FIELD OF THE INVENTION
The present invention relates to a device for accurate calibration of multiple
anvils of outside micrometers. More particularly, the invention relates to a device
for clamping multiple rods of an outside micrometer at desired locations and
allows precise measurement of rod-movements to achieve accurate calibration of
the micrometer. The invention further relates to method of calibration of anvils of
an outside micrometer in an adjustment device.
BACKGROUND OF THE INVENTION
Most of the prior art outside micrometers (with adjustable anvils and having
more than one rod as shown in figure (1) inherit calibration error greater than 10
micrometer and to make them accurate, it is needed to adjust their anvils.
Adjusting multiple anvils is a long process because there is no known means to
measure the distance moved by the rod of the anvil.
Calibration of a micrometer begins with setting of the micrometer at zero by
adjusting a sleeve of the micrometer for any one of the multiple anvils.
Micrometer then exhibits zero for that particular anvil only and the reading of the
remaining anvils may still show the error.

So now there is need to adjust the rest of the anvils. These anvils can be
adjusted only by trial and error method, because once the lock nut is loosened
for adjustment of the first anvil, all the anvil rods are needed to move by the
distance of the order of 10"5 meter. According to prior art, there is no known
method of measuring this minute shift. Moreover, handling of the anvil while
rotating its rod is a difficult task in itself.
Therefore, after providing a random displacement to the anvil rod, the anvil is
once again fixed in the micrometer and reading is taken. This process is repeated
again and again until the next anvil gives Zero on the micrometer. Similar steps
are followed with the third anvil. On an average, according to the existing
process, one micrometer takes at least half an hour or more for adjustment.
Moreover, the handling of type B anvils as shown in Figure 3 is more difficult.
Their round shape makes them more difficult to hold. Therefore, to minimize the
time taken in the calibration of the outside micrometers, there is a need for a
device, which could measure the movement of the anvil rod precisely with a
clamping means so that the anvil rods can be moved easily in the required
direction.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention to propose a device and a method for
accurate calibration of anvils of outside micrometer.

Another object of the invention is to propose a method of calibration of anvils of
an outside micrometer in an adjustment device.
BRIEF DESCRIPTION OF THE ACCOMPANING DRAWINGS
Figure 1 - shows an outside micrometer whose anvils are to be adjusted.
1) Adjustable anvil
2) Micrometer rod
3) Scale where reading is taken
4) Micrometer stand
Figure 2 - shows the first embodiment of the anvils of the micrometer of
Figure 1.9
5) Nut which is fixed in the hole of structure holding the anvil.
6) Lock nut of anvil which is to be loosened.
7) Anvil rod which is to be moved.
Figure 3 - shows the second embodiment of the anvils of micrometer of
Figure 1.
8) Nut which is fixed in the hole of structure holding the anvil.
9) Lock nut of anvil which is to be loosened.
10) Anvil rod which is to be moved.

Figure 4 - shows the base of a clamping and adjustment device of the invention.
11) 4 holes at a distance of 25 mm.
12) long hole for dial
13) T slot for holding the holders of dial and anvil.
Figure 5 - shows the holders of the clamping and adjustment device of the
invention.
14) For the dial,
15) For type A anvil and
16) For type B anvil
17) Hole of the holder where anvil is tightened with help of screws
attached.
18) T slots of the Holders
19) Clamping Screws for clamping of anvils and dials.
Figure 6 shows the anvil of Figure 2 with Dial mounted on the base.
20) Dial Indicator to see the movement of the rod.
21) Locking screws to lock the holders in the Base Holes (11) and (12).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE
INVENTION
The outside micrometer of figure 1 comprises:
1) Adjustable Anvil
2) Micrometer rod
3) Scale where reading is taken
4) Micrometer Stand
According to the invention, and as shown in figure 2, the first embodiment of the
Anvil consists of:
5) Nut which is fixed in the hole of structure holding the anvil.
6) Lock nut of anvil which is to be loosened.
7) Anvil rod which is to be moved.

A second embodiment of the invention shown in figure 3 essentially consists of:
8) Nut which is fixed in the hole of structure holding the anvil.
9) Lock nut of anvil which is to be loosened.
10) Anvil rod which is to be moved.
The base of the damping and adjustment device of the invention shown in figure
4 comprises:
11) 4 holes at a distance of 25 mm
12) long hole for dial
13) T slot for holding the holders of dial and anvil.
The device consists of a plurality of holding means which as shown in figure 5
are:
14) For the dial,
15) For Type A anvil and

16) For Type B anvil
17) Hole of the holder where anvil is tightened with help of screws a
attached.

18) T slots of the Holders
19) Clamping Screws for clamping of anvils and dials.
Figure 6 shows the measuring means mounted on the base of the device
comprising:
20) Dial Indicator to see the movement of the rod
21) Locking screws to lock the holders in the Base Holes ((11 and 12)).
Figure 1 shows an outside micrometer having at least one adjustable anvil (1) at
least one micrometer rod (2), a scale (3) where reading is taken, and a
micrometer stand (4).
Figure 2 shows a first embodiment of anvil, and figure 3 shows a second
embodiment of an anvil which are to be adjusted. Each anvil is equipped with a
nut (5) which is fixed in a hole (17) of anvil adjuster, a lock nut (9) an anvil rod
(7) which is to be loosened and the anvil rod (7) which is to be moved.

Figure 4 shows the base of the inventive device. It has four holes (11) at a
distance of 25 mm and a long hole (12) for movement of a dial (19). The dial
can be tightened anywhere in the slot with the help of screw (17). It is equipped
with a T slot (13) which is designed to hold the T slots of a Holder (18).
Figure 5 shows the holders for the dial. All the holders (14 to 16) have threaded
holes (17 to 19) at the base. By inserting the screws (17), these holders can be
tightened on the base as shown in Figure 6.
Figure 6 shows one of the anvils of first embodiment with its holder (15) attached
on the device. Here by unlocking the lock screw (17) of the anvil, movement of
the rod (9,10) can be noted in the dial (20).
Procedure of Calibration of Anvils
The first step while calibrating an outside micrometer is to measure the length of
the rods in a measuring means. Now each rod should give zero reading with its
corresponding anvil. If reading is not zero then adjustment of the anvils is
required.
Before adjusting the anvil the micrometer reading is noted carefully to know the
accurate error. Now, the anvil is fixed in the hole of the holder, and mounted on
the device along with the dial as shown in figure 6. The lock nut is loosened, so
that the rod of the anvil can be moved freely. The rod is moved by a distance
equal to the previous error. The value of distance moved can be read easily in
the dial indicator (20) as shown in the figure 3.

In order to validate the accuracy of measurement, the anvil is fixed on the
micrometer and the reading is taken, which should be Zero this time. Similar
process is repeated with the rest of the anvils. For adjusting the other anvils, the
holder is shifted by changing the position of the screw.
Both the anvil rod and the rod of the dial tester should be exactly opposite to each
other so that the movement of the anvil rod can be read precisely in the dial tester.
To maintain this right angle position, T SLOT (13) is provided in the base and
corresponding T slot (18) configured in the holders. These slots are made using the
T slot cutter on milling machine.
The anvil holders shown in figure 5 are having clamping screws (19) which are
used to fix the rear nut of the anvil in the hole. Once the anvil is fixed in the device
as shown in figure 6, then its bolt ((6) or (9)) can be loosened with the help of a
spanner. There is also an arrangement for movement of the dial indicator. Before
loosening the bolt of the anvil, pressure is applied in the dial and with the help of
the screw, the dial can be clamped at that position and at this position the dial is
set at Zero position. Now, the rod of the anvil can be moved freely and reading of
movement can be seen in the attached dial indicator. All the four anvils can be
adjusted by inserting them in appropriate holes (11).

WE CLAIM:
1. A device and a method for accurate calibration of anvils of outside
micrometer, the micrometer comprising a plurality of adjustable anvils (1), a
micrometer rod (2), a scale (3), and a micrometer stand (4), each anvil
comprising a nut (5, 8), an anvil rod (7, 10), and a lock nut (6, 9), the
device comprising :
- a base having multiple holes (11) and T-slots (13) corresponding to
the number of anvils (1), the holes (11) being configured at
equidistant locations on the base, the T-slots (13) being configured by
a T-slot cutter;
- a movable dial indicator with rod (20) which can be clamped on the
base;
- a plurality of holders (14 to 16) which can be tightly fixed on the base
of the device, the holders accommodating the anvils (1) and the dial
(20) and having a plurality of holes (17) to lock the anvils (1) on the
base by corresponding number of locking screws (21), and further
having T-slots (18),
wherein the anvils (1) and the dial (20) is clamped on the holders (14 to 16) by
clamping screws (19).

2. Method of calibration of anvils of an outside micrometer in an adjustment
device, the method comprising the steps of:
- measuring the length of the anvil rod in a measuring machine, each
rod providing a zero-reading with respect to its corresponding anvil;
- determining the accurate error of the anvils before re-calibrating the
micrometer;
- mounting the anvil on the holder of the device, and loosening the lock
nut to allow adjustable movement on the anvil rod in which each
movement of the rod equals the distance representing the previous
error measured, the value of distance moved directly displaying on the
dial;
- fixing the anvil once again on the micrometer to validate the previous
readings which ideally exhibiting zero;
- shifting the holder one after another for the remaining anvils by
changing the earlier positions of the screw and repeating the process.

3. The method as claimed in claim 2, wherein the anvil rod and the rod of the
dial is opposedly disposed to allow precise display of the anvil rod
movement, and wherein the T-slots (13, 18) of the base and the holders
are maintained at right angle.

ABSTRACT

The invention relates to a device and a method for accurate calibration of anvils of outside micrometer, the micrometer comprising a plurality of adjustable anvils (1), a micrometer rod (2), a scale (3), and a micrometer stand (4), each anvil comprising a nut (5, 8), an anvil rod (7, 10), and a lock nut (6, 9), the device comprising : a base having multiple holes (11) and T-slots (13) corresponding to the number of anvils (1), the holes (11) being configured at equidistant locations on the base, the T-slots (13) being configured by a T-slot cutter; a movable dial indicator with rod (20) which can be clamped on the base; a plurality of holders (14 to 16) which can be tightly fixed on the base of the device, the holders accommodating the anvils (1) and the dial (20) and having a plurality of holes (17) to lock the anvils (1) on the base by corresponding number of locking screws (21), and further having T-slots (18), wherein the anvils (1) and the dial
(20) is clamped on the holders (14 to 16) by clamping screws (19).