Metal lathe or Machining question

[Gspragge]

It has been suggested that the three holes in the base of this 1 Pr is to mount or centre it on a lathe.
I have never seen this before on a military projectile and I would be very surprized to see one
accepted for service like this. But does any one have any knowledge of this kind of thing ?

 

[.*.*.]

I have seen the three holes in Pak 37 cases - I am not sure if it was to centre on a lathe but they are exactly the same. I have one somewhere and will try to find today to show as an example. WF

 

[BMG50]

To get three equaly spaced hole you can use an indexing tool either on a milling machine or lathe.

 

[wichitaslumlord]

The use of indexing holes would seem to be an inefficient way to hold the workpiece. It would require a separate drilling operation. Items machined around this time period would most likely have been done on a manual turret lathe which would have used a standard chuck to hold the workpiece against either a live or dead center for turning. The use of a collet would have also been a possibility once part of the outside was machined or if bar stock was being used.
These may well be original but it is an odd way of holding the item. Pat

 

[Tmine35]

I have not seen a Pak 37 case with 3 holes, but with 4 holes - combined case with brass jacket and steel base. Holes on base are for wrench to tighten the nut binding parts together.

 

[Gspragge]

Does seem odd unless it has been machined twice ? These are usually cast then machined to a final shape. There is nothing to tighten as it is one piece.

 

[HAZORD]

It could be an early variation of tracer. The 120mm tank projectiles have 4 tracers arranged this same way, except being newer they screw in.

 

[2pounder]

to get a smooth flat face the easy way is to face it on a lathe, not machine it across like the rest of the marks show. I'm with the theory you're producing thousands so do it the cheapest and therefore quickest way possible. I'm no expert but turn of the century technology would imply cast or forge near to final shape and then turn and thread in a capstan lathe or similar. to put 3 holes in the base is un necessary.