I would like to thank all for their help and advice. I found that in addition to the posts the screw bosses were also damaged. They had broken away completely from the body of the calculator. This is how I made the repair.
Methylene chloride is not easily available due to its dubious effect on health. I used Methyl Ethyl Ketone (MEK)which is a good solvent for ABS. To reinforce the weld I used snall pieces of 50 micron ABS film carefully building up a strong weld over the bosses by melting the sheet into the body with MEK. A couple of layers have provided an extremely strong repair.
To repair the posts I preformed a cylinder of ABS fro the same film around a small diameter wire. This I inserted into the centre of the post welding it in place with MEK. I did the same on the outside of the post. The thin fil melts under the influence of the MEK filling up any cracks in the post again forming an extremely stron repair.
I left the repair for 48 hours before reassembling the calculator which is again working perfectly.
Best regards to all HP repairers.
Roger Hubbert