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

[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.

PXL_20210918_005741482.PORTRAIT.jpg

PXL_20230902_223547734.jpg

(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....02#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....02#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.