I have done a lot of pens with polyurethane glue. It is my glue of choice for pen making. I use it for every pen, other than a few special needs (e.g., translucent pen blanks). I usually glue about 8 or 10 pen blanks at a time. I do it inside the house where it is comfortable, but with great care not to make a mess. I have never had a failure. It is hard for me to imagine that the failure above occurred, but it did. Here are a few notes and clarifications about polyurethane glue.
How To Apply Polyurethane Glue for Gluing Brass Pen Tubes in Pen Blanks:
Materials:
* Pen tubes and matching drilled pen blanks
* Sandpaper - Any small throwaway bit of sandpaper will do, in any grit that is
not extra course.
* Q-tip type cotton swab - If you have a lot of pens to do, you may need more than one, as they get swollen and yucky in use.
* Disposable glove
* Paper towel - If you have a lot of pens to do, you may need more than one sheet. Keep a waste can nearby - polyurethane can be messy.
* Wax paper - Used to protect your work surface from foaming glue as it cures. Those Rockler silicone project mats work great, and they are reusable.
* Water - I use an empty plastic pill bottle to hold the water, for convenience
* Polyurethane Glue - I use Gorilla Glue (original) and White Gorilla Glue (see comments below)
* Chisel
* The long "drill bit" part of pen mills that match your pen tubes, used to push out dried glue.
Instructions:
1. Roughen the outside of the brass pen tube with sandpaper. The sandpaper type doesn't matter. Wipe or blow off the sandpaper and brass dust when finished.
2. (Optional) Plug the brass pen tube with the material of your choice: dental wax, PlayDoh, etc. In theory, this prevents the glue from getting inside the brass tube. I don't bother. I find it easy to clean out the dried polyurethane glue. I do not find it easy to clean out dental wax or PlayDoh.
3. Repeat steps 1 and 2 for each pen tube you are planning to glue. Keep each tube with its matching pen blank to avoid confusion.
4. Put the disposable glove on your hand that will hold and insert the pen tubes
5. Polyurethane glue needs moisture. Take a Q-tip type cotton swab, dip it in the water, and then use it to moisten the inside of the hole in the pen blank.
6. Hold the pen tube in your gloved hand.
7. Use the other hand to apply the polyurethane glue in a spiral around the pen tube.
8. Set the glue bottle down and pick up the wetted pen blank.
9. Using a twisting in-and-out motion, insert the gluey pen tube into the pen blank. Your motion should spread the glue uniformly around the tube and inside the pen blank. Relax. There is time to do it right.
10. Use your gloved thumb to push the tube fully into the pen blank hole. I like to take my gluey thumb and wipe off the excess glue from the top of the pen blank.
11. Use the paper towel to wipe the excess glue from your gloved thumb. Put the sticky, messy paper towel in a safe place.
12. Set the pen blank on its side, down on the wax paper. Leave room so that the foaming glue won't go past the edge of the wax paper.
13. Repeat steps 5 through 12 for each pen blank and matching tube.
14. When you're done, wipe the top of the glue bottle clean with a clean, new paper towel. Squeeze the glue bottle to remove the air, and while squeezing, screw the cap back on the glue bottle.
15. Allow the polyurethane glue to cure for 24 hours or more.
Caveat: I have heard rumors that the foaming glue can push the pen tube partly out, beyond the top of the pen blank, but it has never happened to me. I make sure that the pen tube is fully inserted, slightly below the top of the pen blank, to leave room for milling. I leave the pen blank on its side, level, while the glue cures.
16. After the glue cures, use the chisel to knock off the excess glue from the top of each pen blank.
CAUTION: Never never never allow a finger or thumb to be in the path of the chisel!! Use a clamp to hold the pen blank and/or keep your fingers below the surface that you are scraping.
17. Use the "drill" part of a pen mill to push the dried glue out of the inside of each pen tube. It usually comes out very clean for me, but on extremely rare occasions, I need a rattail file to clean it
gently.
Notes and Clarifications about Polyurethane Glue for Pens:
* Gorilla Glue (original) and White Gorilla Glue are both polyurethane glues. Both should be used with water. Polyurethane glue foams as it cures. The original Gorilla Glue cures to a pale yellow. White Gorilla Glue cures white.
* White Gorilla Glue works just as well as original Gorilla Glue. It is more runny, which I don't like because it tends to drip before I can get the tube in the pen blank. White Gorilla Glue hardens faster than the original Gorilla Glue, but I still recommend waiting a full 24 hours to cure before turning the pen.
* Clear Gorilla Glue is NOT a polyurethane glue, it is a a silane-based glue. It does not foam. It can also be used for pens. It still requires 24 hours to cure.
* There are other brands of polyurethane glue, and they are equally good. I buy Gorilla Glue for the convenient small size.
* I buy the smallest bottles of Gorilla Glue for pens. They cost around $5 each at any hardware store. Read the label carefully to make sure you are getting original Gorilla Glue and not Gorilla Wood Glue or some other product.
* The smallest bottle will glue 40-50 pens or more. Even though you get a better value from buying larger quantities, I can't use up that much before it goes bad - in about a year.
* Protect your polyurethane glue from moisture. Don't store it in the refrigerator or freezer. When you remove it, the condensation will kill it.
* Before putting the glue away, clean the tip with a clean, dry paper towel. Squeeze the air out of the bottle to remove as much airborne moisture as possible. While squeezed, apply the cap to seal it.
* You know your polyurethane glue is done when it gets thicker and harder to squeeze out of the bottle, or it changes color. Throw it away and buy another.
* Despite the hype, polyurethane glue is not stronger than other glues typically used in woodworking. Epoxy is stronger. So is wood glue (for wood joinery, never for pen tubes).
* I like how polyurethane glue expands to fill gaps between pen tubes, but that foamy glue does
not form a strong bond.
Polyurethane glue will not compensate for a pen blank hole that is too large for the pen tube. I like the foaming action because it prevents the pen tube from wiggling during assembly and use where there are small chips or minor gaps.
* If you have a pen blank with a hole that is too large for the pen tube (but still possible to salvage). Do not use and count on polyurethane to "fill the gap." See the note above. Instead, use epoxy to provide adhesion and structural strength. Add prayer after it cures.
Some Reasons Why a Polyurethane-glued Pen Failed During Turning:
* Hole too large for pen tube. The polyurethane foaming action fills the gap, but that foamed glue is weak.
* The pen turner did not allow enough time for the polyurethane glue to cure.
* Lack of moisture in the pen blank made a weak cure.
* Polyurethane glue was not applied sufficiently and spread well-enough to make good contact between the pen tube and the pen blank. Instead, the glue foamed to make it appear well-glued, but as I said above, the foamed polyurethane glue is not strong.
* Polyurethane glue was too old.
* Polyurethane glue was subjected to undesirable environmental conditions, such as extreme heat or cold, or moisture in the bottle.
* The root cause has nothing to do with the type of glue used and the pen would have failed with epoxy or CA just as well. Punky wood, dull tools, poor technique, lathe speed, etc. etc. etc.
* Pen Turner is unlucky.
(Note: Not all of these apply to the OP.)
