A Morso guillotine cutter is standard industry equipment picture framers use to cut corner joints of frames. Like all machine tools, it is only as good as the craftsperson is skilled at using it. Cutting flush corners with the Morso is never a function of the framer’s calf muscle strength.
When I started framing I couldn’t understand why my first corners were not meeting flush. My framing teacher couldn’t explain why either. It took me a lot of analysis to work it out and the solution turned out to be rather simple.
A framer’s natural instinct is to be economical with moulding and so when they make their first cut into a length of moulding they try to shave off as little as possible from one end.
A Morso has two very sharp cutting blades. The inner cutting surface is flat and the outer surface curved. To achieve a clean cut the framer needs to use both cutting blades to make the first cut.
If only one blade is used to make the cut the length of moulding is not secured by the other blade and as the outer cutting blade’s surface is curved the length of moulding moves a little in the direction of least resistance as the guillotine makes the cut.
That folks explains why the two cut surfaces of joints are often not flush. One of the cut edges has a slight curve in it as a result of the lateral movement of the moulding. Some wastage is therefore inevitable and desirable.
To sum it all up, instead of making the first cut with only one cutting blade picture framers should use both blades to make the first cut.