Vacuum Veneering - Oil or Oilless Pump?


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I wouldn't want to use mine in the woodworking shop.  I open the door to the mechanic shop, and sit it outside even when I'm using it on a vehicle.  The oil you have to replace in it goes somewhere, and you can see the mist in the air coming out of it.

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7 minutes ago, Gary Beasley said:

If you get the oilless carbon vane pump it normally has a felt filter to catch any carbon dust from the outlet and one for the Inlet to catch dirt. They last an incredibly long time and are very simple to rebuild if the vanes wear out.

Will they pull as much vacuum as will an "oil pump"?

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I doubt it.  Mine is a two stage.  It also gets hot enough that I don't think you're supposed to put it in anything.  It'll peg the gauges hooked up to a vehicle AC system.   You don't need that much vacuum for a vacuum bag.  Atmospheric pressure does the work, once the air is evacuated.  For an air conditioning system, you have to get all the moisture out, as well as air, so it's a bit more complicated than a vacuum bag

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2 hours ago, Mark J said:

Will they pull as much vacuum as will an "oil pump"?

Not quite as much as a high quality oil pump, but close. Definitely good enough for veneer work. They were used for platemaking contact frames for decades, that requires tight contact. Total atmospheric pressure on a decent sized vacuum bag would be measured in tons. I know with my vacuum chuck I have to be careful how much vacuum I put on a thin wall bowl to avoid collapsing it. 

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I'm not an expert on this, but I was doing some investigation on hobby vacuum kilns before the pandemic.  First order answer is yes, placing wood in a vacuum lowers the vapor pressure and hence lowers the boiling point of water.  But it doesn't lower it enough on it's own to dry out a large piece of wood quickly.  So in the time it would take for glue to cure a piece of veneer in a vacuum press should not loose much more water than if clamped with cauls.  And most of the adhesives that would be used contain some water, too.  

With a vacuum kiln there is also some source of heat in addition to the vacuum.  In the units I'm exploring that is a mini electric blanket.  

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14 hours ago, Gary Beasley said:

If you get the oilless carbon vane pump it normally has a felt filter to catch any carbon dust from the outlet and one for the Inlet to catch dirt. They last an incredibly long time and are very simple to rebuild if the vanes wear out.

That's the type used in general aviation airplanes with piston engines. They can last a long time, but when they fail (usually without warning) poof! But as you said, they can easily be rebuilt.

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I suppose you have already considered this, but I'd you have a reasonably sized air compressor, think about a venturi pump. I have one that came in a kit I bought from on of the online veneering sites. I think it was joewoodworker. Anyway, the kit cane with all of the fittings and electrical parts. I added a switch, cord, electrical box and a couple of pieces of 4" PVC pipe with end caps. 

It pulls down to 5" easily, which.is plenty good for veneering. The air runs for a few minutes as the bag is pulled down. Then it cycles.once every few minutes for a 20 seconds and shuts off again. Works like a champ. No oil or other maintenance. My compressor only cycles every few hours (60 gallon tank).

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