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(4) Different materials being tightened
When a bolt is tightened into a soft material such as aluminum, plastic, wood, etc., the
tightening torque is considerably less than when the bolt is tightened into a hard material such
as steel.
(5) Different tightening conditions
The tightening torque may vary in accordance with bolt torque coefficient (depending on
manufacturing process specified by bolt manufacturers), bolt grade and bolt length, even
though the dimensions of the bolts are the same. Tightening torque may also vary depending
on the surface finishing state of tightening materials (steel, aluminum, etc.), and materials to
be tightened. In addition, if there is seal packing, clearance, etc. between tightening materials,
the tightening torque is decreased.
(6) Wear and looseness of the socket
With extended use, the hexagonal portion of the socket which is fitted to the head of the bolt or
drill bit, and/or hexagonal portion of the driver chuck which is fitted onto the anvil in the main
body will become worn and loose. Wear and looseness will cause a proportionate loss of
tightening torque. In addition, use of an incorrect size socket (slightly larger than the bolt being
tightened) will also result in decreased torque.
(7) Bolt and nut rotate together
Tightening torque that can be achieved will be considerably decreased if the bolt and the nut
rotate together during the tightening operation. The customer should be advised to carefully
observe the operation and ensure this does not occur.
8-4. Suggestions and Precautions for the Efficient Use of the Charger
(1) Batteries may not be rechargeable immediately after use
If the storage batteries are exposed to direct sunshine for an extended period, or if the
temperature of the batteries is 40
°
C (104
°
F) or higher immediately after they have been used
in the tool, the pilot lamp may not light up when the batteries are connected to the Model
UC 18YRSL charger. This is because the built-in thermostat functions to stop the charging
when the temperature of the storage batteries reach 40
°
C (104
°
F) or more. In such a case,
the customer should be advised to place the batteries in a shaded area with a good airflow,
and allow sufficient cooling before recharging.
This phenomenon is common to all existing batteries which employ temperature sensitive
overcharge devices. The cooling time required before charging can be accomplished varies
from a few minutes to about 30 minutes, depending on the load, duration of use, and ambient
temperature.
