Bore gauge set 18 - 160 mm

Precision inside measuring device for measuring internal dimensions such as cylinders and bores for dimensional accuracy, ovality, and taper. Self-centering with interchangeable feeler legs. By replacing the fixed measuring stop, a wide measuring range can be covered. The use of the precision dial indicator allows for measurements with very low error margins.

The set consists of 3 precision inside measuring devices with measuring ranges of 18-35 / 35-50 / 50-160 mm. Supplied with a dial indicator (graduation of 0.01 or 0.001 mm).

• Measuring depth: 150 mm
• Fixed measuring bolt made of steel
• Moving measuring bolt made of carbide
• With dial indicator
• In a robust aluminum case

Measuring with the precision inside measuring device

Design

The precision inside measuring device is a comparison measuring device for measuring internal dimensions, mainly bore diameters. It consists of a measuring head and a shaft, at the end of which the dial indicator is mounted.

A fixed measuring stop is mounted on one side of the measuring head. This can be replaced, thereby adjusting the measuring range of the device. This allows large measuring ranges to be covered. Opposite this is a moving measuring bolt, whose movement is transmitted to a rod in the shaft and thus to the measuring bolt of the dial indicator. Depending on the model of the precision inside measuring device, the travel of the moving measuring bolt is 1-3 mm.

a moving measuring bolt b fixed measuring stop c spring-loaded stop bridge with bow-shaped ends d shaft e redirection of the measuring bolt movement by lever

Pre-setting

With the precision inside measuring device, measurements with very low error margins are possible, provided that the pre-setting and the measurement are carried out correctly. Before use, the precision inside measuring device is pre-set as follows:

The interchangeable measuring stop that brings the length of the measuring head closest to the dimension to be measured is mounted. The dial indicator is inserted with a slight preload (approx. 1-2 turns) and clamped.

Since the dial indicator only determines the deviation from a known dimension, an exact internal dimension must be defined using a comparison standard. The comparison standard can be, for example, a bore gauge, a setting ring, or another setting device. The scale of the dial indicator is now set so that the 0 on the scale aligns with the position of the pointer at the reverse point. This should be done as accurately as possible to prevent errors in measurement.

Measurement

The spring-loaded centering bridge on the side of the moving bolt centers the measuring head in the bore. In the horizontal position, the measuring head must be aligned by hand to find the reverse point of the dial indicator: You rock the measuring device slightly back and forth until you find the maximum deflection of the dial indicator pointer (reverse point). This is the desired measured value.

a Set the measuring device to the comparison standard using a setting ring or end gauge; set the dial indicator to zero b Insert the measuring head into the bore; determine the bore dimension at the reverse point of the pointer by rocking motion; read the deviation

Evaluation

The measured dimension must now be compared with the pre-set comparison standard. If the reverse point of the pointer is after the 0 on the scale, the dimension is smaller. Thus, the measured value is subtracted from the comparison standard. If the reverse point is before the 0, the dimension is larger and the measured value is added.

Measured size = Comparison standard - Measured value

Example:

The precision inside measuring device was pre-set to 70 mm and a deviation of 0.02 mm was measured. The diameter of the bore is therefore 70 mm – 0.02 mm = 69.98 mm.