23
gates can be used. Once the hole is bored, a cylinder hone is used to smooth the
surface and achieve a good surface finish. A great deal of care should be taken
when using a hone to prevent making the hole bellmouthed or out-of-round.
surface and achieve a good surface finish. A great deal of care should be taken
when using a hone to prevent making the hole bellmouthed or out-of-round.
VI. REASSEMBLY
6.1
Torque or stretch of bolts
In order for a bolted joint to function as intended, the bolts must be tightened
uniformly and to the proper preload. The most common method of preloading bolts
is with a torque wrench. There are numerous tables available with suggested torque
values for various sizes and grades of bolts. While these tables can be very helpful,
it should be noted that the torque required to achieve a desired preload on a bolt can
vary a great deal depending on the condition of the threads and the type of lubricant,
if any, used. If the threads are cleaned up with a thread chaser or tap or die, and the
lubricant specified on the torque table is used, in most cases, a torque wrench is
adequate for tightening bolted joints.
uniformly and to the proper preload. The most common method of preloading bolts
is with a torque wrench. There are numerous tables available with suggested torque
values for various sizes and grades of bolts. While these tables can be very helpful,
it should be noted that the torque required to achieve a desired preload on a bolt can
vary a great deal depending on the condition of the threads and the type of lubricant,
if any, used. If the threads are cleaned up with a thread chaser or tap or die, and the
lubricant specified on the torque table is used, in most cases, a torque wrench is
adequate for tightening bolted joints.
A more accurate method of measuring the preload of a bolt is to measure the
amount the bolt stretches as the nut is tightened. In many cases, this is not possible,
but on shaft coupling bolts, it is relatively easy to measure the length with a
micrometer.- Unless otherwise specified by the manufacturer, as a rule of thumb, the
coupling bolts should be stretched to one-half of their yield strength. Equation 1
can be used to determine the amount of stretch, in inches, required to achieve a
preload of one-half of the yield strength.
amount the bolt stretches as the nut is tightened. In many cases, this is not possible,
but on shaft coupling bolts, it is relatively easy to measure the length with a
micrometer.- Unless otherwise specified by the manufacturer, as a rule of thumb, the
coupling bolts should be stretched to one-half of their yield strength. Equation 1
can be used to determine the amount of stretch, in inches, required to achieve a
preload of one-half of the yield strength.
Equation 1
There are several methods of stretching the coupling bolts. One method uses a
sledge hammer and slugging wrench. This method is very labor intensive and time
consuming. Usually one person holds the wrench while another person hits it with
the sledge hammer. The bolt must be
sledge hammer and slugging wrench. This method is very labor intensive and time
consuming. Usually one person holds the wrench while another person hits it with
the sledge hammer. The bolt must be