Vacuum Fixtures

[steve_g]

http://www.talkshopbot.com/forum/sho...highlight=gast

The Gast pumps have been well spoken of in the past

sg

[bob_dodd]

What you do not want is a vac pump for service air cond . as they are rotary vane type with a oil res. ,, One like joewoodworker.com is a dry diaphragm type and cycles on and off as needed

[Ger21]

Gast oil less rotary vane and Thomas diaphragm pumps are the most common. Most of the cheap pumps on Amazon are the oil spewing variety.

[Burkhardt]

Get one of the oil-less GAST or Thomson pumps that are being sold refurbished on e-bay for $150 or so (Google). They usually come with starter capacitor and power cable (check). No oil and they can run for days continuously. I guess they are more industrial than a Chinese consumer device.

HDPE is fabulous for pods but since I have unintentionally destroyed a few I just use 3/4" Baltic or even solid wood. The porosity is insignificant compared to other leakages (work piece, seals etc.). Another advantage is better friction on the table. The HDPE pods tend to slide around on my aluminum table when not bolted down well. I use 3/8" foam o-ring cord from McMaster. The o-ring channel is undercut with a ball end bit so that the o-ring is captive and can not jump out.

I use a standard size pod (5x5" or 5x9") for surface cuts that don't go through and where the material is rigid. For through-cuts and flexible material I make disposable "spoil adapters" that sit on top of the pod with a few through holes and adhesive 3/16" flat gasketing tape around the known un-cut areas. To avoid flexible material to be sucked/bowed in between the gaskets, I may create a gasket grid pattern that supports the entire surface evenly. I heard Allstar is good quality gasket but have not tried it yet. I usually take the rubber foam weather strip (Frost King R338H) from the hardware store that compresses under vacuum to less than 20/1000" but will recover. When replacement is needed it scrapes off with a chisel easily

[GeneMpls]

The ones on ebay seem to be 1/3 HP- how much of a vac fixture
will that support? Thinking 18x36" approx. Thanks Gene

[Ger21]

Depends on how much leakage you have, and/or how porous the material you're holding. My 1/4HP Gast is rated at 3CFM.

[Burkhardt]

The ones on ebay seem to be 1/3 HP- how much of a vac fixture
will that support? Thinking 18x36" approx. Thanks Gene

I have one that is 3/4 hp and it can do four 5x5 pods holding solid wood or plywood.

For 18x36 you will need more volume. For such a large surface you may be better off with a Fein or Lighthouse.

[bobmoore]

Yes gasketing should pull down to 0. Makes your Z much more predictable. I use 3/8 O.D. surgeons tubing (like you used to make sling shots out of). I have even used the round weather seal material from Home Depot in a pinch. Allstar gasketing sells excellent vacuum stuff although a little pricey it works great (try their cover gasket for dedicated fixturing with a central vac motor). Brady Watson and some others did extensive research and writing about vacuum on this forum if you can search the archives. Bob

[gbradley]

We are working on making up half rolls for the folks that are not in the high production end of the cnc world. Hope fully that will make the cost more affordable to the guys with the smaller machines.

[barrowj]

Bob, is that the same as Latex Surgical tubing, Amazon sells 50' of 1/4"id - 3/8"od for $28 Prime