What are "Tommy Holes"?

[GaryK]

I am looking at the drawing for the Stuart twin launch and came across something I've never heard of before.

The drawing for the piston call out 2 "Tommy Holes". Now only don't I know what they are but I have no idea what they are used for. See drawing below:

My English to English translator doesn't seem to be working.

The only possible use I can see for them is for a spanner to keep the piston from rotating when the piston rod is screwed in, but they seem a little small even for that.

Any help would be appreciated.

Gary

 

[goldstar31]

Tommy Bar? All it is a couple of pegs properly spaced and the right size on a handle which fit the two holes to tighten up or slacken the part.

If you look at the spanner for the average angle grinder to fit and remove disks etc, that's a Tommy Bar.

 

[RonGinger]

I know about Tommy bars and holes, what I want to know is who was Tommy, and why did his name get attached to these holes? I think it is an English term, but Sherline uses it for their chucks. Maybe it came to Sherline because the machine was originally developed by an Australian.

 

[goldstar31]

Obviously 'Tommy Atkins' who was the apocryphal British soldier- the British Tommy.

 

[Sshire]

Same thing on Elmer's Pumping Engine. The piston is tapped for the piston rod and has two holes for a tool with two pins to adjust the piston up or down in the cylinder during assembly. Elmer does not use the term "Tommy bar or Tommy hole."
According to the Oxford English Dictionary, the term, "Tommy Bar", was first used in WW I.
"A bent wire spanner used by British forces in the disassembly of Mills Bombs (hand grenades.)"
Now you know