My question is what glue/adhesive to use for installing baseboard around outside bullnose using the three piece method, by which I mean using a third piece and mitering the sides of the two joints to 22.5 degrees for 90 degree corners. At this time it looks as if I will be using 5" poplar or perhaps pine (not finger joint) to be painted. I pretty much have ruled out MDF.

I did several practice corners using 4.5" finger joint pine and they came out real nice using medium 2p-10 with the accelerator (wetting agent?), but I question how well the joints will hold over time. In testing, I found that they can be pulled apart along the interface of the adhesive side with the accelerator side, but fairly often not before the fj pine broke at the thinnest spot of the profile. The only other trim glue I have experience with is Titibond II that I used long ago for smaller mitered (not coped) inside crown molding.

It did seem to me that I may have been having a problem with how I was applying the stuff. I was using the tip of the plastic bottle to smear the adhesive over the surface of the cut and I am guessing that may have resulted in it being sucked into the unsealed grain. I noticed this guy on youtube simply runs a bead down the middle of the cut.

So my main question is what "glue" would you guys recommend. Other thoughts.

The guy selling me the 2p-10 said I had to have the accelerator, but I note that the instructions say it needn't be used but setting and curing times are longer. If the joint will be stronger, the time increase isn't significant for me and I don't move that fast, anyways.

Have you any thoughts on using 2p-10 adhesive without accelerator and/or applying it on both sides of the joint?

Should I pin the corners together? I could pick up a 23 gauge pinner for $25 just for this or is it worth it to spend more? A Grex isn't in the cards for me given how little use it would get.

Thanks for your suggestions.

 

Wood glue and a couple 23 ga pin nails.

 

Good job ruling out the MDF, it doesn't take glue well or not at all.
For real wood any wood glue will do. Titebond III or Titebond molding and trim glue is better, the glue is thicker, grabs better and is easier to wipe off.
Tape might be required or not depending on the fit.

 

What would the tape be used for? Holding the joint tight until set is all I could think of.

 

Yes, the tape is like a clamp, or just use the glue plus pin nails as X said.
Either way a glued joint is going nowhere, plus the top will be caulked.

It's not your case, but wood will often break before a glued joint will.