The most convenient and simple way of checking tapers is
to use the taper plug gage (Figure I-367) for internal tapers
and the taper ring gage (Figure I-368) for external tapers.
Some taper gages have go and no-go limit marks on them
To check an internal taper, first make a chalk or Prussian
blue mark along the length of the taper plug gage (Figures I-370
and I-371). Then, insert the gage into the internal taper and
turn slightly. When, you take the gage out, the chalk mark will
be partly rubbed off where contact was made. Adjust the taper
until the chalk mark is rubbed off along its full length of contact,
indicating a good fit. Mark an external taper with chalk and
check it in the same way with a taper ring gage (Figures
I-372 to I-374).
The taper per inch may be checked with a micrometer
by scribing two marks 1 in. apart on the taper and measuring
the diameters (Figures I-375 and I-376) at these marks.
The difference is the taper per inch. A more precise way of
making this measurement is shown in Figures I-377 and I-378.
A surface plate is used with precision parallels and drill rods.
The tapered workpiece will have to be removed from the
lathe if this method is used, however.
Perhaps an even more precise method of measuring a
taper is with the sine bar and gage blocks on the surface plate
(Figure I-379). When this is done, it is important to keep the
centerline of the taper parallel to the sine bar and to read the
indicator at the highest point.
Tapers may be measured with a taper micrometer. Refer
to Section C, Unit 4, for a description of this instrument.
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