Gluing onto Polyurethane Finished Wood?

[tbr]

I would like to glue small wooden letters to wood that has a polyurethane finish. What would be the best glue for this?  Would Titebond work or is there something that will hold better?

[MT Woodworker]

Instead of glue, possibly just use a pin nailer?

[tbr]

MT WoodworkerInstead of glue, possibly just use a pin nailer?

The letters are very small so a pin nail would be too large. But thanks for the suggestion.

[fredhargis]

When folks finish before assembly one of the reasons they tape off the tenons and other spots to be glued is that the finish weakens the joint (considerably). That said, I'm suggesting that any of the PVAs would be a very poor choice. I suspect (but do not know) that something like CA would do what you want. But something makes me think that if it works then you will have your letters glued to the varnish, so the varnish is effectively holding the letters to the workpiece. If true (someone will correct me if it's not) that wouldn't be a very good way to fasten the letters. Maybe clear some of the varnish off where the letters go and use PVA to glue the letters to the wood itself?

[tbr]

Maybe clear some of the varnish off where the letters go and use PVA to glue the letters to the wood itself?

Removing the finish under the letters may be the way to go. I was also thinking about using epoxy. 

[fredhargis]

Even so the epoxy would just be holding the letters to the varnish.

[Willyou]

I think a very small amount of silicone sealer (like that used for fish tanks) would work. Try it first on some scrap finished with the same poly. Yes. It would be holding the letters to the finish. So...

[Cooler]

E6000.  It is like silicone adhesive on steroids.  Remains flexible.  Styrene based.  Excels at adhering non-porous materials.  Widely used in the fashion jewelry industry for gluing in rhinestones, etc.

Available at most hobby stores, Lowes and Home Depot.  But also from Amazon.com.

Yours is likely a low strength requirement and silicone is probably strong enough.  But this is a very handy glue to have in the house.  It can withstand high temperatures and makes an excellent fabric glue too (bachelors' hemming).

[MT Woodworker]

I just used some E6000 to repair some broken display cups for my wife, totally forgot about it until you mentioned it again
I agree, a very good adhesive.

[AHill]

Another vote for a pin nailer. PVA will not work on poly, since it has to penetrate the wood to provide a bond. The poly has essentially sealed the wood. Any adhesive at this point would simply bond the letters to the poly film, which is a weak joint at best.