Est. 1998 — 27 years of woodworking knowledge
Repairing a crack/split in wood
Bill Tindall, E.Tn.
Occasionally a crack will show up in a place that would not be fatal if it could be glued back together. The problem is how to get glue in a crack- Dental Floss.
Put a glob of glue on the outside and pull it into the crack with the floss. Then clamp.
You can see the effectiveness of this procedure in the picture. Glue has squeezed out where the crack is exposed on both edges, even to the bottom of the crack.
Re: Repairing a crack/split in wood
John K Jordan
That's a good technique.
I use dental floss for other things in the shop too. For example, wrap many turns and apply glue to reinforce something, such as a quick ferrule for a tiny turning tool for miniatures or for a functional repair for nearly any small thing when it doesn't have to look pretty, sometimes dousing with CA - very strong. I always use unwaxed, though.
JKJ
Re: Repairing a crack/split in wood
Gary Smyth
My first go to is to use my shop vacuum nozzle underneath the piece. If needed I make a partial seal using gaffer's tape with the nozzle against the work. The vacuum will pull glue into the crack suprisingly effectively. My method can be a bit messy, but it does the job.
I'll try floss next time to see if a small crack problem gets solved as well.
Re: Repairing a crack/split in wood
Ralph Lipeles
I use a small artists spatula. The blade is maybe .005" thick and 1/2" wide. The blade can be pushed into places that dental floss would not go into.
Re: Repairing a crack/split in wood
Bruce, a MN Galoot
Nice one. I used a .002” feeler gauge blade to do the same thing.
Re: Repairing a crack/split in wood
Barry Irby
Good one. I'll file that away under future skills.
I have tried the vacuum technique and I have used the air nozzle to blow it into joints. On small pieces I have stuck the end in my mouth and blown the glue into the joint manually. I am very familiar with the taste of Elmer's.
While we'er at it...
Gary Smyth
I'm with Ralph and Bruce. 
When you make as many mistakes as I do, you need all the help available. Palette knives are an option as are feeler gauges, both as a small thin, strong pry to get in and are inexpensive. Another BIG help are clay sculpting tools. They fit into corners and along edges to scoop the secondary glue seepage that a rag doesn't get and with less disturbance to the wood.
Re: Repairing a crack/split in wood
Dave Bair
Just make sure that it's UNWAXED dental floss.
Re: Repairing a crack/split in wood
AZ in Colorado Springs
I've used the shop vac method several times and yss tooth picks when I need to force glue inti a crack.
Nifty, Bill
Ellis Walentine
My go-to method has always been to lay a bead of glue alongside the crack and squeegee it in with a finger until there's only a hint of glue left on the surface. At that point, the whole bead has been forced into the crack, usually right to the bottom.
Ellis