This old house - dust collection

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

Reply to
Mike S.
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I've been watching re-run of that series. What and awesome house/barn/property. I envy you for getting to take a tour of the place. I remember when they should the new owners. They were a young couple, and NOT woodworkers, pissed me off John

Reply to
Quadindad2

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

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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:

Reply to
Clarke Echols

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