PVC or Metal Dust collection???

[Nova]

"Michael Baglio

I can't find "Silly Putty". Will "Plumber's Putty" (non-union) work if I dye it different colors? ;-)

-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)

[Bridger]

it will work as long as you stand there and tell it bad jokes. as soon as you stop, your dust collector will explode.

[LRod]

You're probably right. I'm not on good terms with the arcane language of moving air. "Static" and "velocity" just seem mutually exclusive to me.

Nonetheless, the DC is for shit with the sander; the shop vac works fine. Let's just say I don't know why.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[Michael Baglio]

Yes, but "Plumber's Pantyhose" won't. The crack in the back lets out too many static ionomers. And stuff.

Michael "SillyPutty. It isn't just for breakfast anymore."

[DJ Delorie]

Quick primer:

Velocity depends on pressure differential (suckage) and flow resistance (pipe size, bends, smoothness of pipe walls, etc).

CFM is velocity times cross section area of the flow conduit. CFM is a measure of the volume of air moved under a given load (resistance). You get the most CFM at no load, since you get highest velocity then.

Static pressure is the maximum pressure differential under infinite load (resistance).

When figuring out how useful a given vacuum will be, you need to consider a few things:

• Dust remains suspended at a given air velocity. To work, you need to keep the velocity at or above this.

• CFM for a given collection area. Larger areas (sanding tables, lathe hoods) require more CFM, as larger areas reduce velocity.

• Excess static pressure compensates for losses along the conduit, allowing you sufficient static pressure at the outlet to create the CFM you need.

Now consider the motor. It runs at a given speed with a given pump, which limits CFM. But the engineering of the motor/pump determines how hard it can pull when the air is blocked. A rotary vane pump can get you to nearly 29 inches of vacuum at very low CFM. A 20" box fan can get lots of CFM with little static pressure.

So, a shopvac works as long as the collection area (and hose diameter) are small enough. Also, a shopvac will continue sucking even under heavy loads (I've pumped water through the 2.5" hose with mine - 16 gal in about 10 seconds :). A DC, however, will work with much larger hoses and collection areas, but it won't work as well at sucking up bowling balls and other larger items.

At least, that's the theory.

[LRod]

Thanks.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[Larry Bud]

Oh well, hook, line, and sinker! But I HAVE read completely serious websites which claim you can "ground" a PVC system...

I hate all of you :-)

[Tbone]

Sure you can (as far as static electricity is concerned) but the real question is do you need to?

LOL

[Keep it to Usenet please]

Let me fine-tune that comment a bit. If you're using 45's you'll often get a side benefit of being able to shorten the total pipe length, so you will get less resistance, but for a different reason.

[Keep it to Usenet please]

Misuse of the word. If they said "drain static build-up so you don't zap yourself bumping into the pipe" then they'd be OK.