Would an AC vacuum pump work for vacuum press?

[Greg Peterson]

There is a AC vacuum pump on craigslist for $35. I don't know if such a unit produces enough vacuum to work for vacuum pressing veneers. What is an appropriate level of vacuum so I can ask the seller if this unit produces that level of vacuum.

I haven't done any vacuum veneer work, mainly because every vacuum pump I've seen is slightly out of my price range. For $35, I would be happy to try my hand at it.

[Bruce Page]

Funny you should ask. I just picked up one of these today for $60 off of CL : http://www.amazon.com/JB-DV-200N-Pla...jb+vacuum+pump (http://www.amazon.com/JB-DV-200N-Platinum-Vacuum-Motor/dp/B003M5NCKU/ref=sr_1_2?s=industrial&ie=UTF8&qid=1401400978&sr=1-2&keywords=jb+vacuum+pump)
It's a 7CFM unit and seems to be in good condition. I want to use it with vacuum pucks for small part cutting on my CNC and plan on building the EVS detailed here: http://www.veneersupplies.com/produc...Press-Kit.html (http://www.veneersupplies.com/products/Project-EVS-Auto-Cycling-Pump-Vacuum-Press-Kit.html)

There's also lots of good info here: http://www.joewoodworker.com/veneering/vacuumclamping.htm

[Thomas Hotchkin]

Greg
Small vacuum pumps take a long time to pull a vacuum on your bag before your glue open time starts to run out. You can help this with vacuum supply tank. I use a old 5 gal propane tank, think BBQ, make sure you wash it out before using. Tom

[Greg Peterson]

Thanks for the input guys.

[Loren Woirhaye]

I doubt my little Gast vacuum pump is 7 cfm and it works fine for a bag. I use it for work-holding jigs too. I should get a tank but I haven't needed on. The pump is rated for continuous operation anyway and is not loud.

[Charles Lent]

Refrigeration vacuum pumps need to pull 29" + of vacuum or they are worthless for refrigeration work. This should be more than enough vacuum for veneering, but the pump may not have enough volume pumping capability to do well if your vacuum bag is large, but it should do fine for smaller bags or when used with a vacuum tank. With a tank and pump you could run the pump ahead of time and build a good vacuum in the tank, then open the valve from your vacuum bag and get a quick evacuation of the larger bag.

Charley

[Mike Cutler]

There is a AC vacuum pump on craigslist for $35. I don't know if such a unit produces enough vacuum to work for vacuum pressing veneers. What is an appropriate level of vacuum so I can ask the seller if this unit produces that level of vacuum.

I haven't done any vacuum veneer work, mainly because every vacuum pump I've seen is slightly out of my price range. For $35, I would be happy to try my hand at it.

Greg

Short answer is that yes it will produce sufficent vacuum to do veneer work.
The maximum amount of vacuum you willl get on this planet is essentially 14.7 psi of pressure applied to your workpiece, minus any changes in barometeric pressure. A cheap vacuuum pump will pull 22"-27" of mercury a good quality pump may get to 29" of mercury, and a big dollar pump will get you to maybe 29.5+. All dependent on barometric pressure.
There are many plans available for making a vacuum rig, but the basics are that you will need some manner of a reserve volumn tank to diminish pump cycling, a simple vacuum gauge and a vacuum pressure switch. It may take longer to obtain the initial drawdown, but once there the pump should be able to keep up as long as the system is tight.
You'd actually be surprised at just how well and how fast a regular shop vac can accomplish the initial drawdown on a system.. ;)

[Rod Sheridan]

There is a AC vacuum pump on craigslist for $35. I don't know if such a unit produces enough vacuum to work for vacuum pressing veneers. What is an appropriate level of vacuum so I can ask the seller if this unit produces that level of vacuum.

I haven't done any vacuum veneer work, mainly because every vacuum pump I've seen is slightly out of my price range. For $35, I would be happy to try my hand at it.

Any HVAC vacuum pump will do fine, it will have a lower pressure rating than most others.

It's what I use in my shop................Rod.

[Mike Henderson]

Refrigeration vacuum pumps need to pull 29" + of vacuum or they are worthless for refrigeration work. This should be more than enough vacuum for veneering, but the pump may not have enough volume pumping capability to do well if your vacuum bag is large, but it should do fine for smaller bags or when used with a vacuum tank. With a tank and pump you could run the pump ahead of time and build a good vacuum in the tank, then open the valve from your vacuum bag and get a quick evacuation of the larger bag.

Charley
I agree with Charles. An A/C vacuum pump is designed to pull a deep vacuum, but it doesn't have to pull it very fast. Normally, when you're evacuating the coolant lines on an A/C, you want to get all the moisture out of the lines, as well as any air so that when you introduce the coolant there's nothing to react with the coolant. You don't really care how long it takes to pull the vacuum (within reason) so the pumps usually don't have a high CFM.

When doing vacuum bag work, the bag can have a lot of air in it so if you don't use some technique to get most of the air out, it can take a long time to get the work into press. A vacuum cleaner can be used to suck the majority of the air out before you cut over to your A/C pump, or you can use a reservoir, as others have described.

Mike

[Bruce Page]

I have learned that these oil bath pumps/refrigeration vacuum pumps exhaust out a significant amount of oil in the form of a very fine mist – not an ideal situation in a woodshop. I’ll have to come up with a way to vent the exhaust outdoors.

[Chris Padilla]

Pulling the air out of your bag SLOWLY is not necessarily a bad thing if you're veneering something curved or oddly shaped and you need time to adjust the bag around the item.

[HANK METZ]

Sure can, works just fine:

http://www.youtube.com/watch?v=atTLzekpCkM&list=UUu_V0DUQ3ESxRWmqEWqUhJw

[Greg Peterson]

Thanks for the info guys. I did not get the unit, but the info everyone has provided has been helpful none the less.

[Mike Henderson]

Pulling the air out of your bag SLOWLY is not necessarily a bad thing if you're veneering something curved or oddly shaped and you need time to adjust the bag around the item.
That can be true, Chris. But a problem with some veneer is that it curls when it absorbs moisture. When you put your glue on, you normally only put it on the substrate (to keep moisture away from the veneer). Then you lay the veneer in place and get it into press before the veneer has time to absorb much moisture. So you want the press to happen really fast.

If the veneer absorbs moisture and expands before you have it in press, the veneer will buckle, even under a caul, and you'll have ruined work. It won't buckle if it absorbs moisture after you have it in press.

For many veneers this is not a problem, but for burls and any rotary cut veneer (bubinga, birds eye maple, etc.) it can really be a problem. And it's even worse when you lay veneer in a radial match.

When I lay veneer, I have everything laid out and set up. I have some reservoirs on my vacuum pump and they're pulled down. Once I lay the veneer on the glue, I'm moving FAST. If there's someone to help me, I have them hold the bag open and as soon as the work is laid in the bag, it's sealed and the vacuum valve is opened. I'm usually leaning on the work to put some pressure on it until the bag pulls down.

Mike

[Mike Cutler]

Hank

Thank you for posting that video.
Everyone seems to approach vacuum veneering as of some type of mysticism is involved in the process. Your video demonstrates just how easy, and more importantly, successful, the process can be with just a minor investment in equipment.
Well done!!

You got a video on steam bending??;)

[Jamie Buxton]

That can be true, Chris. But a problem with some veneer is that it curls when it absorbs moisture. When you put your glue on, you normally only put it on the substrate (to keep moisture away from the veneer). Then you lay the veneer in place and get it into press before the veneer has time to absorb much moisture. So you want the press to happen really fast.

If the veneer absorbs moisture and expands before you have it in press, the veneer will buckle, even under a caul, and you'll have ruined work. It won't buckle if it absorbs moisture after you have it in press.

For many veneers this is not a problem, but for burls and any rotary cut veneer (bubinga, birds eye maple, etc.) it can really be a problem. And it's even worse when you lay veneer in a radial match.

When I lay veneer, I have everything laid out and set up. I have some reservoirs on my vacuum pump and they're pulled down. Once I lay the veneer on the glue, I'm moving FAST. If there's someone to help me, I have them hold the bag open and as soon as the work is laid in the bag, it's sealed and the vacuum valve is opened. I'm usually leaning on the work to put some pressure on it until the bag pulls down.

Mike

A different solution to this problem is to use epoxy. It takes hours to set up, so you have plenty of time to get the work in the bag, and get it sucked down.

Another advantage of epoxy is that there's no water introduced. If I'm making thin panels that must be flat -- like doors -- I'm wary of the water in PVA.

I use West Systems 105 resin. Usually I use the fast hardener -- 205.

[HANK METZ]

Hank

Thank you for posting that video.
Everyone seems to approach vacuum veneering as of some type of mysticism is involved in the process. Your video demonstrates just how easy, and more importantly, successful, the process can be with just a minor investment in equipment.
Well done!!

You got a video on steam bending??;)

Thanks for the thumbs up Mike, veneering was one of my early adventures when I turned pro and hung out my own shingle decades ago. My first big commission was a wall unit in Red Oak, and I wanted to do a slip match for the door fronts. At the time, contact cement was being touted as a miracle product for applying veneer according to an old woodworking supply house in Bronx, New York. So I got a kit of stuff from them, did the job according to instructions, and it looked great. About two moths later I got a call- back; the veneer was bubbling away from the fronts. A hot iron effected a rebind, but after a few days it let go again. I then recalled a recent article in Fine Woodworking at the time, about a guy who constructed his own economical vacuum veneer press and did cold glueups with no failures, so I made my own rig using a shower curtain from the home center and a rotary vane vacuum pump purchased from Graingers and did a n/c make- good on the defective job. I have never had a failure, and use the simplest of supplies and technique, and still make my own bags from shower curtains found in the closeout bins of the home centers. In a pinch, I have even used plastic garbage bags for smaller projects, and when I taught the method back then, I showed how effective they can be; it especially wows 'em when you do a serpentine drawer front with a Glad trash bag.

[John Downey]

I have learned that these oil bath pumps/refrigeration vacuum pumps exhaust out a significant amount of oil in the form of a very fine mist – not an ideal situation in a woodshop. I’ll have to come up with a way to vent the exhaust outdoors.

There are exhaust filters available, though they do tend to be expensive. Vacuum equipment seems to suck the bills right out of your wallet! :D

[Bruce Wrenn]

If it's an electric unit, it will pull 3-7 cubic feet per minuter. If it's an air powered unit, forget it. They are AIR HOGS, unless designed for uses other than HVAC. Air-Vac makes the air powered units that are the basis of most of the commercial ones that use compressed air to generate vacuum. I have Air-Vac unit, another commercial unit (air), Thomas diaphram pump, HVAC vac pumps (plural), and home made unit from auto air conditioning compressor. Just picked up another compressor last week to make another unit. If your air compressor has a "screw in air filter," you can remove filter, and using necessary fittings adapt it to become a vacuum pump. But with all these pumps, you should have a filter before inlet to pump. I use a metal gas line filter from NAPA, attached with short section of rubber hose and clamps.

[Mike Henderson]

A different solution to this problem is to use epoxy. It takes hours to set up, so you have plenty of time to get the work in the bag, and get it sucked down.

Another advantage of epoxy is that there's no water introduced. If I'm making thin panels that must be flat -- like doors -- I'm wary of the water in PVA.

I use West Systems 105 resin. Usually I use the fast hardener -- 205.

Yep, I've used epoxy. For some veneers, it's the only reasonable solution. It's just a whole lot more expensive.

Mike

[Mike Henderson]

If it's an electric unit, it will pull 3-7 cubic feet per minuter. If it's an air powered unit, forget it. They are AIR HOGS, unless designed for uses other than HVAC. Air-Vac makes the air powered units that are the basis of most of the commercial ones that use compressed air to generate vacuum. I have Air-Vac unit, another commercial unit (air), Thomas diaphram pump, HVAC vac pumps (plural), and home made unit from auto air conditioning compressor. Just picked up another compressor last week to make another unit. If your air compressor has a "screw in air filter," you can remove filter, and using necessary fittings adapt it to become a vacuum pump. But with all these pumps, you should have a filter before inlet to pump. I use a metal gas line filter from NAPA, attached with short section of rubber hose and clamps.
The vacs for evacuating A/C systems are generally not 3-7 cubic feet per minute - or at least I've never seen A/C vacs that pull that fast. There's no reason for them to pull that fast and generally, if a pump pulls high vac, it pulls it slowly (not very many cubic feet per minute).

I do agree that you should use a filter ahead of the pump to keep trash out of the pump.

Mike

[Bruce Wrenn]

The vacs for evacuating A/C systems are generally not 3-7 cubic feet per minute - or at least I've never seen A/C vacs that pull that fast. There's no reason for them to pull that fast and generally, if a pump pulls high vac, it pulls it slowly (not very many cubic feet per minute).

I do agree that you should use a filter ahead of the pump to keep trash out of the pump.

MikeLooking in Johnstone Supply cat, at the JB vacuum pumps. Smallest is 3 CFM,and largest is 10 CFM (free air.) That's what is in the bag before evacuation. So yes they do pull in the multiple CFM range. When they no longer pull in the MICRON range, they are trashed as new is cheaper than rebuild. Rebuild kits are readily available. But no time loss waiting on rebuild.

[Jamie Buxton]

Yep, I've used epoxy. For some veneers, it's the only reasonable solution. It's just a whole lot more expensive.

Mike

True, it is more expensive than PVA. It is around $100 per quart. However, a quart of epoxy is likely years of projects. Or compare the cost of a thin layer of epoxy to cost of the veneer you're sticking down with it. The epoxy film is vanishingly thin. It costs maybe pennies -- way less than the cost of the veneer. So it really doesn't matter.