I can't seem to find one...
They are dropped by various mechanical enemies after first half of Tier 1 (depth 5 or lower)
http://wiki.spiralknights.com/Iron_Gear See "Obtained From"
EDIT: The wiki is a bit outdated. Lumbers seem to no longer drop any kind of gears.
They are dropped by various mechanical enemies after first half of Tier 1 (depth 5 or lower)
http://wiki.spiralknights.com/Iron_Gear
See "Obtained From"
EDIT: The wiki is a bit outdated. Lumbers seem to no longer drop any kind of gears.