Cracked Jinhao 992. My preventable mistake. (Hypothesis)

[KB3K]

The Jinhao 992 is cheap, and it’s hardly the end of the world if you crack one, but this could apply to more expensive pens. The cracks started on the barrel where it is threaded inside and out to connect to the section and cap respectively. The section has a rubber o-ring that provides friction to hold the parts together. After the cracking had begun I kept using the pen. I noticed the crack would cause the barrel to expand if the section was screwed in with anything but a minimal amount of torque. This could easily prevent the cap from threading onto the now-oversized barrel. I think the o-ring acted as a wedge splitting barrel apart, possibly in conjunction with the cap applying force to the barrel which would have been under tension prior to cracks forming. I know that over tightening can damage o-rings and gaskets, so I don’t think I ever applied what would typically be considered excessive torque.  This makes me think that 992s might last longer if the section is lightly tightened just enough to hold things in place, and not “finger tight, or “snug”.

 

A more expensive pen with a similar design would (hopefully) be made with better material and have threads formed more precisely, and could possibly last a lifetime being tightened the way the Jinhao was, but there are individuals who have tough hardened hands that could torque a cap down harder than I ever could without them really meaning to. Could they crack a high-end pen? It’s an interesting question, but one probably best left unanswered.

 

Or… my idea might be completely wrong, applied torque may have had nothing to do with the cracking I observed and I may have just contributed to the heap of misinformation on the internet. It’s not really worth designing an experiment to find out, but if you’ve had experiences  that support or detract from this idea I’d like to know. (If your children are desperate for a science fair project, a pen based experiment would be better than soaking teeth in soda. I’ve seen more teeth in soda than you would believe). 
 

I do like the Jinhao 992, and will continue to use them. Since using minimal torque is unlikely hurt anything I’ll probably try that. If they crack anyway, I’ll report back and eat crow. (Is “eating crow” too obscure of an idiom? It’s hard for me to know, considering the international nature of the forum.)

[Mech-for-i]

well, as one who actually used to work engineering I can tell you any parts with a thread that mates to another parts , whether made in plastic, or metal or anything else risk damage with over tightening and/or tolerance or mis-threading or any combo , cracking of a part especially with threaded parts ( and any adjoining ones ) is not uncommon and in fact contribute to fair large portion of mechanical failure from a split barrel to downing the first ever Jet liner ( yeah the famous Comet metal fatigue ) 

 

it is definitely possible for user to break or introduce undue stress onto fountain pen barrel / cap / whatever pars with threading action so long its not tightened properly , over tighten or even loosely tighten ( leaving parts rattling and hammering into each other ). Seen ofte in vintage pens , cracked cap lips , barrels and so are really frequently seen

[Ron Z]

Cracked cap lips are usually because the cap was posted on the barrel with too much pressure.

 

Cracked barrel edges, or caps that are cracked in the middle of the cap, above the cap band, is usually because of over tightening.  Snug, OK.  Torquing the cap on the pen, no.

[Paganini]

I've had 992s crack in the way you describe while sitting unused on tables. Not to say that your concept of physics is wrong, but in the specific case of the 992 the inside parts seem to be slightly too large for the outside parts that they nest in, meaning that the extremely flimsy plastic all the parts are made from is under constant stress. 

[sansenri]

I agree that the problem here is that the cheap/fragile material and the type of plastic used tend to favour the cracks.

I've read of repairing and even preventing the cracks in this pen, that typically develop on the bottom of the barrel, using epossidic be-component sealer.

[Mech-for-i]

those stress probably originated from the manufacturing of the parts during the molding and extraction process , which is rather common in injection molded plastic parts

[sansenri]

1 hour ago, Mech-for-i said:

those stress probably originated from the manufacturing of the parts during the molding and extraction process , which is rather common in injection molded plastic parts

no doubt,

the point is this specific pen is subject to cracking in a very high percentage of cases,

try googling "jinhao 992 cracking" you'll see what I mean.

Some have discovered that not only you can repair the cracked barrel especially if caught early, but you can even prevent it (again, if you act early enough, some people reported their pens developed cracks within a few days of receiving them...).

At the same time you can seal the pen so as to use it as an eyedropper.

Best way seems to be using be-component epossidic glue which stops the cracks developing, but is tricky to use and should be handled with gloves.

 

 

[KB3K]

It sounds like the design has a bit too much going on all at one spot to be produced so inexpensively. Section mating barrel on one side and cap mating barrel just through a thin plastic wall.  I’ve had better luck with the Jinhao Sharks, which are even cheaper, but seem have a simpler and more robust design.

 

I really do like the design. I might have to break down and buy a Sailor Compass 1911, which looks astonishingly similar. (I wonder what they thought when they found out they each designed the exact same pen?;) I haven’t heard about the Sailors cracking, but I’m glad that if I caused the crack on the Jinhao I made the mistake on a super cheap pen.

[bugsydog55]

This particular pen does not require the user to do anything at all.  Of all the pens I have purchased over the years, the 992, and to a lesser extent the 991, have been the only pens to self destruct in a pen case.  Cap finials have snapped off, sections crack, caps actually have chunks fall off, barrels separate from threaded areas, barrel bottoms split and all of this with new and unused pens.  The type of design hits such a perfect spot for a lot of users and I still have a few that have held up over the years.  I cannot say what the difference is, why would one work out and the twin fall apart.  For all of that, I still like the pen and I will use one or two every other month or so.  But the number of these keeps going down.  I'll not be getting any more of these but they will have been a lot of fun while they lasted.

[sansenri]

10 hours ago, KB3K said:

It sounds like the design has a bit too much going on all at one spot to be produced so inexpensively. Section mating barrel on one side and cap mating barrel just through a thin plastic wall.  I’ve had better luck with the Jinhao Sharks, which are even cheaper, but seem have a simpler and more robust design.

 

I really do like the design. I might have to break down and buy a Sailor Compass 1911, which looks astonishingly similar. (I wonder what they thought when they found out they each designed the exact same pen?;) I haven’t heard about the Sailors cracking, but I’m glad that if I caused the crack on the Jinhao I made the mistake on a super cheap pen.

 

It's not you, as we are trying to say and bugsydog55 explains well, this pen will self destruct like in mission impossible...

[sansenri]

20 hours ago, KB3K said:

(Is “eating crow” too obscure of an idiom? It’s hard for me to know, considering the international nature of the forum.)

 

Btw this is a fun bit, I had never really heard of the expression "eating crow" despite, although being Italian, I have some knowledge of English language.

The meaning was rather clear before actually looking the meaning up on google.

I have this picture in my mind of Oliver Hardy eating his hat, so I immediately guessed what it might mean.

And it is confirmed (I also read that it might have been Kipling in one of his tales bringing this idiom into the language).

[KB3K]

5 hours ago, sansenri said:

 

Btw this is a fun bit, I had never really heard of the expression "eating crow" despite, although being Italian, I have some knowledge of English language.

The meaning was rather clear before actually looking the meaning up on google.

I have this picture in my mind of Oliver Hardy eating his hat, so I immediately guessed what it might mean.

And it is confirmed (I also read that it might have been Kipling in one of his tales bringing this idiom into the language).

The virtue of a phrase like “eating crow” is that it is obviously not literal. What can really throw people for a loop are things like the American use of “How are you doing.” I tried to write a primer about navigating this phrase with Americans, but my 992 blew up….

 

It’s too bad too, the 992 has just about everything I look for in a fountain pen; Classic looks, light weight, and a sleek simple grip. I don’t expect a cheap pen to last forever, but it would be nice if it could outlast a Bic or two. I also like giving pens and a few ink cartridges to friends who have never tried a fountain pen before, but if it breaks before they can decide if they want to invest in something nicer, it isn’t really helping the cause. If one dies on me, no big deal. I’m already hooked on fountain pens. There are definitely pens that cost a bit more that are reliable, but the cheaper I can go, The more freely I’ll pass them along.
 

(The primer is real, but off topic. If someone is actually curious they can message me)

[BrassRatt]

Stress left in from manufacturing . . . 

 

Is it possible to anneal that particular plastic, by heat, to relieve these stresses?  This works for some plastics; some must not be annealed using hot water but only dry heat; the required temperature and time vary quite a bit.  

 

I have not tried to anneal Jinhao 992s yet.

 

 Has someone? 

 

[Mech-for-i]

In theory it's possible but we are talking temp way beyond what boiling water can provide .. but it's never a waste to try .. in a fashion it's not annealing but more like tempering , I have no idea what's the property of the plastic but putting them into a pot of boiling water on the stove and let it cook for might be 30 sec to a minute, then turn off the heat and cover the pot , let it cool naturally sound the way to go

 

Why does it sound like some culinary instructions !!

 

In real world industrial application, tempering are usually done over fair period of time in mineral oil ( retain and can get to pretty high temp without boiling )