Operation Manual

6.6 Setting the Underthread Tension

Caution Risk of Injury !

Turn the main switch off.

Setting the underthread tension only with the sewing

machine turned off.

Setting the underthread tension

The underthread tension must be set so that a seam as shown in Illus. a)

in Chapter 6 results.

–

With a recommended underthread tension of e.g. 30g, 15g should be achieved

through the brake spring 1 and 15g through the tension spring 4.

–

The following applies as the base setting for the tension spring 4:

The bobbin case must slowly lower under its own weight. See sketch in Chapter 6.5.

The brake spring 1 hinders a running-on of the bobbin during the thread trimming

sequence.

To regulate the two tension values one proceeds as follows:

–

Turn adjusting screw 3 back so far that the tension of the tension spring 4 is

completely released.

–

Set the brake spring 1 by turning the screw 2 so that half of the recommended

hook thread tension value is achieved through the brake spring.

Attention !

Not for classes: 271-140432, 271-140442, 273-140432

–

Insert the bobbin into the hook base and thread the underthread (see Chapter 6.5).

–

Insert the bobbin case with the bobbin into the hook.

–

Turn the handwheel until the sewing machine has conducted a stitch.

–

Pull the underthread to the top of the needle hole with the aid of the needle thread.

–

Pull off the underthread in the direction of sewing at an angle of 45°. About half of

the tension value should be felt.

Then tighten the adjusting screw 3 to the recommended tension value.