letter/spring scale for small weights

letter/spring scale for small weights
accuracy from 2 grams

wanted on my desk a small scale to weigh e.g. letters.

needed are:
7 cm steel/welding wire Ø 0.8mm or a straight bent paper clip.
2x M3 x 6mm countersunk screw
1x M3 x 12mm cylinder head/ lens head screw
1x M3 nut
1x tension spring Ø7.6mm - length 30mm - wireØ 0.5mm
please note: the spring must not have too much pre-tension, otherwise the pointer will react too late. therefore, stretch the spring a little beforehand by pulling it carefully so that the coils lie against each other but without pre-tension.

assemble the scale as shown in the pictures.

first put the spring on the pointer (part 3) and the holder (part 6).
then put the moving parts together (parts 1 to 4). make the wire pieces 16mm long - insert and close the holes with glue or soldering iron.
important: the 4 moving parts must move easily.

then screw the fixed part (part 1) to the base (part 5) with the 2 screws (6mm). screw the screw (appro