UnionSpecial 63900 Adjustment Manual

Also see for 63900 Series: Instructions for adjusting and operating

Contents

UnionSpecial 63900 Adjustment Manual Manual pdf 13 page image

13BOBBIN THREAD TENSION (CONT.)Remove the bobbin case from its holder and turn set screw in springin a clockwise direction to apply more tension or counterclockwiseto release tension.When the bobbin thread tension is correct, it rarely becomes nec-essary to make any changes as varying the needle thread tensionwill usually attain a good stitch.NEEDLE THREAD TENSIONThe needle thread tension is varied by turning the tension regulatingnut (G, Fig. 3). Turning the nut in a clockwise direction increases thetension, while counterclockwise decreases it. This should not bedone when the presser foot is in its raised position, but is generallydone while the machine is sewing on a piece of scrap material.CHANGING THE STITCH LENGTHUnless otherwise specified machine Styles 63900AM, AML and AT willbe equipped with upper feed regulator gear No. 63949-39 andlower feed regulator gear No. 63949-41 to produce 9 stitches perinch (S.P.I.), while Styles 63900AW, and AAE will be equipped withupper feed regulator gear No. 63949-37 and lower feed regulatorgear No. 63949-43 to produce 10 S.P.I. Other gears are available and may be ordered separately. Referto "Gear Chart" below for the gears necessary to produce S.P.I. other than previously described.GEAR CHARTS.P.I. UPPER GEAR LOWER GEAR6 63949-47 63949-337 63949-44 63949-368 63949-41 63949-399 63949-39 63949-4110 63949-37 63949-4311 63949-36 63949-4412 63949-33 63949-47To remove feed regulators gears, first remove feed drive gear cover located under arm of machine. Nowloosen screws (A and B Fig. 11) and slide gears (C and D) off their respective shafts. Replace with gears fordesired stitch length. After new gears have been installed be sure to reset needle feed stitch length toagree with the continuous turning roller feed.