UnionSpecial 39500 Series Instructions For Adjusting And Operating

SETTING THE LOWER KNIFEReplace lower knife hold-er assembly. Lower knife (A.Fig. 12) should be set withcutting edge flush with throatplate surface. Adjustmentsare made with hexagonal headscrew which holds lower knife.Lower knife is spring pressedagainst upper knife, so nola-teral adjustment is necessarywhen width of trim is changed.Fig. 12Fig. 11Lower knife may be secured in any position bytightening screw (B) and locking nut (C) against sup-port bracket. Because screw (B) also serves as latchp in for the cloth plate latch spring, it should alwaysbe locked with nut (C) even when screw is not tighten-ed against lower knife holder.SETTING THE UPPER KNIFEReplace upper knife assembly. Clamp upper knife(D, Fig. 12) in position. setting nut (E) to hold clamp(F) in its most clockwise position against upper knife.At bottom of its stroke, front cutting edge of upperknife should extend not less than 1/64 inch below cut-ting edge of lower knife. The chain guard (G) shouldbe set down against the upper knife and slightly backfrom the cutting edge.After upper knife has been set for proper width oftrim, screw (H) should be tightened to lock upper knife holding block (J) in place.This will simplify resetting when upper knife is replaced.SETTING THE STITCH LENGTHLength of stitch is determined by the combination offeed eccentrics used. Outer (left) eccentric (A, Fig. 13)actuates main (rear} feed dog; while the inner (right)eccentric (B) actuates the differential (front) feed dog.In assembling feed eccentrics, be sure hubs arefacing each other. Be careful not to damage shaft or k e y.Tighten nut (C) securely.To change feed eccentrics, remove nut (C) and wash-er (D) from end of shaft (E). Turn handwh el i n operating Fig. 13direction until key slot in eccentric is toward front.Using hooked eccent r ic extractor (F), supplied with machine, reach behind eccen-trics as shown and withdraw eccentrics. It may be necessary to move handwheelback and forth sli g htly during extraction.11From the library of: Superior Sewing Machine & Supply LLC