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www.ferrometal.fi3. Threads
Thread dimensions and accuracy of the profile are crucial when determining:
•
whether the fastener can be surface treated
•
whether the parts can be jointed together without problems
•
whether the thread can transmit the forces for which the components are designed
Thread’s main dimensions are: nominal diameter, pitch and minor diameter:
There is different tolerance fields for screw and nut thread: screw thread dimensions are located below the nominal dimension and nut thread above. This leaves necessary
clearance for surface treatment. Standard ISO 965 recommends following tolerance fields for commercial grade fasteners:
6e
6G
Ulkohalk.
Kylkihalk.
Välys ennen
pintakäsittelyä
6H
6g
6e
6G
Major diam.
Pitch diam.
Major diam.
Pitch diam.
Clearance before
surface treatment
For threads M1,4 and above following tolerance fields are standard:
Screw Nut
Surface treatment
6g
6H
plain, phosphated or electro zinc plated
6e
6G
plain (big clearance) or thick platings