HP 41 screw post repair

[Martin Hepperle]

In the past I have used ready-made brass inserts with M2 threads and knurled outer surfaces e.g. to replace posts in HP 75 calculators.

These parts can be found im many, many variants, e.g. on Aliexpress. They are usually for being heat pressed into injection molded parts or added directly during the molding process.
There are also small boxes with an assortment of lengths which are very handy. The smallest thread size seems to be M2, the outer diameter is about 3 mm but could be reduced slightly on a lathe.

In these repairs I have removed to old, completely cracked and brittle posts completely and drilled a small hole to about 2 mm depth to screw the brass insert into the plastic base plate.
Then I applied steel filled gray epoxy to the connection. Depending on the counter-part one has to add a small M2 washer unter the screw head to provide enough surface area to distribute the pressure exerted by the screw head.

Martin