Vacuum Press

[Don Abele]

I'm getting ready to finally build my kitchen table. I have some awesome looking curly maple that I'll use for the field of the table and wrap it with some walnut. I cut the maple into 1/8" thick "veneers" - it's the only way I could make the most of the one board I found. I chose to use a thick veneer as it's a kitchen table and with my 2 small girls, it'll take a lot of abuse and I don't want a thin veneer that will chip (like our current table). The maple will get glued to baltic birch as a substrate.

After talking with several people, most have suggested using a urea resin glue (specifically unibond 800) and a vacuum press.

I don't own a press and was directed to http://www.joewoodworker.com for parts and instructions to build my own. They have a neat concept for using an air compressor in a venturi effect to draw the vacuum. Since I just bought an IR compressor, this seems like a very cost effective method (and good use of my new compressor).

Anyone have experience with this type of press? Or have any other words of wisdom on the project or vacuum presses?

I also plan on buying the sheet vinyl from them and making my own bags, again, any advice?

Thanks.

[Chris Padilla]

What are the dimensions of the "veneers" you will be gluing up?

For something that thick (1/8"), I'd just use normal yellow glue or most likely, I'd use Gorilla Glue (or a poly) and just weight the top with cinder blocks and scrap wood. I'm not sure why a vacuum press is needed. What have the "several people" said about why they'd use a vacuum press? I'm very curious.

I've made lots of laminations of plywood (albeit 3/4" on 3/4") and poly glue is my favorite to use. I just slather it on, mate the two pieces, add cauls and Bessey's or top it with scrap to protect it and toss cinder blocks on the whole thing and then ignore it for a day.

In fact, this is my very plan for the many $$$s worth of figured maple I've been accumulating for the entertainment center.

[Don Abele]

Chris, the veneers are each 6 inches wide by 48 inches long. Here are what several others (from here, another forum, my local woodcraft, and from an online veneering place) specifically said:

- Yellow glue will creep, even with wood 1/8" thick. Of course, I was also told that using poly or urea glue may lead to splitting from wood movement.

- Poly glue will make a mess with the foaming and possibly cause problems with the joints (right in the middle of the table) and it's expensive for a glue-up this size.

- With the overall size of the glued up top (36 x 48), it would be very difficult to exert enough equal force to ensure a complete bond throughout the entire surface.

[Jim Becker]

Don, I've seen venturi devices advertized for vacuum applications. It's an effective way to get a vaccum inexpensively, athough noisy. I think it would be fine for occasional use, but a pump is what you want if you plan on using veneer as a regular part of your projects. You might want to PM Dave Avery as he's often posted about vacuum veneering here, but hasn't been around much lately.

[Bob Hovde]

Doc,

Type of glue aside, I assume you've dimensioned the 1/8 in. thickness exactly (planner, sander). Otherwise, any clamping system, including a vacuum system, would have trouble exerting even pressure across each joint.

Bob

[Don Abele]

Jim, thanks - I'll send Dave a PM. I read about the noise and don't think that's really all that big of an issue. I've never done any veneering in the past and can't say I will do it very often in the future, so this is for a single project and the possibility of maybe onesies and twosies here and there.

Bob, yes, all the pieces are exactly 1/8". For any possible uneveness though, I will make a platen that has cork on one side which will help even things out. David Marks (DIY Woodworks) does it this way all the time. Though I did ensure they are sized exactly so this is just a precaution.

[jerry cousins]

hi don - i'm presently using a straight vacuum pump for veneering - but originally i bought a venturi pump from joewoodworker. it worked well for "once in awhile" pressings - but now am doing lots and lots of pressings. it does put a demand on the compressor. i used it just a few times and now it sits in the corner of the shop.
i tried to attach some pictures - but if it didn't work can send them to you and would be willing to work a deal. if you're interested send me an e-mail.

as to the glue - i use cold press veneer glue - lee valley has it and so does joe woodworker - not very much bleed through and very stabile. i use homemade veneers at 5/64's - and so far pressings have been successful.

jerry

[Don Abele]

Jerry...just sent you a PM. Once in a while pressing is probably all I'll ever do so I'd rather not invest the $200+ in a pump if the $50 venturi will work. As for demand on the compressor, I just bought a 60 gallon ingersoll rand compressor which I'm sure will be more than able to handle this (I used it last weekend to sandblast for over 2 hours, no problem).

As for glue, I was told that cold press can still be subject to creep and that's why they recommended a urea resin glue (like unibond 800). Cold press is $21 a gallon, unibond $22 a half gallon.

[jerry cousins]

hi doc - pictures waiting for you at home.

jerry

[Chris Padilla]

Chris, the veneers are each 6 inches wide by 48 inches long. Here are what several others (from here, another forum, my local woodcraft, and from an online veneering place) specifically said:

- Yellow glue will creep, even with wood 1/8" thick. Of course, I was also told that using poly or urea glue may lead to splitting from wood movement.

- Poly glue will make a mess with the foaming and possibly cause problems with the joints (right in the middle of the table) and it's expensive for a glue-up this size.

- With the overall size of the glued up top (36 x 48), it would be very difficult to exert enough equal force to ensure a complete bond throughout the entire surface.
Ah, I understand now and misunderstood what you were doing (the tabletop). My application will be panels for door and drawer fronts so nothing near as large as a table top.

Still, I wonder if it makes any sense (or saves any money or is easier) to make up panels of your homemade plywood and then edge glue them as if they were boards? I've edge glued plywood in the past very successfully.

However, it sure seems nice to give these veneers a solid continuous backing. I dunno...just more food for thought.

BTW, can someone explain exactly what creep means for glue? Does this mean one can actually see the glue through the wood (blotches??) or is it for where the joints of the veneers meet up? :confused:

[Don Abele]

Chris, my understanding of creep is wood movement. Since yellow glue remains somewhat flexible, it allows the veneer to "slip" over the wood substrate. This could cause gaps or exposed edges when it slides. Of course, I was told this is more pronounced with thin veneers and that I would probably not see it, especially since the entire veneer/ply substrate will be banded with solid walnut. I plan on using the urea to ensure it doesn't move and to provide the tightest bond possible. With our 2 girls, our kitchen table takes a lot of abuse.

For a substrate I'm using baltic birch that I will also be gluing up. A 3/8" and 1/2" piece together, so when the "veneers" are added, total thickness will be 1". The substrate will get done first, allowed to dry, then I'll add the veneers, cut to size and then wrap with walnut. The base is going to be reused from our current table, black wrought iron.

For a finish I am planning on tung/danish oil to pop the grain, seal with shellac, and then topcoat/protect with several coats of water based poly. (I read that "formula" somewhere here).

Thanks Jerry, I'll check them out when I get home and get back to you.

[Jamie Buxton]

Chris --

Creep is an unusual phenomenon in certain "solid" substances. If kept under stress, the "solid" substance flows. Most solids don't do this -- metals, wood, stone, etc. A few plastics creep, but not all. PVA is one that creeps.

In a lot of glue joints, PVA creep is of no consequence. In these joints, the glue is not under constant stress. For instance, consider holding a commercial veneer on to a substrate. The veneer is only 20 thousandths of a inch thick, and therefore can't extert enough stress to make the PVA creep. Or for another instance, consider a good mortise & tenon joint. The joint almost holds togther without any glue. After the joint is glued up, there is really very little stress on the glue. That is, you can safely use PVA for almost all of your woodworking.

In contrast, consider a bent lamination. In this joint, you bend thicker laminates into shape and glue them together. The only thing holding the bend is the glue. That is, the glue line is under stress 24/7/365. PVA may well creep in this use. The result may be that the bend shape changes, or the cured glue may extrude very slightly out the side of the joint. For bent laminations, use a non-creeping glue like urea-formaldehyde or epoxy.

Jamie

[Chris Padilla]

Uh, what is PVA? :) Poly vinyl adhesive? Pressure veneer ? sorry....

[Don Abele]

PolyVinyl Acetate - white glue.

[Jamie Buxton]

PolyVinyl Acetate - white glue.

Yeah, poly vinyl acetate. It is white glue (good ol 'Elmer's Glue-all), yellow glue (Titebond, Elmer's Carpenters, and generic yellow carpenters glues), and even (sorta) Titebond II and III. Those water-resistant yellow glues are fundamentally PVA, but modified somewhat to be water-resistant. They all have PVA's creep behavior. (Of course, if you're exposing wood to water enough that you need waterproof glue, creep is a lesser issue than wood movement.)

[Chris Padilla]

Ah, thanks for the explanation! I still remember being wowed as a kind when I learned that glass techinically isn't a solid...it is a liquid. Old glass in old houses tends to be thicker at the bottom than at top. The explanation of creep reminded me of this little fact.

[Paul Downes]

Hey Don, You have inspired me to perhaps use the gun stock blank my Father-in-law sawed for me too narrow to use for a gun stock! (3"x6"x8') It is premium curl maple and has been sitting in the barn these last 5 yrs. How are you going to do the edge fit ups between the 1/8 veneers? Do you joint and then edge sand them? I have wondered about this because of the different densities of the wood grain. I have a stock pile of figured maple; quilt, curl, and birdseye, and have only used small pieces so far. I don't have a thickness sander yet and a little leary of tearout. Did you resaw and then thickness the boards with a planer, or use a sander?

[Dave Avery]

Doc,

Here goes...... good advice from the other on-line sources/Woodcraft.

I use Titebond Cold Press and have had 1 failure in 50+ pressings, and I think that was due to the type of veneer and finish applied. Most knowledgeable people think urea resin is the best, but most difficult to work with from a health perspective - use a respirator and protective equipment.

Venturi system will work well for you.... particularly with the IR compressor and if noise is not an issue. Count on a full 2 hours press time for max adhesion and glue dry time.

Biggest potential issue that I see is the thickness of the veneer. I use 1/42 commercially cut stuff...... very difficult to work with and seam, but not prone to wood movement. From my research on the subject, 3/16 thick veneer is about the max thickness that you should go before beginning to need to worry about wood movement. Obviously, wood movement and a rigid glue line would be a disaster. My guess, and it's just a guess, is that you'd be OK unless the table is going to be subject to significant swings in seasonal humidity, but only time will tell.

Best of luck......

And, yes, Mr. Becker, I've been a little scarce lately. Big new job (nice promotion)....... new people and difficult learning curve means too little shop time and even less posting time. I still cruise and view a little, and even had intended to answer Doc's post initially, I just got interrupted. Hope to be back more actively soon. Dave.

[Don Abele]

Dave, thanks for the reply. I am very protective in the shop and will heed your advice for the unibond and ensure respirator and excellent ventillation are in place. Thanks also for the reassurance on the venturi press. As for veneer thickness, I also read that about 3/16" being max, which is why I went with 1/8" hopefully that 1/16 of an inch will be to my advantage. As you said, time will tell. I'm hoping with the complete sealing of the bottom with the unibond and complete sealing of the top/sides with poly that any humidity shifts will be kept to a much smaller degree (hopefully to prevent any cracks).

Paul, I resawed my boards on the bandsaw and then ran them through the thickness planer making VERY shallow cuts using just sharpened blades. Even with that I got some slight tear out - I plan on taking care of that after glue-up with a cabinet scraper. As for jointing the edges, the board was well jointed before resawing and afterwards they were still straight and tight. I imagine if I had to I could still run them through the jointer taking VERY shallow cuts.

Thanks all so far for all the great information. I'll probably get the stuff on order early next week to get the project going in a couple of weeks. Any additional advice in the mean time is appreciated.

[Jim Becker]

And, yes, Mr. Becker, I've been a little scarce lately. Big new job (nice promotion)....... new people and difficult learning curve means too little shop time and even less posting time.
Congratulations, Dave!! That's great news. Once you get things settled down, you can get back to the important stuff here at SMC and in your shop...hee hee :D

[Mark C.]

Hi Don -

This is just my first post here, so I hope you don't mind if I make a couple of comments for you to think about.

If you haven't already, then please do just a little research about the type of venturi pump you get. Basically, there is a single stage pump and a multi-stage. The single stage has a single orifice, is loud, and is terribly inefficient. A muti-stage has multiple nozzles where the air going into the first nozzle creates vacuum (low pressure drop) and then enters another nozzle (or set of nozzles), creating further vacuum (level/flow depending on the engineered characteristics of the nozzle). A multi-stage pump can have two nozzles, three, even four meaning that for each unit of air going in you get two, three, four, etc. units of vacuum bring generated. Much more efficient and quieter. The drawback is that they are more expensive, though you'll recapture a lot in efficiency, and for the prices I have seen retail for a lot of these pumps (almost all are single stage) I think you can do better if you go wholesale. Check the website www.piab.com, learn a little more, and then contact one of their distributors - a lot will sell to an individual who just asks.

Also, check the air consumption of the unit you buy and compare it to what your compressor can handle. Some brands have several different models which will give you different vacuum levels and flows. In a sealed application, you aren't really concerned about a high flow pump unless there is leakage or you need to evacuate it quickly. Less flow through the pump means less air consumption demands and a lower cost pump to boot.

A friend of mine used one of these pumps to vacuum bag a recoring job on a boat and it worked very well, which tells you they can handle big jobs when sized right. You can even add a switch so that it shuts off the air supply so that - once the bag is evacuated - it only gives a shot of air to keep the vacuum level up past a preset point, meaning the compressor will rarely turn on. However, now you're adding $$....

I hope the above doesn't complicate things for you, but rather just adds a few ideas to consider. Of course, if you will rarely use it, then the cheap inefficient one might be just fine for your needs. I haven't checked the website you listed so maybe you've already covered this all. I just cringe when I see some of the prices out there for inefficient and noisy pumps when I know there are other options available. Sorry for jumping in here. As a new poster, I would rather just ask questions for awhile :o

- Mark

P.S. Since I first registered here, it looks like most people use their last names for their user ID. Should I be doing that, and if so, how do I change it?

[Jim Becker]

P.S. Since I first registered here, it looks like most people use their last names for their user ID. Should I be doing that, and if so, how do I change it?
Just send Jackie Outten a PM with the correct last name to be added. SMC is a "real names" community, so yes, you'll want that fixed. And Welcome!! Do a thread to introduce yourself to the boys and girls! (with pictures...hee hee)

[Robert Ducharme]

Mark, I also give you a big howdy do. Welcome.

[Don Abele]

Mark, welcome to the creek and thanks for your suggestions. The unit that I am looking at requires 4.2 CFM at 90 psi to produce maximum vacuum (28" Hg). My new Ingersol compressor is 60 gallons and can put out 11.3 CFM at 90 psi - so I have no worries there. As for noise, the shop is well insulated from the outside and rest of the house so I'm not concerned. I'll just were muffs while in there. I have gotten information from several others that use this type of venturi with positive results, albeit slow to draw from a large bag.

I did look at piab (it's a listed site on joewoodworker), as well as several others. While they may have more efficient models, the cost brings them up there with the price of a stand-alone vacuum pump. As this could very well be for a single project only (or maybe an occasional one here and there), I don't want to spend too much for it. Oddly enough, most of the stuff required to build this, I already have laying around the shop. I basically only need to buy the venturi pump, pressure controller, and mac valve (less than $75 total). Oh, and the material to make a bag.

Once I get everything I'll be sure and let all know how it works. Again, welcome to the creek and thanks.

[Mac McAtee]

I have been turning over an idea for a very, very simple vacuum pump for about a year now.

Say you take a piece of 2" Sch. 40 PVC pipe about 8 ft. long. On one end you weld on a cap. In the cap you drill and tap 3/8" female pipe thread. Put some kind of connector in that hole, hose barb or what have you. Hook a hose and a few of valves. One valve goes to the hose that ataches to the vacuum bag, one valve to atmosphere. You suspend this pipe so the bottom, open end, is ca. 8 ft above the ground.

Make a piston that would fit into the pipe and seal. On the piston you put an eye bolt. To the eye bolt you attach a flexible wire 8 ft. + long.

Now, you open the valve to atmosphere and close the valve to the vacuum bag. Take a ramrod and push the piston to the top of the pipe. Close the atmospheric valve and open the valve on the hose to the vacuum bag.

Then on the end of the wire you hook a five gallon plastic bucket. You put sand in the bucket, adjust the amount as needed. The weight of the sand would cause the bucket to drop. As it dropped it would pull the air out of the vacuum bag. The amount of sand (weight) would determine how much vacuum was produced. If, due to leaks, the bucket hit the floor you fix the leaks. Then close the valve to the vacuum bag, open the atmospheric valve and shove the position back to the top. Close the atmospheric valve, open the bag valve and let go the bucket again. When you have sucked all the air out of the bag, and fixed leaks, the bucket would stop dropping and hold a vacuum. Again, more sand = more vacuum.

Why wouldn't this work? No electricity, no venturis. No nothing but some cheap PVC pipe and some kind of seals to make the piston vacuum tight.

[Jamie Buxton]

I have been turning over an idea for a very, very simple vacuum pump for about a year now.



Mac --
One problem might be this: air expands as the pressure drops. You can only remove the cylinder's volume of air on each stroke. But because the air expands, you remove fewer and fewer gas molecules with each stroke. The same effect -- but in reverse -- can be seen in using a hand pump to pump up a bicycle tire. To go from 5psi to 10 psi isn't too difficult, but to go from 80 psi to 85 psi takes lots and lots of strokes.
My guess is that your pump will initially remove a lot of air pretty easily, but you'll find that the getting the last few psi is a lot of work. (In addition, the leaks get worse as the pressure in the bad gets lower, so again that causes more work near the higher vacuum.)
Jamie