Downdraft table + sander collection ideas

[Steve Hepditch]

Hey all,
With the addition of a piped dust collection system I am planning to add a downdraft table for collecting fine dust while hand sanding. I would also like to pipe a hose to the port on the sander itself (Porter-Cable ROS) to maximize efficiency. I can do this in several ways and I'm looking for opinions as to what might work best and be the least cumbersome with which to work.

I am planning to run 6" pipe all the way to the machines and a 6x6x6 wye will be dedicated to a shop-made downdraft table that will essentially be a 8" tall box with a pegboard top and 6" connection on the end. To this setup I will be adding a 1 1/2" hose that will run to the dust collection port on the sander.

My question is, should I connect the 1 1/2" hose directly to the main DC pipe and run it to the sander from there or can I use the downdraft "box" as a plenum and attach it to the far end? i.e. run the 6" flex hose to one end of the box and put a 1 1/2" port in the box, to which I attach the 1 1/2" hose to the sander OR run both the 6" flex and 1 1/2" hose from the main drop - one to the box, one to the sander?

Attaching the smaller-diameter hose to the box is going to be the more convenient option, I just don't know if there will be enough suction to pull from the sander's port after going through the downdraft box. Has anyone tried a setup like this and how is the collection? Also, any recommendations for the smaller-diameter hose to the sander? I've looked at Festool and Fein hoses that seem a little pricey so I'm leaning toward a 12-ft hose from "Mr. Nozzle" - any opinions or recommendations?

The system is being powered by a 3hp Grizzly with a Thien separator and 6" pipe. The sanding setup will be pretty close to the blower unit so there won't be more than 20' of pipe and a couple hard elbows between it and the downdraft box setup.

Thanks,
Steve

[Lee Schierer]

You probably will have trouble getting much air flow through the 1-1/2" hose. I'm certain unless you carefully calculate the size openings in the down draft table that you won't get any flow connecting the hose to the side of the table chamber. You might get some air flow off a separate connection to the main 6" line; however, the air is going to take the path of least resistance and that may well be the openings in the top of your downdraft table. You may have to have a butterfly valve in the line leading to the table to restrict the flow enough to get the desired suction through your 1-1/2" hose.

[Steve Hepditch]

How about if I change the parameters to reduce the 6" main to a 4" flex to the downdraft table? Would I still be better off the cut a 1 1/2"(could do a 2 1/2" - only limiting factor is what size flex I can get and how to interface with the sander) into the main or could I potentially use the downdraft table in that scenario?

[Ed Hazel]

I basically have the same set up with a 3 hp Oneida cyclone and a shop made downdraft sanding table. I have a six-inch pipe going to the sanding table and have the expensive green hose plugged into the sanding table Plenum. I have the Porter cable 390 which has a fan in it so I do not need a whole lot of suction from the hose it actually does a really good job.

I put a lot of thought into how many holes and how big the sanding area should be on the sanding table but once I got it up and running I discovered that it was pretty easy to regulate the flow by covering or uncovering some holes on the table.

The Festool hose connects right up to the 390 and is only about an inch in diameter and it works fine I would think a larger hose would just tend to get more in the way to be more awkward.