I just received a Delta 14-651 Hollow Chisl Mortiser and when setting
it up found that the fence is not square with the base (tilts back
about 1/8"). The Instruction Manual does not cover this adjustment.

I went and checked my mortiser --- the same model. The fence was right
on. Since the fence is a casting, it could have been damaged or
improperly machined. It should sit flat on the base. Check to see if
there's something between the fence bottom and the base. If not, I'd
get a replacement from Delta.

Joel