OK, now I am curious too. The Hegner manual reads:
"Before operation and afterevery ten hours of use, oil each main bearing supporting the upper and lower
reciprocating arms. Use heavy machine oil in the oil ports (#34 on parts diagram)
for Polymax. On Multimax 14, 18, and 22 use light machine oil on both ends of
the bearings (#8 on parts diagram). If you cannot reach the inside ends of the
bearings, drop oil near the edge of the arm above the bearing – it will run to the
proper spot. Wipe off any excess oil."
I have been doing in every couple of months too.