaving a small space for airflow at the door by shifting the lexan in different positions. When I did that, I had fines in the corners of the cabinet. It worked much better to have the front opening completely sealed.

That's what worked for me. Best wishes as you adjust your RT to improve the DC!

[Jim Becker]

Keep in mind that the purpose of the small, carefully sized air inlets on the door is to provide a "sweep" of air to help clear out the bottom of the cabinet.