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Thread: Vacuum Hold Down RULES

  1. #1
    Join Date
    Apr 2005
    Location
    Sleeper Woods Design/Mendocino College Woodworking Program, Lakeport, CA CA
    Posts
    152

    Default Vacuum Hold Down RULES

    Folks -

    My Father in Law and kluged together a bastardized vaccum hold down setup after reading about using refridgerator compressors here on the forum. Boy oh Boy!

    We took a compressor and an old surplus propane tank to use as a vacuum reservoir along with a few fittings. It easily pulls over 25" of mercury and I can't budge my workpieces... Rose and I hadn't yet used it, we were still just toying with it, but today we tried it out.

    Our total investment in the whole shebang is under $20 in fittings and vacuum hose. The parts are held rock solid - we did some v carving and just swapped out each workpiece as we finished - no screws, no clamps, no bridges (I donn got to chsow you no steenkeeen briges!) I put registration marks on the corners of the vacuum puck, lined everything up and off we went.

    The set-up is SO simple, I'd encourage everyone to give it a go... I can post pics of the setup if anyone wants (or email). It isn't pretty, but works like a charm.

    Cheers,

    John Moorhead
    Lakeport, CA

  2. #2
    Join Date
    Mar 2001
    Location
    Somerset, UK
    Posts
    315

    Default

    I'd like to see that John. Sounds cool.

    John

  3. #3
    Join Date
    Apr 2006
    Location
    Arizona
    Posts
    113

    Default

    John M,
    We would also be interested in some pics. We are going to be needing all the help we can get very soon. By the way, where do you all get the "pucks". I'll do a search later, but thought maybe there is a favorite ordering place.
    Thanks,
    Shari

  4. #4
    Join Date
    Mar 2005
    Location
    Sappwoodworking, Moore Oklahoma
    Posts
    50

    Default

    John,

    I would love to see them as well

  5. #5
    Join Date
    Jul 2005
    Location
    Des Moines, Iowa
    Posts
    499

    Default

    I got my pucks from Morris Dovey at http://www.iedu.com/DeSoto/vacuum.html but you can make your own also.

  6. #6
    Join Date
    Apr 2005
    Location
    Sleeper Woods Design/Mendocino College Woodworking Program, Lakeport, CA CA
    Posts
    152

    Default

    Folks -

    If the upload Gods will deign, I have attached 3 fotos here. Our vacuum setup consists of an old refrigerator compressor, a "party" helium tank as a vacuum reservoir and a little trolley that I built to hold the contraption.

    I got the pump/compressor out of an old freezer (a fridge is okay too) When you remove the compressor, just cut the lines and have Al Gore help you collect any surplus Freon moleules. You'll end up cutting a couple of power wires that'll lead to the thermostat and probably the light. Just cut the suckers, don't worry about it.

    Okay, after we got the compressor out, I plugged it in and shorted the thermostat wire out to one of the power leads and the compressor kicked on. If it just hums, try another terminal... you can see I wasn't real worked up about having a schematic.

    We plumbed the compressor into the tank and braised 3 fittings for connections. If you use a propane tank, I'd pull the fill valve and fill the tank with water a couple of times so you're sure you don't have any propane gas in the tank when you weld. If you don't get this part, take up fly tying...

    The three connections I have at the tank are a supply line that goes to the compressor, a line that goes to the vacuum gauge, and then the last line that goes to the vacuum hold downs. The reason I went with 3 separate fittings instead of a single manifold/tee arrangement is that I was afraid of sucking shavings, dust and crud into either the vacuum gauge, or the compressor. Now the debris needs to rattle around in the tank first. I suppose I could put a simple filter in the vacuum puck line to capture any sawdust.

    The vacuum pucks are off-cuts from some sheet PVC I was working with. You could just as easily use plastic cutting board material. Don't use MDF, though - it won't hold a vacuum at all. I got the gasket material from allstar
    per Bill Palumbo's suggestion
    ( http://www.allstaradhesives.com/ )

    Making your own vacuum pucks is easy - I just drill a hole for the OD of the hose in the edge, and another inside the "Vacuum field" and surround the area with gasketing. I leave room around the edge for a couple of screws.

    To use the system, I turn on the vac pump and evacuate the tank until I get ~20" or better of vacuum. Then I have my workpiece positioned on the puck and open the valve. It sucks right down - if you hear a vacuum leak check it out right away...

    My Father in Law is going to get a vacuum switch so that the pump will start and stop automatically in use. Currently, I just turn it on and keep an eye on the gauge - I don't leave the pump running the whole time...

    This setup is the BOMB.... email me if you have any other questions.

    John Moorhead
    Lakeport, CA
    13127.jpg
    13128.jpg
    13129.jpg

  7. #7
    Join Date
    Oct 2001
    Posts
    2,941

    Default

    For the folk nervous about welding on propane tanks, visit a junkyard and look for truck "brake" tanks. You can use the existing single entry point to the tanks (propane/brake) and use T-pieces in the plumbing. Remember that this DIY tank stuff is for vacuum only - think very carefully before you connect a compressor to blow instead of suck.

  8. #8
    Join Date
    Feb 2000
    Location
    Chapman Carved Signs, Elgin TX
    Posts
    218

    Default

    I have no experience working on refrigerators, but I have experience servicing car ac's which must have oil in with the R-12 or R134A.
    Isn't there oil circulating with the freon in refrigerators/freezers, and if so won't the seals and eventually the unit fail when it's just pumping air?

  9. #9
    Join Date
    Apr 2005
    Location
    Sleeper Woods Design/Mendocino College Woodworking Program, Lakeport, CA CA
    Posts
    152

    Default

    Don -

    I asked a refridgeration guy about lubrication, and he said that if you keep the compressor level - or however it was mounted in the fridge you will be okay for quite a while. He said that while the pump may eventually fail, given the price, it isn't that big a deal.

    On the side of caution, I don't let my compressor run more than about 10 minutes at a stretch. I've got a good airtight system, so it holds vacuum for quite a while. I am going to put in a vacuum switch to run the compressor when it gets down to say 15" and cut out at 20 or 22"

    The remarks about truck air tanks are good. I am probably going to plumb additional reservoir capacity into my system.

    Good point to bring up, thanks!

    John

  10. #10
    Join Date
    Feb 2000
    Location
    Chapman Carved Signs, Elgin TX
    Posts
    218

    Default

    I do know the importance of keeping refrigerators upright.
    Some years ago I sold a working old-but-cold fridge to someone who insisted on transporting it lying down in the back of his pickup and then he complained about it not cooling when he got it home.

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