There are a few reasons why this occurs. You should never try to remove more material than recommended by the manufacturer; this can result in a heavy volume of large shavings that may plug the hood outlet opening. If the hood is supplied with a 4″ outlet then you should be using 4″ diameter piping, hooked to an appropriately sized dust collector. Reducing a 4″ opening with an adapter so that you can use a Shop-Vac further restricts the flow of shavings and can cause the hood to plug at the adapter. If you must use an adapter, use a tapered design.

If you are planing cedar, you will find that you get longer shavings than with pine, and these have a greater tendency to plug the hood outlet. Most of the companies that have side discharge hoods designed them for two reasons: to rid you of the problem of having your collection hose catch or drag on the boards as they exit the planer, and to make the return rollers usable. Keep in mind that although air can make abrupt changes in direction of flow, shavings cannot, and if they fall out of the air stream they tend to initiate plugging.

Deciding that I wanted to economize, I went to the local hardware store and picked out the following heating and ventilating fittings: a 4″ x 10′ X 4″ universal end boot, which has a centre discharge, and a 4″ side takeoff.

I modified the end boot to pick up the shavings from the thickness planer. First let’s have a closer look at the factory chute because I used it along with the end boot.

The business end of the factory chute is tapered. It’s narrow at the top and wide at the bottom, but does not extend to the rear edge of the cutter head housing. I built an extension for this chute to guide the shavings into the new hood. The extension also makes it easier to add on the hood.

I incorporated an opening in the side of the chute closest to the jointer as the jointer fence support post can protrude into the chute. The extension piece consists of a 4″ x 14″ piece of 20 gauge steel, bent to fit over top of the existing chute. Three pop rivets hold it in place, but I riveted from the inside out to ensure that there are no protrusions into the chute area that could snag and hold passing shavings.

I took the end boot and drilled out the four rivets that held the sides together, enabling me to shape the end boot to conform to the chute. Notice in the picture of the new hood that I used a piece of steel flat bar to fasten the lower edge of the new hood in place. The bar stock adds rigidity to the lower edge of the hood and ensures a tight seal. From the photo you can also see that I decided to angle the boot outlet up slightly, thus rendering the return rollers virtually useless. (I never used them much anyway).

The original jointer chute is basically a simple deflector. When designing a hood it is important to keep in mind that the last thing you want to do is to create another hazard.

The opening under the cutter head is short and wide. My first thought was to use a top takeoff fitting but this would have oriented the outlet to the side of the jointer, placing the collection hose directly in the path of the person using the jointer. The position of the motor also blocked the easy use of the same fitting with the outlet pointed in the direction of the flow of the shavings. The use of the top takeoff would allow the hose to be directly under the jointer bed and give clear access to the user along the side of the jointer.

The modified side takeoff has heavy gauge brackets fastened to it. One side uses the same fasteners that held the factory chute, but I had to add another bracket to secure the inside of the hood. I had to drill a hole in the underneath side of the jointer bed.

The hood is fastened in place with clear access to the side of the jointer. This hood provides a second safety feature in that the cutter head is now inaccessible to little hands that are now starting to tour grandpa’s workshop.