Cold chisel mystery

[Rudi McAnichal]

There’s a hole in my chisel …

Big cold chisel, acquired in a box of junk. The head was in a sorry state, and looked as though flakes of metal might fly off in all directions if struck hard, so I thought it would be safest to saw the end off. Doing so revealed a 0.25 inch diameter hole drilled almost the whole length. I have never seen anything like it before, but I don´t make a habit of sawing up cold chisels. There must have been a very good reason for it, because drilling a 14 inch deep hole in tool steel is not a trivial task.

The stock is hexagonal, whereas cold chisels are commonly octagonal. Maybe it was originally intended for something else, and then forged into a chisel. But why would anybody need a hexagonal bar with a central hole?

 

[Rudi McAnichal]

Sorry, must have inserted the same picture three times.

 

[Paul99]

My guess is that it's a section of air rifle / rifle barrel - we have a very old .25 air rifle here with a hexagonal barrell just like that - possibly something a gunsmith made up from scrap for a certain job that required a big chisel.

 

[glynygof]

Your chisel looks like it is made out of a section of an old rock drill.Compressed air is admitted through the centre drilling to blow away the dust from the bottom of the hole being drilled.They were made in long lenghths to enable deep holes to be drilled for blasting.

 

[Rudi McAnichal]

Thanks for those ideas.

Air rifle barrel? It is a smooth bore hole, but there were plenty of smooth-bore air guns in the past. I ought to have mentioned that the hexagon is 1 inch across flats, so it would have to be a very heavy barrel, the sort of thing you might find on a .577 for shooting heffalumps.

Rock drill? I cannot recall where the chisel came from (it has been lying in my garage for 20 years or more), but this suggestion reminds me that it could possibly have been via my late mother-in-law, whose own grandfather was a rockman in the slate quarries at Glyn Ceiriog.

 

[Paul99]

Thanks for those ideas.

Air rifle barrel? It is a smooth bore hole, but there were plenty of smooth-bore air guns in the past. I ought to have mentioned that the hexagon is 1 inch across flats, so it would have to be a very heavy barrel, the sort of thing you might find on a .577 for shooting heffalumps.

Rock drill? I cannot recall where the chisel came from (it has been lying in my garage for 20 years or more), but this suggestion reminds me that it could possibly have been via my late mother-in-law, whose own grandfather was a rockman in the slate quarries at Glyn Ceiriog.

Ah much to heavy for a barrell then - the old hex barrelled .25 we have is seriously heavy but no where near that. I believe that cutting rifling (button rifling) into a smooth bore was more common back in the distant past which coupled with the size of the bore got me thinking about being barrell. Rock drill shank sounds good - would be the right kind of steel for a cold chisel too...

 

[Rudi McAnichal]

I watched rifling cut by hand in little machine shops on the North West Frontier, about 40 years ago.

They simply heated and twisted a long steel strip (probably about 60mm x 5mm section), then fitted a swivel handle at one end, and a rod with a single point cutting tool at the other end (like a boring bar). The twisted strip ran through a fixed slot. As the operator pushed and pulled on the swivel handle, the rod and cutting tool created a groove inside the barrel, following the same twist rate as the steel strip. Simples.