Which Glue?


I am currently restauring a hp45 and I have a problem with the ON/OFF switch, its base is broken in two. I would like to glue it back together but I fear gluing it to the metal part on which it is sliding as well. I don't want to open the calc for that.
Any idea which kind of glue would glue the plastic together but not the metal?

I would also like to know how to unweld the tabs in the battery pack. If possible. I have been trying to search the archives for hp45 but it does not seem to work.

Thank you,



See my caution below, and proceed at your own risk!

I think that methylene chloride might do the trick, though I've never tried it in a situation such as you describe. I found it (in the NW U.S.) as "Ambroid ProWeld" in a hobby shop. (I understand that what I have is not 100% methylene chloride, and that a stronger solution, if found, would be better.) I've used it for several things HP-related.

You need to hold the pieces to be glued together closely, and let the glue be drawn into the joint by capillary action. The pieces must be held in close approximation for some time. (At least an hour?) The methylene chloride (a highly volatile aromatic hydrocarbon, if I've got my chemistry straight) melts the plastic and fuses the pieces together. A few of the things on which I have used it (including an HP-97 battery compartment door, broken right in half) seem as strong as new. (But it hasn't worked on everything.)

I worry, however about applying it to anything attached to a calculator, and to anything that needs to move again someday. If at all possible, take the switch out of the calculator before using any glue.


Actually methylene chloride is a chlorinated hydrocarbon, aliphatic, not aromatic, even if it does have a powerful aroma, AND IS A SUSPECTED CARCINOGEN (okay, so what isn't?)!

As for other solvents as glues, if this works, then you need one of low polarity (not the battery or circuit kind) like gasoline or one of its components, though these are all less than friendly compounds, as far as our health is concerned. But I suppose you'd only need a little bit.

Oh! A flash(back)- old fashioned model glue! This stuff is toluene based, which is also a nonpolar substance, and should dissolve the same stuff methylene chloride does, but is not carcenogenic. But kids used to get high on this stuff. One other problem- this stuff is usually sold in rather viscous form as compared to the pure solvent and may leave some surface marring if you're not like an expert craftsman or model builder. Maybe a slightly beaten looking HP is better than a nonfunctioning one.


Regarding the battery terminals, what I do is slide a strong but thin knife under the material and pry up. Worst case, it will leave a little of the material behind exactly where the weld was. However, there is usually plenty of material left to solder to, particularly if the replacement nicads you're using have solder tabs.


I've rebuilt a lot of HP and TI packs. I guess I take a less precise approach.... I tear off the metal tabs by twisting into a circle using needle-nose pliars (hemostat), then straighten them, flatten, and grind. When tinned, they make a nice, strong, flat joint with the tinned end of the battery. (It also is a quick way to detach from leaking batteries without much handling.) Despite the warnings, with a really hot iron there seems to be no damage to the batteries from the brief heat. (Besides, modern NiCd's can get normally quite hot in use in a high-drain device. Many manuals have said to let them cool before charging.) But mostly:
I don't have a spot-welder.

I take a more delicate approach to a lot of other things.... honest.

(sound of crashing and breaking),


This Message was deleted. This empty message preserves the threading when a post with followup(s) is deleted.


Appart from the fact that it is just slightly older than me (1301), there is some sentimental value. This one was just given to me by my dad as a birthday present so like said in a post, I prefer an estheticaly challenged calc to a functionally challenged calc so I won't open this one. I have a couple of others as spares (one with the same switch problem) so I might explore one of these.
As to cleaning the keyboard, I found that window cleaning liquid (windowlene here in the UK: mostly some kind of alcool or an other I believe) works wonders when used with coton buds.

Thanks all for your help.



After looking around I didn't find methylene chloride glue so I went to the model shop. I had to go anyway for chrome paint for the same calc, that works wonders if you have a steady hand. I asked for the most liquid glue and it worked. I just had to move the switch when the glue was getting dry to avoid getting the switch glued to the calc body.
Thanks for all your help.


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