Gluing metal ring cores to wood with CA glue?

[Tarn Faulkner]

Hi All!

I made a number of rings as gifts over the holidays and have had two fail. I'm trying to figure out what happened, and if I might see more failures.

The cores were titanium (simple ring, not the two-part with a groove to hold the wood) with the titanium sanded to 180 grit on the glue side and cleaned with alcohol. The two that failed were both made with Padauk wood, which was glued immediately after having its recess made with a negative rake HSS scraper (sharpened with 180 grit wheel). The metal ring fit in the recess snugly but did not need force to slide in.

The glue used was Stick Fast CA Flexible (sold by Rockler), with enough used that there was a rim of squeeze out all the way around. The glue was purchased just a month before. Accelerator was sprayed on very lightly after the metal ring was fully in place.

It appears that the glue itself failed, since the metal separated from the wood, leaving bits of glue on both the titanium and the Padauk.

I'm guessing this was because the Stick Fast CA Flexible isn't actually very flexible? Or might I be running into problems from titanium or Padauk?

Hoping others with more experience have thoughts on what might have happened, how I can avoid this in the future, and what glues might be better for this case.

I recently made a couple similar rings with Padauk, using Mercury Adhesives Medium Flex CA glue to attach the titanium core to the Padauk. Haven't mailed them off yet because I'm afraid they might fail.

 

[hockenbery]

CA will fracture. It is one glue that is not stronger than the wood.
when I use CA to mount a glue block the CA fractures with a chisel and some sticks to the bowl,and some to the glue block If the metal contracts or expands It can fracture the glue.

i glued a lot of Paduk finials to ornament balls with Titebond 2 and to my knowledge none failed.
Titebond might work but it can corrode some metals.

i would use a 10 minute epoxy.
That bonds to metal and wood

 

[Mike Johnson]

You might try Eclectic E6000 adhesive, it stays somewhat flexible and bonds to every surface. Metal and Wood expand and contract at different rates a flexible bond will allow for some expansion and contraction between the two different materials.

 

[Tarn Faulkner]

Well crud. Thanks for the info. You would think I'd have learned by now to not believe labels for glues or finishes. I guess "Tung Oil" finish that includes no tung oil and is actually varnish goes right up there with "Flexible" CA glue that is actually brittle.

Guess I'll mail off the rings done with the Mercury Medium Flex glue anyway, and just ask the recipients to let me know if/when the rings fail. Good thing they were all going to family members! Next time I'll use a flexible epoxy.

 

[Clifton C]

I have made a few rings and bracelets, the two part kind. Here's my thinking... The wood is going to move. Even if sealed, due to environmental and or body heat. The movement of the wood and metal are not the same. I want some wiggle room between the wood and the core. How much? Kind of unmeasurable, but the wood should spin easily around the core. Let the wood rest/cool after turning before test fit. To glue up, I use silicone adhesive, assemble parts, twist the wood around the core to distribute glue. The excess silicone is wiped off, any leftover will get buffed off later. Over night drying is a must, but what this does, in my mind anyway, is give a thin cushion layer between the two dissimilar materials.

 

[Bill Boehme]

When doing your fit check I think that it would be a good idea to heat the ring to about 100° F (at least body temperature) and aim for a fit that is slightly loose. I like Clifton's suggestion of using silicone adhesive. Another possibility might be polyurethane glue, but it tends to be a bit messy.

 

[Bill Wells]

Tom, I had the same problem with the titanium core, padauk, and CA glue: the glue failed.
I'm now using two part epoxy by Locktite. Seems to be working much better. Not sure about "flexible" CA, it all seems brittle to me. CA is not a wonder cure-all glue. It's just fast, and everybody wants fast.
Also, don't try to make the wood too thin.

 

[Tarn Faulkner]

Good idea for heating up the metal ring a little, Bill. I should at least make sure that the fit isn't too tight if the metal is warm.

I'll have to experiment with epoxies. One I've used in the past that is both waterproof and flexible is System Three T-88. Works really well, but may be a little too thick for this application.

 

[Craig White]

I've made a couple rings and used West Systems epoxy. So far, so good. In addition, the wood was stabilized.

 

[Mike Adams]

Paudauk is pretty oily, too. That can't have helped, even when gluing over a fresh cut.