Putting a new tuning key on

[Wayfaring Stranger]

Well,i bought an old German flatback with one of the tuning keys missing. I also bought an extra key at a music store but am at a loss as to how i put it on. The hole on the spare key is much smaller in diameter than the metal peg sticking out of the mechanics. I have a vague assumption to use heat - could that be right?
Greetings,
WS

[sunburst]

Could be.
If it is the button you are missing and the shaft is intact, there are replacement buttons that go on the shaft with heat. Obviously, the machines have to be off of the mandolin, and you can heat the shaft with a soldering iron or a lighter, (matches aren't very good because they cover the part with soot) and push the button on.
Otherwise you can do the Frank Ford method like
this (http://www.frets.com/FRETSPages/Luthier/Technique/Tuners/NewButton/newbutton.html).

[Wayfaring Stranger]

Wow, great help! I'll try this tonight (the drilling method that is).
Greetings from Germany,
WS