Apparatus for gauging the diameter and concentricity of a bore

An apparatus for gauging the diameter and concentricity of a bore in a workpiece, the bore having an inner surface, the apparatus comprising a base, a first surface engaging member supported by the base for movement along an axis and relative to a reference point, a selectively adjustable second surface engaging member supported by the base for movement along the axis, the second surface engaging member and the reference point defining the diameter of a circle, a third surface engaging member movably supported by the base and located on the circle, the third surface engaging member moving in response to movement of the second surface engaging member to maintain location of the third surface engaging member on the circle, the first, second, and third surface engaging members being adapted to be housed in the bore and to engage the inner surface of the bore, and the first surface engaging member being biased away from the second surface engaging member and against the inner surface of the bore, and a gauge for indicating movement of the first surface engaging member from the reference point.

BACKGROUND OF THE INVENTION 
The invention relates to apparatus for gauging the diameter of a bore, and 
to apparatus for gauging the concentricity of a bore. 
Apparatus for use in gauging the diameter and concentricity of a bore are 
used in various machining applications, including, for example, the 
machining and honing of a crankshaft bore in the end of a piston rod. The 
prior art apparatus have complicated constructions, are expensive to 
manufacture, and are also difficult for the operators to use. 
Attention is directed to the following U.S. Patents: 
______________________________________ 
Street 2,197,198 Apr. 16, 1940 
Johnson et al. 
2,599,835 Jun. 10, 1952 
Eisele 2,565,844 Aug. 28, 1951 
McElhose 2,949,675 Aug. 23, 1960 
Kaifesh 3,638,324 Feb. 1, 1972 
Kaifesh 3,762,057 Oct. 2, 1973 
Baker et al. 
3,821,855 Jul. 2, 1974 
Muhlethaler 4,128,943 Dec. 12, 1978 
Feller et al. 
4,266,329 May 12, 1981 
Hreha 4,326,336 Apr. 27, 1982 
Dressel et al. 
4,538,357 Sep. 3, 1985 
______________________________________ 
SUMMARY OF THE INVENTION 
The invention provides an apparatus for gauging the diameter and 
concentricity of a bore, which apparatus is relatively inexpensive to 
manufacture and is easy to use. 
The apparatus has a planar upper surface and includes three pins extending 
upwardly from the surface and generally defining the vertices of a 
triangle. Two of the pins define the diameter of a circle, and the third 
pin is located on the circle at a point spaced from each of the other 
pins. The workpiece is placed over the pins so that the pins are housed in 
the bore and engage the inner surface of the bore. One of the pins on the 
diameter of the circle is movable, and the diameter of the bore is 
measured by measuring movement of this pin. The concentricity of the bore 
is gauged by rotating the workpiece about the pins and measuring movement 
of the movable pin. 
More particularly, the apparatus comprises a base plate, and guide plates 
mounted on the base plate such that spaces between the guide plates define 
first and second slots disposed at a angle relative to each other, with 
the first slot also defining an axis. The apparatus also comprises a first 
support member supported by the base plate for movement along the axis and 
supporting a first pin. The apparatus further comprises a second support 
member slidably housed in the first slot for movement along the axis and 
supporting a second pin. The second pin and a reference point, relative to 
which the first pin is movable, define the diameter of a circle. The 
position of the second support member, and thus of the second pin, is 
selectively adjustable via an adjustment knob. This permits the diameter 
of the circle to be varied. 
The apparatus also includes a third support member slidably housed in the 
second slot and supporting the third pin. In order to maintain the third 
pin on the circle, the second support member has therein a third slot 
which extends, in one embodiment of the invention, perpendicular to the 
second slot and at a 45.degree. relative to the first slot, and the third 
support member is also slidable in the third slot. Accordingly, whenever 
the position of the second support member is changed, the position of the 
third support member changes so that the second and third pins and the 
reference point always define a 45-45-90 triangle. 
The apparatus further includes a cover plate mounted on the base plate so 
that the guide plates and support members are positioned between the base 
plate and the cover plate. The cover plate has therein fourth and fifth 
slots respectively supperimposed over the first and second slots so that 
the first and second pins extend through the fourth slot and the third pin 
extends through the fifth slot. The cover plate provides the 
above-described upper surface of the apparatus. 
The apparatus also includes means for biasing the first pin away from the 
second pin and against the inner surface of the bore, and a gauge for 
measuring movement of the first pin. The apparatus further includes a 
linear indicator having a digital readout for measuring the diameter of 
the circle defined by the second pin and the reference point. 
The apparatus is used as follows. First, the position of the second pin is 
adjusted so that the indicator shows that the diameter of the circle 
defined by the first and second pins is equal to the desired diameter of 
the bore. Any movement of the second pin also results in a corresponding 
movement of the third pin such that the three pins define three points of 
a circle having a diameter indicated by the readout of the linear 
indicator. The workpiece having a bore is then placed over the pins so 
that the pins extend into the workpiece. The gauge indicates any deviation 
of the first pin from the reference position. If the first pin is in the 
reference position, the gauge shows zero deviation, and the diameter of 
the bore is as desired. Concentricity of the bore is measured by rotating 
the workpiece about the pins. If the gauge shows zero deviation throughout 
the rotation of the workpiece, the bore is concentric. 
Other features and advantages of the invention will become apparent to 
those skilled in the art upon review of the following detailed 
description, claims, and drawings.

Before one embodiment of the invention is explained in detail, it is to be 
understood that the invention is not limited in its application to the 
details of construction and the arrangements of components set forth in 
the following description or illustrated in the drawings. The invention is 
capable of other embodiments and of being practiced or being carried out 
in various ways. Also, it is to be understood that the phraseology and 
terminology used herein is for the purpose of description and should not 
be regarded as limiting. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
An apparatus 10 which is used for gauging the diameter and concentricity of 
a bore 12 in a workpiece 14, and which embodies various features of the 
invention, is illustrated in the drawings. 
The apparatus 10 comprises (see FIGS. 2 and 3) a base plate 16 having a 
generally planar upper surface 18. A wall 20 extends upwardly from the 
upper surface 18 and around the periphery of the base plate 16. 
The apparatus 10 also comprises (see FIGS. 2 and 6) first, second, and 
third guide plates 22, 24, and 26, respectively, mounted on the upper 
surface 18 of the base plate 16. While the guide plates can be mounted on 
the base plate 16 by any suitable means, in the preferred embodiment, the 
guide plates are mounted on the base plate 16 by bolts 28. The guide 
plates 22, 24, and 26 have substantially equal thicknesses. The first 
guide plate 22 has first and second linear edges 30 and 32, respectively, 
disposed at an acute angle relative to each other. Preferably, the first 
and second edges 30 and 32 are disposed at a 45.degree. angle relative to 
each other. The second guide plate 24 is rectangular and has a linear edge 
34, and the third guide plate 26 is rectangular and has a linear edge 36. 
As shown in FIG. 6, the guide plates 22, 24, and 26 are mounted on the 
upper surface 18 of the base plate 16 with the first edge 30 of the first 
guide plate 22 facing and spaced from the edge 34 of the second guide 
plate 24 to form a first slot 38 centered on an axis 40, and with the 
second edge 32 of the first guide plate 22 facing and spaced from the edge 
36 of the third guide plate 26 to form a second slot 42 disposed at a 
45.degree. angle relative to the first slot 38. 
The apparatus 10 further comprises a first support member 44 supported for 
movement along the axis 40 and having thereon a first surface engaging 
member or pin 46. In the preferred embodiment, as shown in FIGS. 2 and 3, 
the first support member 44 is mounted on the end of a shaft 48 extending 
along the axis 40, and the shaft 48 is slidably housed within a guide 
block 50 mounted on the upper surface 18 of the base plate 16. 
The apparatus 10 further comprises (see FIGS. 2 and 6) a second support 
member 52 having a portion supported in the first slot 38 for movement 
along the axis 40 and having thereon a second surface engaging member or 
pin 54. The second support member 52 preferably includes a block 56 
including upper and lower surfaces. The upper surface supports the second 
surface engaging member 54, and the lower surface has mounted thereon four 
blocks 58, 60, 62, and 64. The blocks 58, 60, 62, and 64 are connected to 
the block 56 by bolts 65 (FIG. 6). The blocks 58, 60, and 62 have 
substantially equal thicknesses, and the block 64 has a thickness greater 
than the thicknesses of the other three blocks. The block 64 has a width 
just slightly less than the width of the first slot 38, and the portion of 
the block 64 extending beneath the other three blocks 58, 60, and 62 is 
slidably housed in the first slot 38. The blocks 58 and 60 have generally 
parallel, spaced linear edges defining a third slot 66, the reason for 
which is explained hereinafter. The lower surfaces of the blocks 58, 60, 
and 62 slide along the upper surfaces of the guide plates 22, 24 and 26. 
The apparatus 10 further comprises (see FIGS. 2-5) a third support member 
68 slidably housed in the second slot 42 and having thereon a third 
surface engaging member or pin 70. The third support member 68 is 
generally L-shaped, as shown in FIG. 4, and has a generally vertical 
portion 72 and a generally horizontal portion 74. The third surface 
engaging member 70 is mounted on the upper end of the vertical portion 72. 
The horizontal portion 74 of the third support member 68 extends along and 
is slidably housed in the second slot 42. 
The apparatus 10 also comprises (see FIGS. 1 and 3) a cover plate 76 
mounted on the base plate 16 so that the guide plates 22, 24, and 26 and 
support members 44, 52, and 68 are positioned between the cover plate 76 
and the base plate 16. In the preferred embodiment, the cover plate 76 is 
mounted on the wall 20 and on a plurality of spacers 78 (FIGS. 2 and 3) 
extending between the base plate 16 and the cover plate 76. As shown in 
FIGS. 1 and 3, the cover plate 76 has therethrough fourth and fifth slots 
80 and 82 respectively superimposed over the first and second slots 38 and 
42 so that the first and second surface engaging members or pins 46 and 54 
extend through the fourth slot 80 and the third surface engaging member or 
pin 70 extends through the fifth slot 82. The fourth slot 80 has a width 
less than the width of the first slot 38 and the fifth slot 82 has a width 
less than the width of the second slot 42 so that the second support 
member 52 is slidably trapped between the cover plate 76 and the base 
plate 16 in the first slot 38 and the third support member 68 is slidably 
trapped between the cover plate 76 and the base plate 16 in the second 
slot 42. 
The surface engaging members 46, 54, and 70 are adapted to be housed in the 
bore 12 in the workpiece 14 and to engage the inner surface of the bore 
12. As shown in FIG. 1, the second surface engaging member or pin 54 and a 
reference point 84 define the diameter of a circle 86. When the first 
surface engaging member or pin 46 is located on the reference point 84, 
the first and second surface engaging members 46 and 54 define the 
diameter. As also shown in FIG. 1, the third surface engaging member or 
pin 70 is also located on the circle 86. The significance of this is 
explained hereinafter. 
The apparatus 10 also comprises means for selectively adjusting the 
position of the second surface engaging member 54 relative to the 
reference point 84, i.e., relative to the base plate 16. While various 
suitable means can be employed, in the preferred embodiment, this means 
includes the second support member 52 and means for selectively adjusting 
the position of the second support member 52. Preferably, the means for 
adjusting the position of the second support member 52 includes (see FIG. 
2) an internally threaded bore 88 in the second support member 52, an 
externally threaded shaft 90 threadedly received in the bore 88, and means 
for supporting the shaft 90 on the base plate 16 so that the shaft 90 is 
fixed against axial movement relative to the base plate 16 and is manually 
rotatable relative to the base plate 16. In the illustrated construction, 
the shaft 90 is supported by the wall 20 and is fixed against axial 
movement by retaining rings 90 located on either side of the wall 20. The 
outer end of the shaft 90 has thereon a knob 94 for facilitating manual 
rotation of the shaft 90. Because the shaft 90 is fixed against axial 
movement, rotation of the shaft 90 causes movement of the second support 
member 52 along the shaft 90. 
The apparatus 10 further comprises means for moving the third surface 
engaging member 70 in response to movement of the second surface engaging 
member 54 to maintain location of the third surface engaging member 70 on 
the circle 86. While various suitable means can be employed, in the 
preferred embodiment, this means includes the third support member 68, and 
the third slot 66 in the second support member 52. More particularly, as 
shown in FIG. 4, the horizontal portion 74 of the third support member 68 
has thereon an upwardly extending pin 96 slidably housed in the third slot 
66 so that the third support member 68 is slidable in both the second and 
third slots 42 and 66, respectively. Furthermore, in the preferred 
embodiment, the third slot 66 is perpendicular to the second slot 42 and 
is disposed at a 45.degree. angle relative to the first slot 38. Because 
the first, second, and third slots form a 45-45-90 triangle, with the 
hypotenuse of this triangle being the diameter of the circle 86, and 
because the third surface engaging member 70 is always maintained at the 
right-angle corner of this triangle, the third surface engaging member 70 
is always maintained on the circle 86. 
The apparatus 10 further comprises means for biasing the first surface 
engaging member 46 away from the second surface engaging member 54 and 
against the inner surface of the bore 12. While various suitable means can 
be used, in the illustrated construction, this means includes (see FIGS. 2 
and 3) a clip 98 on the shaft 48, and a spring 100 extending between the 
guide block 50 and the clip 98 for biasing the shaft 48 to the right (as 
shown in FIG. 2). 
The apparatus 10 further comprises (see FIGS. 1 and 2) means 101 for 
indicating movement of the first surface engaging member 46 from the 
reference point 84 so that, when the workpiece 14 is positioned with the 
surface engaging members 46, 54, and 70 engaging the inner surface of the 
bore 12, the indicating means 101 indicates deviation of the diameter of 
the bore 12 from the diameter defined by the second surface engaging 
member 54 and the reference point 84, and so that, when the workpiece 14 
is rotated about the surface engaging members 46, 54, and 70, the 
indicating means 101 gauges the concentricity of the bore 12. While 
various suitable means can be employed, in the preferred embodiment, the 
first support member 44 has thereon a surface 102 (see FIG. 2) disposed at 
a 45.degree. angle relative to the axis 40, and the indicating means 101 
includes a conventional gauge 104 secured to the base plate 16 by clips 
105 and having a plunger 106 biased against the surface 102. Movement of 
the first support member 44 along the axis 40 is translated into axial 
movement of the plunger 106. Thus, if the gauge 104 is zeroed when the 
first surface engaging member 46 is located at the reference point 84, the 
gauge 104 will indicate movement of the first surface engaging member 46 
relative to the reference point 84. 
The apparatus 10 further comprises (see FIGS. 1 and 2) means 108 for 
indicating the distance between the second surface engaging member 54 and 
the reference point 84 to thereby indicate the diameter of the circle 86 
defined by the second surface engaging member 54 and the reference point 
84. While various suitable means can be used, in the preferred embodiment, 
the means 108 includes a slide member 110 connected to the second support 
member 52 by a clip 109 and thus to the second surface engaging member 54, 
and means on the base plate 16 for sensing the position of the slide 
member 110 relative to the base plate 16. Preferably, the means for 
sensing the position of the slide member 110 includes means 111 for 
providing a visual display indicating the distance between the second 
surface engaging member 54 and the reference point 84 (i.e., for 
indicating the diameter of the circle 86). Preferably, the means 111 is a 
digital readout that is visible through an opening in the cover plate 76. 
In the preferred embodiment, the slide member 110 and means for sensing 
the position of the slide member 110 are a conventional linear indicator 
112. Once the linear indicator 112 is calibrated to indicate the known 
distance between the second surface engaging member 54 and the reference 
point 84 when the second support member 52 is in a given position, the 
linear indicator 112 will properly indicate the distance between these 
points when the second support member 52 is in any other position. Thus, 
it is not necessary to have a sample workpiece in order to properly 
position the second surface engaging member 54. The second surface 
engaging member 54 is positioned simply by turning the knob 94 until the 
linear indicator 112 shows the desired diameter. 
The apparatus 10 is used as follows. First, the knob 94 is turned to move 
the second surface engaging member 54 to the desired position. The second 
surface engaging member 54 is in the desired position when the linear 
indicator 112 shows the desired diameter. Next, the workpiece 14 is placed 
over the surface engaging members or pins 46, 54, and 70 so that the pins 
are housed in the bore 12 and engage the inner surface of the bore 12. 
Because the first surface engaging member 46 is biased away from the 
second surface engaging member 54, it pulls the workpiece 14 to the right 
(as shown in FIG. 1) and therefore maintains the inner surface of the bore 
12 in engagement with the second and third surface engaging members 54 and 
70. Because the third surface engaging member 70 is located on the circle 
86 at a point spaced 90.degree. from the second surface engaging member 54 
and the reference point 84, it insures that the first and second surface 
engaging members 46 and 54 stay on the diameter of the bore 12. Any 
deviation of the diameter of the bore 12 from the desired diameter is 
shown by the gauge 104. If the diameter of the bore 12 is too small, the 
gauge 104 will show a negative distance. If the diameter of the bore 12 is 
too large, the gauge 104 will show a positive distance. In order to gauge 
the concentricity of the bore 12, the workpiece 14 is rotated about the 
surface engaging members. If the gauge 104 shows zero deviation throughout 
the rotation of the workpiece 14, the bore 12 is concentric. The amount of 
any deviation from concentricity will be indicated by the gauge 104. 
Various features of the invention are set forth in the following claims.