Basically the main differences in the #18 and the #20/22 are described by the following points.
- #18 soft bed ways, #20-22 hardened and ground replaceable ways.
- #18 normally has three bearings in the main spindle and a tapered shaft for the grinding wheel mount.
- The #20/22 has two bearings and a straight shaft for mounting wheel mount.
To address the first point, on the #18 once the machine has been totally disassembled, the base must be put up on a mill to mill the cast iron way surfaces. The #20/22 bed ways upon disassembly can be removed and reground or if necessary completely replaced. Because the ground and hardened ways run with an oil lubrication system, they are longer lasting and wear much better than the cast iron ways which need grease lubrication. Point number two is the main spindle, #20/22 use Timken Class #3 precision bearings. Often when disassembled the #18 tapered wheel hub has damage around the key way and even on quite a few it is cracked which is un-repairable.
The final and most telling point is that the #20/22 machines do not have web bases, which are aggravating to clean out on a weekly base. The newer base style allows you to dump the coolant out the back (D-style) sweep the sludge out of the base automatically (K style) or at least have a tub style easy access base to clean out (No letter designation). The actual cost to fully rebuild the #18 is close to the price of a rebuilt #20/22 and at the end of the day you still have a soft way machine with tapered mount and webs in the base.