There are different styles of inductuner. After you open yours and operate the mechanism, it's not hard to see which parts make electrical contact (and should be carefully cleaned) and which moving parts need to be (carefully) lubricated. Here's the style of tuner used in my RA-113:
This article has more info & photos of that tuner, if it's the type you have:
http://antiqueradio.org/DuMontRA-113Television.htm
It's not uncommon for these to be frozen with old, petrified grease. If yours is hard to turn, be gentle until you have freed that up. The older type has a ceramic shaft that may break if forced.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html