WINTER 2021

THE DISTRIBUTOR’S LINK 163
BRUNO MARBACHER THREAD TOLERANCES ASSURE FASTENERS CAN BE ASSEMBLED EASILY from page 162
According to European structural standards, high
strength structural bolts (HV-series) property classes
10.9 must be supplied in sets. Only then can an
adequate load capacity and proper assembly ability be
guaranteed.
Civil/structural engineering requirements per
DIN 18880, now EN 1090
¤ All components of the set must be from 1
manufacturer
¤ Components of each set must be shipped as a set
The same rule essential applies to structural bolt
assemblies per ASTM A325
Thread Inspection
Screws with a 6g and nuts with 6H tolerance are
typical inspected with either a ring gage or a plug gage,
respectively. Plated or coated screws are to be tested
with a 6h ring gage or can be checked with a gaging
system. It should be noted that screws produced to
the lower limit and plated
to the minimum specified
thickness will accept the
6h no-go gage.
Normally, for screws
with other thread tolerance,
the checking is limited to
measuring the pitch diameter and major diameter. If frequent
testing of these types of screws is necessary, one may have
to invest in gages or a gaging system.
Weld nuts to DIN 928 and DIN 929 are furnished
with a thread in the 6G tolerance class, thus accepting
a 6H no-go plug gage. Nuts threads with a 7H tolerance
will accept the 6H no-go gage as well.
This covers the critical information regarding thread
tolerances for metric fasteners. Some of the information
is more relevant to the quality and engineering teams,
but the article also addresses vital information for the
sales team.
BRUNO MARBACHER