maximum thickness is about 3/8" depending on what you are sewing. not 3/8 veg tan leather mind you but it will sew thru some decent items. We use the machine a lot in the manufacturing of hockey gear.
Is it a B, C or D class and is it an H2, 3 or 4. The class tells you how heavy it can handle items. The H is the lift of the presser foot. H2 is 7mm. H3 11mm, H4 is 14mm.
glenn