This old house - dust collection

Galvanized will rust through in a few years unless the soil is really
dry and free of corrosives, salts, alkalais, etc. Plastic will hold
up very well. One big mistake is using 2" or 4" ducting which has such
high static pressure loss it won't conduct enough air to get good collection.
A 10" table saw, for example, needs at least 400 CFM underneath and 350 CFM
or more over the blade for good collection that keeps the air clear of
fine dust coming from the machine. For selected other tools, CFM
requirements are listed at http://www.cleanshopair.com/SystemSize.html.

Another issue with ductwork is accessibility for cleanout and unplugging.
The advantage of overhead rather than under floor is that blocks of
wood and such don't get carried up into a pipe they can't get through
(at least most of the time), and if they do get caught, you can get it
apart easily to unplug. You can't do that under a concrete floor. But
on the other hand, it's nice to have a smooth, open space with everything
out of sight. It's all about trade-offs.

To prevent plugging, air velocity in vertical ducting needs to be at least
4000 ft/minute and 3000 ft/minute on the horizontal runs. 6" pipe can carry
that kind of velocity without excessive static pressure losses, but it
increases very rapidly if you drop to 4" lines, especially if your dust
collector has a 12" or smaller blower that can't carry high CFM at 8-10"
of static pressure.

CE

"Mike S." wrote:
>
> It's been several weeks I was watching TOH show on the Milton House. They
> turned the extension off the barn into a woodshop. I caught part of it where
> Norm said they would bury the dust collection duct in the gravel/dirt before
> pouring the concrete. What I was curious about is what material did they
> use. Never heard that mentioned. Some type of galvanized duct or pvc???
> Anyone know?
> Thanks
>
> --
> Mike S.
> [email protected]
> http://members.tripod.com/n0yii/woodworking.htm

<<It's been several weeks I was watching TOH show on the Milton House. They
turned the extension off the barn into a woodshop. I caught part of it where
Norm said they would bury the dust collection duct in the gravel/dirt before
pouring the concrete. What I was curious about is what material did they
use. Never heard that mentioned. Some type of galvanized duct or pvc???
Anyone know?>>

I had a chance to tour that house after they completed it and I seem to
recall seeing PVC pipe coming through the floor by all the stationary power
tools.
I forgot to ask them whatever became of that huge French door they removed
from the end wall of the structure they knocked down and replaced with the
shop. It certainly didn't get reinstalled in the shop (or anywhere else on
the property).

Lee


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