Interested in Vacuum pump / bag for veneering flat and curved

[Phillip Mitchell]

I’m looking for some basic details as well as more nuanced, experienced advice in putting together a vac pump / bag setup sometime over the next handful of months for some upcoming projects I have.

Never used a vacuum bag before, but watched plenty of videos so I’m at least familiar with the concept. I have spent a fair amount of time reading on the Joe Woodworker and Veneer Supplies websites so far and gotten some basic details there.

I would love to get into having the option to veneer my own sheet goods for certain projects. Not sure if a full 4x8 sheet will need to be done all at once for my needs, but seems like that’s a threshold / common size for bags (54”x108” bags seems common) so a pump that could at least handle that. I also have an upcoming project (months out) for a curved wall cabinet that I’m thinking has veneering and vac bag written all over it.

Biggest issue is available workshop space to set up and put a platen that size. Currently have a 40”x75” 3/4” mdf assembly table that is dead flat but maybe not large enough for a 4x8 sized platen to stay flat or? The workshop is tiny with limited useable wall space so not sure a fold up table would work at least not for that size.

I have plans to expand my shop into the garage and would have plenty of space there to earmark for a large 4x8 ish assembly table that could do platen / bag duty but not there yet.

Of course I’m trying to evaluate all options for budget reasons including used but don’t know exactly what to look for. I’m not opposed to piecing things together here and there if it helps over all cost and is a clear-ish path, but not really looking to build my own pump.

I see the veneer supplies kits and seem a like the Excel 3 or Excel 5 is at least the size I’d want?

https://www.veneersupplies.com/categories/Vacuum__Press__Items/Vacuum__Press__Kits/

Alternatively, the shop I apprenticed in has at least an extra setup with a Vacu-press pump (can’t remember what size, but must be at least 15-20 years old) and I think 4x8 platen and bag, but unsure of bag quality and material. They may be open to selling me one of the setups which could be convenient and local.

Assuming I want a poly bag over vinyl or? What thickness is needed? I see options for 20 mil and 30 mil bags on veneer supplies.com

I’m sure I’m leaving out important questions out of inexperience and trying to sort out what matters, what doesn’t and what some of the more nuanced parts are that are helpful to have in a small shop professional environment...any thoughts?

Thanks,

[Alan Lightstone]

I bought the assembled Veneer supplies pump a number of years ago. Works just great. No issues at all. Can't remember which version I bought.

[Mick Simon]

I can't help with specific recommendations for one brand vs the other. I use a Vacu-Press system at home and at school - both work well, even at 7000' altitude.
My one thought is based on something I plan to try. I currently use the retired outfeed table from my Sawstop to set up my bag. It takes up a lot of space. I'm going to wall-mount it with hinges and fold down legs. Takes wall space, but not floor space except when in use.

[Kevin Jenness]

Vacupress is a reliable source for pumps and bags as well as advice. Daryl Keil knows as much about vacuum pressing as anyone and the forum on their site, although not that active, is a valuable resource.

I have a couple of 1/4 hp Gast rotary vane pumps bought used for <$200 - they can be found on Ebay and industrial equipment sites - simple, long-lasting, not excessively loud and repairable. I added a vacuum switch and valve to the one I use for pressing which allows it to cycle on and off but I have run it continuously for hours numerous times without a problem. The other one I use for reverse turning on my lathe, and a pump is very useful for obstruction-free clamping of all sorts of parts.

Polyurethane bags are more flexible but 30 mil vinyl works fine and will last a long time. I have had a (well-patched) 54 x 108 vinyl bag for decades. The bag allows for fairly large volume curved forms (which require substantial internal bracing to resist implosion). For large curves a bag and laminates can be wrapped around an external form.

For flat and lightly curved work I made a wooden frame with polyurethane membrane that is hinged to a laminate-covered assembly table/platen. This is far easier to load than sliding layups in from the end of a bag. The frame lives in my plywood rack when not in use. Vacupress has a zippered bag available which should be equally easy to load.

I have set up my bag on a 40" x 84" torsion box with no problems. The 3/4" x 49" x 97" melamine base platen is stiff enough to remain flat despite the overhang.

[Phillip Mitchell]

Thanks for the replies and Kevin, for all the details as always.

Good to hear that I may have a chance putting a ~4x8 platen on my slightly undersized assembly table to start with until I get more space to work with in the future.

Is it reasonable to expect either a vinyl or poly bag to last for multiple decades in storage without degrading if kept indoors/rolled up properly and not physically ripped or damaged?

Heard back from my old shop boss on at least the pumps that they have. It’s a VLT 100 press with 49x97 platen and bag to fit. Not sure if it’s vinyl or poly but sounds like either way will work. I looked up the pump and it’s nearly 10 CFM, which seems huge / fast. I will likely go this route if I can get the setup for a reasonable price. The pump is probably 20 years old at least (and hasn’t been used in at least 12) but current day replacement cost on the VLT 100 is ~$1700 + with shipping.

I wish I had room for a frame table with integrated bag/lid. Looks like at awesome setup but no space currently, unfortunately.

Im open to any other suggestions and knowledge as well. Thanks!

[Richard Coers]

Vacupress is a reliable source for pumps and bags as well as advice. Daryl Keil knows as much about vacuum pressing as anyone and the forum on their site, although not that active, is a valuable resource.

I have a couple of 1/4 hp Gast rotary vane pumps bought used for <$200 - they can be found on Ebay and industrial equipment sites - simple, long-lasting, not excessively loud and repairable. I added a vacuum switch and valve to the one I use for pressing which allows it to cycle on and off but I have run it continuously for hours numerous times without a problem. The other one I use for reverse turning on my lathe, and a pump is very useful for obstruction-free clamping of all sorts of parts.

Polyurethane bags are more flexible but 30 mil vinyl works fine and will last a long time. I have had a (well-patched) 54 x 108 vinyl bag for decades. The bag allows for fairly large volume curved forms (which require substantial internal bracing to resist implosion). For large curves a bag and laminates can be wrapped around an external form.

For flat and lightly curved work I made a wooden frame with polyurethane membrane that is hinged to a laminate-covered assembly table/platen. This is far easier to load than sliding layups in from the end of a bag. The frame lives in my plywood rack when not in use. Vacupress has a zippered bag available which should be equally easy to load.

I have set up my bag on a 40" x 84" torsion box with no problems. The 3/4" x 49" x 97" melamine base platen is stiff enough to remain flat despite the overhang.
Another fan of Daryl. My wife was born in Maine so stopped by his shop and talked with him for advice. Bought his system about 20 years ago. Still using same bag and no issues with the pump over all that time.

[Kevin Jenness]

If you can get that vlt setup in running order for a decent price go for it. If stored out of the light the bag should be ok. The pump shown on the vlt site is a Gast rotary vane similar to mine and the 10cfm version is big enough to run several bags.

[Don Stephan]

Another poster is correct, the Vacupress forum is very quiet, but a TON of information there - read through all the discussions. I bought a Vacupress thinner vinyl bag and put together my own vacuum system, and have always regretted not spending the extra $ to get a VAcupress system.

If they are still available, Darryl Kiel's videos are very good and quite helpful. Contact Vacupress to inquire. Good luck.

[Mike Henderson]

You can get by without a bottom platen but use breather mesh (see Joe Woodworker for that). Then you can roll up your bag when not using it.

My advice is to buy a 4x8 as your first bag. You can put small stuff in a big bag but you can't put big stuff in a small bag. You may want to purchase a smaller bag later if you do a lot of veneering. The only negative of a big bag is that it takes longer to pull a vacuum initially.

Joe Woodworker also sells vacuum pumps and a kit to make it into a vacuum system for pressing. Check his site.

Mike

[Brian W Evans]

You can't go wrong with Joe Woodworker. I have the Excel 5 and it has done everything I asked of it for 6 years. I don't have a strong opinion about the bags, other than I am a "buy once - cry once" kind of guy. The poly bags are on sale right now, too. I agree with Mike that the big bag is the way to go, for the reasons he mentioned. Breather mesh is a must, and very cheap.

If space is an issue, maybe a Bora Centipede (https://www.woodcraft.com/products/centipede-4ft-x-8ft-unit-4-x-cups-4-quick-clamps-c-s-bag-bora) will work. I have a 4x8 version that I keep on a shelf for when I need a large work surface. It's light and takes up very little space when collapsed.

[Kevin Jenness]

There are differing ways of setting up and operating a vacuum press. I started out with and still use Daryl Keil's setup with a grooved 3/4" base platen made of melamine coated particleboard inside the bag. I use oversized 1/4" mcp cookie sheets under layups and top platens of the same material. This ensures full air evacuation and a smooth, stiff surface to press thin veneer flat to the substrate, and allows for sliding layups into the bag. I wax the platens to ease glue cleanup and throw a 6 mil pvc sheet over the load to keep glue off the bag. All sharp edges and corners are eased to prolong bag life. A patch kit often comes in handy.

Some people omit the platens and cookie sheets and just use breather mesh. Whatever the setup it's fundamental to have a flat base and to pull uniform vacuum by avoiding air pockets.

If using pva glue you need to work efficiently and get pressure on the glueline as quickly as possible. I use a Klebo canister glue spreader and a re-usable roller with pva to get a uniform smooth spread on quickly. With catalyzed adhesives I use a disposable foam roller.

A full size table or sheet under the bag minimizes bag sag and keeps drawdown time to a minimum. When using a curved form a vacuum cleaner can help with the initial air evacuation. Throughput can be increased by using an electric blanket, especially with catalyzed glues and in colder conditions.

[Mitch schiffer]

Another vote for vaccupress. They can help you get what you need even if your not really sure. Just give them a call and tell them what your plans are. I have been happy with everything I have gotten from them.

[Mike King]

Rather than going all in on a top of the line vacuum setup, you might consider first trying your hand at it. You can achieve just as good of results using clothing storage bags with the hand pump that draws a vacuum. If you find that you need much larger capabilities and are using the technique frequently, you can later spend the big bucks to get a large bag and pump.

Just my 2 cents.

[Phillip Mitchell]

I understand that sentiment. I have been thinking about adding in a vac pump/bag for a couple years now but had mostly written it off prior due to perceived cost and lack of space. Looking a bit deeper now, I’m seeing that it’s a little more reasonable than what I had in my head initially.

There is no doubt that a vac setup will be a game changer in general, as well as for some existing and upcoming projects that I have booked, and immediately add value and efficiency to my work. I do this professionally full time and generally want to go straight to a place of equipment/setup that makes sense long term and is going to give me the (reasonably) best chance of success. I don’t really have extra time and patience in this particular area to experiment with a home brew solution and would rather start with the best that I can afford and know that it’s proven and well supported.

For curious/hobby use, I can agree with easing into it with a homemade setup.

[Jim Becker]

It was a long time ago, but I obtained a surplus Gast vacuum pump when I was setting up to do vacuum bag veneer, etc. As long as the unit meets the minimum specs for the application that resources indicate are needed to do the job and has the voltage/amperage setup supportable by your shop, (mine is 120v), you're good to go.

[Robert Engel]

I have an vacuum pump for AC use, I've been told it will work, but I've never tried it.

I think its worth looking for used pumps, as they can be quite expensive and hard to justify if you don't use much.

[Jim Morgan]

What is an "mcp cookie sheet?"

[Kevin Jenness]

What is an "mcp cookie sheet?"

A piece of melamine coated particleboard under the layup, atop the grooved base platen.

[Kevin Jenness]

I have an vacuum pump for AC use, I've been told it will work, but I've never tried it.

I think its worth looking for used pumps, as they can be quite expensive and hard to justify if you don't use much.

AC pumps are typically very high vacuum low volume units. For veneer pressing you want a pump that will draw at least 2cfm at >20" hg.

[Dwayne Watt]

The inexpensive, yet very effective route is a hand pump or a venturi pump. I have a venturi setup and can evacuate my roughly 4' x 4' bag in less than 2 minutes using a pancake air compressor. I have used this a total of 6 times in the 10 -12 years that I have owned it. The investment was about perfect in my case. Unless one has plans to veneer pieces on a near daily basis, there is little need to invest in a vacuum pump. Of course, that same or similar pump could potentially be used to power a vacuum chuck if you are a wood turner.

[Jeff Roltgen]

Anyone using a bag system, regardless of vacuum source: have your shop-vac at the ready. Once bag is closed, manually hold vac-hose over nipple on the vacuum bag. (Festool's rubber hose fitting is particularly good at this) It will empty a 4x8' bag in 10-15 seconds, even registering a few inches of pull. Now do a fast swap back to actual vac-pump fitting, and things will be snug in seconds, not minutes.

The faster you can get those veneers snugged down, the higher the likelihood of a very successful bond.

I use a Vacu-press air powered (venturi) style, which is very good in and of itself, but once I discovered this trick, I employ it every time. Especially helpful with the volume of air involved with bent-laminations and other various types of formers.

jeff

[Jim Becker]

That's kewel tip, Jeff!!

[Don Stephan]

A 3/4" bottom platen offers the best chance for a flat pressing to be truly flat. Breather mesh without a 3/4" bottom platen doesn't offer the same likelihood for a flat pressing to be truly flat. To each their own.

[Bruce Wrenn]

AC pumps are typically very high vacuum low volume units. For veneer pressing you want a pump that will draw at least 2cfm at >20" hg.


The ones I have pull about 6 CFM. Main thing is some kind of filter between bag and pump, as it will suck in glue vapors. For Venturi pumps, go to Air-Vac Engineering's web site. Their AVR093H is the basis for many small commercial systems.

[Kevin Jenness]

The ones I have pull about 6 CFM. Main thing is some kind of filter between bag and pump, as it will suck in glue vapors. For Venturi pumps, go to Air-Vac Engineering's web site. Their AVR093H is the basis for many small commercial systems.

My mistake. Thanks for setting me straight.

[Mike Henderson]

The CFM is mainly an issue of how fast you can get the air out of the bag after you turn the vacuum pump on. Once you have vacuum pulled, a very small pump will maintain it.

If you have a low CFM pump, you can use your shop vac to pull the initial air out, and then quickly switch over to your vacuum pump.

The reason you want to pull vacuum fairly quickly is that we often use water based glue and only apply it to the substrate. Once we lay the veneer on the substrate the veneer starts absorbing the water and will expand or otherwise cause problems. So the process is, roll your glue on the substrate, lay the veneer on and put blue tape to keep it in place, put a caul on top and get it into the bag as quick as you can. A helper is good to have to hold the bag open as you slide the work in.

Then close the opening and hook up your vacuum pump. Once the vacuum is pulled, the veneer is not going to cause problems so you want to get the work under vacuum as quickly as possible.

Mike

[Mike King]

The CFM is mainly an issue of how fast you can get the air out of the bag after you turn the vacuum pump on. Once you have vacuum pulled, a very small pump will maintain it.

If you have a low CFM pump, you can use your shop vac to pull the initial air out, and then quickly switch over to your vacuum pump.

The reason you want to pull vacuum fairly quickly is that we often use water based glue and only apply it to the substrate. Once we lay the veneer on the substrate the veneer starts absorbing the water and will expand or otherwise cause problems. So the process is, roll your glue on the substrate, lay the veneer on and put blue tape to keep it in place, put a caul on top and get it into the bag as quick as you can. A helper is good to have to hold the bag open as you slide the work in.

Then close the opening and hook up your vacuum pump. Once the vacuum is pulled, the veneer is not going to cause problems so you want to get the work under vacuum as quickly as possible.

Mike

Note that PVA glues (water based) will not dry in the vacuum bag. They will become more stable, but they will need to dry and set when you remove them from the vacuum and expose them to an atmosphere that allows the water to flash. So, be careful about your adhesive, the time in the bag, and as importantly the time out of the bag to allow them to set before working the resulting piece.