FIELD OF INVENTION
This invention relates to a device for accurate calibration of anvils
for outside micrometer in the range 200-1000 mm. More particularly, the
invention relates to a device which is capable of measuring the movement of the
anvil rod precisely and of clamping the anvil properly so that its rod can be
moved easily in the required direction.
BACKGROUND OF THE INVENTION
Most of the outside micrometers (with adjustable anvils and having
more than one rod as shown in figure 1) that come for calibration have the error
greater than 10 micrometer and to make them accurate it is needed to adjust
their anvils. Adjusting 3 anvils is a long process because there is no method to
measure the distance moved by the rod of the anvil.
Calibration of micrometer begins with making the micrometer zero
by adjusting the sleeve of micrometer for any one anvil. Micrometer will give
zero for that particular anvil only and the reading can vary for other anvils.
So now there is need to adjust the rest of the anvils. These anvils
could be adjusted only by hit and trial method as after loosening the lock nut
anvil rods are needed to move by the distance of the order of 10"5 meter and
there is no way of measuring this minute shift. Moreover handling of the anvil
while rotating its rod is a difficult task in itself.
After giving a random displacement to the anvil rod again anvil is
fixed in the micrometer and reading is taken. This process is repeated again and
again until anvil gives Zero on micrometer and these steps are followed with
three anvils. Most of the time, with only one micrometer this long and tedious
process takes half an hour or more. In order to minimize the time taken in the
calibration of one micrometer an equipment is needed which could measure the
movement of the anvil rod precisely and simultaneously it should have proper
arrangement of clamping the anvil so that its rod can be moved easily in the
required direction.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for
accurate calibration of anvils for outside micrometer in the range 200-1000 mm
which is capable of adjusting the anvil only one time avoiding random process of
anvil adjustment.
Another object of the invention is to propose a device for accurate
calibration of anvils for outside micrometer in the range 200-1000 mm which is
able to adjust every anvil only with changed corresponding rod attached to the
dial indicator of the device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - Shows an outside micrometer with adjustable anvil and micrometer rod
1) Locking Screw
2) Adjustable Anvil
3) Micrometer rod
4) Scale where reading is taken
5) Micrometer Stand
Fig.2 - Shows anvil which is to be adjusted.
6) Nut which is fixed in the hole of structure holding the anvil
7) Lock nut of anvil which is to be loosened.
8) Anvil rod which is to be moved.
Fig.3 - Shows the device with hole to fix anvil's nut and a dial indicator
9) Base
10) Clamping Screws
11) Hole to fix anvil's nut
12) Screw to fix dial indicator
13) Dial indicator of least count 0.001 mm
Fig.4 - Shows the process of adjusting outside micrometer's anvil along with
dial indicator's rod
14) Anvil which is to adjusted
15) Corresponding dial indicator's rod
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Fig.1 shows a complete micrometer having a locking screw (1), an
adjustable anvil (2), a micrometer rod (3), a scale (4) where reading is taken and
a micrometer stand (5).
Fig.2 shows an anvil which is to be adjusted. The anvil is equipped
with a nut (6) which is fixed in the hole (11) of anvil adjuster, a lock nut (7) of
anvil rod (8) which is to be loosened, and an anvil rod (8) which is to be moved.
Fig.3 shows the device/equipment (D) for adjusting anvil known as
anvil adjuster. The device has a base (9), clamping screws (10) to hold the anvil
in the hole (11). The hole (11) is provided to fix anvil's nut (6), a dial indicator
(13) having least count 0.001 mm and a screw (12) to fix the dial indicator.
Fig.4 shows the process of adjusting outside micrometer's anvil in
the device (D). Anvil (8) which is to be adjusted is clamped in the device while
corresponding dial indicator's rod (15) moves freely when reading of movement
is observed in the dial indicator (13). Two structures (14, 16) welded on the base
(9) hold the anvil (8) and the dial (13) respectively and make right angle with
the base (9).
Fig.5 shows the anvils (8) and its corresponding dial indicator's rods
(15).
The first step while calibrating an outside micrometer is to measure
the length of the rods using length measuring machine. Now each rod should
give zero reading with its corresponding anvil. If reading is not zero then
adjustment of anvils is required.
Before adjusting the anvil micrometer reading is noted carefully to
know the accurate error. Now anvil is fixed in the hole (which is designed
specifically to fix the rear part of the anvil) as shown in the Fig 2 and Fig 3 and
the lock nut is loosen so that rod of the anvil can be moved freely. Now the rod
is moved by the distance equal to the previous error. The value of distance
moved can be read easily in the dial indicator as shown in the Fig 3.
Now to verify the accuracy the anvil is again fixed in micrometer
and the reading is taken. It should be Zero this time. Similar process is repeated
with the rest of the anvils. For every anvil the rod attached to the dial indicator
needs to be changed. Anvils with their corresponding dial indicator's rods are
shown in Fig 4.
Both the anvil rod and rod of dial tester should be exactly opposite
to each other so that movement of the anvil rod can be read precisely in the dial
tester. To maintain this position it should be ensured with the help of try square
that at the time of welding both structures (14, 16) holding the anvil and holding
the dial make right angle with the base.
The Anvil adjuster shown in Fig 3 is having clamping screws (10)
which are used to fix the rear nut of the anvil in the hole. Once anvil is fixed in
the device (D) then its bolt can be loosened with the help of spanner. There is
also arrangement for the movement of the dial indicator. Before loosen the bolt
of the anvil some pressure is given in the dial and with the help of the screw, dial
can be clamped at that position and at this position the dial is set at Zero
position.
Now rod of anvil can be moved freely and reading of movement
can be seen in the attached dial indicator.
WE CLAIM
1. A device(D) for accurate calibration of anvils for outside micrometer in the
range 200-1000 mm comprising;
a base (9);
a fabricated structure (14) welded on the base (9) and having a hole (11)
for holding the anvil (8);
a structure in the form of tube (16) welded on the base (9) for holding a
dial indicator (13);
characterized in that,
the two structures (14, 16) are welded on the base (9) perfectly at right
angle to the base so that the anvil rod (8) and corresponding dial
indicator's rod (15) are properly aligned for making the movement of the
anvil rod (8) smooth and for obtaining precise dial indicator reading.
2. A device (D) as claimed in claim 1, wherein the rear nut (6) of the anvil
(8) is fixed in the hole (11) by clamping screws (10).
3. A device (D) as claimed in claim 1, wherein the screws (12) fix the dial
indicator (13) on the structure (16)
4. A device (D) as claimed in claim 1, wherein the dial indicator is having a
least count 0.001 mm.
5. A method of calibrating an outside micrometer by the device claimed in
claim 1 comprising;
noting the micrometer reading to know the actual error;
fixing the anvil (8) in the hole (11);
loosening the lock nut (7) of the anvil to allow the rod of the anvil to
move freely;
allowing the rod of the anvil (8) to move by the distance equal to the
previous error;
observing the reading of the value of distance moved in the dial indicator
(13);
characterized in that,
the checked anvil (8) is again fixed in the micrometer to confirm zero
reading in the dial indicator (13) when the process is repeated with the
rest of the anvils (8) with corresponding rod attached to the dial indicator
wherein the anvil rod (8) and rod of dial tester (15) are kept accurately
aligned in a horizontal direction to allow smooth movement of the anvil
rod and to get precise reading in the dial tester.

The device for accurate calibration of anvils for outside micrometer
consists of a base (9), one fabricated structure (14) welded on the base (9) and
having a hole (11) for holding the anvil (8), another structure in the form of tube
(16) welded on the base (9) for holding a dial indicator (13). The two structures
(14, 16) are welded on the base (9) perfectly at right angle to the base so that
the anvil rod (8) and corresponding dial indicator's rod are properly aligned for
making the movement of the anvil rod (8) smooth and for obtaining precise dial
indicator reading.