Hi
- Lo Plastic Tapping Screws
The Hi-lo
fastener, with its unique thread form, improves fastener
performance in a broad range of automotive grade plastics.
This fastener is designed with a double lead, consisting
of a high and a low thread. The high thread is sharper than
a conventional thread, having a 30° included angle as compared
to the conventional 60° included angle. The low thread has
the 60° included angle and a height that is 40% to 50% of
the high thread height.
The superior
performance of the Hi-Lo fastener increases product quality
and decreases costs. The 30° included angle of the high
thread form reduces radial or bursting pressure over that
generated by a conventional 60° included angle thread form.
Boss cracking in plastic is dramatically reduced and smaller
diameter bosses can often be specified.
The Hi-lo
screw thread configuration has a smaller minor diameter
than a conventional screw. The high threads make a deeper
cut into the material leaving a greater volume of material
between the threads. There is also a greater amount of material
in contact with the high, sharp thread and the axial shear
area is increased. All of this contributes to greater resistance
to pull-out and stronger fastening.
| Thread
Form In Soft or Hard Materials |
The threads of the Hi-Lo Plus fasteners have a unique
bi-level shape that directs the displaced material
upward, flowing it around the threads.
Heads
on Hi-Lo Plus fasteners are made to standard
ANSI/ASME dimensions. |
 |
In
forming mating heads in the work piece, the unique
Hi-Lo Plus Screw accommodates the displaced material
between the widely spaced high threads, actually
increasing thread engagement while minimizing outward
pressure.
The
30° included angle of the high thread displaces
less material when it is driven into the mating
plastic, and therefore, requires lower driving
torques. A greater amount of material remains
between the high threads, increasing the stripping
torque. Low driving torque and high stripping
torque provides maximum protection against stripping
failures. |
Conventional
Thread Form |
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| Hi-Lo
Plus Thread Form |
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