RA Dust collection project (pics)

[Paul Schaefer]

Thanks to all who responded the other month with suggestions for setting up dust collection for my DeWalt MBF RAS. Here's some pics of what I've come up with. I still haven't hooked it up to the ducting, so I don't know how well it's going to work, but I'm cautiously optimistic.

Unfurtunately, the darn pictures are rotated 90 degrees - anyone have a fix for that?

[Aaron Inami]

Hmmm, I wonder if there's a way you can cover sections of those holes. I'f you're doing a straight cut, you don't need the outer edges. And with a 45 degree cut on the right, the hole sections on the left are not needed. This would increase the suction and CFM on only the "used sections".

[Jim Becker]

Hmmm, I wonder if there's a way you can cover sections of those holes. I'f you're doing a straight cut, you don't need the outer edges. And with a 45 degree cut on the right, the hole sections on the left are not needed. This would increase the suction and CFM on only the "used sections".
It would not increase CFM for sure...you can't fit more air through a smaller space unless you found a way to greatly increase velocity. It might increase static pressure ("suction") but only slightly because DCs focus on moving volumes of air (CFM) rather than suction like a vac. The "ideal" for a pickup like that is for the area of the small holes in total to be close to the area of the large port used to connect to the system. The one thing I'd consider for the OP's solution is a little bit of a taller "splash guard" above the open ports to catch a little more material that's launched higher and direct it to fall down to be collected. The other difficulty here and "nature of the beast" is that the material being cut is going to block or partially block the collection ports, depending on the thickness of the material. These machines truly are a challenge to collect from.

[Paul Schaefer]

As usual, Jim has the truth of it...

"The "ideal" for a pickup like that is for the area of the small holes in total to be close to the area of the large port used to connect to the system."

Yes. Cross-section of a 6" pipe is about 27 square inches. Each of those 1" holes is a cross section of .75 square inches, for a total of about 18 square inches. The ratio of 'holes in the fence' to 'cross section of inlet' is...not good. I may square the tops of the upper row of holes to get a little more cross-section. The 'good' news is that if I fabricate a new blade guard with a ~2" pickup, I'll be in a little better shape.

"The one thing I'd consider for the OP's solution is a little bit of a taller "splash guard" above the open ports to catch a little more material that's launched higher and direct it to fall down to be collected."

Again, yes. I have some plexiglass lying around. I may cut a rabbet in the front edge of the fence, and attach a support on the front end of the table. That traps a lot more of the debris where airflow can pick it up.

"The other difficulty here and "nature of the beast" is that the material being cut is going to block or partially block the collection ports, depending on the thickness of the material. These machines truly are a challenge to collect from."

Once again, yes! Not a horrible problem with 1x stock, but 2x stock is...again, not good. Worse, the saw comes stock with a 9" blade, and some folks over on the Delphi DeWalt forum suggested stepping down to an 8.5" blade because even the 9" can be a stretch for the motor. I did that, which means the fence has to be lower, and there's less cross-section to put hole into.

There's a reason I made this out of shop scraps and didn't apply a lot of 'polish' to it. I think there will be a lot of fiddling about before I'm done. For example, I originially wanted to be able to make 45 degree cuts on either side, but a 45 degree cut on the left will only cut a 1" x 2", so that's not really worth it. I also cut slots for 30 degree cuts on the left and right, but thinking about it, I don't know that I've EVER made a 30 degree cut!

[Andrew More]

If you were to split this into two 4" sections, one going to the fence, and the other traveling with the blade you might get better results. A shroud on the blade is tricky though.

[Jim Becker]

No harm in experimenting with a variety of different ideas on this, Paul. Make each idea easily removable so you can switch things around to find what works "best", as it were, for your particular situation. If you're keeping the machine locked to only 90º cuts that also helpful because you can be sure exactly what your clearance is to set up the boundaries for containing dust/chips. One you have "best found", leave it on in the un-pretty form for a bit and see if you made the right choice before getting things all fancy and sparkly with unicorns flying about all mesmerized by your work. :) :D

[Mike Wilkins]

Go to Frank Makes and check out his videos on fabricating a dust collection solution for his 2 radial arm saws. Very interesting set-up.