Advice: Gluing Proofgrade Solid Woods

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#1

In making my “maker sign” I glued up the sign using the tabs with Titebond III. My question for the serious woodworkers on the forum, is what is the best way to glue these tabbed items up.

I use a glue brush on the face of the cut-outs with the Titebond, but I realize that most of it is attaching to the finished part of the wood, so a bit worried about strength. It’s seems to have bonded OK for the sign (which isn’t a structural item anyway) but for the cat shelf project if I had done it in Proofgrade that would have been a concern.

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#2

Light sanding on the finished portions to be glued (I use a nail file for accuracry) and a few drops of CA glue (super glue) works perfectly for non-structural projects. Dries fast, clear and a really strong bond. Love your posts! Keep-em coming!

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#3

You’re right, Titebond III would need non-finished surfaces to really stick properly. A bit of sanding over the surfaces that need to join would definitely be called for. However, even that might not be enough.

The glue needs to be able to seep into the fibers on both joining surfaces in order to make it’s strong bond. Stain, Oils, Lacquers, wax, Shellak will all “Fill” those spaces in between the fibers and will prevent your best bond.

Once you have a finished surface, it’s not the easiest to get it back to a state where you can properly glue it to another surface.

However, with the finger joints and those kind of joints, you have exposed unfinished surfaces on the sides of each finger. THAT is where your strongest bond will occur. So If you were to make the cat shelves out of proofgrade, I would suggest increasing the number of finger joints and focus most of your “holding” glue on the joining exposed unfinished faces.

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#4

Thanks. I was worried that my only bonding was occurring on these spots, which is a pretty tiny surface area. For this purpose that’s fine, so I like the suggestion of increasing tab count.

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#5

Typically a glue joint is as strong if not stronger than the wood it joins, the wood itself will break first.

Another idea is to adjust the joinery, using a captured tap/slot to reduce the amount of load the glue joint has to support.

I have to wonder about the resin/soot/char the laser leaves behind effectively sealing the wood from glues being able to penetrate. On the other hand, 1/4" wood isnt exactly heavy structural material and the glue joint is probably more than sufficiently strong for the intended use.

If you compare the kitty’s weight against the total glued surface area, the stresses on the glue joints are probably very low and not much to worry about here.

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#6

I had posted a similar item on these in one of the tools or accessories for your Glowforge ™ posts, but aggain, these are fantastic for precision and tight area sanding. (Found on Amazon and Hobby stores (use those coupons)).

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#7

Oh cool. Have to get some of those.

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#8

A link to that post for those who read later:

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#9

I’ve got some of those, but you know what I use that works even better? Package of emery boards from the drugstore. (Nail care fellas.)

They’re cheap, they have a rough grit and a fine grit, you can cut them into extremely small shapes to get into tight corners, and when you’re done…pitch it.

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#10

Unless we are talking about Omar:

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#11

To be fair, it’s not that you can get NO holding power on a finished surface, but it will be orders of magnitude weaker than an unfinished surface to unfinished surface.

For an example. I made a stand for my printer that was simply a box with dividers for the various reams of paper that I was going to store there. It was butt joint construction with the only “fasteners” being the glue on the ends of the butt joints (quick construction, not meant to be quality). To make things easier, I decided to stain all the pieces before gluing them together.

When I went to set the piece down (after it had dried overnight), it was jostled and the bottom fell off…It was fairly obvious from looking at it that the stain had prevented a good glue joint. A couple of screws later and it was secured enough for my purposes.

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#12

Very true, but also keep in mind that if the glued up surface area is the size of a 1/4" thick twig, that will break far quicker than a 1" thick branch.

On the same train of thought, a bunch of 1/4" twigs together are far less likely to break than a single one.

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#13

My wife’s practice does have a 30lb cat they see, but not too worried that it’s going to climb up the wall on narrow steps. It didn’t get to 30lbs by over-exercise…

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#14

LMAO! I just got yelled at by my wife for taking all of hers.

One by one over the past couple of months and now there are none. She was unamused.

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#15

Alas, you get a lot more force on those joints than you think, because torque. So I wouldn’t bet on things holding with glue alone, or at least not holding rigidly (regular wood glue creeps a little, which is good if you think about it). Another thing to consider is some of the more resilient cyanoacrylate formulations, because once you scuff the surface CA will probably adhere pretty well to the finished side. You might have to seal the unfinished side of the joint with CA because otherwise you’re just tossing random glue in the direction of end grain.

But yeah, if you can figure out joints/designs that don’t rely entirely on the glue, or joints that reduce the torque, you’ll be much better off. I’m also planning on pinning joints where I can.

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#16

In addition to the sanding suggestions, if it’s 1/4" stock or better I use pins driven at angles. The 23ga pins are really tiny so don’t make a mess of the surface and when pinned at an angle they provide lots of holding force in addition to the glue (I use CA myself although it can be irritating to the eyes if you are doing a lot of joints). It’s hard to use the gun to drive them into 1/8" tabs and the shortest ones are far longer than needed.

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#17

Yeah, the cat shelves are in compression so the glue is just holding the parts in place while the force is on angle braces.

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#18

You have a Glowforge - just make some! And they’d probably be better with your skills!

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#19

Great advice here. At the office, we use and recommend a cyanoacrylate glue. We also use Titebond although it is a little fussy. In my recollection we have not had issues with structural integrity at the glue joints.

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#20

http://www.fastcap.com/estore/pc/viewPrd.asp?idproduct=12826&idcategory=0

While anything but cheap, fastcap wood CA is the bomb. I’ve been using it on everything wood PG.

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