First let us clarify the main difference between a Dial Indicator(DI) and a Dial
Test Indicator(DTI). A dial indicator has a plunger which moves in and out to detect
the measurement being taken Photo 1, whilst the dial test indicator has a swinging
stylus to make the test, Photo 2. Also, the dial indicator has a much larger measuring
range, typically 10mm compared to 1mm. Dial indicators are therefore used mainly
to measure distance whereas dial test indicators are used to set position.
The method of mounting a DI is by gripping the barrel,
in which the plunger moves, photograph 1, or a lug on its rear, Photo 3. A DTI has
a small dovetail on its rear on which an adaptor (usually provided) is fitted. Photo
Often the problem with using a DI or DTI is getting it into position for the test
and having a method of securing the assembly at the non working end. The photographs
that follow(except photograph 8) all use my DI/DTI accessories for the purpose. LINK
Often the jaws of a machine vice set up on the milling machine table require to be
accurately in line with either the X or Y axis, Photo 5 shows this being done for
the Y axis.
When setting parts accurately on the faceplate, suitably placed toolmakers buttons,
assisted by a DTI, can be used, Photo 6. Much easier though is to position the part
whilst the faceplate is horizontal and this can be done using my faceplate balancing
fixture, Photo 7.
Photo 8 shows a DTI being used to position a round bore central below the milling
machines spindle. This assembly uses the DTI mounting facility provided with a Wiggler
workpiece positioning kit.
If a part needs to run perfectly true on the lathe the four jaw is used for this
as the three jaw cannot be guaranteed to give the accuracy required. Photo 9 and
Photo 10 show methods of setting up the DI for checking the result.