Cross
threading - it occurs every day in many factories as products are
assembled with threaded fasteners. At some sites it is so common that
for the more troublesome applications, special repair screws of the same
pitch, but one size larger in diameter are stocked for replacement
purposes. The rework and repair costs can be huge, but are often
accepted as standard operating procedure. Now, there is a fastener
designed to prevent cross threading and its associated costs - The
TRU-START® fastener. The unique TRU-START® point design not only
prevents cross threading in tapped holes, but also locates and aligns
the fastener when entering a tapped hole. The absence of threads along
one side of the fastener prevents the fastener from engaging the nut
threads while the fastener is at an angle. The orientation and angle of
the point were developed in relationship to the fastener’s thread helix
angle.
All these features add up to cost savings, because cross
threading, even in a small percentage of assemblies, can be very
expensive. Cross threading can damage or destroy an assembly causing
unnecessary down time, expensive repairs, and/or the complete loss of an
expensive component. An even higher cost can result from cross threaded
joints that are not detected at assembly, because cross threading is
not always readily apparent during assembly. Often the joint appears
satisfactory and offers little evidence that the joint formed is
incapable of withstanding its intended design loads. TRU-START®
fasteners were developed in response to end-user demands to reduce costs
by preventing cross threaded joints.
Applications
Primary applications for TRU-START® fasteners are when:
1. Cross threading is likely to occur:
- Limited visibility
- Difficult or restricted access
- Soft metal nut members
- Fine pitch fasteners
- Mis-aligned components
2. Cross threading is hard to detect:
- Automated assemblies
- Soft metal nut members
- Small diameter fasteners
- Low torque applications
- High speed power driven fasteners
3. Cross threading causes costly repair:
- Expensive castings
- Complex assemblies
- Automotive bodies and engine blocks
- Any fastener installed in the final assembly stages
-
Expensive downtime
Availability
The TRU-START® point style places little restriction on the configuration
that you can specify for a TRU-START® part. TRU-START® fasteners can be
manufactured with virtually any head, drive, or shoulder style. Metric
and inch sizes are both available. Any finish can be specified.
Off Angle Capability
Off angle driving is typically what causes cross threaded assemblies. While
few applications are intentionally designed for off angle driving, due
to limited visibility, awkward access or operator fatigue, off angle
driving conditions actually occur in many cases. TRU-START® fasteners
are self-aligning and pick up the nut thread correctly when introduced
to threaded nuts at an angle.
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