Compound Sliding Miter Saw Dust Collection - #2 Completion & Testing

After the front piece is cut the long back brace piece is next.  It’s cut to height and longer than needed since I don’t know yet where the right end of the collector will end up.  The vertical attachment point is also made although for now it’s just roughly clamped in place.  The final location shown here gets set once the collector is completed.

Next the two sides of the collector’s dust chute on the far right are cut out of ¼” plywood and screwed in place.  These are a couple of pieces that got cut more than once before I got everything square, aligned correctly and tight.  Once they get fitted the left end piece is made from ¾” plywood and screwed in place.

Here the top photo shows the back spacer with a hole in it where the vacuum hose will get connected.  The spacer just adds some thickness to make the hose’s friction fit more stable.   It is glued and screwed on the long back brace.  Now, when initially installed the long back brace did not have a hole.  Once the glue cured a hole is drilled through the spacer and the underlying long back piece.  Because I don’t have a bit the same size as the hose the closest smaller bit got used followed by enlarging it with the oscillating drum sander.  Also shown is a filler piece better shown in the bottom photo which it taken with the collector upside down.  The bevel on the left side of it goes up against the rounded rotating part of the saw’s mechanism.

At this point the collector is mostly built except for a couple of small braces that get glued to the left and right sides of the collector’s dust chute (red arrows) plus the top which is screwed but not glued in place.

Next, is a simple manifold built for the two hoses that come off the chop saw.  It also includes a hole in its bottom and a connector for the HEPA vacuum hose.  Speaking of the hoses, the ones that connect the saw to the manifold came from an old hand-held vacuum that we hadn’t used in years.

These two photos show how the vacuum is attached to the PVC connector that comes out the bottom of the above manifold.  In the center of the right photo there is an electrical cord plugged into the vacuum.  That’s the power cord for the chop saw.  When the chop saw is started the vacuums senses that then turns itself on.  When the saw is stopped the vacuum runs for another 15 seconds to clear the hoses of dust then shuts off.

Next is to make a connecter to go between the top dust port and the hose.  This is done using a short section of PVC pipe turned down using the lathe so it fits inside the dust port on the saw.  The setup for turning the piece on the lathe is shown in the top photo.  The bottom photo shows it (red arrow) in place along with a 45-degree PVC fitting and the hose all connected.  On the back side of the saw there is a screw that holds the PVC connector in place.

Last before final testing is to locate and attach the vertical attachment point then add a bolt and wing nut that will hold everything in place yet allow the dust collector to be easily removed when rotating or tilting the saw.

With that done everything is all together and ready for final testing.  The first thing to do is to make the blade relief cut through the top of the collector by bringing the fully retracted saw down to make a full depth cut.  The red arrow points to the completed cut in the collector. 

Next is to start making test cuts to see if and how everything works.  The good news is that most of the dust gets captured and sucked into the vacuum under the saw.  I say most because there were some places where the collector did not fit tight enough against the rotating part of the saw and some sawdust was escaping out some pretty small gaps.  Once identified those spaces get blocked with some foam weatherstripping I had on hand.  The top photos below show views of the left and right sides of the collector while the bottom one shows the underneath side of the collector. 

Once in place they blocked off the escaping sawdust and the whole collector/vacuum assembly works really well.  Depending on the cut the dust collection is not 100% but I think better than 95% of it gets captured and am happy with that.  The photo below shows the finished collector system done and in place with the left-hand adjustable fence removed for clarity.  I will say that having the vacuum come on with the saw then run after for a bit is really nice since I don’t have to remember to turn the vacuum on before making a cut.

Compound Sliding Miter Saw Dust Collection - #1 The Start

The approach and my presentation on this project is going to be really different than previous projects.  No detailed plans or 3D drawing, not even a paper napkin sketch.  Also, I am going to start with the finished item and work backward showing which pieces got made in which order.  I had thought about following the making of each piece through the process but decided not to as there was more than a little bit of trial and error.  Parts got added, revised and during assembly problems showed up that needed addressing which at times required going back a step or two.  The actual woodworking process are fairly simple limited to a jigsaw, Dremel tool and drill plus a few straight cuts on the table and chop saw.  There is one exception which is a connector that got made on the lathe that I will touch on when it comes up.

Woodworking generates a lot of dust and chips which if inhaled can cause respiratory problems.  To minimize airborne dust in the shop all of my stationary power equipment has some sort of dust collection but even so I wear a dusk mask.  There is however one glaring exception when it comes to dust collection, my chop or miter saw.  This type of saw (photo below) is notoriously difficult to get good dust collection on.   My saw came with a small bag connected to the back near the top of the saw that on a good day managed to capture just a little sawdust.  In use it is mostly worthless.  When I first mounted the saw in the workbench, I built a hood around the saw that contained maybe a quarter of the chips but was ineffective in capturing the rest, particularly the finer dust that hangs in the air.  So, while I was making things for the shop, I decided to tackle this problem.

The obvious place to start is to find out where the dust went when making a cut.  After observing a bunch of cuts looking at just that, I found that a lot of the dust gets ejected right out the back of the saw off the blade.  I did note that with the bag on the top port not much sawdust got collected in it.  However, with it off there was a fair bit of dust coming out of that port into the hood I had built.  My guess is there is little or no air flow through the bag which restricts the flow of the dust into the bag.

There is also some sawdust that gets ejected off the saw blade in front of and to either side of the fence. I believe that’s caused by the zero-clearance wood fence.  If that gap is opened up then there was much less dust kicked out to either side but doing that precludes the zero-clearance function which I want to keep.

Next, I considered how the saw is actually used.  Way over 90% of the cuts made are with the saw square with the table making a 90-degree vertical cut.  Rarely do I tilt or rotate the saw to make miter cuts.  However, I do want to keep that functionality available although if required dust collection for those cuts could be omitted.  

One feature of this saw is that the two sections of aluminum fence the wood is backed up against when being cut can have a wood extension screwed to each side it which I did.  This gives me a longer reference surface when making cuts.  Also, since the aluminum fence can be adjusted left and right, I can pull the wood part up to the blade giving me the aforementioned zero-clearance cutting ability.  This is beneficial in that the additional support provided to the piece being cut reduces the saw blade chipout as it exits the back side of the cut.  In addition, it means that as the edge of the wood fence gets worn and the gap widens during use it’s easy to adjust the fence to bring the edge of the wood so it is tight to the blade.  The drawback is the dust collector cannot be attached to the aluminum fence since the fence will need to be adjusted.

With all that in mind I decided to use the existing top mounted dust port and build a box to capture dust as it comes off the back of the saw blade behind the wood zero clearance fence.  This collection box would not be attached to the saw itself but mounted to the workbench allowing the wood fence free adjustment.  Hoses will run from both these points to a common manifold connected to a HEPA shop vacuum sitting under the saw.  Through a fair amount of trial and error here is a photo of the completed collector box and hoses with the saw and everything else grayed out.  The manifold the hoses connect into is hidden by the collector box mounting arm in the lower left part of the photo. 

Removing the left adjustable zero-clearance fence gives a better look on how the collection box is put together.  The box is made out of ¼” and ¾” thick plywood plus some ½” and 1 ¼” thick solid wood.  Nearly all of it is screwed together without glue so I can take it apart and modify the pieces as needed.

The first piece made is probably the most complex and hardest.  It’s shown as non-greyed out in this photo.  To work right is needs to fit snugly over the dished-out center part of the saw’s pivot area and behind the saw fence’s support bracket.  It also has to fit under the saw motor and blade guard when the saw comes down to make the cut.  Adding to the complexity the part’s profile is not square to the piece but needs to follow the off-center arc of the dished-out center part of the saw’s pivot area it sits on.

First is to make a simple heavy paper profile to fit the dished-out center part.  This profile is in the photo’s upper left corner.  It is roughly laid out using the blue finger profile template just below the finished paper profile.  With the paper profile fitted to the saw the shape gets transferred to the blank in the lower right clamped in the bench vise.  Note here it is upside down and reversed left to right.  The center board is a full-size drawing of the curved part of the saw pivot and the horizontal line (top red arrow) represents the face of the part.  This line along with the arcs it intersects allows me to layout the different angles (bottom two arrows) the notch needs to be cut at so the piece follows the curve.

After layout the piece gets rough cut out with the jig saw then the angled transitions get shaped with rasps, files and a Dremel tool until it fits in place.  Here is what the piece looks like upside down so you can see the angled cuts.

Next Up – Completion & Testing