This is an instructable for how I plumbed up a cheap workshop vacuum cleaner to the dust port on my DeWalt table saw and automated the start/stop of the vacuum. Nothing is permanent (except for one small hole), you can unplug the vac and use it for other jobs and you can store everything away separately when done.
You will need:
Vacuum cleaner. I used the ToolPRO Workshop 10 litre Vacuum Wet/Dry around $50 on special.
Table Saw. Mine is the DeWalt DW745-XE.
An extension lead.
A small grommet to fit the extension lead wire.
Two piggy back spade terminals.
65mm rubber cap.
Step 1: Open the Power Switch on the DeWalt
Disclaimer: If you're not confident with basic wiring and electrical knowledge then get someone who is. You'll want to ensure your circuit can handle the amps being drawn. Some countries prohibit basic electrical work if you are unlicensed so check your local laws.
The DeWalt power switch is pretty straight forward, from the back of the switch you can see the mains power lead coming in and a power lead going out to the saw blade motor. I pulled the main power switch on my DeWalt apart, there are only two or three screws holding it in place. When you open it up you can clearly see the active and neutral wires coming in from the mains plug to the switch, and then the active and neutral wires going out from the switch to the saw blade motor. We want to piggy back off the active and neutral that are connected to the saw blade motor so that when current is applied to the motor we also get current to our vacuum.
Step 2: Piggy Back Off the Table Saw Power Switch
Cut your extension lead so the female end has around 30 - 50cm of lead on it. Strip it back to expose the wires. The earth wire isn't used so cut that off and cap it. Drill a small hole in the back of the DeWalt switch plastic housing, push a rubber grommet in and push your cable through the hole. You can see that DeWalt simply used piggy back spade terminals on their switch, so using the same type of terminal crimp on two new spades to your extension lead. Unplug the blue neutral terminal from the switch that feeds current to the saw blade motor and connect your blue neutral piggy back terminal in its place, then plug blue neutral terminal from the saw blade motor onto your new connector. Repeat for the active brown wire. Make sure everything is nice and secure, then reassemble the switch. You now have a power outlet from the saw that is only active when you power on your saw.
Step 3: Make a Dust Port Adaptor
The ToolPro vac came with a small flexible step down adaptor which ranged from 15mm to 45mm in equal distance steps. I pushed the tip of my vac hose nozzle into the larger end of the step down adaptor and noted the step where my vac nozzle got tight. I cut off the adaptor at that point and turned it around, it now forms a nice seal to the vac hose nozzle.
I bought a 65mm PVC rubber cap with a hose clamp. Cut a hole in the rubber cap that is slightly larger than the smallest diameter on your newly cut step adaptor but smaller than the biggest step. If you cut the hole close the outside of the cap your vac will be able to suck up most of the saw dust without it piling up in a cavity. Push the step down through from the inside with the smaller end first then pull it through. As the steps get bigger in diameter they will seal and prevent the step from pulling all the way through.
Tighten the hose clamp enough so you have a snug fit. This can slide on and off from both the vac nozzle and the DeWalt dust port for quick storage.
Step 4: Hook It All Up
Plug your vac nozzle into the saw dust port, plug your vac into the piggy back power outlet, turn your vac power switch on and you have an automatic saw dust extraction system.