5.4.1 The piston shall be made of steel. There shall be
insulation at the top as a barrier to heat transfer from the piston
to the weight. The piston shall be prevented from rubbing on
the bore. Most commercially available instruments use a loose
fitting metal guide sleeve, but other methods are acceptable.
The weight of the sleeve shall not be considered as part of the
test load. The land (foot) of the piston shall be
9.4742 6 0.0076 mm in diameter and 6.35 6 0.10 mm in
length. Above the land, the piston shall be relieved to # 9.0mm in diameter (see Fig. 2). The piston land shall be
manufactured by techniques known to produce finishes approximately
12 rms in accordance with ANSI B46.1. If
corrosion is a problem, the piston or piston land, if removable,
shall be made of corrosion resistant material.