Adjusting The Tension Of The Thread Tension Spring; Adjusting The Clearance Between The Rotary Hook And The Needle Plate - Brother T-8421D Instruction Manual

Adjusting the tension of the
thread tension spring
The standard tension of thread take-up springs R (1)
and L (2) vary in accordance with the machine
specifications as shown below.
For foundation garments
(-T[]F)
For light-weight to
medium-weight materials
(-[][]3)
For heavy-weight
materials (-405 and -407)
<Measurement method>
Adjusting thread tension spring R (1) (for right
thread)
1
Loosen the set screw (3) and then turn the
adjustment nut (4) to adjust the tension.
2
Tighten the set screw (3).
Adjusting thread tension spring L (2) (for left
thread)
0.25N
0.34N
0.70N
3
Loosen the tension nut (5).
4
Use a screwdriver (small) to turn the tension stud
(6) to adjust the tension.
5
Tighten the tension nut (5).
Adjusting the clearance between
the rotary hook and the needle
plate
The clearance (A) between the rotary hook (1) and the
needle plate (2) is adjusted according to the values in
the table below at the time of shipment from the
factory.
Model
T-8421D
T-8422D/T-8452D/T-8722D/
T-8752D
• Check the clearance (A) after replacing parts such
as the rotary hook (1) and the needle plate (2) which
have an effect on the clearance (A).
• When adjusting the clearance (A), replace the thrust
ring (4) between the rotary hook (1) and the rotary
hook base (3).
Dimension (A)
0.9 to 1.2mm
1.4 to 1.7mm
75