UnionSpecial 63900 Adjustment Manual

Also see for 63900 Series: Instructions for adjusting and operating

Contents

UnionSpecial 63900 Adjustment Manual Manual pdf 18 page image

18THREAD CONTROL (CONT.)Sew slowly on a piece of material and observe the action of the check spring. The thread from the checkspring to the take-up bracket should be taut when the take-up is at the bottom if its stroke. Slight changesin needle thread tension may necessary at this point, but a reasonable tension should be used to maintaina uniform and consistent stitch. The machines are sewn off with 4 to 8 ounces maximum needle threadtension on T120 or similar thread, using a postal scale (A, Fig. 21). Depress check spring when checkingtension. The check spring will feel heavy to you, but this is a required setting for Class 63900, and as a result,the tension on the discs can be reduced.BOTTOM COVERBefore removing bottom cover, place machine on bench so that the plug screw is accessible fromunderneath. Remove this plug screw and catch reservoir oil in some convenient container. Tip machineback, loosen and remove the two cover screws. Cover should be tapped free with a wooden block ormallet. Do not pry the cover loose with any sharp instrument as the gasket may become damaged.CAUTION! When the bottom cover is removed, care should be taken not to mar or scratch the gasketseat area of the machine bottom.Before replacing cover, the machine gasket seat should be wiped clean and free of all lint and dirt. Thecover gasket should also be inspected for damage and cleaned of dirt. Two additional gaskets are usedto seal the bolts and must be cleaned before assembly. Carefully set the cover in place and tighten the twobolts securely.To replace a damaged cover gasket, proceed as follows:1. Clean cover gasket recess of any foreign matter.2. The gasket in cross section is triangular in shape with a groove in the top or widest part. With the coverresting as it does in the machine, oil distributing plate to your right, begin inserting in the middle of theback recess. The grooved wide edge of the gasket should be up and the ling sloped edge inward.Continue pressing the gasket into the cover recess until gasket is in place.The bolt sealing gaskets may have a tendency to fall out when the cover is being installed and may betemporarily cemented in place by applying grease to their recesses. Torque to 72 inch lbs.HOOK SHAFTThe hook shaft (A, Fig. 22) is held inposition by the pinion (B) and collar(C) thrusting against hard steel wash-ers (D) between the long left handbushing (E) and the short right handbushing (F).S h o u l d h o o k s h a f t s e t t i n g b e d i s -turbed, the left and right position canbe determined by measuring from thehook end of the hook shaft to thepoint of a new needle (G) and read-ing 9/16 inch on a scale.