Marking specifications and sizes on the end faces of long pipes with thin wall thicknesses is difficult and time consuming. Since I had a tough time centering the character punches on these thin walls, I manufactured a letter-punching jig that fits over the pipe face to punch equal-distanced and symmetrical characters.
The hardened jig has an annular groove that accommodates the pipe's I.D. and O.D. and a machined slot that accepts three to four punches simultaneously. With the jig on the pipe, I arrange the required punches in the slot and hammer them.
S. Ram Murthy
Andhra Pradesh, India