Pfaff Industrial 937 Guide

ADJUSTMENT MANUAL
296-12-19 340/002
Instruction Manual engl. 10.16
937
This adjustment manual applies to machines
from the serial number 8 300 001 and
software version 0435/005 onwards.

Reprinting, reproduction and/or translation of PFAFF adjustment manuals
(including parts thereof) is only permitted with our prior agreement and citation of the source.
PFAFF Industriesysteme
und Maschinen GmbH
Hans-Geiger-Str. 12 - IG Nord
D-67661 Kaiserslautern

Table of Contents
Contents ..................................................................................Page
3
13 Adjustment ........................................................................................................................... 5
13.01 Tools, gauges and other accessories .................................................................................... 5
13.02 Abbreviations ......................................................................................................................... 5
13.03 Explanation of symbols.......................................................................................................... 5
13.04 Checking and adjustment aid................................................................................................. 6
13.05 Adjusting basic machine ........................................................................................................ 7
13.05.01 Compensation weight............................................................................................................ 7
13.05.02 Needle in needle hole centre (in sewing direction)................................................................ 8
13.05.03 Needle bar parallel guide ....................................................................................................... 9
13.05.04 Locking lever........................................................................................................................ 10
13.05.05 Zero stitch and zigzag stitch scale ....................................................................................... 11
13.05.06 Needle in needle hole centre (crossways to sewing direction) ........................................... 12
13.05.07 Zigzag stitch width............................................................................................................... 13
13.05.08 Zigzag stitch movement ...................................................................................................... 14
13.05.09 Needle hole symmetry ........................................................................................................ 15
13.05.10 Needle position adjusting lever............................................................................................ 16
13.05.11 Thumb wheels for the top feed (in machines without -918/14)........................................... 17
13.05.12 Differential zero setting (in machines without -918/14) ....................................................... 18
13.05.13 Top and bottom feed synchronous position (in machines with -918/14) ............................. 19
13.05.14 Position of the stitch length adjusting wheel (in machines without -918/14) ...................... 20
13.05.15 Position of the stitch length adjusting wheel (in machines with -918/14)............................ 21
13.05.16 Bottom feed dog zero position (in machines without -918/14) ............................................ 22
13.05.17 Bottom feed dog zero position (in machines with -918/14) ................................................. 23
13.05.18 Top feed dog connecting rod............................................................................................... 24
13.05.19 Top feed dog zero position .................................................................................................. 25
13.05.20 Torsion spring for the reverse-feed key (in machines without -918/14)............................... 26
13.05.21 Torsion spring for the reverse-feed key (in machines with -918/14).................................... 27
13.05.22 Torsion spring for the differential regulating shaft (in machines without -918/14)............... 28
13.05.23 Torsion spring for the differential regulating shaft (in machines with -918/14).................... 29
13.05.24 Bottom feed dog sliding movement .................................................................................... 30
13.05.25 Bottom feed dog lifting movement .................................................................................... 31
13.05.26 Driving belt in the gear box.................................................................................................. 32
13.05.27 Hook bearing bracket .......................................................................................................... 33
13.05.28 Hook lubrication ................................................................................................................... 34
13.05.29 Pre-calibrating the needle height ......................................................................................... 35
13.05.30 Needle bar rise, hook-to-needle clearance and lower bobbin position finger ...................... 36
13.05.31 Readjusting needle height ................................................................................................... 37

Table of Contents
Contents ..................................................................................Page
4
13.05.32 Bobbin lifter position ........................................................................................................... 38
13.05.33 Bobbin lifter movement ....................................................................................................... 39
13.05.34 Bottom feed dog height ...................................................................................................... 40
13.05.35 Clearance between the presser foot and needle plate........................................................ 41
13.05.36 Top feed dog feed driving and connecting lever.................................................................. 42
13.05.37 Top feed dog lift................................................................................................................... 44
13.05.38 Top feed dog lifting movement ........................................................................................... 45
13.05.39 Top feed dog sliding movement .......................................................................................... 46
13.05.40 Feed difference.................................................................................................................... 47
13.05.41 Top feed dog and presser foot pressure ............................................................................. 48
13.05.42 Thread deflection bow ......................................................................................................... 49
13.05.43 Knee lever travel limit .......................................................................................................... 50
13.05.44 Knee lever backlash ............................................................................................................. 51
13.05.45 Bobbin winder...................................................................................................................... 52
13.06 Adjusting thread trimmer -900/24 ....................................................................................... 53
13.06.01 Axial control cam position ................................................................................................... 53
13.06.02 Control cam (pre-calibrating) ................................................................................................ 54
13.06.03 Thread catcher position and test cut .................................................................................. 55
13.06.04 Control cam (recalibrating) .................................................................................................. 56
13.06.05 Needle thread tension release ............................................................................................ 57
13.07 Parameter settings ............................................................................................................. 58
13.08 Internet update of control P40 CD ...................................................................................... 58
14 Circuit Diagrams 91-191 584-95 ....................................................................................... 59

Adjustment
5
13 Adjustment
Observe and comply with all instructions in the instruction manual's chapter
1 Safety! In particular make sure that all safety covers are installed again
correctly after making adjustments, see chapter 1.06 Instruction manual
hazard information!
Unless otherwise stated, the machine must be disconnected from the mains
before all adjustment work!
Risk of injury due to accidental machine start-up!
No screw clamp may be fastened to the needle bar on the PFAFF 937!
This may damage the special needle bar coating.
Notes on adjustment
All adjustments in this manual are based on a fully assembled machine and may only be
carried out by technical staff trained for this purpose. Machine covers, which have to be
removed and replaced to carry out checks and adjustments, are not mentioned in the text.
The order of the following chapters corresponds to the most logical work sequence for
machines that have to be completely adjusted. Both the preceding and following chapters
must be observed if only specific individual work steps are carried out. The screws and nuts
indicated in brackets ( ) are fastenings for machine parts, which must be loosened before any
adjustment and tightened again afterwards.
13.01 Tools, gauges and other accessories
O1 set of screwdrivers with blade widths from 2 to 10 mm
O1 set of wrenches with jaw widths from 7 to 14 mm
O1 set of Allen keys from 1.5 to 6 mm
O1 metal ruler, order no. 08-880 218-00
O1 feed dog setting gauge, order no. 61-111 651-33
O1 adjustment pin (5 mm diameter), order no. 13-030 341-05
O1 hook bearing bracket setting gauge, order no. 91-129 996-05
13.02 Abbreviations
t.d.c. = top dead centre
b.d.c. = bottom dead centre
13.03 Explanation of symbols
Activities to be performed or important information in this adjustment manual are
emphasised by symbols. The symbols used have the following meaning:
Note, information
Maintenance, repairs, adjustment, service work
(only to be carried out by technical staff)

Adjustment
6
Fig. 13 - 01
13.04 Checking and adjustment aid
It is possible to precisely locate the required needle bar positions through
insertion in holes 1 - 5.
OTurn the handwheel until the needle bar has almost reached the required position.
OPlace the adjustment pin in the corresponding hole provided and press it down.
OTurn the handwheel slightly back and forth until the adjustment pin engages in the crank
cutout behind the bearing plate, thus blocking the machine.
Hole 1 = 2.0 mm after bottom dead centre of the needle bar (2.0 after b.d.c.)
Hole 2 = top dead centre of the needle bar (t.d.c.)
Hole 3 = 0.25 mm after top dead centre of the needle bar (0.25 after t.d.c.)
Hole 4 = 1.0 mm after top dead centre of the needle bar (1.0 after t.d.c.)
Hole 5 = 4.0 mm after bottom dead centre of the needle bar (4.0 after b.d.c.)

Adjustment
7
Fig. 13 - 02
13.05 Adjusting basic machine
13.05.01 Compensation weight
OMove the needle bar to b.d.c.
OTurn the compensation weight 1 (screws 2)according to the rule.
1
2
Rule
When the needle bar is in b.d.c., the largest eccentricity of the compensation weight 1
should be in the top position.

Adjustment
8
13.05.02 Needle in needle hole centre (in sewing direction)
Rule
At zigzag stitch setting "0"and the "Middle" needle position setting, the needle should
pierce the middle of the needle hole looking in the sewing direction.
OMove the needle bar to b.d.c.
OTurn the eccentric pin 1 (nut 2 and screw 3)according to the rule.
Fig. 13 - 03
2
1
3

Adjustment
9
13.05.03 Needle bar parallel guide
Rule
The guide bar 5 should be parallel to the needle bar.
OMove the needle bar to t.d.c. (hole 2).
OLoosen the screws 1 and 2 and the nut 3.
OPosition the largest eccentricity of the pin 4 to down.
OMove the cutout of the guide bar 5 until it abuts the eccentric pin 4,turn the eccentric
pin 4 according to the rule and tighten the nut 3.
OSlide the guide bar 5 down and up again up to the stop. The bushing 6 must not move
sideways (re-adjust the eccentric pin 4 if necessary).
OMove the guide bar 5 until it abuts the eccentric pin 4 and tighten the screws 1 and 2.
Fig. 13 - 04
1
34
6
2
5

Adjustment
10
0
1
2
6
5
3
4
Fig. 13 - 05
13.05.04 Locking lever
Rule
The zigzag stitch adjusting lever 3 should lock in any position.
OLoosen the screw 2.
OPress the locking lever 1 until it pushes up against the zigzag stitch adjusting lever 3.
OTurn the pivot pin 4 to the left until it stops.
ORelease the locking lever 1.
OThe locking lever 1 should be parallel to the zigzag stitch adjusting lever 3.
OTighten the screw 2.
1
3
2
4

Adjustment
11
Fig. 13 - 06
13.05.05 Zero stitch and zigzag stitch scale
Rule
At zigzag stitch setting "0",
1. the needle bar should not move sideways when turning the handwheel,
2. the mark "0"on the scale 1 should match the mark 2.
OSet the needle position adjusting lever 4 to "Middle" and loosen the screws 5 and 6.
OAllow the machine to run slowly and turn the zigzag stitch adjusting lever 3 to the right
until the needle bar no longer moves sideways.
OSwitch off the machine, move the screw 5 until it abuts on the right and tighten.
OLoosen the screws 7 and adjust the scale 1 according to rule 2.
OTighten the screws 7.
The screw 6 remain loosened for the subsequent adjustments.
1
23
4
5
6
7
7

Adjustment
12
13.05.06 Needle in needle hole centre (crossways to sewing direction)
Rule
At zigzag stitch setting "0"and the "Middle" needle position setting, the needle should
pierce the middle of the needle hole looking crossways to the sewing direction.
OTurn the eccentric pin 1 (nut 2)according to the rule.
Fig. 13 - 07
1
2

Adjustment
13
Fig. 13 - 08
13.05.07 Zigzag stitch width
Rule
At the largest zigzag stitch setting, the mark 1 should match the largest zigzag stitch
indication on the scale 2.
OTurn the zigzag stitch adjusting lever 3 according to the rule.
OMove the screw 4 until it abuts at the top and tighten.
Should the machine be fitted with a needle plate that has a smaller needle hole
than the zigzag stitch width on the scale, the zigzag stitch limit must be set
according to the needle hole width of the needle plate.
4
2
3
1

Adjustment
14
Fig. 1 3- 09
13.05.08 Zigzag stitch movement
Rule
If the needle bar is in t.d.c. coming from the right bottom dead centre (adjustment hole "2"),
the needle bar should not move sideways when moving the zigzag stitch adjusting lever
back and forth.
OMove the needle bar to t.d.c. coming from the right bottom dead centre and insert the
adjusting pin into hole " 2 " of the bearing plate (block machine).
OTurn the zigzag eccentric 1 (screws 2)according to the rule. Make sure that the zigzag
eccentric 1 protrudes about 5 mm from the right inner side of the cast wall.
OPull the adjusting pin out of the bearing plate.
21
5 mm

Adjustment
15
Fig. 13 - 10
13.05.09 Needle hole symmetry
Rule
1. At zigzag stitch setting " 0", the needle puncture position should be in the middle of the
needle hole.
2. At the largest zigzag stitch setting, the needle hole should be the same distance from
the middle puncture position on the left and right.
OLet the needle pierce paper in the required zigzag stitch settings.
OAdjust the zigzag eccentric 1 (screws 2)- without turning it - according to the rule.
21

Adjustment
16
13.05.10 Needle position adjusting lever
OLoosen the screws 1 and 2.
OSet the needle position adjusting lever 3 to "Middle" and the zigzag stitch adjusting
lever 4 to the largest zigzag.
OPlace a piece of paper under the presser foot and pierce on the left and right with the
needle.
OSet the zigzag stitch adjusting lever 4 to "0"and slide the needle position adjusting
lever 3 to the right and left until the needle is positioned exactly over each of the previously
punctured holes.
OMove the screw 1 until it abuts in the left needle position and the screw 2 until it abuts in
the right needle position and tighten.
Rule
The left and right deflection of the needle should be the same size at both the largest
zigzag stitch setting and the left or right needle position.
Fig. 13 - 11
2
1
4
3

Adjustment
17
Fig. 13 - 12
13.05.11 Thumb wheels for the top feed (in machines without -918/14)
OLoosen the screws 1.
OTurn both of the thumb wheels 2 so that the guide pin 3 is located in the middle of the
slotted lever. The ends of both of the racks 4 should be in line.
OTurn both of the scale rings according to the rule and tighten the screws 1.
Rule
If the guide pin 3 is located in the middle of the slotted lever and the ends of the racks 4
are in line, the zero marks of the thumb wheels 2 should be opposite the mark 5.
4
2
3
1
2
5

Adjustment
18
Fig. 13 - 13
13.05.12 Differential zero setting (in machines without -918/14)
OUnscrew the screw 12 and the needle plate in machines with the stitch length N24.
OSet both of the thumb wheels 1 to "0".
OLoosen the screws 2, 3, 4, 5 and 6.
OAdjust the reverse-feed key 11 and the clamp crank 7 with the stop element 8 according
to the rule and tighten the screws 4 and 5.
OTurn the clamp crank 9 so that it is parallel to the clamp crank 7 and tighten the screws
2 and 3.
OTurn the clamp crank 10 so that it is parallel to the bed plate and tighten the screw 6.
OScrew in the screw 12 and mount the needle plate in machines with the stitch length
N24.
Rule
The reverse-feed key 11 should be in its highest position at the largest stitch length
setting. In addition, the clamp crank 7 with its stop element 8 should abut the top
regulating shaft.
4
5
2
8
3
7
9
10
6
12
11
1

Adjustment
19
Fig. 13 - 14
13.05.13 Top and bottom feed synchronous position (in machines with -918/14)
OSet the stitch length to "1.5"and both of the levers 1 to "0".
OWhilst continuously turning the handwheel, turn the shaft 2 (screw 3)according to the
rule.
OMove the clamp crank 4 upwards until it abuts and tighten the screw 3.
Rule
With a stitch length setting of "1.5"and when both of the levers 1 are in position "0", the
top feed dog and bottom feed dog should move by the same stroke when turning the
handwheel.
43
2
1

Adjustment
20
Fig. 13 - 15
13.05.14 Position of the stitch length adjusting wheel (in machines without -918/14)
OTurn the stitch length adjusting wheel 1 in the direction of the arrow until it stops.
OTurn the eccentric pin 2 (nut 3) according to the rule.
Rule
With a stitch length setting of "0", the pointer 4 should be opposite the mark "0"of the
scale 5.
4
3
2
1
5