LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
(b) A bored taper may be checked with a plug gage by marking the gage
with chalk or Prussian blue pigment.
Insert the gage into the taper and
turn it one complete revolution. If the marking on the gage has been rubbed
evenly, the angle of the taper is correct. The angle of the taper must be
increased when there is not enough contact at the small end of the plug
gage, and it must be decreased when there is not enough contact at the large
end of the gage.
After the correct taper has been obtained but the gage
does not enter the workpiece enough, additional cuts must be taken to
increase the diameter of the bore.
(c) An external taper may be checked with a ring gage. This is achieved
by the same method as for checking internal tapers, except that the
workpiece will be marked with chalk or Prussian blue pigment rather than the
gage.
Also, the angle of the taper must be decreased when there is not
enough contact at the small end of the ring gage and it must be increased
when there is not enough contact at the large end of the gage. If no gage
is available, the workpiece should be tested in the hole it is to fit. When
even contact has been made throughout the workpiece, but the tapered portion
does not enter the gage or hole far enough, the diameter of the piece is too
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