Book: # 1
Book: # 4

These balances are calibrated in Newton's. 

A zero setting adjustment is located on the back of the balance near the lower end of the suspension hook. If adjustment is needed, loosen the lower knurled nut and adjust the pointer to read zero (while balance is in a vertical position and with no load) by means of the upper knurled nut. Tighten the lower knurled nut. 

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These balances are calibrated in newtons, the MKS unit of force now in common use.  

A zero setting adjustment is located on the back of the balance near the lower end of the suspension hook.  If adjustment is needed, loosen the lower knurled nut and adjust the pointer to read zero (while balance is in a vertical position and with no load) by means of the upper knurled nut.  Tighten the lower knurled nut. 

INSTRUCTIONS FOR ZEROING:
On an Ohaus Dial Spring Scale, an internal nylon drive gear is attached to the pointer shaft by means of friction fit.  If the mechanism is subjected to more than normal stress, the pointer shaft will slip within the gear.  This built-in feature protects the mechanism and prevents the pointer from becoming loose on the shaft.
If the scale should require zeroing, it can be accomplished by means of the friction fit as follows:
 1.  Note amount of adjustment necessary.
 2.  Rotate pointer counter-clockwise until resistance is 
     felt.  Then force the pointer to rotate further by the 
     amount necessary to zero scale.
 3.  If zero is not perfect, repeat 1 & 2.