It is possible to squeeze out a few extra degrees below 15. Reversing the collars/paddle rods will gain you perhaps .25 to .75 degrees and then if you have a broad blade clamped high by its spine in the vise ignoring the depth placement tool this time, you might gain another degree or two depending on the height of the blade above the vise. So you might get down to 12+/- degrees per side. If you find the collars slipping because the dimples are not securing them in the reverse, applying a little Purple Loctite to the screw threads will give things a better non-slip grip.(See the post on Purple Loctite).
Hope this helps.
Leo
