# ASME B89.1.5-1998 pdf download

ASME B89.1.5-1998 pdf download.MEASUREMENT 0FPLAIN EXTERNAL DIAMETERS FOR USE AS MASTER DISCS ORCYLINDRICAL PLUG GAGES.

Note thai the flat-co-sphere method gives (he diameter of the cylinder at a point on one side relative to a plane on (he opposing surface. If the gage has imperfect geometry, one may get a different value than if, e.g., a point-to-point method were used. Figure 3 Illustrates some of the problems imperfect geometry introduces when using this technique (see Appendix A).

As in the flat-to-Oat method, it is possible to purchase instruments where the upper probe has a range of 100 or 200 mm. With this Instrument, it is possible to get a zero setting without a gage block because the contaminant problem is less acute with a point-co-flat contact than with a flat-to-flat contact.

On some instruments of this type, if an attempt is made to move the cylinder under the probe to obtain a maximum reading, bending of the probe spindle will introduce errors Into the measurement. The same precautions must be taken to correct for deformation as when using a standard gage block comparator.

If a laser interferometer is used as thc measuring scale, one must correct for the temperature of thc cylinder and for the index of refraction of the air if they deviate from standard metrological conditions.

6.1.3 Sphere-to-Sphere (Fig. 1. Illustration (C)]. It’ a gage block-syle comparator with opposing Contacts is available, measurements at a specified location can be made without concern for the geometric errors discussed in the single probe method. In this case, corrections for the difference in elastic deformation, although small, will be larger than in the flat-to-sphere contact because point contact will exist at both the top and bottom probes.

As in the flat-to-sphere contact, if the reference gage block and test cylinder are not of the same material, the deformation corrections will be much larger. The sphere-to-sphere technique also has the same potential for cumulative errors in a gage block stack and/or the transducer scale errors as in other methods.

Again, similar to the single ball contact, the danger exists that a flat spot will have worn on the ball Contact if it has been used extensively. A flat contact means that accurate deformation corrections cannot be made. if the condition of the probe is unknown, one must use a gage block of the same material as the cylinder. Since this makes a small correction even smaller, it will be safe, in all but the most exacting measurements, to ignore the elastic deformation corrections. The probe geometry must be known, or experiments must be made to determine the deformation, if a reference of different matenal is used. Equations to compute elastic deformation are available in Puttock and Thwaite’s CS1RO Technical Paper No. 25.

It cannot be assumed that the axes of the two probes are collinear. In fact, it is almost a certainty they will not be in line at all positions. Because of this lack of collineanty, he test cylinder must be aligned parallel to the plane that contains the axes of the two contacts. This orientation can be found by searching for the largest reading with the cylinder in various orientations. This orientation can then be marked. ft is not necessary to make the search each time a measurement is made. A measurement made at any other orientation would represent the length of a chord rather than the diameter.

The sphere-to-sphere technique does not work well with small cylinders. It is very difficult to find the maximum diameter when the cylinder is less than 3 mm in diameter.

Dual contact gage block comparators that use a laser as the measurement sensor exist. If a displacement laser inierferorneter is used, then one must correct for the temperature of the cylinder and for the index of refraction of the air.