Or the cabinet is too small and vac is too big.
Mine has alot of leaks so no need for a fresh air hole. LOL I put the vac hose on the top in the corner where very little sand hits. You could try making a baffle for the inside or put a piece of fine screen on the opening.
When the sand is new, I don't even use the vacuum. It's only after it's been used a few times that it starts to produce alot of dust. Then you have to turn it on just to see the part!
I too agree, it's one of the best tools I have. My other favorite is my welder. The work on my cars improved dramatically with these tools.
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63 Impala*66 Chevelle SS*69 Chevelle*69 C10 Stepside*71 Cheyenne 20*72 Chevelle
Parts for sale:
http://www.angelfire.com/trek/mr409/items4sale.html