Then measure the gauge with a micrometer

Most micrometers have a locking lever (6) on the frame to hold the setting in place, allowing the item to be removed from the micrometer. • Some micrometers have a vernier scale on their sleeve, providing an even finer measurement to be taken, in 0.001 increments of a millimetre. Take the sleeve and thimble measurement as described above, then check which graduation on the vernier scale aligns with that of the annular scale on the thimble Note:The eye must be perpendicular to the scale when taking the vernier reading - if necessary rotate the body of the micrometer to ensure this. Multiply the vernier scale figure by 0.001 and add it to the base and fine measurement figures.

In the example shown the item measures 46.994 mm (see illustrations 3.5 and 3.6):

Internal micrometer

• Internal micrometers are available for measuring bore diameters, but are expensive and unlikely to be available for home use. It is suggested that a set of telescoping gauges and small hole gauges, both of which must be used with an external micrometer, will suffice for taking internal measurements on a motorcycle.

• Telescoping gauges can be used to

measure internal diameters of components. Select a gauge with the correct size range, make sure its ends are clean and insert it into the bore. Expand the gauge, then lock its position and withdraw it from the bore (see illustration 3.7).Measure across the gauge ends with a micrometer (see illustration 3.8).

• Very small diameter bores (such as valve
guides) are measured with a small hole gauge.
Once adjusted to aslip-fit inside the
component, its position Is locked and the
gauge withdrawn for measurement with a
micrometer (see illustrations 3.9 and 3.10).

Vernier caliper

Note:The conventional linear and dial gauge type instruments are described. Digital types are easier to read, but are far more expensive.

• The vernier caliper does not provide the precision of a micrometer, but is versatile in being able to measure internal and external diameters. Some types also Incorporate a depth gauge. It is ideal for measuring clutch plate friction material and spring free lengths.

• To use the conventional linear scale vernier, slacken off the vernier clamp screws (1) and set its jaws over (2), or inside (3), the item to be measured (see illustration 3.11).Slide the jaw into contact, using the thumb­wheel (4) for fine movement of the sliding scale (5) then tighten the clamp screws (1). Read off the main scale (6) where the zero on the sliding scale (5) intersects it, taking the whole number to the left of the zero; this provides the base measurement. View along the sliding scale and select the division which

Date: 2016-01-14; view: 884