I spent a number of years as a Singer Dealer in a past lifetime.  I've serviced and repaired just about everything out there at one time or another.  I own about a dozen machine at the presnt time, strictly for My own pleasure.  Any quality domestic machine will sew thick layers of denim and leather, etc.  Very few folks NEED a true Industrial machine. .....An example that comes to mind is the Singer 185's that are billed as "Industrial Strenght"  They are not.  They are a fine, troublefree Domestic machine that was quite inexpensive when the were sold new.  I've used Mine to sew sails for My sailboat easily with complete satisfaction...........Another pet peeve is the verbose prose extolling the virtues of a particular sewing machine and then the caveat....We haven't had a chance to test it, As is, No returns.    Husband of Judy 112346.