4-Inch Pre-separator

A cheap and lazy shop-built solution.

SHOP OWNER: Tom Berninghausen
LOCATION: Wilsonville, OR

    This Dust Collector Pre-separator is a classic example of why I began my current activity in woodworking. I like doing things with my hands, and, sometimes, I can build something better than I can buy, anywhere, for cheap. When I got my Jet 1100 dust collector, I picked up a garbage can pre-separator lid and a galvanized thirty gallon garbage can, hooked up the four inch flex pipe to the system, and carried on. Id spent about $40.00 for the pre-separator setup. When the garbage can was about half full (or 15 gallons), the shavings moved into the bags of the collector and I began the experience of having to empty the bottom bag of the DC often. This was not a pleasant job!
    As I wandered from Internet forum to Internet forum gathering information, I found a link to a fellow's website where he described a pre-separator he'd built out of plastic barrels. With some modifications to what he did, here is a guide to what I've done. For a mere cost of $20.00 at most, it will collect about 80 gallons of shavings before you need to empty it and send mostly wood flour to your dust collector bags or canister filter.
6-Inch Pre-separator

    The lead shot is a four-inch setup and this shot is a six-inch setup. I used a jigsaw, my router (not the first time), some rivets, a hot glue gun, and a hammer.
    The first step is to locate two 55-gallon plastic barrels (I got mine from the local Coca Cola bottling plant for $3.00 each), a five gallon plastic bucket (restaurants usually have them for $1.00 or free), and a small piece of clear plastic.


Barrel #1


    Cut barrel number one as indicated by the tape.
Bucket Barrel #2

    Cut barrel number two as indicated by the tape and cut the bucket as shown.

    Set the bottom of barrel one on top of barrel two, hammer it tight and put some rivets in the assembly.
Top #1

    Now take the top of barrel one, cut a hole in the center of the top the size of your pipe, cut a piece of your pipe long enough to hang the dimension of your pipe down into the top and stick up a couple inches above the top. Glue the pipe to the top, maybe a six-inch length for four-inch pipe and nine inches for six-inch pipe. You'll place an elbow on this pipe to create your outlet to your dust collector. Then cut a hole in the side of the top of barrel number one for your inlet pipe. Start with a round hole and then elongate the hole to an oval shape so your pipe reaches to the center of the top. I use bolts to attach the inlet pipe to the top.
    In a cyclone dust collector, this is referred to as a neutral vane, if my memory is correct, and guides the dust into the side of the cyclone to begin its swirling action. Cyclones may also use ramps to guide the dust, mathematics to calculate the size, slope, and pressure, and other complicated methods to assure the dust goes where it's supposed to go.
Top #2

    This pre-separator uses a used pickle bucket and lets the dust figure out where to go. Cut a hole the size of your pipe in what was the bottom of the bucket, slip this up inside the top around the pipe, and attach it to the top. In the six-inch version, the bucket and the pipe are a little snug, so I used a heat gun to soften the pipe to get things to fit. I use bolts to attach the bucket. The bucket gives the dust some confusion as to where to go, and I guess it gives up and drops into the barrel.

    If you are better than I am at making ovals on cylinders, your inlet pipe will fit tightly into the hole you made in the side of the top. I used three or four sticks of hot glue to fill the gaps in my sloppy hole. This takes a little while to build up the filler, so while the glue is setting up, cut a window in the side of the bottom assembly and screw/glue a piece of clear plastic over the hole. Finish building up your insert pipe seal, set the top on the bottom and tap it with the hammer, and youre done.
Emptying #1

    After you hook everything up, eventually you will see shavings and dust in the window and you will know it's time to empty the thing. This is a simple process.
Emptying #2

    Using your hammer, tap the pipe to get the pre-separator separated from your piping.
Emptying #3

    Take the top off, tip the barrel over, and dump the shavings out.
    This pre-separator is still a work in progress for me. I get wood flour in the bags until I let the shavings build up too much, then I got some shavings. Recently I upgraded to the Wynn cartridge and piped six-inch PVC. Since I haven't fired up my planer to fill the barrel, maybe I'll need to modify the setup to make the thing work with the six-inch pipe. What I'm sure of is that when I do go to a cyclone, I will still use this pre-separator. I just can't see emptying a twenty-gallon can repeatedly when I can empty an eighty-gallon barrel setup once. That and it takes the same floor space as a garbage can pre-separator for less money than the cost of the top alone. I guess I'm just cheap and lazy!

. . . Tom Berninghausen



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