Results 1 to 13 of 13

Thread: Holdfast Rotary Vacuum Adapter

  1. #1

    Holdfast Rotary Vacuum Adapter

    I Just received the Holdfast Rotary Vacuum Adapter for my Grizzly G0800 lathe. The quick disconnect on my vacuum hose does not stay on the male end coming off the vacuum adapter. Does anyone know how to make the connection between the vacuum adapter and the vacuum hose? Thanks.

  2. #2
    Join Date
    Sep 2015
    Location
    San Diego, Ca
    Posts
    1,246
    When I look at the picture of the holdfast, the "nipple" looks like it is for a push-on tube and isn't a quick disconnect. Is this the situation?




    My vacuum setup just uses push on (semi-rigid) poly tubing. Everything stays in place

  3. #3
    Join Date
    Nov 2007
    Location
    Houston, Texas
    Posts
    99
    I have to agree with Brice. That end is what I think is called a barbed fitting, so the tubing just pushes onto that fitting.
    Don't let it bring you down,
    It's only castles burning,
    Just find someone who's turning,
    And you will come around

    Neil Young (with a little bit of emphasis added by me)

    Board member, Gulf Coast Woodturners Association

  4. #4
    Join Date
    Mar 2013
    Location
    Eastern NC
    Posts
    158
    Try a small wire tie. If that does not work, try wrapping a piece of wire around it and twisting it tight. Be careful of loose, pointy ends.

  5. #5
    Brice's picture is what I have. The 3/8" ID hose I use for my vacuum system will slide on to the nipple. I'll try putting a cable tie around the hose end on the nipple.

    Brice - is your push on poly tubing connected in some way to a quick disconnect? Is your poly tubing a direct connect to the Holdfast System? I use a Gast vacuum pump. Thus, the set-up with compressor hose and quick disconnects.

  6. #6
    Join Date
    Sep 2015
    Location
    San Diego, Ca
    Posts
    1,246
    I'm using a Thomas pump (very similar to the Gast) and I have (IIRC) 3/8" threaded fittings that screw into the pump but the other end of the first fitting is a barbed fitting. I slide the semi-rigid poly tubing over the barb and they fit tight enough that I don't need or use clamps. I think that for the vacuum gauge and the bleed valve that I had to use a 3/8 pipe-to-barb fitting.

    I have my vacuum bearing mounted in a disk of wood with a dovetail that my regular chuck grabs. The other side of the wood disk has the craft foam on it. the vacuum bearing has a fitting glued into it to which a 1-1/2" long nipple of poly is permanently attached. The I.D. is perfect in that my poly tube slips inside of it with a decent vacuum fit. So when I remove the vacuum chuck, I just slide the smaller tube out of the slightly larger tube. Same at the other end. So my poly tubing acts as my "quick disconnect" of sorts.

    All of this is from Bob Leonard's frugalvacuumchuck design. Check out his website for ideas and to get a visualization of what I described. Even with two slip fits (with the poly) and the barbs w/o clamps, I can easily get 25 inches of vacuum (and I'm at about 2,000 feet so that will cut out roughly a couple of inches).

  7. #7
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    8,454
    Quote Originally Posted by Brice Rogers View Post
    ..... I can easily get 25 inches of vacuum (and I'm at about 2,000 feet so that will cut out roughly a couple of inches).
    Curious as how you figured that. 2000 ft is about 600 meters.

    The Engineering Toolbox (very handy web site, btw: https://www.engineeringtoolbox.com/a...ure-d_462.html) gives
    • 29.9" at 0 meters (sea level)
    • 28.9" at 1000 meters (about 3300 ft)
    • 27.8" at 2000 meters (about 6500 ft)

    Do you mean you're at 2000 meters instead of 2000 ft? Or maybe I don't understand atmospheric pressure and vacuum.

    I've heard nothing but good things about the frugal vacuum, talked to him at symposiums. If I were buying today I think I'd get things there. https://www.frugalvacuumchuck.com/home.html

    JKJ

  8. #8
    Quote Originally Posted by Brice Rogers View Post
    I'm using a Thomas pump (very similar to the Gast) and I have (IIRC) 3/8" threaded fittings that screw into the pump but the other end of the first fitting is a barbed fitting. I slide the semi-rigid poly tubing over the barb and they fit tight enough that I don't need or use clamps. I think that for the vacuum gauge and the bleed valve that I had to use a 3/8 pipe-to-barb fitting.

    I have my vacuum bearing mounted in a disk of wood with a dovetail that my regular chuck grabs. The other side of the wood disk has the craft foam on it. the vacuum bearing has a fitting glued into it to which a 1-1/2" long nipple of poly is permanently attached. The I.D. is perfect in that my poly tube slips inside of it with a decent vacuum fit. So when I remove the vacuum chuck, I just slide the smaller tube out of the slightly larger tube. Same at the other end. So my poly tubing acts as my "quick disconnect" of sorts.

    All of this is from Bob Leonard's frugalvacuumchuck design. Check out his website for ideas and to get a visualization of what I described. Even with two slip fits (with the poly) and the barbs w/o clamps, I can easily get 25 inches of vacuum (and I'm at about 2,000 feet so that will cut out roughly a couple of inches).
    Thanks Brice

  9. #9
    Join Date
    Sep 2015
    Location
    San Diego, Ca
    Posts
    1,246
    John,

    I've been using a rule-of-thumb for a while and you made me recheck it. I thought perhaps that I was wrong and had been for several years. So, I did a quick google search and came up with this: https://anver.com/vacuum-lifters/atmospheric-pressure/

    Altitude Above
    Sea Level
    (feet)
    Altitude Above
    Sea Level
    (meters)
    Atmospheric
    Pressure
    (psi)
    Maximum Vacuum
    Level Attainable
    (inches Hg)
    Vacuum Level
    Loss at Altitude
    Maximum Vacuum Level Possible at
    this Altitude
    0 0 14.70 29.921
    1000 305 14.16 28.9 3.4% 96.6%
    2000 610 13.66 27.8 7.1% 92.9%
    3000 914 13.16 26.8 10.4% 89.6%
    4000 1219 12.68 25.8 13.8% 86.2%
    5000 1524 12.22 24.9 16.8% 83.2%

    So, I thought that I should double check that with another un-associated site. I also looked at another "hit" on the google search that gave this rule-of-thumb: "As a general “Rule of Thumb”, for every 1000 feet above sea level, the maximumpossible vacuum is reduced by approximately one in-Hg (0.491 psi). By using this ruleone can quickly determine the maximum possible vacuum for the area. " (reference: https://vacmaster.zendesk.com/hc/en-...um_Systems.pdf)

    I don't understand why the Engineer toolbox site would differ so much. It does seem to be a feet-to-meters error somewhere.

    BTW, I really like the bearings that I get from the frugalvacuumchuck guy. I learned the hard way that many so-called sealed bearings are "non-contact" seals. That is, for a vacuum chuck they leak pretty badly. Bob's bearings are good. I can turn off my pump and my part will stay in place for perhaps 30 seconds.

  10. #10
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    8,454
    Quote Originally Posted by Brice Rogers View Post
    John,

    I've been using a rule-of-thumb for a while and you made me recheck it. I thought perhaps that I was wrong and had been for several years. So, I did a quick google search and came up with this: https://anver.com/vacuum-lifters/atmospheric-pressure/
    ...
    Thanks for that! Gives me a reason to do some more looking. Maybe even drag out some old textbooks. [Gasp!]

    JKJ

  11. #11
    Join Date
    Feb 2016
    Location
    Walworth, NY
    Posts
    94
    The table below indicates air pressure at elevations below and above sea level.
    Altitude Above Sea Level Absolute Barometer Absolute Atmospheric Pressure
    feet metre inches Hg mm Hg psia kg/cm2 kPa
    -5000 -1524 35.7 908 17.5 1.23 121
    -4500
    aprox. deepest point under sea level of Sognefjorden, Norway
    -1372 35.1 892 17.2 1.21 119
    -4000 -1219 34.5 876 16.9 1.19 117
    -3500 -1067 33.9 861 16.6 1.17 115
    -3000 -914 33.3 846 16.4 1.15 113
    -2500 -762 32.7 831 16.1 1.13 111
    -2000 -610 32.1 816 15.8 1.11 109
    -1500
    shore of the Dead Sea, Palestine, Israel and Jordan (-1371 ft)
    -457 31.6 802 15.5 1.09 107
    -1000 -305 31.0 788 15.2 1.07 105
    -500 -152 30.5 774 15.0 1.05 103
    01) 0 29.9 760 14.7 1.03 101
    500
    aprox. Møllehøj, Denmark
    152 29.4 746 14.4 1.01 99.5
    1000 305 28.9 733 14.2 0.997 97.7
    1500 457 28.3 720 13.9 0.979 96.0
    2000 610 27.8 707 13.7 0.961 94.2
    2500 762 27.3 694 13.4 0.943 92.5
    3000 914 26.8 681 13.2 0.926 90.8
    https://www.engineeringtoolbox.com/a...ure-d_462.html The first column is feet.

  12. #12
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    8,454

    pressure and altitude

    Well I finally took a closer look and I believe your table is correct. All I can imagine is a probable brain burp, er senior moment! The same table I used earlier doesn't say what I thought it did yesterday morning. I found other tables and a couple of pressure/altitude calculators. (Anything to avoid doing the math!)

    My only defense is I'd been operating power equipment early and suddenly started to feel dizzy so I turned everything off and came up to the house to rest a bit. At least I was thinking clearly enough to quit! Thanks for the correction!

    PS, how did you copy that section of the table from the web page into your message? It looks great. I've tried to do that before without typing in a bunch of code but did succeed.

    JKJ

  13. #13
    Join Date
    Feb 2016
    Location
    Walworth, NY
    Posts
    94
    John, all I did was highlight, copy & paste. Not sure why it works most times and not others.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •