Mending cracks

[jbb]

Is there anything that is used to mend hairline cracks in plastic? I'm not too concerned about the looks just the function. If this has been already discussed to death can someone point me towards a post on it. Thanks in advance.

[framebaer]

Depends on what plastic the pen is made from.

" determine what plastic you have so you can use the correct solvent (methylene chloride, methy ethyl ketone, diethyl ether, xylene, all work on different plastics). "

Above quote ( ZeissIkon) from an old thread. I suggest you search "solvent welding") to get more threads.

 

Edited March 12, 2010 by framebaer

[jbb]

Depends on what plastic the pen is made from.

" determine what plastic you have so you can use the correct solvent (methylene chloride, methy ethyl ketone, diethyl ether, xylene, all work on different plastics). "

Above quote ( ZeissIkon) from an old thread. I suggest you search "solvent welding") to get more threads.

 

Gee, I was hoping for something more along the lines of "just buy a tube Handy-Dandy Fountain Pen Crack Fixer." How about for a Sheaffer school pen for starters? I've got a crack in the nib/feed part of one of those.

[ZeissIkon]

Cracked sections are the worst place to attempt a repair, because the wedge action of the nib and the leverage of writing pressure put a lot of tension on the joint, but at least Sheaffer cartridge pens have sections made from a plastic that can be welded. Best technique is to knock out the nib and feed (which I haven't tried on one of those pens, perhaps someone else can suggest how to approach it), spread the crack a little (insert something into the section bore to do this), apply solvent so it wicks into the crack, then clamp the repair until the solvent has evaporate. For that material, I'd try methylene chloride for a start; it's most available in the USA as Ambroid ProWeld, sold in hobby shops for building plastic scale models.

 

Hint: when reinstalling nib and feed, if you have a choice, orient the repaired crack so it's under the feed rather than on the sides or on top of the nib; writing pressure applies the least stress in that location.

[jbb]

Thanks!

[tmenyc]

I'd try methylene chloride for a start; it's most available in the USA as Ambroid ProWeld, sold in hobby shops for building plastic scale models.

 

I agree -- I'm one of those plastic scale model builders -- Ambroid is great for some uses. Know, however, that it's a relatively hot solvent. If your bottle comes with a little brush built into the cap, DON'T USE IT for this job! Feather it in with a drafting pen or (knowing your stuff)a xf dip nib, using only a little bit, because it will craze surrounding plastic pretty quickly if you miss your target. Ambroid will get into the crack by capillary action, although it's not the thinnest solvent around for that. Make sure your barrel is well vised in somewhere so you can walk away from it; the Ambroid will need a good hour to cure; leave it for half a day if you're going to sand over it.

 

Ambroid is not a good gap filler, but it will weld a pretty wide range of plastics. Note that the key word here is "weld" -- it's not a glue. It is a solvent, so it gets into the plastic and welds it together. Ambroid is not best for small pieces of polystyrene; it's a little heavy for that. But for sealing a crack or creating a strong joint that has a little length (essentially the same thing), I've not found better.

 

Finally, depending on where you work and the condition of your lungs, I'd recommend closing the bottle up right away and venting the area. It's not as toxic as lacquer thinner or a good snort of toluene, but it's up there...

 

Tim

Edited March 16, 2010 by tmenyc