Upload
animesh-saha
View
219
Download
0
Embed Size (px)
Citation preview
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
1/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
UNIT II: Mechanical Measurements
(Screw thread, Gears, Circularity and Surface finish
Measurements)ME 302: Mechanical Measurements and Instrumentation
Course Instructor: Satadru Kashyap
Tezpur University Intranet: Uploaded E-course Material
Department of Mechanical Engineering
Tezpur University
mailto:[email protected]:[email protected]7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
2/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Lead: The axial distance advanced by the screw in one revolution
Pitch: distance between the corresponding points on two adjacent threads
in the same axial plane. pitch = lead / no. of thread starts.
Minor diameterMajor diameter
Pitch/Effective diameter
Helix angle
Flank angle
Height / Depth of thread
External thread
Internal threadAxis of the thread
Screw Threads
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
3/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Screw Thread types
Metric Threads
Whitworth thread has an included angle of 55between the flanks and equal radii at crest and
root. (standard nuts, bolts and pipe work.)
Metric Threads: clearance at crest and root so
that contact between mating threads takes
place only on the flanks (included angle of 60).
Buttress Thread (unequal flank angles)
Knuckle Thread
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
4/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Measuring Elements of a screw thread: measure the following:
1. Major diameter
2. Minor diameter
3. Effective or pitch diameter
4. Pitch
5. Thread angle and form.
Screw Thread Measurement
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
5/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Measurement of Minor Diameter:
Floating carriage micrometer
Applicable for most threads. Vee-pieces - various sizes having suitable radii at the edge.
Standard kept between the micrometer anvils with the help of V- pieces. The fiducial indicator anvil - maintain constant pressure.
The diameter (standard cylinder)known d1 by V-pieces in position r1.
Fix the position of fiducial indicator anvil, the standard cylinder is replaced by screw.
The reading is now taken for screw thread in position r2.
Minor diameter, d = d1+ (r2r1)
Screw Thread Measurement
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
6/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Measurement of Major Diameter:
checked by the use of micrometer or vernier calipers.
The major diameter is measured by bench micrometer (Figure).
Measurements made at constant pressure. Fixed anvil is replaced by fiducial indicator.
Standard cylinder (approx. equal to major diameter) held between anvils. Micrometer
readings noted.
Cylinder is replaced by threaded work pieces and the readings are noted (same process as
minor diameter).
Major diameter = d1 + (r2r1)
Screw Thread Measurement
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
7/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Measurement of Effective/Pitch Diameter:
Two WireMethod:
- place two wires or rods of identical diameter between the flanks of the thread,- measure the distance over the outside of these wires.
The effective diameter E = T + P
T = Dimension under wires = M2d
Screw Thread Measurement
- wires of hardened steel tosustain the wear and tear.
- They are given a high degree
of accuracy and finish by
lapping.
T can also be determined - place wires over a standard cylinder of diameter (S) greaterthan the diameter under the wires and noting the reading R1 and then taking reading with
over the gauge wires, say R2.
Then T = S - (R1 - R2)
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
8/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Measurement of Effective/Pitch Diameter:
Two WireMethod (contd.):
P - depends upon the diameter of wire (d) and pitch of the thread (p).
- constant value (to be added to the diameter under the wires to get the effective diameter).
e.g. P = 0.9605p 1.1657d (Whitworth thread) and P=0.866pd (metric thread).
Screw Thread Measurement
In Figure, since BC lies on the effective diameter line
=1
2 =
1
2
=
2
2
= =
2
2
2=
2[
2 1]
=
2=
4
2 =
1
2 =
1
2
1
2
= = 4
2
2
[ 2
1]
, =
; Hence = =
[
- 1]
3 wire method: two wires on one side help in aligning the micrometer square to the thread
while the third placed on the other side permits taking of readings.
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
9/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Determination of Best Wire: For effective diameter, always best wire to be used.
The wire diameter, such that, - the wire touches the thread on flank portion only.
Effective diameter can be measured with any wire having any diameter, which makescontact on the true flank of the thread; BUT
The best wire size for the given screw thread, is a wire having it's diameter, such that it
would contact the screw thread exactly on the pitch diameter point (shown in the Figure).
Screw Thread Measurement
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
10/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Determination of Best Wire:
At D the wire touching the flank of thread lies on the pitch line or the effective diameter line.
Screw Thread Measurement
In the Figure, OC and OD perpendicular to CGand DG at point C and D which lies on pitch line.
Metric thread = 60: db= (p/2) Sec(60/2)=0.577p
Whitworth thread = 55; db = (p/2) Sec(55/2) =
0.5636p
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
11/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
The main parts of the instrument are:1. Rotatable table 2. Swingable head 3. Projection screen
4. Objective lens 5. Measuring stage 6. Ocular
7. Micrometers 8. Prism.
Working: Test piece illuminated by light passing through it.
Illumination - lower side of work piece - objective lens
- prism (deflects the light) - ocular - projection screen.
Objective lens (1X, 1.5X, 3X and 5X)
So, total magnification of 10X, 15X, 30X and 50Xachieved with an ocular of 10X.
The direction of illumination can be tilted with respect
to the work piece by tilting the measuring head and the
whole optical system (screw thread measurement)
Tool Makers Microscope
- optical measuring machine used for external and internal length measurements as
well as measurements on screw threads, profiles, curvatures and angles.
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
12/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
The scale value of this microscope:
0.01 mm for length measurement. 3' for angle measurement with rotatable table.
1' for angle measurement with angle measuring ocular.
Applications:
(1) Finding the relative position of various points on workby measuring the travel necessary to bring a second point
to the position previously occupied by first.
(2) Measurement of angles by using a protractor eye-
piece.
(3) Comparison of thread forms with master profiles
engraved in the eyepiece and measurement of pitch and
effective diameter.
(4) Comparison of an enlarged, projected image with a
scale tracing fixed to the projection screen.
Tool Makers Microscope
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
13/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
M/C parts can be out of roundness - clamping distortion, presence of dirt and chips
on clamping surfaces, heat and vibration etc.
Circularity: characteristic form of the entire periphery of a plane (one plane only).Roundness:
condition of a surface of revolution (cylinder, cone or sphere) where all points on surface
intersected by any plane perpendicular to common axis or passing through a common
center are equidistant from the axis.
It is geometric form of a body of revolution in all three dimensions. Distortion may cause breakdown of lubricant film, press fitted parts may collapse under
high load, sealed fits may start leaking.
Lack of roundness in bush bearings - wobbling of the shafts. Roller/ball bearings loose
efficiency and make noise due to roundness errors.
Roundness and Circularity
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
14/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Errors of circularity at a cross section
Ovality: This error occurs when there is a difference between the diameters.
Error = Maximum diameter - Minimum diameter = Major axis - Minor axis
Lobbing: In this case, the diameter measured at any two position remains constant. Say
D1but still it is not exactly equal to the original diameter D.
Irregularities of no specific form: In this case, the variation in the diameter occurs due
to irregular surface profile.
Roundness and Circularity
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
15/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
dial indicator is placed above the work piece (WP) - divided into 12 equal parts.
The WP held in a V-block dial indicator touches it at position 1.
It is rotated from position 212. Variation in surface profile noted by the dial indicator. Procedure repeated 3 times (higher accuracyaverage)
Polar Plot: Circle of dia. = 4 X maximum reading drawn and divided into 12 equal parts.
Inside big circle, draw a small concentric circle of dia. (say 0.5times of work piece).
Values of WP readings plotted & joined (to get actual profile) between small & big circle.
Error = (Error measured from the polar graph / K);where K = constant ; value depends on the shape and work piece and angle of V-blocks;
obtained from a standard chart.
Roundness Measurement by Polar Graph
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
16/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Limitations of the method:
V-block angle influences the circularity error (e). It may be possible that indicator shows
no variation ore or 2 e or 3 e for different V block angles. Position of instrument (measurement taken from top or bottom).
Number of lobes on WP (elliptical, triangular, quadrilateral etc).
Instrument position (plunger) and point of contact of WP with V-block --- same vertical
plane.
A leaf spring inserted between indicator plunger and WP surface --- else circularity
readings might be affected by surface roughness.
K determination from standard chart
Roundness Measurement by Polar Graph
WP shape
Angle of V-blocks
60 90 108 120
Top Bottom Top Bottom Top Bottom Top Bottom
Elliptical 0 2 1 1 1.38 0.62 1.58 0.42
Quadrilateral 0.1 2 0.415 2.4 1.01 2.01 0.38 1
And so on for different shapes
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
17/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Intrinsic Datum System:
simple but they do not give the exact image of the work piece.
Reference is the point on the work piece itself (hence the name intrinsic) and all thevariations in readings are taken with respect to that point.
They do not require expensive tooling for the tests and used for roundness testing.
Roundness Measurement
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
18/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Extrinsic Datum System:
Slightly difficult but highly accurate.
They give the true image of the work piece. The reference used is a member of checking/measuring instruments.
Expensive as they require the magnification and recording system and used for roundness
testing where high accuracy is needed.
Roundness Measurement
S f Fi i h
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
19/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
SF - determines the deviations from the nominal surface w.r.t drawing.
SF obtained by - turning, milling, shaping, planning and grinding, show marked variations
when compared with each other.
SF - judged by degree of smoothness. (visual inspection); - fails to differentiate between
surface produced by same machining operation but under different cutting conditions.
Hence, quantitative evaluation is required.
Surface Roughness (surface texture): They are series of regularly repeated deviations in the
form of a wave, with a ratio of pitch to height.
produced by the trace of an edged cutting tool and plastic flow of the metal. height of the irregularities measured in microns; width is measured in mm.
If surface too rough - wear particles larger - act as abrasives - wear continues at high rate.
If surface too smooth - initial wear slow.
Factors affecting surface roughness are:
Type of coolant usedCutting parameters such as feed, speed and depth of cut
Type of machining
Rigidity of the system (fixtures, cutting tool, WP etc.)
Vibrations Material of tool and work piece.
Surface Finish
S f i i h
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
20/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Any material machined by conventional machining process cannot be finished
perfectly. The surface generated will have some irregularities:
First Order: irregularities developed due to the inaccuracies in the machine tool such as lack
of straightness of guide ways, on which tool post is moving.
Second Order: irregularities developed due to the vibrations and rigidity of m/c tools.
Third Order: irregularities due to the cutting parameters (cutting speed, feed, depth of cut).
Fourth Order: irregularities developed due to the rupture of the material during the
separation of the chip from the already finished surface of the work piece.
Surface Finish
S f Fi i h
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
21/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
C.L.A Index (Ra): Centre line Average Index
To calculate the value of Ra, from a graph it is necessary to have a mean line.
Mean line divide the profile so that, Area above the line = Area below the line. A suitable length L is selected which is called Sampling Length for the given surface.
The average height Ha is calculated as follows:
Ha = (Summation of all area above and below the line / Sampling length) = (A / L)
Ha
= (A / L) = [(A1+A2+A3)+(B1+ B2)] / L
Surface Finish
S f Fi i h
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
22/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
R.M.S Average (Root Mean Square Number):
Geometrical average of the ordinates of the profile about the mean line.
Mean/Centre line = Sum of areas above the line = Sum of areas below the line. Ifn measurements are made from the mean line above and below the points on the surface
profile denoted by Yi .
Then R.M.S value is
Hrms = ( Yi2 / n)
Surface Finish
S f Fi i h M
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
23/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Representation of Surface Roughness:
machining method is milling,
sampling length is 3mm. Direction of lay is perpendicular to the surface,
machining allowance is 1mm and
Representation will be as shown in Figure (b).
Surface Finish Measurements
S f Fi i h M t
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
24/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Surface Finish Measurements
Indication of Surface Roughness
The value orvalues defining the principal criterion ofroughness areadded to the symbols
a- surface roughness value
If it is necessary to impose maximum
and minimum limits of the principal criterion ofsurface roughness, both values shall be shown
maximum limit (a1) ;minimum limit (a2).
Roughness a obtainedby any production
process
Roughness a obtained byremoval of material by
machining
Roughness a shall beobtained without removal
of any material
S f Fi i h M t
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
25/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Surface Finish Measurements
S f Fi i h M t
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
26/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Mechanical Methods using Stylus:
A stylus (fine to follow the tiny surface deviations) is lightly pressed on the specimen and
is moved along the surface.
Simultaneously, recordings made - vertical and horizontal displacements.
In some instrumentsrecord stylus movement on a chart - surface contour (2D / 3D).
Datum for the up and down movement - provided by stylus skids.
Vertical magnifications - very high to record small values (microns),
Horizontal magnifications - low (mm).
Stylus - light beam, a jet of air, or a condenser plate; most commonly, diamond having a
cone and a spherical tip of 0.0005 in or 0.0001 inch is used.
Diamond can be formed into above shape and stays that way with uniformity (hard
material).
Difficult to confine the light beam, air jet, or condenser plate to a small enough size to beable to follow the surface irregularities.
Surface Finish Measurements
S f Fi i h M t
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
27/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Tomlinson Surface Recorder:
Construction and working:
The tip of the diamond probe has aradius of about 2 microns.
lever is attached to a vertical
cylinder on one end and a diamond
needle supporting a smoked glass.
Surface irregularities detected by theprobe magnified by vertical cylinder
on to the needle/glass combination.
Magnification = lever length /dia. of
vertical cylinder.
The record obtained on the small
glass is further magnified by optical
projection.
Surface Finish Measurements
S f Fi i h M t
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
28/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Tomlinson Surface Recorder:
Advantages:
simple. low cost.
gives reliable results.
Disadvantages:
delicate and requires great care.
slow in operation.
not suitable for rapid and continues
use on the shop floor.
Surface Finish Measurements
S rface Finish Meas rements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
29/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
The Talysurf Surface Roughness Tester:
Construction and working: (operates on electrical principles).
The measuring head is fitted with the probe and the skid.
Motion of the measuring head - given by Gear Box.
The unit can be moved vertically over guide ways (hand wheel & lead screw).
The diamond probe (radius ~ 2 m) and gear box (give max travel of 12 mm) to it.
The averaging meter & pen recorder - provides graphical record.
Surface Finish Measurements
Surface Finish Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
30/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
The Talysurf Surface Roughness tester: Construction and working:
The arm carrying the stylus forms an armature (pivoted - center of E-shaped arm).
Two legs of E-shaped armtwo induction coils carrying an A.C. current.
A small air gap is left between the armature and outer limbs of E-shaped arm. movement of stylus changes air gap of primary and secondary coils. This modulates the
carrier wave. After amplification, modulated carrier wave demodulated and separated out to
get the information on surface roughness.
Surface Finish Measurements
Gear
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
31/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear is a mechanical drive which transmits power through toothed wheel.
Accuracyprime importance in manufacturingtest and measure the gears precisely.
Proper inspection concentrate on raw materials, check the machining of blanks, heat
treatment and the finishing of teeth.
Gear blank - tested for dimensional accuracy (face width, bore, outside diameter), and
eccentricity, tooth thickness. Precise gears - tip radius, shape of root provided and surface
finish are also measured.
Types of gears
1. Spur gear
2. Spiral gear
3. Helical gears
4. Bevel gears
5. Worm and Worm wheel
6. Rack and Pinion etc.
Gear
Gear Terminology
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
32/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Pitch circle diameter(PCD): diameter of a circle
which will produce the same motion as the
toothed gear wheel.
Pitch circle: imaginary circle of gear that rolls
without slipping over the circle of its mating gear.
Addendum (A) = (1/Pd) = m.
Dedendum circle (or) Root circle
Pressure angle (a): angle made by the line of
action with the common tangent to the pitch
circles of mating gears.
Module (m): ratio of PCD to no. of teeth (D/T)
Circular pitch: distance measured along
circumference of pitch circle from a point on one
tooth to the corresponding point on the next tooth(Pc = D/T = m)
Diametral Pitch: number of tooth of the gear per
mm of pitch circle diameter. (Pd= T/D)
Gear Terminology
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
33/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Measurement of gear tooth thickness:
Gear tooth Vernier:
Tooth thickness varies from the tip to basecircle of the tooth
Instrument must be capable of measuring the
tooth thickness at a specified position.
Only possible fixed position available for
measurement. Tooth thickness - generally measured at pitch
circle (pitch line thickness) of tooth.
The gear tooth in the vernier has two vernier
scales
set for the width w of the tooth & the height h from the top (at which w
occurs).
Gear Measurements
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
34/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
35/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
36/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Constant chord method for measuring tooth thickness:
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
37/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Constant chord method for measuring tooth thickness:
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
38/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Base Tangent Method:
David brown tangent
comparator:
consists of a fixed and
movable anvil.
limited movement
micrometer on the moving
anvil side.
base tangent is adjusted by
setting the fixed anvil at a
desired place with a locking
ring.
The number of teeth overwhich measurement is to be
made is obtained from a
gear handbook.
of vernier
calliper
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
39/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Gear Testing Machine:
Composite gear checkingtooth-tooth variation and total composite variation.
Parkinsons Gear Tester: principle - standard gear (fixed vertical spindle) and gear to betested (spindle on a sliding carriage).
Both gears maintained in mesh by spring pressure.
As gears are rotated, movement of the sliding carriage is indicated by a dial indicator.
It is used to detect (i) poor tooth form (worn or inaccurate cutting tool) (ii) pitch circle
eccentricity (inaccurate centering of the gear blank prior to tooth cutting).
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
40/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
Gear Tooth Profile Measurement:
Toolmaker`s microscope:
Gear tooth profile can be inspected on the screen of toolmaker`s microscope connected to a
profile projector. Measuring gear tooth profile is projected on the projector`s screen, and then standard involute
profile is also projected on the same screen.
Comparemeasured and standard profile - deviations of the measured tooth profile .
Method is good for gears with module < 1.
When the width of the gear blank is large, it is necessary to give proper illumination so thatthe projected tooth should be free of shadow.
In order to conduct test on successive teeth the gear blank must be properly clamped on the
rotary table of toolmaker`s microscope.
Advantages:
This method can be used for small gears (module up to 1 mm).
Method can also be used for measurement of tooth thickness, base pitch, space width etc.
Limitation:
Gear`s size limits this technique.
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
41/42
SATADRU KASHYAP ME 302(Mechanical Engineering, Tezpur University) (Mechanical Measurements and Instrumentation)
Gear Measurements
The Klingeluberg involute tester: gear tooth profile (an involute curve)
Disc dia. = base circle dia. of gear under test.
Gear mounted on same spindle as disc.
Straight-edge contact the disc (move tangentially) - disc will be rotated without slip.
Magnification lever fitted with a diamond stylus that contacts the tooth flank at the base circle
is hinged at A.
Movt. of stylus magnified (250X) through a lever and gear mechanism and then recorded.
Gear Measurements
7/29/2019 @UNIT II ME302 (Thread, Gear and Circularity Measurements)
42/42
SATADRU KASHYAP ME 302
Gear Measurements
The Klingeluberg involute tester: gear tooth profile (an involute curve)
Due to the linear motion of the straight-edge and the rotational motion of the gear tested, the
stylus, which will trace an involute curve, will slide over the tooth flank.
If profile of flank - exactly involute, the lever will remain stationary.
Then, recorded curve - straight line parallel to the direction of the motion of the flat surface.
Irregularities in straightness of recorded line - errors in the gear tooth profile.
Inclination of the recorded line to the direction of motion of the recording paper - the errors of
the base circle.