Adding a dust collection system to my shop was a great move, but it wasn’t cheap. I did manage to save money by making my own blast gates. The main component of the dust gates is a 3-in. PVC coupler. It cost me only $1 at my local home center, and a 4-in.-dia. dust hose fits perfectly over it.
With a jigsaw, I cut the hole for the coupler in the 3/4-in. plywood mounting board. I attached the coupler with a screw from each side and the bottom and added some caulk around the opening. I used 1/4-in plywood for the spacers. The gate fit tightly, so I sanded it a little thinner with my belt sander to make it slide freely, but I left it snug enough so it stays up when open. The gate goes all the way through the mounting boards. This prevents dust from building up at the bottom of the gate. Instead, a small amount of air gets sucked through the bottom when the gate is open and keeps the slot clean.