Stahl dozer gear boxes and drive motors

[SmallHaul]

That is great that you found the gears. I wouldn't drill the gear out to 2mm because you want a pressed/interference fit. Make the hole .002 (two thousandths) smaller than the shaft and press the gear on.

It is best to practice on similar material making the interference hole because when you drill the hole it will often be larger than the size of the bit when you measure the shaft. Drilling a hole accurately to the thousandths of an inch is a bit of an art (pun intended).

A good read:

https://www.quora.com/Machining-If-I...resultant-hole

What i have found that works well is to make a pilot hole about .01 (ten thousandths) smaller than your final hole size and then allow the part to cool and then run the final bit size through it.