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HP Forum Archive 09

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HP41 Repair Cracked Posts
Message #1 Posted by Peter Graves on 4 Nov 2002, 10:04 a.m.

I have an HP41C with one cracked and one missing screw posts both on the lower part of the calculator. Does anyone have some tips how to repair this?

Re: HP41 Repair Cracked Posts
Message #2 Posted by David Smith on 4 Nov 2002, 3:07 p.m.,
in response to message #1 by Peter Graves

I fix cracked screw posts with a plastic welding solvent available at most hobby shops. It comes in small bottles and contains the solvent methylene chloride (a.k.a. dichloromethane). It works by melting the plastic togteher. Standard and super glues will always fail.

My fix for sheared off screw posts (or missing ones) is much the same. However, I drill out the hole in the post until the screw slides into it without threading. I then fuse it to the place where the old posts was, and thread a 1/4" longer screw through the hole into the case, tighten it down and let the weld set 24 hours. The screw post now just acts like a bushing, with no screw stress on it. The longer screws thread down into the case plastic where there is a lot of reinforcing, etc.

As far as where to get the longer screws... lotsa luck finding them. They are 2-28 self tapping sheet metal screw with a type "B" point. Also something called "Plastite" (?) screws are preferred.

To replace a missing post you will need to make one either by cutting a post off a truly defective HP41 or out of ABS/styrene plastic. The diamter is non-standard (something like 11/64"?). You will need to machine down some larger rod material.

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