DB2-B720 series (English)
CONTENTS
1. NAMES OF MAJOR PARTS
......................
0
1
2. MACHINE SPECIFICATIONS
.....................
0
3
3. OPTIONAL PARTS (B722/B724)
..............
0
5
4. WORK TABLE
...............................................
0
7
5. MOTOR (B721/B723)
..................................
0
8
6. INSTALLATION
.............................................
0
9
6-1.
Installing the oil pan ............................ 10
6-2.
Installing the machine head ............... 11
6-3.
Installing the knee lifter assembly
(Except -90
M
) ....................................... 12
6-4.
Installing the belt ................................. 13
6-5.
Installing the bobbin winder ............... 14
6-6.
Installing the belt cover ....................... 15
6-7.
Installing the cotton stand .................. 18
6-8.
Ground Wire Connections
(B721/B723) ........................................... 18
6-9.
Lubrication ............................................ 19
6-10. Checking the machine pulley
rotating direction .................................. 20
7. PREPARATION BEFORE SEWING
........... 21
7-1.
Installing the needle ............................ 21
7-2.
Removing the bobbin case ................. 22
7-3.
Winding the lower thread ................... 23
7-4.
Installing the bobbin case ................... 25
7-5.
Threading the upper thread ................ 26
7-6.
Adjusting the stitch length .................. 27
7-7.
Using the thread wiper
(B722/B724-40
M
, 90
M
, option) ........... 28
8. SEWING
......................................................... 29
8-1.
Sewing .................................................. 30
8-2.
Backtacking ........................................... 30
9. THREAD TENSION
...................................... 31
9-1.
Adjusting the thread tension .............. 31
9-2.
Adjusting the presser foot
pressure ................................................ 32
9-3.
Adjusting the trailing length after
thread trimming (B722/B724) .............. 32
10.CLEANING
..................................................... 35
11.STANDARD ADJUSTMENTS
................... 39
11-1. Adjusting the thread tension
spring .................................................... 40
11-2. Adjusting arm thread guide R ............ 42
11-3. Adjusting the presser foot height ...... 43
11-4. Adjusting the feed dog height ............ 44
11-5. Adjusting the feed dog angle ............. 45
11-6. Adjusting the needle bar height ......... 46
11-7. Adjusting the needle and feed
mechanism timing ............................... 47
11-8. Adjusting the needle and rotary
hook timing ........................................... 49
11-9. Checking the rotary hook and B-case
holder position bracket clearance ...... 50
11-10.Adjusting the upper shaft and
rotary hook lubrication amount ......... 51
11-11.Adjusting the synchronizer
(B722/B724) ........................................... 52
12.REPLACING THE FIXED KNIFE AND
MOVABLE KNIFE (B722/B724)
................ 54
12-1. Replacing the fixed knife ..................... 54
12-2. Replacing the movable knife .............. 55
13.TROUBLESHOOTING
................................. 56