Improving dust collection from Kapex SCMS - Need help with overkill method

[Alan Lightstone]

This is one of my big pet peeves. Dust collection from my Kapex miter saw is terrible. And, supposedly, it's much better than competing models.

So, in my typical overkill fashion, I've been working on a solution.

I bought and installed a Rockler 1250CFM dust collector, and with tons of help installed it on the wall. It's got 6" flexible duct attached to it.

My present setup is with a Festool Mini shop vac with 36mm hose attached. Lots of wood dust scatters on the floor in front of the saw, as well as tons behind and around the saw.

I'm going to build some type of enclosure around the Kapex, and hook that up to the dust collector. Lots of videos on this on Youtube. Some good, some awful. None are taking this approach, because they're sane.

Which would be the preferred approach?

1.) Splitting the 6" dust collector hose into two 4" hoses, one for the Kapex shoot, and one for the box around it.
2.) Continuing to use the Festool vac for the dust shoot and using the 6" hose to connect to a box around the Kapex, so using both.
3.) Any other thoughts?

I know the shop vac will provide more static pressure and the dust collector far more CFM.

[Jim Becker]

My opinion is that you should still be using collection from the vac to the tool's dust port.

Check out Jay Bates' miter station on the 'Tube for a good method for a surround for the tool so you can utilize the DC for catching the 'splash' which is the nature of any miter saw.

[Aaron Inami]

Not sure if a Rockler 1250CFM is enough, but I have a friend who built a down-draft table which the Kapex sits upon. Combined with the normal Kapex dust collection, it works extremely well.

[Rob Sack]

I've mentioned this before on the Forum. I too have a Kapex and felt that having to invest in a Festool "Extractor" with the appropriate Festool hose, setting me back somewhere between $800 and $900+, was out of the question. After doing some research, I found a Ridgid Shop Vac, Model No. WD7000, from (Ugh!) Home Depot along with a proper 35 mm Bosch hose from Amazon and an automatic vacuum switch also from Amazon. I was able to demo the Festool Kapex with the recommended $800+ Extractor set up at AWFS. In all fairness, the combination was rather effective. As near as I can tell, my set up works just about as well for less then half the cost. Dust collection seems to be on par and my vacuum goes on automatically when I turn on the saw. As a bonus, my shop vac can be used as an actual wet/dry vacuum if I choose, unlike the Festool Extractors and comes with a limited life time warranty, also unlike the Festool Dust Extractors.

[Aaron Inami]

In response to Rob's comments, I can definitely see how the Rigid shop vac is giving better performance compared to a Festool dust extractor when using it for the Kapex stock dust ports. The Rigid shopvac will have significantly higher CFM, somewhere in the 180-200 CFM range depending on who you talk to. This is because the intake filter on the Rigid has significantly more surface area than the Festool dust extractor and there is no bag/filter on the Rigid (though this makes it more of a hassle to clean out the debris/sawdust from the Rigid).

The Festool excels on other devices because you can adjust the suction using a dial and the Festool design will produce consistent suction/CFM even when the filter/bag fills up. The CFM on the Festool is tested to range between 130 and 159 CFM (wide open). Once you start using the 36mm hose, it will actually drop down. Using larger diameter hoses will reduce the amount of hose restriction on the CFM.

You could try getting a 50mm hose on the Festool (with reducer) and trying that with the stock dust port on the Kapex:

https://www.festoolusa.com/accessory/452888---d-50x2,5m-as

https://www.festoolusa.com/accessory/452897---d-50d-36-as#Overview

Or get a shopvac if you don't want to build a dust collection cabinet/downdraft for the Kapex.

The Rockler 1250CFM dust collector will do almost nothing if you reduce it down to a 1-1/2" or a 2" hose connection.

[Ron Selzer]

no 2 sounds like the best option to me, let us know how it turns out
Ron

[Andrew More]

#2 - This is pretty much how I have mine setup, after years of looking into the issue. Essentially the problem is you've got a blade moving at 100+ MPH, you _might_ be able to get the DC/shop vac to run at 40 at the edge of the outlet. I know of no way to get that close to the blade. The ports on most miter saws get closer than you can with an outlet from the DC, but you can't really get good suction from a DC through one, because of the small port, so a shop vac is necessary.

So the dust is going to get flung in whatever direction it's going to go.

The good news is just like flinging a hand full of snow, it's not going to go far, but it's going to be enough to make a mess around the saw, and there is no solution to this. The other good news is that the blade flings things back from the saw, which is why the box is a good idea. Also running the DC into the box seems to capture most of the fine particles, which are the main safety hazard. You might also be able to improve the performance from the shop vac port with a better scoop, I've got the Shop Nation one attached to my Bosch (https://shopnationstore.com/collections/miter-saw-dust-collection).

One other minor point, I think a dust extractor is total overkill for this problem, unless you've already got one. Personally I like the Dewalt stealth sonic shop vacs (https://www.lowes.com/pd/DEWALT-12Gal-5-5-PHP-Quiet-Vac/5013026391), because they're super quiet, but really any cheap shop vac will do. If you must have the auto-on, you can get an adapter for that for like $30, and save some money.

[Aaron Inami]

I had been recommending the Dewalt stealthsonic to people because of noise. Looking further, I think I need to retract my recommendations.

Be aware that the quietness of the Dewalt stealthsonic comes at a price on CFM. Actual CFM on these stealthsonics are in the 90-105 CFM range depending on model. This is actually less than any Festool extractor!!

The Fein and Bosch vacuums do much better at 150 CFM ratings. There are some Rigid "shopvac" style vacuums that indicate 170-180 CFM, but these are likely to be the extremely loud and annoying models.

[Kevin Jenness]

I have a shroud around the miter saw made of 3/4" ply decks and a bending ply back with a 5" DC drop in the bottom deck which works well. It wouldn't hurt to have a separate shop vac on the tool but it seems redundant. It would help a bit on wide cuts where the exhaust is in front of the shroud. I use the stock filter bag which helps in that scenario.

[Rob Sack]

There are some Rigid "shopvac" style vacuums that indicate 170-180 CFM, but these are likely to be the extremely loud and annoying models.

The Ridgid shop vac I am using is rated at close to 200CFM and as far as noise is concerned, is significantly quieter than either of my Craftsman shop vacs. However, the Ridgid is louder than the Festools I tested and would have to be louder than the new, quieter Dewalts.

[Michael Burnside]

Alan, sane or insane, doesn't matter, it's your shop and your money. You might find the 1250 works great for something that surrounds the Kapex, but you'll probably end up still needing the Festool vac attached to the dust port of the saw. I don't think the 1250 can give you the CFM you need at the tool.

Having said that, if you want truly overkill, I occasionally attach my Oneida Supercell to the Kapex port and have a couple wings funneling towards the back and I get little to no dust. The Oneida is probably close to 4-5x what the 1250 can do on a 2.5" hose (I have both, I know) and they are not even comparable. The Oneida is a monster, but it's overkill at 2700 bucks :D

Unless I'm cutting a lot of material, which I rarely do on my Kapex (I prefer the Carvex), I'll just hook up my Festool CT-26 with a 36mm hose (1.5 meters long) and it works pretty well with my setup. I'll try to send a picture of the setup sometime.

[Alan Lightstone]

I actually have a 5HP Oneida, but due to my design mistakes with cabinets, and having to rout the metal ducting upwards to the Kapex in an area where it would be very difficult, I took this route. Wouldn't have been a cheap solution for the Nordfab for that either. I have no doubt that the Oneida cyclone could do the job (at least on the outside shroud, perhaps not on the inside dust shoot of the Kapex).

I'm working on a wood shroud to cover the Kapex, but still allow for 45° cuts by allowing removable pieces (similar to approaches Jay Bates, Fisher's Shop, DIY Montreal and others have posted on YouTube videos. I'm thinking of holding the front pieces on with rare-earth magnets, as I think that would be the easiest to remove for the 45° cuts. The first job I am working on is filling up the gap below the back of the Kapex, as dust always fills up back there, as well as to the sides of it.

I'm really thinking this won't do enough to prevent the dust that sprays out in front of the saw on the floor. We'll see.

[Jim Becker]

Having a dedicated collector for the miter station isn't unusual and it can be effective if you build in the necessary "controls" to contain the stuff spewing off the blade so it can be collected.

[Chris Parks]

For a start that 1250CFM is not 1250 as every manufacturer embellishes their flow numbers but a very few do not state them because measuring flow is like rounding up a herd of cats.

A saw, any saw generates both fine and heavy dust and mitre saws are one tool that have to be in a housing and a very high flow extractor used to capture the fine dust. The standard port captures the heavier dust to some extent but the fine dust that results from cutting does not get captured very effectively and ends up floating around the operator which is not good. My mitre saw is in a housing that comes back to the fence and the extraction is done by a CV1800 running at 75hz and it still does not capture all the fine dust just most of it.

Alan, I know you are very aware of dust issues but mitre saws are a very difficult tool to effectively capture all the dust. There are a large number of videos on YT but most of them do not use a big enough DE and very few of them use 6" ducting which is the absolute minimum and given a capable extractor a larger diameter would be better.

[Allan Dozier]

509056509057509058509059I am looking for suggestions too. Here is what I have so far but I was planning on building some sort of hood to try to catch more. I have a 5 hp Clearvue and my miter saw is directly on the end of the 7" run. As you can see the smaller hose Ys off and attaches to the Kapex. So I get a good bit of flow but still get sawdust scattered on the base and the floor. The other thing I think may help is that I usually pull the saw like a radial arm saw unless I am cutting small width boards. I think this tends to direct more sawdust back to the rear where the round duct opening is behind the saw. I know this is not how it is recommended but I've done it for years. The flex duct goes to a floor sweep which I don't use that often and stays closed.

[Chris Parks]

It is the fine dust spray that is the issue with a mitre saw. On a table saw that can be controlled well with an overhead hood but obviously that is not possible with a mitre saw. Th3e heavy stuff can be swept up so is not a problem except walking it around on shoes but I have an answer for that, I don't wear shoes at any time. :)

[Alan Lightstone]

For a start that 1250CFM is not 1250 as every manufacturer embellishes their flow numbers but a very few do not state them because measuring flow is like rounding up a herd of cats.

A saw, any saw generates both fine and heavy dust and mitre saws are one tool that have to be in a housing and a very high flow extractor used to capture the fine dust. The standard port captures the heavier dust to some extent but the fine dust that results from cutting does not get captured very effectively and ends up floating around the operator which is not good. My mitre saw is in a housing that comes back to the fence and the extraction is done by a CV1800 running at 75hz and it still does not capture all the fine dust just most of it.

Alan, I know you are very aware of dust issues but mitre saws are a very difficult tool to effectively capture all the dust. There are a large number of videos on YT but most of them do not use a big enough DE and very few of them use 6" ducting which is the absolute minimum and given a capable extractor a larger diameter would be better.
Thanks, Chris. Informative as always. Yes, I know, 1250CFM is overstated. But running a 6" hose to the shroud I'm building is better than 4" or 2.5". I'll get somewhat more flow that way.

I have agreed with the sentiment above and will be using both the Festool vac and the Rockler DC with a 6" hose to the shroud. I know this will not get all the small dust, but I'm hoping it will make a substantial dent in it.

FWIW, I now have a Grit Automation Dust Collector module hooked up to the Festool, and both my Jet 1000B and Jet 2000 turn on for several minutes when I use the Kapex. But they are in the middle of the shop, and the Kapex is at the end, so it must take them time to clear the small airborne dust. I have another Grit Automation module to hook up to the Rockler DC. Not sure how I'll get both to turn on. Time to run that by Joel at Grit Automation. I'm sure that's a way.

So, when completed, I'll have the Rocker DC and the Festool Vac, as well as two overhead air cleaners turn on when I use the Kapex. Certainly overkill, but also, sadly, I'm sure not totally effective. Let's see how the shroud does. I think that will help a lot. I'll post pictures when completed.

[Chris Parks]

Thanks, Chris. Informative as always. Yes, I know, 1250CFM is overstated. But running a 6" hose to the shroud I'm building is better than 4" or 2.5". I'll get somewhat more flow that way.

I have agreed with the sentiment above and will be using both the Festool vac and the Rockler DC with a 6" hose to the shroud. I know this will not get all the small dust, but I'm hoping it will make a substantial dent in it.

FWIW, I now have a Grit Automation Dust Collector module hooked up to the Festool, and both my Jet 1000B and Jet 2000 turn on for several minutes when I use the Kapex. But they are in the middle of the shop, and the Kapex is at the end, so it must take them time to clear the small airborne dust. I have another Grit Automation module to hook up to the Rockler DC. Not sure how I'll get both to turn on. Time to run that by Joel at Grit Automation. I'm sure that's a way.

So, when completed, I'll have the Rocker DC and the Festool Vac, as well as two overhead air cleaners turn on when I use the Kapex. Certainly overkill, but also, sadly, I'm sure not totally effective. Let's see how the shroud does. I think that will help a lot. I'll post pictures when completed.

Alan, our system with the DE controlled from a VFD has a timed delay which can be changed as needed and I would be very surprised if the GRIT system does not. After using the saw the delay could be used to clear most of the dust and then shut down and it would be nice if a dust monitor could be incorporated into the system to control the delay. We use a VFD for all installations due the control it gives us and some Men's Sheds leave at least on BG open and the VFD drops the DE speed and it "scrubs" the air between uses and automatically ramps up when a machine is used. In an old system the DE runs at full speed the whole time the shed is in use but that was done many years ago before we had better technology.

[Jack Frederick]

I’ve not run a Kapex and don’t use my Hitachi C8FB that much, primarily due to space issues. In looking at the tube and this thread would it be of benefit to install an intake below the saw? It would have to be flat with an inlet across the base of the saw facing up so sweeping up. A screen would be necessary to prevent unwanted debris from hitting the DC. Possibly add sliders on each side depending upon how the dust flies on each sides cut. This might catch the low dust coming off the saw table. So the DC connection below the table to a triangular, say 3” deep plenum to the sweep on the front. In this, every system has a personality due to the saw, DC/vacs, etc so each is trial and error.

[Alan Lightstone]

I’ve not run a Kapex and don’t use my Hitachi C8FB that much, primarily due to space issues. In looking at the tube and this thread would it be of benefit to install an intake below the saw? It would have to be flat with an inlet across the base of the saw facing up so sweeping up. A screen would be necessary to prevent unwanted debris from hitting the DC. Possibly add sliders on each side depending upon how the dust flies on each sides cut. This might catch the low dust coming off the saw table. So the DC connection below the table to a triangular, say 3” deep plenum to the sweep on the front. In this, every system has a personality due to the saw, DC/vacs, etc so each is trial and error.
I think no question having the DC duct below the saw would be helpful. But cabinet design restraints, and the location of the joints on the raised access floor make this impossible. I very much wanted to do this, and using ducts from my 5HP Oneida cyclone which would work far better than this plan. Ce la vie.

[Rush Paul]

Sorry to hear you can't get your 6" duct from you 5HP Oneida to the Kapex. But, for what this may be worth to some others, in our community workshop, we set up a downdraft table connected to a 6" duct from our ClearVue CVMAX cyclone dust collection system. We used a 4" takeoff from that same duct to connect to the Kapex's vacuum port rather than attaching a shop vac. Overall dust collection has been very good -- no side curtains or shroud. This installation is taken from a design posted by a user in the Festool Online forums.

509063

509064

(Sorry for the rotated view on the first image -- I can't see a way to correct that.)

[Andrew More]

We used a 4" takeoff from that same duct to connect to the Kapex's vacuum port rather than attaching a shop vac. Overall dust collection has been very good -- no side curtains or shroud. This installation is taken from a design posted by a user in the Festool Online forums.



You should take an anemometer to it and determine your CFM. I'm going to guess the restriction is sufficient that most of the suction is going through the 6" opening, bypassing the 4"->Kapex connection. It's better than nothing, and the blade is going to fling a lot of stuff in there, making collection easier, but in terms of raw horse power I think you're going to get better results from a shop vac.

The downdraft table is a really interesting idea, what's the surface area of the holes cut into the table vs the surface area of the 6" duct? Do you have a lot of dust collecting in the front or on the wall behind it?

[Aaron Inami]

The downdraft table is a really interesting idea, what's the surface area of the holes cut into the table vs the surface area of the 6" duct? Do you have a lot of dust collecting in the front or on the wall behind it?

Rather than re-posting the picture, I'm referencing my original post:

https://sawmillcreek.org/showthread.php?303997-Ideas-on-Miter-Saw-Station&p=3261402#post3261402

It looks like he did 1/2" holes.

[Andrew More]

Rather than re-posting the picture, I'm referencing my original post:

https://sawmillcreek.org/showthread.php?303997-Ideas-on-Miter-Saw-Station&p=3261402#post3261402

It looks like he did 1/2" holes.

Looks like about 308 holes (22 x 14 grid) which is about 241 sq in, vs 28 sq ins for a 6" duct, so I'm guessing he's likely seeing some fall off the further away from the opening you get. Not sure if that effects performance or not, but I'd guess it does.

[Chris Parks]

You should take an anemometer to it and determine your CFM. I'm going to guess the restriction is sufficient that most of the suction is going through the 6" opening, bypassing the 4"->Kapex connection. It's better than nothing, and the blade is going to fling a lot of stuff in there, making collection easier, but in terms of raw horse power I think you're going to get better results from a shop vac.

The downdraft table is a really interesting idea, what's the surface area of the holes cut into the table vs the surface area of the 6" duct? Do you have a lot of dust collecting in the front or on the wall behind it?

A couple of things here that require some explanation....

Anemometers can't be used due to turbulence at the duct entry amongst other things.

Most ducted systems have only one port open at a time.

Down draught tables require huge amounts of air because the first thing fine dust wants to do is float away and if most of the table is covered by whatever is being sanded the air flow is blocked by the part being sanded.

A ducted system is restricted by the smallest part of the system no matter how big the ducting is upstream.

To avoid getting ripped off when buying a dust extractor ignore the HP and flow numbers as they mean nothing and ask how big the impeller is, anything under 14" is not worth buying.

[Rush Paul]

Andrew, the holes are 2.5" or larger with a total area of 2.5 times the 6" duct. No material dust accumulation on surfaces in front or behind the saw. Noticeable reduction in collection without the saw mounted hose.

[Chris Parks]

Rush, no material saw dust accumulation does not indicate that the fine dust spray from the blade was adequately suppressed and that is what it is all about. the big visible material can be swept up or collected some other way but the fine unseen dust is the stuff that gets into our lungs and stays there. The dust inhalation problem gets much worse as we get older and Alan the OP might expand on that though he has explained it before in this forum.

[Rush Paul]

Yes, you are absolutely correct, Chris. This is why we constantly cross check against our particle count meter in the shop.

[Alan Lightstone]

Rush, no material saw dust accumulation does not indicate that the fine dust spray from the blade was adequately suppressed and that is what it is all about. the big visible material can be swept up or collected some other way but the fine unseen dust is the stuff that gets into our lungs and stays there. The dust inhalation problem gets much worse as we get older and Alan the OP might expand on that though he has explained it before in this forum.
Yeah, really don't want to make this a medical discussion, but the key piece of information is that the smaller the dust particle is, the farther it can go down your respiratory tree, even to your alveoli, which deliver oxygen you breathe to your red blood cells. Damaging these is far worse than your upper airways (although you really want to have good lungs. I've very fond of keeping mine in good shape.)

I actively monitor the large and small particles in my workshop, and use a good P100 mask/respirator when those levels get above what I would breathe outside (ambient). And I go to pretty great lengths to clean the air in my workshop with several air cleaners and now two dust collectors.

I'm heavily into building the outer shroud. Mostly done. I'll do some tests afterwards to see how it works, and I do hate vacuuming up the wood dust and chips on the floor in front of my Kapex, as well as all those that get in all those nooks and crannies of the Kapex, so I'm really hoping this setup will help.

No question my 5HP Oneida would do a tremendously better job than this setup (and be quieter as it's in a sound controlling closet), but this is my complicated/expensive plan B.

[George Yetka]

This is on my list of things to eventually tackle. My kapex is probably the messiest tool I own. I do want to put a box around it and add the 4" port to it. I cleaned my TS last night and wanted to see how well it did with DC. I vacuumed 80% of what was in there out, turned on the DC and sprayed compressed air in. Almost nothing came out of it. I dont think we can expect this from the kapex with any kind of enclosure but there is still room to improve. Stock the kapex does OK but add zero clearance inserts and fence and it deteriorates quickly.

Ive read that using it as a SCMS DC is better than using it as a chop saw. The dust is fired up to the collector in doing this vs back
Also read that if your seeing excessive dust check the collection points and hose to extractor , wet wood/slivers may have clogged you up a bit.

[Chris Parks]

George, the Kapex is no different to any other SCMS, chop saw, mitre saw, call it what you will and they all require a lot of work to minimise the fine dust problem. 4" ducting unfortunately will not flow enough air and any impeller under 15" is in the same boat in fact I overdrive my Clearvue CV1800/15" with a VFD but that is somewhat defeated by only being able to source 6" PVC in Oz where 7" would be far better and the air flow would increase by a lot. It is simply not practical to capture all the fine dust at source and all we can do is maximise fine dust capture on a SCMS.

[Alan Lightstone]

So, been real busy building this. I think I'm done, although I'm already thinking of a modification.

Here are some pictures of the shroud:
509283509284509286

509287

I'm seriously thinking of making two removable magnetically attached covers for the front openings for the two holddowns, so that if I'm not using them (which I usually do) I can close off that opening to help with suction.

Joel at Grit Automation was great in helping me connect a trigger module to the Kapex, and two collector modules - one for the Festool vac, and one for the DustRIGHT dust collector. The reason for this, I think, is pretty cool, and should help with dust collection. I have it programmed so that the Festool vac turns off 30 seconds after the Kapex completes its cut, and the DustRIGHT collector turns off 1 minute after the cut is completed. These delays, I think, should significantly improve dust collection. Yes, I could have plugged the Kapex directly into the Festool vac as I have for years, but it always struck me as a mistake that the vacuum turns off immediately after the Kapex stops cutting. That prevents removal of a bunch of wood dust from the shoot and around. My Grit Automation system, hopefully, will improve that by adding the delays.

Haven't had a chance to test it yet. And I'm not going to weigh sawdust like one of the Youtube videos, but I'll get a subjective test.

[Jim Becker]

That's a good implementation that will really help a lot with capturing the fines while using the miter saw and it still gives you the ability to do those non 90º cuts when necessary. I'll go as far as saying that if you have another angle that you "frequently use", it wouldn't be a "yuge" effort to make a couple of alternative pieces that match that saw position, too.

[Alan Lightstone]

45° comes to mind, but that might be in both directions, and it really wasn't terribly fun to make those front pieces. I did space the left and right walls so that the Kapex has room for those cuts. I'll likely just cut without one of the front pieces if I choose to do that. But, who knows...

[Chris Parks]

It would be neat if GRIT could tie in a dust monitor that turned on the extractor and opened at least one BG when the fine dust levels rise over a set level. A major problem we found when training users is that someone can walk up to a mitre saw, do a cut and walk away before the DE has reached anywhere near full speed, in fact I sometimes do it myself when not thinking about what I am doing. GRIT are the first company to put some real R&D into the dust issue but I shudder to think what it has cost and hopefully they have some real success in the market place.

Some photos of my mitre saw hood.

509321509322509323509324509325

This works opposite to every other shroud by pulling air into the bottom of the plenum and then drawing the dust and air up through the curved plenum into the 6" duct which if I had my way would be 7" but that size does not exist in Oz. Since these were taken I have removed the manual blast gate at the top and added one of our automatic blast gates instead. Like all other shrouds it does not collect all the fines even though I can faintly detect the air flow on my body and the difference between having the DE at full speed or not can be seen by how the visible dust behaves along with the smell of the dust which is floating in the air.

[Alan Lightstone]

That's a really interesting design, Chris. As I said in a previous post, I couldn't run ducting from the bottom (sigh) but I do see its advantages in causing the dust particles to move that way. I didn't mention it, but I did heighten the floor behind the miter saw so that the duct is closer to the floor. The movement of the saw limited that further, though you had an interesting solution to that.

Actually, with the time delays, my Grit Automation system will keep the dust collector and vacuum running after the miter saw is turned off, so solving the issue you mentioned. Just having the Festool vac hooked up to the miter saw would have it turn off instantly, which I agree is certainly suboptimal.

My Grit Automation system has two air quality modules that turn on my two Jet air cleaners if the particle count exceeds the level I set, so it does accomplish what you said.

[Scott Winners]

May I please ask a stupid question?

I live in Fairbanks, Alaska. My shop is a single car garage @ nominal 12x24 feet. I too found a miter saw to be the gateway drug better woodworking in the mid 1980s. A miter saw is an impressive tool, and they have come a long way since 1986. But in my mind this is a construction tool to use on jobsites, an outdoor tool, like a frisbee or a soccer ball or any of the hockey stuff.

I have a $300 folding cart/dolly doohickey under my miter saw. If I really need it that bad I am happy to shovel off my driveway and drag my mitersaw outdoors at -20, -30 Fahrenheit for whatever rough cuts I want to do that bad. I got sharp handsaws in my shop, I've got good filtration in my shop, I have good particle counts on my instruments while using my hand saws. Don't tell me a miter saw is a joinery tool, I got better sense than that.

I know some of you guys (statistically) are under HOA oppression, but there is a bunch of power tool users from the heavy hitting group in this thread.

The stupid question I have is why are y'all working so hard to use an outdoor tool, like cleated sneakers or a football helmet, inside your shop space? Dad wants to know. You are not my kids and you don't have to answer me. But if you were my kids you are already looking at one raised eyebrow and I got an itchy trigger finger over my belt buckle trying to understand why you think it is a good idea to make this big of a mess inside the house when I already spent good money on your outdoor clothing that is suitable for the weather we have.

Thanks.

[Jim Becker]

Scott, everyone works differently. I rarely use my miter saw and it's been that way for years. So it's on a compact portable stand and, at least when it's "nice" outside, I can open the "big door" and park the saw so it spews forth outside. But if I was going to invest in a highly accurate miter saw with intent to use it frequently, I'd likely opt for a workstation not unlike what's being discussed here because I do try to pay attention to dust control and the only tool harder to do that with than the miter saw is a lathe. :)

[Alan Lightstone]

So ran my first test today. No question that the setup reduces dust. Not totally, as I still see some small woodchips/dust in the openings in the front of the Kapex, an area I knew would be an issue. So far, not sure anything has reached the floor, which always was an issue in the past.

Here's an after picture:
509372

I can feel suction coming through the holes for the clamps, and this is probably wasted suction, so I think I will make magnetic inserts to close those holes when not used, though they will be a little inconvenient.

Also, I'm wondering if I should enlarge the gap on the sides of the dust shoot. I think some sawdust is shooting off on an angle towards the back and maybe not being captured there. Any thoughts as to the wisdom of this? Here's a picture of the front with the small gap to the sides of the native dust chute:
509373

[Chris Parks]

It might be that the shrouding has reduced the air flow, this sort of stuff is always suck and see.

[Jim Becker]

I can feel suction coming through the holes for the clamps, and this is probably wasted suction, so I think I will make magnetic inserts to close those holes when not used, though they will be a little inconvenient.

Alan, the dust collector works by moving a large quantity of air at high velocity but low static pressure. That in turn moves the dust. It's not "suction" like a vac extractor which moves a small amount of air, but with very high static pressure. If there is no airflow into the enclosure, dust collection will be reduced. So you have to balance things so you have air coming into the box that at least gets close to the geometric size of the dust collection port to get maximum performance. You can, however, control "where" that air comes in from and use that to benefit and influence the direction that the dust is moved...towards the DC port.

Folks used to try and seal up their cabinet saws to get "better dust collection" and in turn got worse performance. That got fixed by finding ways to increase air flow, both at the collection side by larger ports and by making sure that the cabinet wasn't closed off too much such that it inhibited air coming in to allow for the volume necessary to carry the dust. The same thing applies here.

[Alan Lightstone]

Alan, the dust collector works by moving a large quantity of air at high velocity but low static pressure. That in turn moves the dust. It's not "suction" like a vac extractor which moves a small amount of air, but with very high static pressure. If there is no airflow into the enclosure, dust collection will be reduced. So you have to balance things so you have air coming into the box that at least gets close to the geometric size of the dust collection port to get maximum performance. You can, however, control "where" that air comes in from and use that to benefit and influence the direction that the dust is moved...towards the DC port.

Folks used to try and seal up their cabinet saws to get "better dust collection" and in turn got worse performance. That got fixed by finding ways to increase air flow, both at the collection side by larger ports and by making sure that the cabinet wasn't closed off too much such that it inhibited air coming in to allow for the volume necessary to carry the dust. The same thing applies here.
Good points, Jim. I was really thinking that the air flow into the shroud then dust collector should be closer to where the cut is being made, which those cutouts for the clamps really don't fit that paradigm. Especially the one on the right which is closer to the dust collector hose inlet.

I'm making two pieces of wood to cover those now. Of course I screwed up the first one, so repairs being made now. Once those are done, I really probably have to increase the open area of the shroud near the blade so that it is roughly equal to the area of the 6" dust collector duct (28 sq in). Have to do some rough measurements to see what that is.

[Jim Becker]

Absolutely target the air low "into" the hood as best as you can. It will truly make things as optimal as it can be. There's no perfect solution 'cause the tool throws stuff a whole bunch, but keeping the air flow as high as possible will help capture more of the fines which are the truly dangerous particles.

[Chris Parks]

Alan, you could use a blast gate as an air inlet to control & adjust the inlet flow.

[Alan Lightstone]

Alan, you could use a blast gate as an air inlet to control & adjust the inlet flow.
Shouldn't I want the inlet flow from the dust collector, and by extension the front of the shroud to be as much as the dust collector can produce?

I finished the two pieces of wood with magnets to place on the front holes when not using the clamps. Just waiting for the paint to dry.

Unfortunately I can't remove those front bottom pieces. Didn't think of this and inside is a reinforcing piece that glues to them. So probably going to hand saw two diagonal cuts in front to increase the open area around the Kapex shroud.

[Jim Becker]

Calculate the approximate open area around the saw and compare that to the area of the DC port inside the box. If it's less, you'll want more air from somewhere. If it's more...fagetaboutit. :)

[Chris Parks]

Shouldn't I want the inlet flow from the dust collector, and by extension the front of the shroud to be as much as the dust collector can produce?

Alan, in all honesty your guess is as good as mine. I think the ideal might be to maximise the air flow where the blade is cutting the timber but the chances of doing that are most probably zero because these saws have so many inbuilt impediments to good dust collection. In the end I think we have to accept that ideal dust collection is not going to happen. Most users simply don't have the air flow available to achieve any more than a token effort but any effort is better than none. I did an installation using a 17" impeller at 60hz and while it is better the mitre saw dust collection is saw 1 dust extractor nil in the sense that it is not perfect.

[Alan Lightstone]

OK. Looked at the system, and decided on one more modification (LOL, I'm sure there will be others.)

The gap over the top of the Kapex's arm had to be pretty big, and is clearly not useful for collecting dust during sawing. It just will reduce the CFM going through the important areas. But it has to be kept open for the saw's arm to move.

So I took some CNC dust boot I had left over from using it on the Overarm dust collector for my SawStop and glued it to the inside of the box, allowing the saw to move, but effectively cutting down the airflow through that area when the saw is cutting. Time will tell if this helps, but I figure it seems like a good idea and can't hurt.
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Still debating slightly enlarging opening on both sides at the bottom near the zero clearance insert. If I hadn't glued those pieces on, I would have already done that. As is, it's a handsaw operation.

[Jim Becker]

Good idea to use the "Hula Skirt" material for a "no seal seal" situation like that.

[Alan Lightstone]

Still tinkering because, well, that's what I do.

I thought there is too much dead space on the top half of the shroud. A more direct path for air/chips should help things, cut down turbulence, and hopefully improve air flow.

Looking at the box, I attacked the right side first, closest to the air intake from the dust collector. Again, having to keep the ability to maximally rotate the saw, I made a triangle box with the slope going at 45 degrees from the front of the box to the dust chute. Hard to explain.

Time will tell if this helps things.

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Left side box (easier build) likely to follow. Still debating whether to make those diagonal cutouts near the zero clearance insert.

[Alan Lightstone]

Well, I measured and built a second internal box to cut down on the dead space inside the shroud. It's amazing how much I had to decrease the size of these to allow the saw maximal movement from side to side for angled cuts. I could have just settled for 45° angles instead of the larger amount the saw allows and made those larger, but I didn't want to decrease the capacity of the saw.

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As it turns out, it was absolutely necessary to make those angled cuts at the bottom of the enclosure to allow the saw to make those cuts also. I'm hoping those increase the efficacy of the dust collection. I think they will.

Now, in retrospect, I think those inside boxes will prevent some beveled cuts, which I very rarely make, so probably not an issue. And I could always make those on my table saw. And they are removable with two screws, so I could always temporarily remove them.

As far as how well this works... I'll test it out sometime. No question that the dust collection is more effective with the two holes for the clamps closed up. And it was a mistake using 1/2" magnets. Way too strong. You can easily get your finger caught while it slams shut. 1/4" magnets would have been a better choice. The shroud itself doesn't collect all the dust on the bottom. A bunch stays in there. But that's not stuff that you breathe, and to a certain extent, "Out of sight, out of mind". And, every once in a while I can vacuum inside it.

[Scott Winners]

Alan, you are on a mission. And I know you are checking your particle counts in the shop space. I wish you the best of luck and hope you make a million dollars off your successful build.

[Alan Lightstone]

Alan, you are on a mission. And I know you are checking your particle counts in the shop space. I wish you the best of luck and hope you make a million dollars off your successful build.

Thanks, Scott. Not ever going to be sold, just me following a thought to its ridiculous ending. Ah, OCD...

And yes, most people would kill for the particle counts in my shop. And my lungs love me for it.