The indicator shaft may come loose from the plunger. If it falls out without anyone noticing, a mask will incorrectly be failed and be permanently destroyed. If the plunger only loosens, it will reduce the amount of pressure the mask punch provides when the indicator shows that the punch is at 12kg and thereby passing a mask that should fail. In order to safeguard against this, apply lock-tite onto the threads of the punch where it screws into the indicator shaft. In use, before using on each and every mask you test, take the mask punch apart and inspect the punch and ensure that the indicator shaft is screwed onto it tightly.
Experience shows that use and transport routinely loosen the indicator shaft.
Uhlmann The Uhlmann mask punch is the smallest unit available. It has a small aluminum barrel and no indicator hole in the end for tactile usage. Instead, on its barrel are two shoulders. The shoulder nearest the barrel is the visual indicator. This mask punch is extremely portable.