Mitre saw: extreme make-over part 1
Because of the difficulties with collecting dust from such saws, I narrowed the focus of this article to include only the simple compound miter saw. I also spread the article over two consecutive issues, so that you have enough details to improve the dust collection from your mitre saw.
Contoured hood guides dust in but flow is restricted with reduced diameter
Exhaust pipe adapters more great dust ports
Arm pivot point is area to be modified
New port fastened in place
New panel, held by guide fastening bolts guides sawdust to port
Inner tube forms side flap on both sides of arm
Flaps contain airflow and sawdust
In this first installment, I will help you to improve the existing dust collection on your saw. In the next issue I will cover additional improvements that you can make to better collect dust from your mitre saw.
Most older model mitre saws came equipped with a single dust port fitted with a bag. The location of the port and bag on the mitre saw was probably based on the location of ports on radial arm saws.
Unfortunately, such placement of dust collection ports on mitre saws provides less than adequate dust collection. That inadequacy is compounded by a rather small dust collection bag. If you choose not to use the small collection bag, most ports are able to attach to vacuum cleaners. If you use a vacuum cleaner, always be sure that it is equipped with a fine, pleated filter and that you wear hearing protection.
The original dust port has a contoured shaped hood to guide the dust into it. That is how it should be. Closer examination however, reveals a restriction inside the diameter of the port itself. That is not how it should be. Although the restricted diameter allows for the attachment of a deflector hood, such a hood is not worth the lost efficiency that results from restricting air flow. To rectify this problem I enlarged the port opening and added a new port. That helped, but I noticed that all of the dust wasn’t getting to the port opening. To solve that situation I added flexible sides to the saw arm.
Unplug Your Saw
Remove the saw blade to get a better view of how the dust port is held in place. Because you are going to enlarge the port opening, be sure to check that the casting is robust enough to do so. I could enlarge my opening, but the opening had to be oval. Also, look for sturdy attachment points for the new port. The attachment has to withstand the movements of your saw while attached to 3″ flex hose.
I like to use inexpensive, easy to get, materials when I work in my shop, so when I needed to fabricate this dust port I headed down to the local auto parts store. There, I picked up two exhaust pipe adapters: one 2 1/4″OD-2 1/2″ID; the other 2 1/2″ ID-3″OD.
To make sure that the new port position didn’t interfere with the operation of the blade guard-operating arm, I made the shape of the fitting slightly oval.
Position the fitting on the arm. Then trace inside the fitting to mark out the new size for the hole.
After shortening the fittings, I used a wire feed welder to tack them together and secure them to the port with hold down tabs.
I then drilled the tabs and marked their location on the cast arm. Next, I drilled and tapped the arm so that I could use a couple of 10/24 bolts to hold the new port in place.
Inside Top Cast Arm
To streamline the airflow I removed the steel guide from the leading edge of the blade and fashioned a steel panel to cover the web openings behind the guide. The new steel panel is held in place by the guide fastening bolts and acts as a guide for the sawdust.
Sides Of Arm
The sides of the arm is where the sawdust starts its trip to the dust port. To maximize the air flow in this area I needed to close it in to better contain the airflow.
To close that area in, I needed a flexible material from which to form side flaps. I figured that I could do what was needed with an old inner tube so I headed out to my local garage. Before cutting the rubber, I used construction paper to make a pattern for each side. Using the paper pattern allowed me to move the saw through it’s various positions as I confirmed unobstructed clearance.
I then transferred the patterns to the inner tube, cut them out and pasted them to the saw arm.
With these adaptations, your mitre saw will have a larger more efficient dust port connected to a 3″ hose. (From past articles you know that 3″ is the minimum diameter of hose that you can use to collect dust effectively.) This make-over also provides better deflectors to efficiently guide the dust into the dust ports.
When using my particular saw, the saw blade travels through the table and becomes exposed below the table (i.e. it is not ‘captive’, as some models are).
Even after completing this make-over, the rear dust port is only effective while the blade is still above the tabletop. Once the saw blade travels through the material being cut and goes below the tabletop, the sawdust is blown around under the table. To collect dust effectively from this saw I will have to explore the underside of the saw to determine how best to contain and capture that dust.
The second part of this article will take this make-over to the next level and address fugitive dust below the table.
The next time that you purchase or upgrade a mitre saw, be sure that you consider it’s dust collection. Such a consideration should rank right up at the top along with accuracy, capacity, and special features, such as a laser guide.