Several Cracks Restored - Waterman 42 Hard Rubber

[siamackz]

I haven't restored many cracked pens. This one had both - open ended and closed ended cracks, and so it was a real challenge. Pics and documentation below explain the process I followed. I hope it helps other amateur restorers.

[Ron Z]

Based on experience, I am rather skeptical about how long repairs will hold in hard rubber, especially when it is coming in contact with liquid. If it holds, great. But do be honest and come back and tell us if/when it fails.

[siamackz]

Based on experience, I am rather skeptical about how long repairs will hold in hard rubber, especially when it is coming in contact with liquid. If it holds, great. But do be honest and come back and tell us if/when it fails.

Yes good idea. Ill write back.

 

Is there a better way to repair such cracks, or are you suggesting in general that HR cracks are tough to mend permanently?

[Ron Z]

Repairs in hard rubber in general are very difficult. THE best pen mechanics I know (now out of the business) who was a mechanical engineer For Parker in Janesville, says that even when an epoxy sticks to hard rubber we don't know how long it will hold. I won't do repairs on hard rubber pens where the only joint is where the pieces butt together. If they overlap, its a different story. I don't think that I can provide any kind of guarantee that the repair will hold.

 

The strength of epoxy or other adhesives is described in pounds per square inch. With a barrel, the "square inch" part is lacking. Say the crack is 3/8 inch long and the material thirty thousandths thick - 0.375 X 0.030 = 0.011 square inches. Not much contact area - on a dubious bonding surface.

 

There are hardened water resistant cyanoacrylics out there, but not waterproof. I don't trust them for anything critical.

 

I will be interested in the long term success of the repair, and I do mean long term, as in months or years. (bookmark the thread!)

 

BTW, neither rosin nor shellac, nor Captain Tolleys (great stuff bTW) can provide any structural strength. The standard "solvent" for rosin is castor oil. It acts as a plasticizer so that the rosin can be applied to threads with minimal heat. Even when not cut with castor oil, it will soften to liquid as temperature rises. Put a pen in your pocked under a sweater, and the temperature will rise to close to 98F, especially if you're working hard. It doesn't matter with threads because they won't pull apart. Shellac works well because its used where surfaces overlap - cap lips, cap liners, sacs on sac nipples..... The rosin might seal the back end of the barrel because its filling the threads, but it won't give any strength if you're repairing a crack.

[siamackz]

Thanks for explaining, Ron. It seems like there isnt much else that can be done, so lets hope for the best (and learn from the results, I guess). Fingers crossed 🤞

[PaulS]

some additional comments to Ron's very informative and educational notes above, and which may be of interest to others who might at some time have considered using a band clamp, combined with adhesive, for the type of repair mentioned above.

 

Barrel thread cracks are covered at some length by Marshall & Oldfield in their Pen Repair Manual, and they too dismiss adhesives and clamps alone, as failing to provide long term repair. So, quick and simple permanent fixes appear non-existent, but just for the sake of mentioning another method of repairing cracks in barrel throats, these authors give instructions for a workable alternative solution, though this does require a lathe.

Some very small amount of wall thickness is reamed internally from the open end of the barrel, under the external threads, such that a sleeve can be scarfed inside the barrel for about 10 mm, and fixed with adhesive. Problems - thread-fitted sections will no longer have barrel threads to engage with, and will need to be converted to push fit.

 

Obviously there is a lot more to this exercise - details in the above pen manual - and the pen would need to be worth the time and effort - but done correctly this repair appears to provide strength and permanence, though originality is potentially lost.

 

No idea if Ron may at some time have used this method.

Edited September 18, 2018 by PaulS

[Ron Z]

In a sense this is what I do with the Namiki VP barrel repair - including threading. The difference is that the Namiki barrel is fairly thick, and the ID of the tubing when threaded is the same as the original ID. But even though I do a lot of lathe work, I do not sleeve barrels.

 

It is my experienced opinion that you do indeed need a lathe, and some skill in operating it. To do it effectively, you need a boring bar. You have far greater control in how much material is removed and how fast than with a drill or reamer. Cut too fast, or have the drill or reamer snag, and an already vulnerable, brittle barrel can shatter.

 

One reason I don't sleeve barrels is that I have seen multiple pens where someone tried to sleeve the barrel, and then had to shave the section down, only to find that there was no room in the barrel for the sac when on the sac nipple. ...and I've seen too many botched repair attempts to be tempted. Its sort of like the notes on the old nautical charts "There be danger here..."

[PaulS]

thanks Ron.

[siamackz]

Based on experience, I am rather skeptical about how long repairs will hold in hard rubber, especially when it is coming in contact with liquid. If it holds, great. But do be honest and come back and tell us if/when it fails.

Hi Ron, the hairlines did not hold. The pen is leaking again. Maybe a layer of some kind of rubber based adhesive from the inside of the barrel will help? There is some space in there right?

[Ron Z]

Hi Ron, the hairlines did not hold. The pen is leaking again. Maybe a layer of some kind of rubber based adhesive from the inside of the barrel will help? There is some space in there right?

 

Thanks for writing back. I'm sorry to hear that it didn't hold, but I think you are experiencing the problems of hard rubber repair first hand.

 

I really think you have done every thing possible to keep the crack from opening again or leaking the first time around. The cards were against you so to speak, even before you started the repair.

 

Start with the surface area for bonding. The technical data sheet shear strength numbers are for an overlapping joint, not a butt joint like you have. Overlap = a larger bonding area. Take a really good epoxy with a bond strength of 4500 PSI. Say the wall thickness is 25 thousands or 0,025", by 1/4" - so 0.250". Gives you a contact area of about 6 thousandths of a square inch. Not much surface area to bond, which is why I prefer solvent welding, which you can't do with hard rubber.

 

Then you're up against a material that doesn't like to be glued. A clean, fresh break might be repairable if you have enough surface area, or a freshly machined surface. But the oxidation in an old crack will prevent the adhesive from properly bonding to the rubber. Its even worse if "contaminated" with ink, and you try to clean the ink out with water. We know what happens when old rubber is immersed in water, and it will happen to the walls of the crack too.

 

There isn't enough clearance inside for you to put on a coating of a flexible adhesive and have it do any good - you already in effect did that with the rosin. The wall thickness isn't thick enough to allow you to sleeve on the inside, and then tap again. Its just too thin for that kind of operation. The only thing you could do is to put a band on the outside with the adhesive or sealant put in the crack first, and then a band swagged or slipped over the area, with an adhesive, on the outside. But then you're up against the aesthetic issue....

[siamackz]

Thanks so much for the thoughtful response, Ron. This has been a fruitful learning experience for me at least.

[Ron Z]

This has been a fruitful learning experience for me at least.

 

...and for others as well I hope! One of the reasons why I appreciate that you took the time to update us on how the repair held up.

 

This is one of the reasons why I often do a repair on my own pen before I do it for others. I keep the pen in rotation for some time as a test to see how durable the repair is. Once that is established, I feel free to do the repair for others. In many cases I also get to see the long term reliability, as I still have and use the pens many years later.

[siamackz]

Seeing how there arent many options to restore this pen, the owner wishes to experiment with applying some urushi on the inside. This is not my advice as I have no clue what urushi does or doesnt do. But he wishes to give it a shot. If he does so, it will be an experiment worth following and I will share the results once again after a few months.