Here is a downdraft sanding table I made this morning, using the mitre joint method. I used a 91 degree folding mitre bit and 3/4" MDF. The rubber mat was purchased from http://www.leevalley.com/en/wood/page.a ... 3456,43465
Used a 91 degree folding mitre bit with a single cutter and 3/4" shaft. Full depth single pass.
glue up is easy. The bottom sat in dados. The hollow legs were filled with sand and then the mitred caps glued on. This adds weight so it won't shift around when sanding, and will hopefully damped vibrations when using RA sanders.
ready for the top
Underside of the top. I adhered a rubber high friction soft mat on the top, then drilled all the holes.
I sit when I sand my stool legs and chairs, so I made this 24" tall. Keeps stuff from sliding around and getting marked up while sanding. Connects to a 4" dust collection hose.
I didn't tape this before cutting. I cut to the spoil board and then taped and folded the joints after (I needed to remove the top piece to put the rubber mat on and drill the holes in it before gluing together).
This was my first mitre fold attempt in 3/4" MDF. Worked better than I dreamed it could. The glue joint is incredibly strong in MDF, because the surface area of the mitre joint is so large.
NICE Russell
Angled interior baffle not needed with your CFM?
Couldn't cut with my little machine anyways:(, but could you post as a .crv for us VCP guys that DO have a big enough machine?
Always nice work you do
I've learned my lesson well. You can't please everyone,so you have to please yourself
R.N.
Angled baffles weren't a concern of mine, but I've got a 2500cfm dust collector (though I don't think there is that much coming through any of the 4" outlets though). If any sawdust gets trapped, I can simply blow compressed air through the holes while the dust collector is on.
Here is the .crv file for V-carve. NOTE in the Aspire file above, the supports should be 2.625" wide instead of 3" wide.
Thanks Russell, Makes sense.
3 times the airflow of my garage Delta
What was that rubber top like? a Carvers mat?
Getting tired of the router mat marks and the sawdust that sifts down through.
May steal your top design for a small 24X18"
thanks!
I've learned my lesson well. You can't please everyone,so you have to please yourself
R.N.
I posted a link on my first post, showing where to purchase the mat (Lee Valley). Works GREAT for sanding. Soft, non marring, and high friction. Comes in a 2' x 3' piece for around $20.
Yes Wolffie, I adhered the rubber mat on first, then drilled the holes.
Used a 1/4" carbide tipped brad point drill, 5000rpm and 100ipm Z axis speed single pass (no peck drilling). Cut very clean holes through the mat and MDF. Took about 20 minutes for the 640 holes.
I'll apologize in advance, I'm an engineer so bear with me. Great design!!!
The size and number of the holes, was that based on a calculation of air flow?
I checked your file and the holes are spaced every 0.75"
I have a Delta Downdraft Dust Collection Table AP075 with an Oneida 3HP 2700 CFM dust collector that doesn't have enough airflow.
I suspect that the holes aren't larger enough and have been trying to solve my problem mathematically.
The top of the AP075 is metal with some form of non-slip surface.
So I don't want to to make the holes too large since there is no going back if I make them too large.
The rubber top from Lee Valley helps a lot too since I assumed I would have to make a new top rather than cut my existing top.
Any additional info or insights will be greatly appreciated.
I wanted enough cross sectional area of holes to be sure that the flow of air was not restricted, but not enough to weaken the top. I was going to use 3/8" holes, but bent my 3/8" carbide tipped brad point and so I went 1/4" holes. If the combined cross sectional area of the holes is too great, the flow won't be evenly distributed over the whole surface - it will be higher closer to the vacuum connection. If the cross sectional area of the holes is too small, then you will get decreased flow and it won't be as effective.
The cross sectional area of my vacuum connection is 12.566 square inches (4" connection)
The cross sectional area of all the holes combines is 31.415 square inches
This combination seems to give even flow over the whole table top. Not sure if its restricting the flow though (works well enough that I don't feel the need to test it!)
If anything, I would put in slightly more holes next time, or slightly larger holes. The larger combined area of the holes is necessary because of the higher resistance through the 1/4" holes - they are each almost 1" long.
