Impact of hammer impact is sometimes not what happened
There may be a need to replace the broken hammer or you can see leather collar and assembly is intact
Hammer used for a long time, grease thickening. The coupling between the piston, the vice and the cylinder is reduced, and under normal circumstances the impact will be felt when the machine is switched on. It's better to change the grease. Or dilute it with a little oil.
In many cases, the machine needs to be preheated to work, especially in winter. This is normal.
