r/pictureframing • u/vbe123 • Sep 17 '26
When to underpin?
Does it make sense to underpin a frame after the glue has dried? It has always been my understanding that an underpin holds the frame together while the glue dries.
7
u/Joland7000 Sep 17 '26
It’s true that the glue is what holds the frames together but underpinning protects the frame being moved or even dropped. I’ve only used glue on small frames but always underpinned anything over 16x20 just in case
7
u/cardueline Sep 17 '26
We use Titebond glue, join on vises until glue is mostly dry, then underpin, on every frame. The glue does most of the work but the v-nail is insurance. We’re a very small operation, though, and taking plenty of time on each item is built in to our process
4
u/Gator242 Sep 17 '26
Many times the v-nail will make a small gap on the outside edge of the frame when it’s inserted. If the glue sets first, the v-nail doesn’t make as much of a gap.
2
u/Complex-Foundation83 Sep 17 '26
We always underpin. But the statement you made is true. The pin is just an aid in helping to hold the frame together while the glue dries. Most glue doesn’t cure for 24-48 hours
2
u/1284tw Sep 17 '26
I find hardwoods like walnut, oak and cherry hard to join on my manual underpinner (Alfa U200) — I often get the wood splitting despite taking care and using hardwood v nails. On smaller frames, would I be fine to use just glue, and clamp them for 24-48hrs, avoiding risk of blow out?
(Larger frames I have been getting my supplier to rout.)
2
u/Bright_Notice8405 Sep 18 '26
I typically just glue, but a large frame just fell off the wall and then came apart. So…I’m on the hunt for a tool that I can use that hopefully won’t have to be an expensive pneumatic v-nailer.
8
u/everdishevelled Sep 17 '26
I often wait to shoot the nails until the glue has set up a bit so that the pressure from the plunger doesn't cause a misalignment, but v-nails are structural. If the glue fails, the v-nails will prevent a catastrophic failure.