• Hi all and welcome to TheWoodHaven2 brought into the 21st Century, kicking and screaming! We all have Alasdair to thank for the vast bulk of the heavy lifting to get us here, no more so than me because he's taken away a huge burden of responsibility from my shoulders and brought us to this new shiny home, with all your previous content (hopefully) still intact! Please peruse and feed back. There is still plenty to do, like changing the colour scheme, adding the banner graphic, tweaking the odd setting here and there so I have added a new thread in the 'Technical Issues, Bugs and Feature Requests' forum for you to add any issues you find, any missing settings or just anything you'd like to see added/removed from the feature set that Xenforo offers. We will get to everything over the coming weeks so please be patient, but add anything at all to the thread I mention above and we promise to get to them over the next few days/weeks/months. In the meantime, please enjoy!

big'uns, or littl'uns?

sunnybob

sunnybob

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I've started making my down draught sanding table (actually its a insert in my bench top).

I'm about ready to drill holes in the MDF insert. Its 700 mm x 400 mm.
The under bench chamber will be sloped from 25 mm down to 100 mm along the length, with a 75 mm suction connection at the deep end.

So do I drill big holes, or little holes?
I'm leaning towards big holes, because thats a lot less work, and maybe (maybe?) I could use the big holes to dog the piece to be sanded into place.
Whats the consensus of efficiency? Cos if it doesnt work its wasted. :shock:
 
I had never heard of these until today - what a great idea. WIll be interested to see how it turns out, there's loads of varying designs on the internet. Found one that was basically a drawer under a workbench, that was clever!
 
I think (the other) Bob is right.

The area of a 70mm circle (dust port) is 3848 square milimeters, a 20mm circle (dog hole) has an area of 314 square milimeters and a 10mm circle has an area of 78 square milimeters.

So, if you use dog holes completely you could fit 12 dog holes before you begin theoretically losing air flow, with the 10mm holes you could fit 49 holes before losing airflow.

I don't think the total volume of the empty box will matter too much, but it will make a difference.
 
You need more holes than the area of the hose because you need enough holes for the table to be efficient with good coverage to all of the table, bearing in mind some of the holes will/may be covered by the lump of wood being sanded. Also the smaller holes compared to the hose will reduce the air flow. Better to have a little too much air rather than starving the extractor.
 
My dust extractor isnt the most powerful in the world. That has 100 mm pipework. But its not practicable to have a 100 mm hose draped from one side of the workshop to the other where the bench is. Its also not possible to have a 100 mm dust box under the bench so I will have to use about 4 metres of 70mm (approx) hose.

But if I am sanding, then i think that at least a quarter of the holes will be blocked if they are large.
Maybe I need predominately small holes with strategic large holes to help secure the piece.
 
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