Veneer clamp / core question

[Kevin Villas]

I'm back again with another veneer question =)

You guys just answering so I keep em coming!

Well since my glue up is so small I am just giong to use some Titebond III. It is only 10 inches x 10 inches. My question is about the best way to apply pressure.

I was planning on doing a sandwhich between 2 pieces of ply and using bar clamps around the outsides.. 2 each side or so. But I have read that apply weight on top might be better.. I have 2 45lb and 2 35lb circle weights from a weight lifting set. I wasthinking of just laying those on top of the veneer with a piece of plywood over top? Think that is a better way to go? How much weight?

Also would would you think would be a better core for this small glue up. It is going to be a clock face. 3/4 MDF or 3/4 Bitch ply?

Thank you all so much for your help so far. This will be my first attempt at veneer and would just like to figure out as much as possible before I start.

[Earl Kelly]

Kevin, I don't think you will get acceptable results with clamps only around the edges. Think of it this way, the pressure from the clamp decreases as you get distance from the point of pressure. The pressure will appear as a cone shape, if you could see it. these cones need to overlap, where they meet the veneered surface. You neeed to figure a way to clamp or get pressure in the center of the panel. Sometimes when I do a 6x8 in. sample panel I'll use about 8 c clamps of varying sizes. Try using 2 3/4in cauls on top of the veneered surface, this will help spread the load some.

[Don Abele]

Kevin, I'd recommend using the ply for top and bottom sandwiches, and use, as suggested, long cauls across the ply with clamps on the ends. This will distribute the clamping pressure more evenly across the panel. I'd space the cauls as close together as your number of clamps will allow.

Be well,

Doc

[Alan Turner]

Keviin,
Crown the cauls so that there is pressure in the middle,and on the edges. Just a bit should do.
Alan

[Pete Lamberty]

Kevin, you have to get clamp pressure in the middle also. Clamping the out side won't do it. Think of the cone shape being under the pressure points of the clamps. Also your weight idea will not work. I think you said that your piece is 10 by 10. Thats a 100 square inches. And you want to place 160 pounds of weight on top of it. Thats only 1.6 pounds of pressure per square inch. Anybody know what a vacuum bags pressure per square inch is? Around 660 pounds? Is this right. Anyway Kevin you should be able to see that 1.6 pounds just isn't enough. Do you have any big C clamps of F clamps? Some of the other guys gave you good clamp advice. But the one thing that I remember from the class I took is that you should have a thick sandwich of wood on both sides of the work piece to get EVEN PRESSURE. Hope this helps a bit. And show us the pictures or we will get Tyler after you. :D

[Don Abele]

Pete, we brought this up in another thread. A vac system typically exerts around 1415 pounds of force per square foot - so I think that means ( divide by 12 ? ) that it's 118 pounds/square inch. Still much higher than the 1.6 :eek:

Somewhere I remember reading something that gave the pressure that typical clamps can exert. Wish I could remember where...

Be well,

Doc

[Matt Allan]

Hey Kevin.. I think we are working on the space project and are at the same steps. Well I think I kind of stole your project for Christmas gifts actually.. Haha

I posted a while ago for ideas for gifts this year, someone recommended a clock. I spent a week trying to find a design I liked and I came across your question on how to veneer up that clock face. Really liked the design and thought it would be fun to try veneering finally for myself.

I suggest reading the post I made just today, I applied too much and most likely did not apply enough pressure. Luckily it was the back I used so it's not a problem.. Will probably work on the front tomorrow and hope to have better results.

Let me know how yours goes.

[Steve Jenkins]

See my reply to Matt.