Making Your Own Plywood
#11
Huh?  Why would anyone want to make their own plywood?  Well, if you need relatively small pieces of something special, thickness and/or species, it becomes about the only way to get what you need.  I've been making wood gear clocks the past few months, and some of them use 2, 3, 4, 6, 8, and 12 mm plywood.  You can substiture 1/8", 1/4", 3/8" and 1/2", but it's really hard to find 2 and 4 mm, and it's difficult to get cherry or walnut in all of those thicknesses.  If you want to mix species within the plywood then you are really out of luck.  

Fortunately, I've been veneering MDF and plywood substrates for many years and have the equipment to do so.  The leap to laying up all the plies to make my own plywood was a pretty small one.  I start by taking the desired final thickness and dividing by 3 for the thin stuff, like 2 and 3 mm, and by 5 for the thicker ones.  Then I slice shop sawn veneer and drum sand it until those plies are just a little thicker than desired, maybe 0.005".  I'm making some 8 mm plywood right now, so the plies are 1.6 mm (0.063") thick, plus 0.005".  After drum sanding the plies, I cut the cross-band pieces to length.  Here's a photo of one of the cross plies for a 30 x 14" piece.  

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I seam it just like any other veneer assembly.  Then I flip it over, fold the joints open, run a bead of yellow glue in the seams, fold it shut, and scrape off the excess.  Then I lay them on a sheet of plastic and put a flat piece of sheet goods on top and some weight, so the joints stay flat.  

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I let the taped, glued plies dry for at least a couple of hours, then run them through the drum sander to remove the veneer tape, which would interfere with the plywood layup.  Now you understand why I had to glue the seams.  

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To layup a panel, I put the bottom layer on a sheet of plastic and spread the glue on it using a serrated plastic scraper.  Here I'm using TB II with 5% water added to it to increase the open time.  

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I apply glue only to one side, then add the next layer and repeat until all five layers are done.  With the top layer in place I put a couple of pieces of tape on the ends to hold the plies from shifting as I slide everything into the vacuum bag.  

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There is a piece of heavy-duty window screen on the bottom and top of the glue up to allow the vacuum to find every nock and cranny.  With yellow glues I leave it in the vacuum bag for a couple of hours.  It doesn't really dry in the bag but the water in the glue migrates into the wood so it sets up.  When I take it out of the bag I put the glue-up on a flat surface, cover it with a piece of plywood and put some weight on top so it will cure flat.  I leave it like that overnight and then let it cure for at least another day before drum sanding it to final thickness.   

The glue-up I showed has cherry on the outside and center ply, with ash in the cross layers.  I wouldn't want to try this for anything much larger than 2 x 5 ft, since my drum sander is 24" wide and 5' is about the limit of my vacuum bag, but if you have larger equipment and some help it certainly would be possible with a slower setting glue.  

John
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#12
I've never seen veneer taped and glued that way.
I and all others I've seen doing veneer, always taped, applied glue, applied glue to the substrate, flipped the veneer over and applied, then weighted it down.
Steve

Missouri






 
The Revos apparently are designed to clamp railroad ties and pull together horrifically prepared joints
WaterlooMark 02/9/2020








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#13
Thank you John for taking the time to document that.
I have made my own very thin plywood in small batches (4" wide by about 2' long) to make business card holders in the past. a little less than 3/16" thick total. I always used blue painters tape for the seams. After the inner cross banded seem is edge glued together I remove the tape before laminating the three plys together between a couple MDF planks with lots of clamps. Is there some advantage to using the paper tape when it is going to be removed right away?
Proud maker of large quantities of sawdust......oh, and the occasional project!
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#14
(01-24-2023, 09:55 PM)Stwood_ Wrote: I've never seen veneer taped and glued that way.
I and all others I've seen doing veneer, always taped, applied glue, applied glue to the substrate, flipped the veneer over and applied, then weighted it down.

Not sure I understand what you mean.  The way I taped the veneer is in almost every book/article I've seen on the subject.  Small pieces across the seams first, followed by a piece the full length of the seam.  Some people first tape the other side with blue tape, then flip it over to apply the veneer tape.  I've found that unnecessary if the seams fit well. 

I never apply glue to the veneer, only the substrate, when doing conventional veneering on a thick substrate.  Making the plywood, however, requires applying glue to each layer, but again, only one side.  Standard stuff.  If you don't have a vacuum bag or other means to apply a lot of pressure, evenly, then I can see why gluing both sides might be beneficial, but you would have to work very quickly to keep the veneer from curling, as I have to making the plywood.  

John
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#15
(01-25-2023, 06:58 AM)KyleD Wrote: Thank you John for taking the time to document that.
I have made my own very thin plywood in small batches (4" wide by about 2' long) to make business card holders in the past. a little less than 3/16" thick total. I always used blue painters tape for the seams. After the inner cross banded seem is edge glued together, I remove the tape before laminating the three plies together between a couple MDF planks with lots of clamps. Is there some advantage to using the paper tape when it is going to be removed right away?

The only advantage of using paper tape on the inner plies is if the seams don't fit perfectly tight.  I find the blue painters tape not to hold very well if you have to pull the seams together.  After a few frustrating experiences, I've just taken to using the paper tape on everything.  It doesn't let loose if you have to pull the seams together.  It does require an extra step to sand it off after the seams have been glued though.   

I can see how this would be much less of an issue with parts only 4" wide, and painters tape would be faster.  

John
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#16
I do it just like this - I tend to use blue tape only cause I never have the veneer tape, but otherwise the same.. Glue on the substrate only. I even use the cheap "pet safe"  heavy duty screen from home depot for even air removal.
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#17
I too use the blue tape and I have found that only the 3M brand is good enough to work for me.  I used to use veneer tape but I don't like the extra step.

I have not really made flat plywood but more bent laminations which have all the characteristics of plywood except I put all the grain directions the same.  It looks like you rotate yours which I understand for sheets.

I shoot for introducing as little water to my glue ups as I can.  That is why I use Unibond 800 to laminate.  It does have a small amount of water but they have reduced that amount in recent years according to the company.  Unlike PVA glue, Unibond sets hard and does not allow glue creep.  For bent laminations, it holds pretty exactly the shape of the form.  Almost zero spring back.

Everyone has their comfort level and it looks like you have found yours!!
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#18
(01-25-2023, 10:24 AM)jteneyck Wrote: Not sure I understand what you mean.  The way I taped the veneer is in almost every book/article I've seen on the subject.  Small pieces across the seams first, followed by a piece the full length of the seam.  Some people first tape the other side with blue tape, then flip it over to apply the veneer tape.  I've found that unnecessary if the seams fit well. 

I never apply glue to the veneer, only the substrate, when doing conventional veneering on a thick substrate.  Making the plywood, however, requires applying glue to each layer, but again, only one side.  Standard stuff.  If you don't have a vacuum bag or other means to apply a lot of pressure, evenly, then I can see why gluing both sides might be beneficial, but you would have to work very quickly to keep the veneer from curling, as I have to making the plywood.  

John

I tape only one side with the veneer tape, the lesser side.
That tape/lesser side goes down towards the substrate, after applying the tape, let it dry a bit, then glue and apply to substrate.
Steve

Missouri






 
The Revos apparently are designed to clamp railroad ties and pull together horrifically prepared joints
WaterlooMark 02/9/2020








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#19
(01-25-2023, 01:41 PM)Stwood_ Wrote: I tape only one side with the veneer tape, the lesser side.
That tape/lesser side goes down towards the substrate, after applying the tape, let it dry a bit, then glue and apply to substrate.

You put the taped side towards the substrate?  I've never heard or read of doing it that way.  It adds unwanted thickness and a weak glue bond in the most critical area.  If it works for you, great, but I wouldn't do it.  

John
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#20
(01-25-2023, 01:33 PM)iublue Wrote: I too use the blue tape and I have found that only the 3M brand is good enough to work for me.  I used to use veneer tape but I don't like the extra step.

I have not really made flat plywood but more bent laminations which have all the characteristics of plywood except I put all the grain directions the same.  It looks like you rotate yours which I understand for sheets.

I shoot for introducing as little water to my glue ups as I can.  That is why I use Unibond 800 to laminate.  It does have a small amount of water but they have reduced that amount in recent years according to the company.  Unlike PVA glue, Unibond sets hard and does not allow glue creep.  For bent laminations, it holds pretty exactly the shape of the form.  Almost zero spring back.

Everyone has their comfort level and it looks like you have found yours!!

I used to think the same as you.  I still use Unibond 800 for normal veneering work on cabinets/furniture, and for bent laminations, but TB Original, TB II, Gorilla Glue, and epoxy all work equally as well.  If your laminations are thin enough, and if you leave it clamped in the form until it cures, any of them have enough creep resistance to work.  One of my friends builds Hal Taylor rocking chairs.  The back slats are a bent lamination.  He uses TB II and there is no spring back.  The key is to leave it clamped in the mold for at least 24 hours, or until the glue has cured.  

For these plywood panels, the cost of TB II at $25/gal at my local HD wins the day compared to Unibond 800 at around $80 to my door.  

John
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