My old 118 will happily sew through 5/16", but will sew up to 3/8" to go over seams without issues. Anything more than that isn't what I'd call "graceful". The presser foot lifts 1/2". It's great for garments, chaps, purses, etc.--not veg tan belts, or knife sheaths, though. The most I ask from mine is to go through 3 layers of chromexcel (and that's pushing it). Great old machine, but might be too light for dog collars, definitely too light for halters. I'm sure a lot depends on how it's set up.
Hope that helps...
Jen