Thread: Building better dust extraction

I like it. I hope the flexible piping is not obstructed by internal structures, with the saw at 45 deg.
Zelk

Thanks Zelk. The flex doesn't clash with anything but with the new arrangement it will have one extra bend in it. If that diminishes performance too much I can take the rear cabinet door off and exit straight out though there rather than through the cabinet flange. Time will tell.
By the time I had welded the duct to the shroud, finally some of the cobwebs were blown out of my welding and when I got onto the elbow at last I had the settings pretty good and got some good welds in the elbow. I haven't really welded much in the last 10 years. Then I came to do the patch on the bottom and ran out of wire Went to the local hardware and they wanted to sell me gold wire, judging by the price, so tomorrow I'll get twice as much from the welding shop for less money than the hardware.

Looks great mic. If I can get mine looking half as good I'll be happy with it.

Today I finished off the welding (an expert wouldn't call it that) applied a few coats of primer and after that was dry, installed it in the machine ready for the first test. It fits quite well except dopey cut the flex a little too short and will have to buy another piece. I ripped a length of pine and was happy not to see any visible dust above, but not quite so happy with the outcome below. There is still a smattering of dust on the floor. There is obviously a lot more air flow through the shroud, I can feel the difference but I wonder whether the shroud needs to be deeper. Well it is a lot better than it was, but further tinkering must wait, projects await!

Now that you have opened the throat more, I would expect the velocity of the air reduced, explaining the coarser particles that are not captured. However, the increased flow of air is capturing the finer dust. BobL could confirm this.
Zelk

Zelk is probably right.

Completely capturing stuff coming off a TS blade is hard work and operates under some law of diminishing returns. A 12" blade at 3000 rpm is doing a liner speed of 47 m/s or 170 km/hour so the bits coming off the blade start out with that speed. Getting this air speed with 4" ducting and any sort of shroud arrangement is not easy so I think you have done pretty well.

I find blade shrouds a bit of a pain with bits and slivers of wood getting jammed in there and the cleaning out thereof is not easy. I took mine off my saw completely and added an ally hopper bottom immediately under the blade. That is also not ideal because sawdust cruds up the tilt and height mechanism.

Probably a combination of both a shroud and hopper bottom would reduce the amount of dust further.

Thanks guys. I ran my saw a few times while the saw shroud was off being modified and there was sawdust everywhere-what a mess won't do that again.
I tried the flex duct connected directly to the shroud, not via the cabinet flex and collection was slightly better. Then I tried with various apertures on the blast gate extracting from the top guard. Even with the guard closed right off and air howling through the shroud, there is still pretty much the same amount of chip on the floor. So I think that the modification is about as optimised as can be without butting heads with the law of diminishing returns.

I'm at the stage of cutting up lots of blocks for the cutlery boxes and I hate the amount of dust my mitre saw kicks out even with the vacuum connected. I don't care too much for site work but not in the workshop So with a couple of spare hours this afternoon I built this dust shroud to help pick up the stray dust. I can still have the vacuum attached too. Works well, rough as guts.

Hi Mic,
Looks the goods, I did something similliar at the school, built a steel shroud with a pickup slot the full width of the enclosure at the bottom back as well as the pickup right at the blade, worked quite well, lots of air flow there tho which made it possible.
Attachment 180960

With my dropsaw (old Makita or is it a Hitachi) at home I just hooked the vac/cyclone up to where the the bag thing went and wrapped a bit of wide ducting tape at the back of the blade guard to help direct the dust up, that works quite well as well.


Pete

Originally Posted by pjt

Hi Mic,
Looks the goods, I did something similliar at the school, built a steel shroud with a pickup slot the full width of the enclosure at the bottom back as well as the pickup right at the blade, worked quite well, lots of air flow there tho which made it possible.
Attachment 180960

With my dropsaw (old Makita or is it a Hitachi) at home I just hooked the vac/cyclone up to where the the bag thing went and wrapped a bit of wide ducting tape at the back of the blade guard to help direct the dust up, that works quite well as well.


Pete

Lots of room there too by the looks. The Hitachi dust port is abysmal even with the vacuum connected. That reminds me, I need to find a better solution to hooking the vacuum up.

I finally got around to venting my DE exhaust outside the workshop. In the end I didn't go though the ceiling, I just replaced a sheet of tin on the door with ply and fitted a 600mm diameter duct. Works great. I'll get some more photos when I charge my camera.

Originally Posted by mic-d

I finally got around to venting my DE exhaust outside the workshop. In the end I didn't go though the ceiling, I just replaced a sheet of tin on the door with ply and fitted a 600mm diameter duct. Works great. I'll get some more photos when I charge my camera.

Looks good!

How's the noise coming out of the end of the duct outside?

Originally Posted by BobL

Looks good!

How's the noise coming out of the end of the duct outside?

Thanks Bob. Even now without the outer duct fitted it is just a low hum. It is a very quiet dusty anyway. I can hardly hear it at the end of the drive, maybe 8-10m away.

Finally, here are the exterior photos of the duct. When not in use, the vent is covered by plywood secured from inside and the duct folds away neatly for storage. When in use, the duct just gives me that extra bit of separation so little exhaust is likely to be sucked back into the workshop.