ISO 09493:2010 pdf free download – Geometrical product specifications (GPS)一Dimensional measuring equipment: Dial test indicators (lever type)一Design and metrological characteristics.
4.5 Dial and pointer
The circular scale shall be graduated in scale intervals. The scale interval and its unit shall be labelled. Examples of scale layouts are shown in Figure 4 (e.g. scale intervals of 0,01 mm, 0,001 mm, and 0,002 mm).
At rest, the pointer shall be at least 1/10 revolution counterclockwise from the point representing the beginning of the measuring range. This beginning point is normally the 12 o’clock or the 6 o’clock position on the dial. The pointer shall move at least one full revolution beyond this beginning point of the measuring range, to the next occurrence of this point, plus at least another 1/10 revolution before reaching the end of its travel. This range before the measuring range begins is called pre-span, and the range after one full revolution is called post-span. The pre-span and post-span movements shall not be considered in the measuring range of the dial test indicator.
NOTE There are dial test indicators in use with less than 1/10 revolution of pre-span or post-span. In these cases, it is the responsibility of the user and the manufacturer to agree on the amount of pre-span allowed.
In any case, there shall be at least one full revolution of measuring range, plus some agreed upon amount of pre-span and post-span.
The dial test indicator may have a measuring range great enough to allow the pointer to move multiple complete dial revolutions. In practice, some dial test indicators with a measuring range of more than one complete revolution may include a secondary scale and pointer to denote the number of revolutions travelled by the primary pointer [e.g. Figure 4 c)]. When a revolution counting device is provided, the secondary pointer shall indicate the appropriate division on its scale when the pointer is at 12 o’clock on each of its revolutions.
4.6 Stylus
4.6.1 General
The stylus shall be easily interchangeable and shall, unless otherwise specified, have a spherical stylus tip. The stylus tip shall be manufactured from hard, wear-resistant material. It shall be well finished and free of flats or other irregularities which could affect the accuracy of the instwment.
The length of the stylus is an integral part of the accuracy of the instrument. When replacing the stylus, the user should ensure that the replacement stylus is of the same length as the original.
4.6.2 Friction linkage
The stylus of a dial test indicator is affixed to a friction linkage or ratchet mechanism, which allows the stylus to
be positioned over a wide range of possible positions.
4.6.3 Friction linkage forces
The friction linkage force shall be sufficiently higher than the measuring force, so as to allow use of the dial test indicator at any position or orientation of the stylus, without introducing errors to the measurement.
4.6.4 Range of adjustment
The mechanism shall allow for positioning of the stylus at any position within a range from _900 to 00 up to +900 of the long axis of the dial test indicator, as shown in Figure 5.