Mitre saw: extreme make-over part 2

Author: Chester Van Ness
Published: August September 2004
mitre saw
mitre saw

This article looks at collecting the dust that is ejected below your work piece, as the blade cuts through your material and travels below the table.

In our last article we worked on channeling the sawdust (created above your work piece) into a modified port, situated on the saws arm.

First off, notice the gap between the bottom of the saw frame and the work bench. That gap hinders dust collection, so it is one of the areas we will need to work on to make our dust collection more efficient.

 

Opening beneath throat plate hinders air/dust flow

Under-side of saw frame

Gap between saw frame and work bench

Cardboard template for cover plates

Area surrounding dust port to be sealed

Base with skirt attached and in place

Bottom of saw table closed in, seal brushes in place

Saw in place over new opening. Hole in pivot point casting cover

Now remove the throat plate (kerf plate). Notice the opening in the casting, just above the pivot point of the saw table. This opening is another hindrance to effectively collecting the dust being expelled below your workpiece.

Once the throat plate has been removed, you will also notice that the under-side of the table is partitioned by support ribs, but is mostly open. This is the third area that we will have to address in our make-over. By closing some of this area in, we will be able to streamline the air and dust flow more effectively.

To really achieve efficient dust collection, we will need to address all three of these problem areas.

So roll up your sleeves. This extreme make-over involves taking your saw apart, and putting an end to all that dust that you have come expect from your mitre saw.

While you have the saw apart for this makeover, you may as well clean the under-side, inspect and lubricate the pivot point and inspect and clean the table wear plates. So in a sense, this is not only a make-over but a tune up.

Notice the relationship between the saw throat plate opening (as you rotate the table) and the main ribs in the lower half of the table. Add a couple of brush seals at the throat plate to make dust collection more efficient.

Make a template for the cover plates using light cardboard. Once you’ve got a fit that encloses the bottom of the saw table, you will be able to replace the cardboard with metal cover plates.

It is very important that the covers do not interfere with the rotation of the saw table. Use the same bolts that hold the saw table wear plates in place to fasten the cover plates.

Size, fit, and fasten the seal brushes in place and then remove. Install the cover plates and reinstall the brushes. Next, cover the opening in the pivot point casting with a small piece of rubber.

It is a good idea to put the saw back together after each adjustment, to make sure that it still rotates freely. Now let’s look at the saw’s base frame and it’s relation to the workbench.

By closing in the area of the base frame that surrounds the workbench dust port, air and dust flow will be better channeled to the port.

To close in that area, I added a rubber skirt around the inside edge of the opening formed by the cast support struts and the inside edge of the pivot support.

Next, measure the gap between the bottom of the saw frame and the bench top. Then cut an old inner tube (or similar) and make a rubber skirt to adhere to the frame and rest tightly against the bench top. Contact cement works well to fasten the skirt in place.

You will notice that the dust port in my bench top is only 3″ in diameter and positioned under the pivot point. To improve that situation I remade the dust port opening in the bench top. I also had to change the shape of it to ensure that it was totally under the skirted-in area of the saw base.

In addition, I enlarged the hole to a triangular shape and inserted a 4″-3″ HVAC piping reducer into the opening, fastening it in place with 3 #6 screws.

Now the opening is more effective and is totally inside the skirted-in area. Reassemble the saw, test it for freedom of movement, and fasten it in place on the bench.

The saw now has 2 three-inch dust ports and will be hooked up to your dust system using a 3-3-5 tapered “Y”, in conjunction with one 5″ blast gate.

For those of you doing the math, a 3″ diameter pipe has a 7.07 square inch area, a 4″ diameter pipe has a 12.57 square inch area. I could use a 3-3-4 “Y”, but to get the best flow I chose the 5″ diameter, with a 19.63 square inch area.

Keep in mind that there is still going to be a slight restriction created by the blast-gate.


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