Quick Guide to Precision Measuring Instruments

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PG26Gauge Blocks2370153423mm14mm237015123769023mm14mm1237623mm1237690a.Wringing thick gauge blocksb.Wringing a thick gauge block to a thin gauge blockc.Wringing thin gauge blocksCross the gauge blocks at 90˚ in the middle of the measuring faces.Overlap one side of a thin gauge block on one side of a thick gauge block.To prevent thin gauge blocks from bending, first wring a thin gauge block onto a thick gauge block.Rotate the gauge blocks while applying slight force to them. You will get a sense of wringing by sliding the blocks.Slide the thin gauge block while pressing the entire overlapped area to align the measuring faces with each other.Then, wring the other thin gauge block onto the rst thin gauge block.Apply an optical at to the surface of one thin gauge block to check the wringing state.Wipe the exposed measuring face(s) and continue building up the stack, in the same manner as above, until complete. Finally, remove the thick gauge block from the stack.Irregularinterference fringesAlign the measuring faces with each other.The following figure shows the degree of dimensional change when handling a 100mm steel gauge block with bare hands.Time ngers are releasedThe gauge block is held with ve ngers.The gauge block is held with three ngers.512345678910203040506070Lapse of time (minutes)Elongation (µm)The 17th General Conference of Weights and Measures in 1983 decided on a new denition of the meter unit as the length of the path traveled by light in a vacuum during a time interval of 1/299 792 458 of a second. The gauge block is the practical realization of this unit and as such is used widely throughout industry.Select gauge blocks to be combined to make up the size required forthe stack.(1) Take the following things into account when selecting gauge blocks.a. Use the minimum number of blocks whenever possible.b. Select thick gauge blocks whenever possible.c. Select the size from the one that has the least signicant digit required, and then work back through the more signicant digits.(2) Clean the gauge blocks with an appropriate cleaning agent.(3) Check the measuring faces for burrs by using an optical at as follows:a. Wipe each measuring face clean.b. Gently place the optical at on the gauge block measuring face.c. Lightly slide the optical at until interference fringes appear.Judgment 1: If no interference fringes appear, it is assumed that there is a large burr or contaminant on the measuring face.d.Lightly press the optical flat to check that the interference fringesdisappear.Judgment 2: If the interference fringes disappear, no burr exists on the measuring face.Judgment 3: If some interference fringes remain locally while the at is gently moved to and fro, a burr exists on the measuring face. If the fringes move along with the optical at, there is a burr on the optical at.e.Remove burrs, if any, from the measuring face using a flat, negrained abrasive stone. Refer to the gures below for procedures.(1) Wipe any dust and oil lms from the gauge block and the Ceraston (or Arkansas stone) using a solvent.(2) Place the gauge block on the Ceraston so that the measuring face that has burrs is on the abrasive surface of the stone. While applying light pressure, move the gauge block to and fro about ten times (Fig. 1). Use a block rubber for thin gauge blocks to apply even pressure (Fig. 2).(3) Check the measuring face for burrs with an optical at. If the burrs have not been removed, repeat step (2). If burrs are too large, they may not be removed with an abrasive stone. If so, discard the gauge block.*1 Mitutoyo does not offer Arkansas stones. (4) Apply a very small amount of oil to the measuring face and spreadit evenly across the face. (Wipe the face until the oil lm is almostremoved.) Grease, spindle oil, vaseline, etc., are commonly used.CERASTON (Or Arkansas stone*1)RubberCERASTON (Or Arkansas stone*1)CERASTON (Or Arkansas stone*1)RubberCERASTON (Or Arkansas stone*1)Figure 1Figure 2(5)Gently overlay the faces of the gauge blocks to be wrung together.There are three methods to use (a, b and c as shown below) according to the size of blocks being wrung: Denition of the MeterThermal Stabilization TimeSelection, Preparation and Assembly of a Gauge Block Stack