Glue for finger joints

[Joe Hillmann]

A few months ago I had a person come into my shop we talked for a while and the conversation got around to me having a hard time finding a glue that I could use to glue up my finger jointed boxes that is quick, strong and doesn't make a mess. He told me about some airplane glue he uses that would work great.

He came back today and wanted to see the laser run so I threw in a scrap of wood and made a small box for him. When I was going to glue it together with wood glue he told me not to glue it yet and he ran into town and picked up a bottle of glue at the hobby shop. We did a bit of testing and it works great. It is real thin and runs like water and gets sucked into to joint. After it dried for ten or fifteen minutes the wood broke rather than the glue giving way. It holds stronger and is cleaner than the watered down titebond that I have been using up until now. The problems are, the joint has to be held together very tight for it to hold whereas wood glue would fill small gaps, it dries instantly if you touch it and it isn't something you want to breath.

The glue is Mercury Adhesives M5T I assume it is just a very thin CA type super glue but it works way better than other thin super glues I have used.

[Lee DeRaud]

I use CA of various viscosities for almost everything. The lower the number (5 is the lowest I've seen), the runnier it is. Most generic CA is what I would call 'medium-thick, in the 300-500 range. I've found that 50 is the best all-around, thin enough to wick in between pieces without disappearing into the pores and glue-starving the joint. One strategy that works quite well is to use small amounts of medium-viscosity to get everything together and stable, and then flood the joint with thin, letting it wick it in and seal the areas the medium couldn't get to.

[Joe Hillmann]

Lee, is that what the 5 in M5T stands for? I have tried other superglue that were labeled as thin but they didn't suck into the joint nearly enough.

[Glen Monaghan]

The thinner the CYA glue, the better/tighter the joints have to be. Also, it seriously wicks into endgrain which makes for weak joints. You can get thicker, even gel, forms of the glue that wicks much much less, will fill minor gaps, and won't require such tight clamping, but you're still better off not having large gaps in your joints. As I understand it, moisture on your skin causes it to "go off" when you touch it. You can speed up the set time in your work with a special spray, by sprinkling on a bit of baking powder, or just by breathing heavy on it, but rapid set frequently causes fogging of the normally clear glue. There are also low odor versions of the glue.

[Mike Null]

I believe a visit to the turners forum might prove to be fruitful with respect to using CA glue. I think most of them use it for several turning functions.

[Lee DeRaud]

Lee, is that what the 5 in M5T stands for? I have tried other superglue that were labeled as thin but they didn't suck into the joint nearly enough.Probably. You usually need to go to a specialty store like Woodcraft or Rockler to get the really thin stuff...places like Home Depot only sell medium (sometimes mislabeled as 'thin') and thick. Or there's starbond.com, which sells five different viscosities from 2 to 2000.

[Chuck Stone]

Probably. You usually need to go to a specialty store like Woodcraft or Rockler to get the really thin stuff...places like Home Depot only sell medium (sometimes mislabeled as 'thin') and thick.

Plus, they've recently changed from 20g bottles to 15g bottles with no price change.
And if you're not REALLY careful, some of the bottles are only 4g! (but for 30% off)

The M5T is very thin cyanoacrylate (super glue)
I use thin CA all the time on finger joints. Depending on the brand,
if it is thin enough to wick into the joint, it works just fine. I don't
have to hold the parts together though.. the joints are tight enough
when the parts come out of the laser.

[Chuck Stone]

I believe a visit to the turners forum might prove to be fruitful with respect to using CA glue. I think most of them use it for several turning functions.

Yep.. it makes a nice glossy acrylic finish on pens, too

[Gary Gardner]

Something to keep in mind is that CA glue does not holdup to shock and deteriorates over time. After the glue really dries it becomes very brittle and if you drop the item it will come apart at the joints.

Gary

[Joe Hillmann]

Gary, How long until it becomes brittle? I know it probably varies but are you talking about months, years or decades?

[Chuck Stone]

Gary, How long until it becomes brittle? I know it probably varies but are you talking about months, years or decades?

I can tell you it isn't months, and I haven't had any problems over the last
10 years. Haven't checked anything beyond that.
(then again, I don't go smashing my things on the ground to find out,
so that might also be a factor..)

[Lee DeRaud]

I can tell you it isn't months, and I haven't had any problems over the last
10 years. Haven't checked anything beyond that.
(then again, I don't go smashing my things on the ground to find out,
so that might also be a factor..)What he said: in the absence of strong UV, certainly years, probably decades. I've got blobs of it on my workbench dating back to the last century that show no signs of coming off without help from a chisel.

[Joe Hillmann]

Using this thin glue I found that anywhere there are two surfaces touching the glue will work it's way between them no matter how little you put on. That means if you tape your joints like I originally did the glue will work through the joint and then between the face of the wood and the tape which starves the joint of glue and ruins the surface I am working on. Also if you hold the joint and your finger is to close to the joint the glue will get sucked between your finger and the work gluing you to it and causing glue marks on the surface. I found that I can make a jig on the laser that is a friction fit but doesn't touch on any of the corners I can put the glue on so thick that it fills up the joints and begins to puddle in the inside corners of the box but nothing leaks through to the outside and the grain on the outside also doesn't soak it up. With the jig I can now glue up a box that used to take several minutes in less then a minute, which is kind of important because the laser can cut the box in 1minute 19 seconds.

[Mel Fulks]

Sounds like prices on those houses will get even more affordable!

[Chuck Stone]

Using this thin glue I found that anywhere there are two surfaces touching the glue will work it's way between them no matter how little you put on. That means if you tape your joints like I originally did the glue will work through the joint and then between the face of the wood and the tape which starves the joint of glue and ruins the surface I am working on.

With such a thin CA you may not need much.. since it will wick into
(and essentially become part of) the wood itself. In that case I don't
think you would need to tape the joints anyway.. not like you would
with another glue type.

[Gary Gardner]

The time CA takes to break down depends on the quality of the glue, the freshness of the glue (CA actually has a dated shelf life of 1 year) and how dependent the glue is to the joint. I have seen glue joints break in as little as one day or as much as many years. CA is used for closing battlefield wounds, emergency wound closure and surgury closure. The police and FBI crime scene people use it for fingerprint lifting. A study was done by a group of woodturners to see how long the glue joint would last and it varied so much that a definitive answer was not possible but the recomendation was not to use it for long term joining of wood. It is a great crack filler and also makes a good finish but I no longer use it for joining wood.

Hope this helps
Gary

[Joe Hillmann]

It won't make the dollhouses any cheaper. I plan to sell them as kits. I have a 9 drawer tool box that I have been trying to reduce the price enough to be able to sell it as a kit. I had a guy who wanted one (the same guy how brought me the glue) try to assemble one. Even thought I thought I made it very clear that in order for the drawers to fit the joints had to be PERFECT, the first two that he made didn't fit. Which makes me think that if I sell it as a kit customers will have a very hard time assembling it.

Now using this glue and the jigs I can assemble the toolboxes faster than the laser can cut them. I think the first one took me about 15 hours to put together so I have cut my time down a bit.

To be fair to the guy how tried putting one together, the opening that the drawers fit into are only .005" larger than the finished drawers.

[Rich Harman]

I first used CA glue for building RC airplanes about 30 years ago. I have never experienced a problem with the glue joint weakening.

[Kay Bengtson]

R/C Modelers use CA glue primarily for balsa parts and switch to 5 minute epoxy for lite plywood. When they have a wood stained finish to do such as a stained and varnished sheeted fuselage, CA has a big downside in that it fills the pores of the wood and makes the stain apply unevenly. In that case, they opt for the old orange Ambroid cellulose based glue. It sands great and holds well too but doesn't seep into the wood. Water based aliphatic glues have an additional problem for plywood in that they often cause warping.

Kay

[Joe Hillmann]

I am posting these pictures for Mel, I tried to send them by PM but can't figure out how to send pictures that way.

This isn't the tool box I am making now but it is my original prototype(would post pictures of the updated one that is ready for production but I can't find the memory card for my camera). This one is 1/4 ply the one I am working on now is 1/8 is about 12"x 12" x14" and has 9 drawers.

256967256968256969256970256971

[George M. Perzel]

Hi
Thin glue such as that found in inexpensive glue pens works great for finger joints on small projects-put the parts together and dribble on the glue-gets in any crevice or gap. Let it dry and then sand the whole thing. Here's some small boxes made that way-completely sealed on all sides. I use them to store bad thoughts and photos of my mother-in-law. Check school supply stores online for 80ml pens less than 50 cents apiece.257000256999
Best Regards,
George
Laserarts

[Mr Mike Mills]

I am new to using CA type glue for wood projects. I tried using supper glue on a 1/4 plywood finger box cut with the laser. What I noticed was that it seemed to seeps through the top veneer layer tho the point that it has discolored the area where glue was applied. How would you prevent this? Thicker glue?

Thanks

[David Somers]

CA glue is funny stuff. Wood Turners do use a lot of it. Typically we will use it to make sure bark will stay on a natural edge piece or a piece that has bark inclusions on it. Or we will use it to stop drying cracks from progressing or to apply butterflies to a crack for the same reason. (butterflies are usually an X shaped inlay that goes across a crack) We will also use it as a finish on small objects like pens. Or to do inlay work and to saturate granular or powder infills. Or to glue a finial into a lid. And we may mix it with sawdust and use it as a crack filler. Anything of size though, or anything that will be under stress is more likely to be glued with a wood glue like tight bond since it does better at large joints and has some flex to it.
CA has a definite shelf life due to exposure to air and water.
Refrigerating it helps it last longer. Keeping it in bottles with little room for air helps. Avoid contaminating it with back draw from the tip, and don't contaminate the tip by touching it to anything.
The cheaper variety from a hobby shop or box store would likely be fine for what you want provided you don't want volumes of it, and a medium viscosity is probably better for your use. The thin stuff will soak rapidly into the wood and not provide contact across the joint unless you use it first as a sealer, then when cured follow it up with another coat for assembly. Just go to the medium stuff and avoid that.
The thinnest I am aware of is a 2-3 viscosity made by Starbond. I use it to saturate 100 mesh metal powders when using that for an infill. I may also use it as a sealer in a fine crack prior to going up to a thicker version. But as I said, the thin soaks in so readily there is normally little left to provide surface to surface contact and the wood joint is more likely to fail. CA glues tend to be brittle and don't handle flex stresses well.
A spray of fine water will accelerate its curing. If you use it in a joint that wont have much exposed glue you could moisten the joint itself prior to gluing and assembling. Your open time will be greatly reduced though so be prepared to work quickly. Practice and assembly without glue until you are comfortable and then do it with a moist joint and CA glue.
There are low odor varieties, but even normal CA glue is not too bad.

Airplane Glue, also called Model airplane Glue, and perhaps best known in the states by the brand name Testors, is a different type of glue. Not a CA glue. It has a longer open and set time. Is a medium to thick viscosity. And there is a variety made primarily for wood and one for plastic, not counting certain foams. Both CA glue and Testors do NOT work on all materials, and each can disolve some materials so if in doubt, test it on some scraps.

If open time is an issue as you assemble the boxes, try a medium viscosity super glue. Use an atomizer of water to accelerate it. Keep some acetone handy in case you glue yourself to something. Acetone will dissolve it enough to get your fingers free. (It is really embarrassing to glue yourself to a 700lb wood lathe and be out of reach of your acetone. Not that I could personally attest to that of course <snort> This is the wood turners equivalent of the plaintive "Help, I've fallen and can't reach my beer" cry of a frat party attendee. "Help!!! I've glued myself to my lathe and can't reach my acetone!!!!" <grin>)

It will fail over time, but that is really variable based on conditions and how you used it and what you applied it too. On wood I would expect a decent quality glue to last many many years without constant exposure to UV. Any glue will fail eventually so put this in perspective.

I have to admit.....when I look at the tool boxes in your picture a CA glue is not the glue that comes to my mind. It is expensive in quantities. It can be tricky to work with (think gluing yourself to your lathe!) It is brittle and doesnt handle flex stresses well, and if you are sloppy with it you can affect your ability to stain the wood evenly. I would prefer a tight bond glue with the joints clamped till it cures. You are making a tool box after all and that type of box will take some abuse and have some weight in it. Tite Bond will excel. It takes longer to cure, but it is an excellent glue for the life of that type of product. The small boxes George showed us are better candidates for a CA glue.

Hope that helps a bit.

Dave

[Mr Mike Mills]

Thanks mike

[Joe Hillmann]

Mike.

When I use super glue I use sanding sealer as my finish so when the super glue bleeds through it blends in with the finish and I think of it as a plus it means the entire joint is glued. I just make sure nothing is touching the joint where the glue will bleed through so nothing will stick to it.

David.
The reason I used a thin super glue on the boxes is because it allows me to assemble an entire box in about 45 minutes. (not counting cutting the parts). The first four boxes I made I used regular wood glue and they took 4 or 5 hours to assemble and had glue marks when they were done. (the first one actually took about 15 hours to assemble.

[David Somers]

Joe

try moistening the joints and see if that cuts your assembly time with ca. Be cautious since it might be faster than you are initially ready for.

Dave

[David Somers]

Joe

also, check out the starbond glues. You can get large bottles and they provide smaller bottles to refill and also fine tip applicators with the thin. A high quality glue. If you use a medium viscosity on a moistened joint you will get a short open time and less bleed through. Let me know what you think if you try it.

[Joe Hillmann]

David.

The dry time isn't what takes so long. It is the fact that there are 4 or 5 thousand tabs that each need a drop of glue and then brushed on to all four sides of it thick enough to stick but not thick enough to ooze out when it is clamped together. and then figuring out a way to hold everything in place with clamps while it drys.

With the thin super glue I put the parts together, clamp them with a jig made for that drawer and use a syringe to run a line of glue into the corner which gets sucked it into the joint.