"What is it?"

[GrahamW]

Why drill it on the flats ?

[Robert Leigh]

I agree Reckers, it may have been too tight to remove until that drilling was done last, where it wold have streched enough to undo without difficulty.

[Mike Costigan]

Why drill it on the flats ?

The narrowest part, so the area most likely to split.

[Jack in the Box]

Thank you for your responses regarding item 2. I inherited it and did not know what it is for. I have just tried it on the footbrake butterfly nut and it fits perfectly. Well done Scarlet O'Hara.
Alan

[Reckless Rat]

As n°1 was on a special, is it something to do with lowered suspension and a different way of attaching the radius arms?

[JonE]

Reckers - too tiny - the main bolt shank is only 9mm across. (Pity, as fiddling with exactly that at present. Aren't 3/4" bolts expensive?)

[Bob Culver]

A colleague's father was an inveterate Pom "engineer". He used to say thet the only virtue of UNF nuts was that they were easy to split off with a chisel.... He had a point. (And some considered the only advantage of American V bed lathes was that workmen could not sit on them!)

[JonE]

ok, a new one...the one of the right is a three speed box top locator bolt  - but what are the other two?     

[Duncan Grimmond]

Is that a clutch pedal shanked bolt on the left? Difficult without a size 1/4 or 5/16?

[dickie65]

dizzy bolt on the left, used with a spring and big washer on manual advance models ???