Thread: How to test a veneer press?

Originally Posted by Dengue

Hi all, thought I would give veneering a go, so am in the process of making a little veneer press for up to 400 x 300 panels. The press will open to 100mm to allow the veneered substrate to fit between the horizontal pressure plates. These two pressure plates consist of two pieces of 35mm thick bench laminate ( chipboard core) with 19mm ply glued and screwed to each as a stiffener. The laminated surfaces of these plates will be pressed together using a car jack.

Will post pics of it when completed soon

My question is, when testing the finished device with the two laminated surfaces pressed together and nothing in between, how do I know that there is no gap anywhere in that 400 x 300 area? Is there any way of testing this? These plates need to be exactly parallel to work properly with 0.6 mm thick veneer

Maybe a couple of sacrificial pieces of veneer for a test?
You could cut the laminated piece up into strips after the glue has dried to eyeball the joint.
(Even running your fingers over it, you'd hear any bubbles probably.)

You could press this size with 6 or 8 quick action clamps and and the pressure plates ok .
A one action press sounds like a good project though. look forward to seeing it.

I made a press a few years ago , it could do up to 1200 x 1200 . and had 36 screws ,
the job it did on .6 veneer was lovely , clean and dead flat . The pressure a press can do is much better than vacuum , I bought a vacuum set up and got rid of the press, it was a timber one,and had it's faults . now it's a set of shelves in the house. the next one will be steel.

The testing is done with your ears .
Press up a test piece , take it out when dry, and very lightly and quickly rub/ flick your fingers across the veneer, like your trying to flick off dust.
With your ear close to the work, veneer not glued down gives off a loose sound ,and you can find all the faults this way before you go to polish. It either means your no good at spreading glue or your press is not doing it's job.

When looking for these loose bits first flick, then tap tap with the end of your finger to find the exact spot, circle with chalk so you can repair.

Rob

Like has been said tapping or rubbing a finger over the surface is a good way to tell, listening all the while for a hollow sound, which is what you don't want to hear, to test the press you could use some plasticine, as a start cut a few small pieces and spread out in a grid pattern, squeeze and then look at how even the thickness is of each flattened blob, if they all looked the same and flattened I'd say go for it, I'd suggest some wax paper on the platens first tho, you may have to experiment with size of blob and spacing, trial and error!

Pete

Photos enclosed, as promised. All welding done by very good neighbour. This is the 2nd protoype, the first using steel frames as the pressure plate, but could not get them flat enough after welding.

The design is such that there is upward pressure on the 2 only 50 x 25 x 3 RHS (welded together) crossbeam supporting the jack, and on the 6mm 50 x 50 angle iron screwed to the underside of the lower pressure plate 300mm sides, so should not expect any distortion between the plates when it is under pressure, especially as the bottom of the angle iron and the bottom of the lower pressure plate are coplanar thanks to the 50 x 6mm rabbet on the sides of the plate.

The jack was found under my workbench - had to be there at least 7 years - can't even remember where it came from, or what it was going to be used for.

As can be seen on one of the pics, the jack and the upper pressure plate hang loosely from the crossbeam, delicately balanced, so that when it is lowered, the plate takes up a flat position on top of the substrate being veneered.

Next step is to dismantle it, and epoxy the laminated chipboard and the plywood together on each pressure plate, seal the exposed edges and the timber on the angle iron base ( see this thread, not getting far) and paint the whole steel structure, then put into action

Wow ! great little press, nice and neat and uncomplicated too.
Building you own tools like this is a great way to go, and working with steel to produce things like this is rewarding like woodworking is.

Did you get the Hayward book yet?
Edit . better spell his name right.

Thanks for the comments, but most of the credit goes to my practical and imventive neighbour. He knocked it up in a day.

I have obtained the book Practical Veneering by Charles H Hayward, and although old ( first ed 1949, my reprint ed 1979) it was surprisingly very relevant and a good read with lots of good advice. It was a good introduction, thanks for helping me find it.

I also found the downloaded video put out by Popular Woodworking Shopclass 'Getting Started with Veneer" with PW editor Steve Shanesy to be very worthwhile - that cost $15 and ran for two hours.

Hi Dengy,
I made a veneer press a couple of years ago - and its been in use several times a week ever since. Its a bit like yours but is bigger and has 10 screws. It divides into 2 parts - there are 6 screws over the front part and 4 over the rear. I use 70mm of laminate above, and 35mm below but this sits directly on about 150mm of lattice of solid timber. Anyway, the front 6 screws operate over an area of 500mm by 400mm, and seem to be about right as I've never had a failure with it but intuitively I don't think its overprovided. Thus I'm of two minds about trying to press veneer of the size you mention with just one screw. Time will tell - and if it doesn't work you can try putting another jack in. And if that doesn't work then you can keep it for pressing really small things.

As for testing. Just glue up a some veneer and substrate and put it in. With screw presses, the pressure is so intense that it actually changes the look of the veneer - it flattens it - it looks like its been in a press and had the #@$## squeezed out of it (which it has, so why wouldn't it?). Bits that did not receive enough pressure will be visible as unmodified and unsquashed veneer, probably with wrinkles. When I pull something out of the press I can see immediately by looking at the surface how much pressure it was under and how consistent the pressure was - I know that doesn't help you much now but will after some trials.

As for the cauls (caul = membrane, so I'm referring to the flat mdf bits), I saw your other thread on sealing them and what I've found is that I don't bother. I find the surface of the caul gets mangled and dirty long before the moisture-induced swelling takes effect - and my press lives outside on the balcony as I have no room inside so it gets a lot of moist air. I use scrap kitchen counter tops, and replace them for free every council clean up. Lately I've sourced some scrap corian of the right size. I'm thinking that these might make better cauls - or maybe they will crack, I don't know as yet. Anyway, I'm just saying I treat the cauls as disposable short-term things rather then spending money on sealing them.

cheers
Arron

Thanks for this info, Arron, good of you to share your practical experience, much appreciated

Actually, I was thinking today about your original question - how do you know a press is working - and I came up with the following:

Usually when you press something the veneer overlaps the substrate. After pressing, when you remove that overlap, it can tell you a lot about how well the pressing worked. If you can work the overlap up and down, cracking it along the edge where it joins the substrate, break it off, sand it back and still end up with a clean edge, then it worked. I've attached a photo of a piece of 3mm ply laminated on top and bottom with red cedar veneer. I've cracked the veneer along the arise, and am in the process of working it up and down till it comes away. If this was inadequate pressing, its very likely that the veneer would separate from the substrate somewhere along the edge - perhaps just a tiny bit, but its still enough to trash the whole job.

The edge is particularly critical because it takes the most damage, plus its the area most likely for glue to be squeezed out while pressing.

The first time I saw some workers in a veneering company remove the overlap from a job I was really alarmed (it was my job!). They use a thing like a piece of angle iron attached to a handle and simply shoot it along the edge, whether along grain or across grain, cracking the veneer along the arise, and then breaking it free with a second swipe. My pressings till that date were often inadequate and so I had to treat the edges with care. They didn't because they were confident of the quality of the pressing.

By the way, I was at a veneering place yesterday and I asked the owner what pressure he presses at. He said 3000 psi. I said 'always?' and he replied 'sometimes we go higher but 3000 psi is usually enough to get the booglies out'.

cheers
Arron

Thanks Arron, much appreciated. Will give it a go and see what happens. If it breaks away cleanly, then I will be very happy.

Not quite sure I understand about the use of a piece of angle iron on a handle. Can you please give some more details?

Liked your website about Patonga - I always thought it was an island in the Solomons region

Particularly like the neat boxes you displayed - congratulations on some amazing work