Build an Automatic Shop Vac/ Power Saw Switch




About: When I was a boy, I was amazed how my grandfather could make flotsam and jetsam into useful things. I am proud that I have inherited some of his skill.

Intro: Build an Automatic Shop Vac/ Power Saw Switch

In a first class woodworking shop, the craftsman merely pulls the trigger on his power tool and the dust collection system turns on, too, thanks to a device called a current sensing switch.

OK, so my shop is just a tad less than first class, but I still needed to do something about sawdust.

Step 1: The Way It Was...

In order to keep the depth of sawdust on my tools to a minimum, I have repeatedly tried to use my shop vac to suck up dust from my stationary tools. The biggest problem with this idea was that I needed my shop vac for a lot of things so my miter saw usually just blew sawdust into the air.

I had often thought of using an old Electro Lux vacuum as a dedicated dust collector but I never got around to it because the end of the suction hose was much smaller than the saw output.

Eventually, I pulled the vacuum down from the attic and began connecting various hoses and PVC fittings into something that connected my vacuum to the mitre saw. This consisted of a 6 foot hose section from an automatic pool cleaner, 2 45 degree couplings, a short piece of PVC pipe, and some electrical tape.

Once I got the vacuum plumbed to the saw, I still had a slight problem: I had to turn it on and off. Very often, I just use the saw for one or two quick cuts. So why bother to turn on the vac? Easy for me to say, until the dust on everything gets annoying. So I decided to do something.

Step 2: Automatic?

On a scale of costs tools and accessories, a little over $30 for a current sensing switch to turn my vac on and off when I used the saw is cheap enough. Except I would rather spend twice as much money and 4 times as long to make something that works something like the original than buy it.

It wasn't hard to decide on leaving the vacuum switch in the on position and using another switch to turn on the power to both tools at the same time.

Switch off, everything off. Switch on, pull trigger, both on. Simple but I confess only automatic in the sense that when the switch is turned on, current automatically flows.

Still, it works pretty well.

Step 3: How to Do It...

1 - 115 volt receptacle
1 - SPST switch
1 - square wiring box
1 - cover for " with cutouts for
receptacle and switch

Length of flexible electrical cable to suit, 2 conductor with ground, capable of handling saw and vac load
Plug for cable
Screws, wall anchors, etc..


The short extension cord will plug into a nearby receptacle. IMPORTANT: It must have a current handling ability sufficient for your tool so check on that first.

The wiring will be routed as follows: white wire to bright screw on receptical, green wire to ground screw on switch, then to ground screw on receptical, black wire to one screw on switch and from second screw to brass colored screw on receptical.

Mount the completed switch near your power tool and plug in your vac and tool. Turn on your vac switch. Your saw won't run (a safety feature, too) until the switch is on, and then the vac comes on, too. Automatically.

This is a simple project for anyone with a modicum of electrical experience. Safety wise, never fail to observe all safety guidelines; do everything you should and nothing you shouldn't.



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    12 Discussions


    16 days ago on Step 1

    Simple and functional! Thank you so much fot this posting, you solved one of my problems, excelent job!

    1 reply

    Reply 16 days ago

    That's great! I appreciate the comment.


    18 days ago

    Since you're using a metal box, I'd run a pigtail from the box to the ground screw on the outlet. Usually the metal boxes have an extra threaded hole for one of those "hat" style machine screws that come with a short bare copper wire to do this. Other than that, nice project. I would mount the box to wherever your saw is mounted so it's Right There. And Tercero? If it costs more than $50, it's too expensive for us amateurs. Sorry.

    1 reply

    Reply 17 days ago

    Good point. I should have done that even though the switch and receptical are grounded to the box through their frames. You can't have too good of a ground.

    One of my most favorite things to do is improvise; I may someday have a dust collection system but you can bet it will have started life as something else.


    Tip 20 days ago

    Around Christmas time stores have Out Doors lights controlled using a Remote. the remote is the Plug in for the lights, and comes with a remote control to turn the switch on & Off.

    I have been using mine for over 6 years to turn on my home made Cyclone Dust Collector.

    1 reply

    22 days ago on Step 3

    Thanks for this.

    Can I just say though you should probably invest and get yourself a proper dust collector and air cleaner.

    They're really not expensive. If you purchase a dust collector, get the canister add-on vs the bag it comes with. Makes a huge difference. And a roof mounted air cleaner will really cut down on floating particels and make using cabinet saws and the like a lot cleaner.

    1 reply

    22 days ago

    Not exactly sure how you wired this from the vague description. I wiring schematic is usually the better way to show that. But it sounds like you are powering up both the saw and the vacuum via the on/off switch of the saw. If that is so, you now are making the on/off switch on the saw carry way more current then it was originally designed to cover. And if that is so, you will shorten the life of that switch for certain. I better way is to either buy such a setup that also runs the vacuum for a few more seconds when the saw is turned off to clear the hose, or make such a circuit to you are not over-loading any switches. JMHO

    1 reply

    Reply 21 days ago

    No it's not the saw switch turning things off and on, it's the switch in the metal box, which is easily capable of carrying the combined current (or else, the circuit breaker would blow as they are the same current rating.)

    I agree, a schematic would have been better, however as this circuit is merely a receptical being turned off and on by a single pole switch, it didn't occur to me. Maybe I'll add one.


    22 days ago

    First off, I appreciate your 'able. However it just seems that your "automatic" switch is just a switched outlet that you have both your vacuum and saw installed on. I'm not sure what qualifies this as automatic when the operator is turning on and off both of the devices manually (albeit with once switch).

    1 reply

    Reply 21 days ago

    I was kidding.

    See, in step 2 (titled 'Automatic ?'), I say, "I confess only automatic in the sense that when the switch is turned on, current automatically flows."

    Thanks for the comment.