Epoxy Failure

[csb333]

I am trying to make an african blackwood pen with aluminum accents. I first made a blank and then sawed it down the middle lenghtwise and sanded. I sandwiched a thin piece of aluminum, also sanded and glued with Loctite 5 minute epoxy. I clamped and let set for 2 days.Next I cut that piece lenghtwise, sanded and glued another piece of aluminum between the pieces and clamped. If you look at it on end it looks like a crosshair on a scope. This dried for a few days. Then I cut to appropriate length for cap and barrel. I am making the barrel closed end so I glued yet another piece of aluminum about 7/8" square on the barrel blank perpindicular to the other pieces and a short piece of blackwood after that for the closed end area. I drilled a pilot hole maybe 3/32" in each piece and then went with the big bit for the cap (it is a Jr. Statesman 2). The cap flew into two pieces at the aluminum when I started to drill. I got a hole in the closed end part and glued the tube. I turned this piece to about round until it split into 4 pieces, also at the aluminum. Neither of the pieces are damaged so I'm going to glue them back. What type glue do you suggest? Sincerely, Chris

 

[skiprat]

Chris, although I haven't done it with wood,(yet) I have made several with acrylic / brass or aluminium. All of them have been done with medium CA. The only reason I use the medium variety is to give me time to get the bits in the right place and then in to a clamp. What I have noticed since is that the different materials expand and contract differently with temperature. A pen that was perfectly smooth over the joints when made, MAY have a sharp edge later on. In the example that you are attempting, I would be inclined to use a solid wood blank and cut slots for the aluminium accents. Of course you would need the correct kerf / ali match. You would also need to knock up a sled to support it.
I also no longer use turning tools when using metal. I use only a file while turning at a low speed. But then, I'm chicken[:I]
Another thing to look at is, when the blank seperated, which surface still had glue on it? If either the wood or the ali is 'clean' you know that the bond is no good using that glue.
Just to add insult to injury, when you come to fine sanding and polishing, how are you going to keep the black ali slurry from bleeding into the wood? When I asked that question, someone reccommended CA'ing the wood first. Good idea, but I haven't tried it yet.
Sorry for long reply

Whatever you do, I wish you luck. Please keep us posted on how you get on.

 

[Rmartin]

Man, I'm sorry to hear that. I had a rather complex acrylic blank come apart on me when drilling the other day. I used a fifteen minute two part epoxy.

I think Skiprat may be right about using CA glue. I also concur with his idea of looking to see on which side the glue you used failed.

 

[DocRon]

Aluminum has a very stable oxide surface, which does not take glue very well. For instance, to solder it, one uses an acid flux and scrubs the surface with a wire brush while applying the solder. If you follow skiprat's suggestion to inspect the bond and you see no glue on the aluminum, the oxide effect might have been operating. You can give the metal a good scratching with sandpaper immediately before gluing, and that will sometimes help (you probably did that). Epoxy should be the glue of choice, I would think. Sounds like a tough problem, you will be putting a lot of stress at the joint when you start to drill. Good luck. Let us know how it turns out and what you did to solve the problem.

 

[MesquiteMan]

Did you possibly use too much pressure with your clamps and starved the joint" Epoxy requires minimal pressure, unlike wood glue. Just a thought.

 

[MesquiteMan]

Did you possibly use too much pressure with your clamps and starved the joint" Epoxy requires minimal pressure, unlike wood glue. Just a thought.

 

[Paul Downes]

Another possibility is that aluminum is a great conductor of heat which is an enemy to epoxy. If the blank heats up much at all it will soften the epoxy. I would score the aluminum with some coarse sandpaper and try another glue. You might want to do a few experiments with CA or poly glue and see what holds better.

 

[DocRon]

Another thought occurred last night ... How about making the blank with a small center void?. You could cut 4 pieces of wood and four of aluminum and glue them up with, say, 1/8" hole down the middle. That might help guide the drill bit when drilling outt for the tube. I am guessing that your drill may have wandered off center before, which would lever off the wooden strips.
I have made a couple of large lamps that way, to make a channel for the lamp cord, so i did not have to drill 18'' through a piece of oak.

 

[Mikey]

Paul, you would have to heat the epoxy up a whole lot for the bond to break. I'm with the others that mentioned that the clamp pressure was to great. I would have also used some sandpaper on the aluminum so that the epoxy had something to "bite" to.

 

[ilikewood]

Heat was probably the failure when drilling, but like it has been said Aluminum is a tough thing to glue with the oxide surface.

Materials with very hard smooth surfaces don't glue well with epoxy. The best thing to do is ROUGH the surface which allows the glue something to hold onto. This works for oily woods such as Cocobolo as well.