There are basically 3 types of hinge or joint pin ,
1 Solid ,as an integral part of the action body .Used by Webley and Westley Richards as well as many other maker in the past.
2 Loose pin which was driven into the body with an interference fit ,frequently with locking pins of some description .AyA still use this method for example .
3 Screw in .Self explanatory a pin that is threaded and screws into the action. These are depending on the gun a " through pin " as one that goes completely through the action , Purdey being a prime example .Or. A "hidden" pin that only goes through the centre part of the action with caps or cover plates to " fill " the holes on the action bars .On many boxlocks that used either a screw or knock in pin the caps could be removable or blind , as in fitted with no intention of them being removed .
Re-jointing any gun has to be considered on it merits , be it a new joint pin or welding up the hook ,depending on how far back the barrel needs to move .
I have tightened and re-jointed hundreds of guns building up hooks as well as making new over sized joint pins .
In some cases with knock in pins that have worked loose the hole in the body can become elongated so needs to be reamed out and a larger diameter pin made .Knocking out and turning has in my experience been largely waste of time .
As to jointing new guns with loose pins , it was the practice to joint with a slave pin ,then to ream through and fit a correct size matching pin .
