Replies

1. 
   Hempstalk | Jul 31, 2002 09:17pm | #1

   s4s.  A few years ago I needed a vacuum system for a job I did.  There's much to learn about these systems.  It's best to know exactly what you want to do with it now and in the future.  This will help you decide.   There's too much to cover in a post.  Sorry I don't have to much time.  Busy in the shop but I don't mind to help get you started.  There's three basic systems. Electric, air powered automatic, air powered venturi.  If your on a budget a venturi is the cheapest by far.  If money is somewhat of a concern you can get a automatic air powered.  A venturi run continually while pressing.  No good if you have to leave something in the press overnight.  Your compressor will run lots.  Oh yea that's if you have a big compressor already.  They hog air.  On the flip side they work well for vacuum clamping.  An automatic air powered has a pressure switch that shuts off the air flow when a preset vacuum is reached in the press.  This saves the compressor from running too much.  The electric is the most expensive but in my opinion the most flexible.  First you can use the press anywhere with no need for a compressor.  They can press and clamp and you can get many accessories.  Now if you decide on an electric there are still many paths to choose.  The cheapest way would be to pick up a used pump on e-bay or from a used supplier.  You can then buy a separate controller and assemble the whole unit and your in business.  It's fairly straight forward.  Or you can opt to buy one that's ready to go.  They come in a nice box with quick attachments and gauges mounted in the face of the case.  Also many suppliers offer slightly modified pumps to deal with the condensation in water based glues.  Something to keep in mind.  These pumps also come in a few sized to meet different demands.  Rated in cfm they commonly come in 5 and 10 cfm.  5 is plenty for the home of professional shop with a need to press occasionally.  10 is for high production industry use or if you want to run multiple presses ect.  The last and very popular choice in electric pumps is a diaphragm pump.  These are small cheap and made to run continually with no overheating.  Their downside is they are very slow. .75 cfm.  Which means the glue on your press could set before you even get a vacuum on you bag.  For small items and clamping their fantastic.  This is where knowing how often and what you will use the pump for come into play.

      The bags or frames is another area all together.  The bags come in vinal for light use or poly for heavy use.  They also come in a range of thicknesses for different applications.  Again there is a cheaper route.  Make your own.  You can get vinal at a plastic supplier and glue your own bag together.  The benefit is you can make multiple bags of different sizes for different applications at about the same cost as one commercial bag.  One other note is some supplies offer a seamless bag in 20mil poly.  Definitely worth considering.  No seam leaks

     Now cost.  A 5cfm system with a poly bag will cost you about $1200.00.  Different suppliers different cost.  This is just a rough idea.  I paid $1500 Canadian including taxes and shipping to my door.   A small diaphram pump and vinal bag would run under $400.  I think.  They usually have them all packaged as a beginner setup.  Cost can change with your choice of pump type and size of bag and what material the bag in made of.

     There's more to know as well but this should get you started and Im tired of typing.  Got to get in the shop.  I'm pressing some figured maple for a dining table today.

     One last thing.  Check out Vacuum Pressing Systems, Mercury presses and Quality VAK Products.  As well as Vac-U-Clamp.  These places all sell quality equipment and can answer your future questions with more knowledge than I can.  They all have web sites and ,all but Vac-U-clamp, advertise in Fine Woodworking.

1. 
   AlanTurner | Aug 01, 2002 05:36pm | #2

   Wow; what a helpful post you gave me.  Thanks.  I am looking at the suppliers you mentioned.  My current needs are pretty modest in terms of frequency of use, but perhaps I will fall in love with it; who knows.  Mostly I build build furniture, not smaller things.  Resawing is a somewhat new thing for me since I put a riser on my Delta 14" bandsaw, and kicked up the HP to 1.5. 

   Any comments about glue?  All these companies pus the Unibond 800.  A gallon would last me a decade.  Is titebond OK for a flat panel - drawer front?

1. 
   Hempstalk | Aug 01, 2002 07:57pm | #3

   s4s Tightbond is ok.  Keep in mind that water based glues wont cure in the press.  The water needs to evaporate to fully cure.  They will set enough to take the item out of the press and then it can fully cure.  The veneer will also absorb some of the water.  These glues work good for commercial veneers.  I would recommend having some urea resin glue on hand (unibond ect.).  The advantage of this glue is it cures with a chemical reaction.  It will in time fully cure in the bag.  If you intend to do any thin strip laminations this is the glue to use.  If a pva glue is used the stress of the curve in the lamination will case your work to delaminated before the glue fully cures.  Trust me I know.  Not nice to see your hard work self destructing.  Urea resin glues when dry also form a very rigid glue line which will result in less spring back.  It also allows more open time which translates into more screwing around time and less sweating as you press your precious shop saw veneers.  I use a urea resin glue most of the time unless I'm pressing small panels.  One last thing.  I recently found a new catalyst for the urea glue.  Usually you mix a powder acid hardener with the resin creating a tan colored glue.  The new catalyst is a liquid.  You apply it to one surface and let it dry.  You then spread just the resin on the other surface.  The biggest advantage is the dry time 20 min to 1 hr as opposed to 4hrs to 8hrs.  It also drys clear instead of tan colored.  Which reminds me you can use those Transtint dyes to color your glue to match the veneers your using since it's common for the vacuum to pull glue through the pores of the veneers when pressing.  Sorry I don't know the name of this  chemical right now but I'm sure if ask around someone will be able to fill you in.  You will get hooked of the press.  It's a very different and cool woodworking tool.

1. 
   AlanTurner | Aug 02, 2002 03:56pm | #4

   Two more questions on glues. First, will I get bleed through if the veneer is 3/16 - 1/4" thick? Second, as to chemical reaction drying, I have some west system epoxy I used on some exterior garden bences. Worked great. Can I use this?

1. 
   Andrew | Aug 05, 2002 02:56am | #5

   no, you won't get bleedthrough on veneer that thick. if I were you I would go a bit thinner, maybe 3/32 or 1/8. 1/4 is extremely thick for veneer, and remember, you'll have to put 1/4" veneer on the back to stabilize it. one more thing. one of the handiest things when your veneering is a paint roller. with little practice you can apply an even thin layer of glue very quickly which is handy because you want to get the veneer on the panel and in the press as quickly as possible. hope this helps

   andrew

2. 
   AlanTurner | Aug 05, 2002 01:27pm | #6

   Will I need ot back veneer if the base is cherry, and the veneer is flame grain cherry?  Both the same type of wood.

3. 
   Hempstalk | Aug 05, 2002 10:18pm | #7

   s4s

      Sure you can use your epoxy.  I also have some kicking around waiting for a use.  Left over from a cedar strip canoe.  There is a few drawbacks to using it though. First it will stick to your vacuum bag as well as your project.  If it dries before you can remove it it can be problematic.  It could cause problem with future pressing.  Damaging your work or bag.  This of course is a worst case but be aware of it. I would recommend placing a piece of thin plastic like a cheap painting drop cloth or something similar between you work and the bag.  It will save you a lot of cleaning.  I've done at least a twenty pressings before your start to see any glue in the bag.  Second it costs a lot more that Urea glues (around here at least) and if you don't plan on submerging your project under water it isn't necessary.   If you plan on gluing metal to wood it would be a good choice.

      3/16" to 1/4" veneer is too thick.  I know it's a pain to try to get veneer thinner (especially figured woods) without a abrasive sander but it is necessary.  Veneer this thick is likely to cause you problems.  Now if this is a project for your self you could risk it but if this is for a client don't.  If your gluing to other solid woods your a little safer in that both the substrate and the veneer will move but figured wood onto unfigured would worry me a little at this thickness.  Figure woods tend to react a little different because of the grain structure.  You could try but it may fail in time.  Some will agree some will not but it may need repair in time which won't be fun.  I use shop sawn veneers always unless the species is hard to get or extremely expensive in solid form.  I rough saw the veneers to 1/8" then sand with a thickness sander until all the saw marks are gone.  Then the pieces are matched and glued into a panel.  The panel is sanded to 3/32" or close then glued to the substrate.  After any borders or inlays are done the top is finished sanded with scrapers and orbital sanders with should bring the veneer to around 1/16" thick.  This is just one approach which works well for me.   Some of the commercial cut veneers are quite thin before you even start to sand.  The vacuum will remove all the air from the bag even the air in the cells of the wood to a degree which will draw glue though the veneer.  Even your epoxy.  The trick is the right amount of glue.  The use of a paint roller like perviously mentioned will help a lot.  If you end up doing a lot of large table tops a commercial glue spreader would be worth having.

4. 
   AlanTurner | Aug 05, 2002 11:04pm | #8

   Thanks for the info. I do have a 36" thickness sander, which these days does not get much use, but I can certainly crank it up. The piece is for me; I am not a professional.