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UDC 6216332 + 621.83336 : 0014 IS : 2458 ( Part 2 ) - 1984

Indian StandardGLOSSARY OF TERMS FOR TOOTHED GEARING

PART 2 BEVEL AND HYPOID GEARS

1. Scope - Defines the commonly used terms in bevel and hypoid gear industry.SECTION ONE

2. Bevel Gear Terminology2.1 General Definitions

*2.1 .I Bevelgears - Conical in form and operating on intersecting axes.ON AXIS

2.1.2 Pitch surface - The geometrical surface described by the ins antaneous axis Of themovement of the mating gear in relation to the gear under consideration in a given pair.PITCH PLANE-

(PITCH ELEMENT I

2.1.3 Reference surface - An imaginary conventional surface with reference to which the toothdimensions of a gear, considered alone, are defined. It is the pitch surface of engagement withthe basic member.*2.1.4 Pifch cone - The pitch surface of a bevel gear ( see 2.1.2 ).*2.1.5 Pitch element - The instantaneous axis of relative motion of the bevel gear pair alongwhich the pitch cones of the gears roll without slipping ( see 2.1.2 ).*Applicable to bevel gears only.

Adopted 8 February 1984 @October 1934, ISI I Gr 11INDIAN STANDARDS INSTITUTIONMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

( Reaffirmed 2000 )

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IS : 2458 Part 2 ) - 1984PINION AXIS

/GEAR AXIS2.1.6 Pitch angle - The angle between an element of pitch cone and the axis (see 2.1.5).2.1.7 Shaft angle - The angle between the axes of the mating bevel gears; this is equal to thesum of the two pitch angles ( see 2.1.5 ).2.1.6 Pitch plane - The plane tangent to the pitch cone along the pitch element and perpendi-cular to the axial plane.2.1.9 Axial plane - The plane that contains the two axes of the bevel gears pair.

TRANSVERSE PLANEAPEX --b

LlTChPLANE LIRTUALCYLINDRICALGEAR

TRANSVERSE SECTION

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IS:2458 (Part 2 ) - I 9842. 1 I Transverse plane - The plane perpendicular to the axial plane and the pitch plane( see 2.1.9 ).2.1 .I 1 Pitch circle -The circle of intersection of the pitch cone with a plane, perpendicular tothe axis of the bevel gear, on which the pitch has the specified value ( see 2.1.9 ).2.1.12 Pitch point - The point on the transverse plane along the pitch element where the pitchcircles of the mating bevel gears contact (see 2. 1. 9 .

~ 2.1 . I 3 Back cone -The cone whose elements are perpendicular to the pitch elements at theouter ends of the teeth ( see 2.1.14 ).2. 1. 14Root cone - The cone, enveloping the bottom lands of the teeth.

PITCH APEXf-PllCH CONE

2. 1. 15Root circle - The circle of intersection of root cone with the back cone ( see 2.1.14 ).2.1.16 Face cone - The cone enveloping the top lands of the teeth.

BE APEX

2. 1. 17Front cone - The cone whose elements are perpendicular to the pitch elements at theinner ends of the teeth.2.1.16 Crown - The point defined by the intersection of a face cone element and a back coneelement ( see 2. 1. 19 .

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IS : 2458 ( Part 2 ) - 19842.1 I 9 Crown circle - The circle ot intersection of the back cone and face cone.

CROWNCIRC% FACE CONErWN

2.1.20 Front-crown - The point defined by the intersection of a face, cone element and a frontcone element.PITCH ANGLE1

FRONTCROWN 1 FACEGLE

ANGLE

2.1.21 Face angle - The angle between an element of the face cone and its axis ( see 2.1.20).2.1.22 Root angle - The angle between an element of the root cone and its axis ( see 2.1.20 ),2.1.23 Back angle - The angle between an element of back cone and a plane of rotation and is

equal to pitch angle unless the back cone is modified in the gear blank ( see 2.1.24 ).2.1.24 Addendum angle - The angle between elements of the face cone and the pitch cone.FACE APY ,,KH APEX

ADDENDUM AN ANGLE

ANGLEFRONT ANGLE\

2.1.25 Dedendum angle - The angle between elements of the root cone and pitch cone (see2.1.24 ).2.1.28 Front angle - The angle between an element of front cone and a plane of rotation and isusually equal to back angle ( see 2.1.24 ).2.1.27 Pitch apex - The point defined by the intersection of the bevel gear axis and a pitchelement. ( Also called pitch cone apex ) ( see 2.1.24 ),

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2. 1. 28element.2. 1. 29element.

IS : 2458 ( Part 2 ) - 1984Face apex - The point defined by the intersection of the bevel gear axis and a face cone( Also called face cone apex ) (see 2.1.24 ).Root apex - The point defined by the intersection of the bevel gear axis and a root cone( Also called root cone apex ).

ROOT APEX

2. 1. 30Face width - The width over the toothed part of the gear measured along a pitch element(see 2. 1. 29 -,2. 1. 31Pitch diameter - The diameter of the pitch circle ( see 2.1.29 ).21.32 Outside diameter - The diameter of the crown circle ( see 2. 1. 29 .2. 1. 33Face angle distance - The perpendicular distance of a face cone element from the pointof intersection of the axis with the locating surface on the back,

PITCH APEX

CACE ANGLE

2.1.34 Back angle distance -The perpendicular distance of a back cone element from the pitchapex ( see 2.1.33 ).5

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IS : 2458 ( Part 2 ) - 19842. 1. 35Outer cone distance - The distance between the pitch apex and the back cone measuredalong a pitch element. INNER CONEmTANCE

2. 1. 36Mean cone distance - The distance from the pitch apex to the middle of the face widthmeasured along a pitch element ( see 2.1.35 ).2.1.37 Inner cone distance - The distance from the pitch apex and the front cone measuredaloWa pitch element ( see 2.1.35 ).2.1.38 Pitch apex to crown - The distance along a bevel gear axis from the pitch apex to thecrown ( see 2. 1. 39) .2. 1. 39Pitch apex to back - The distance along the bevel gear axis from the pitch apex to thelocating surface on the back of the gear blank.

PITCH AmPITCH APEXrTO BACK

CROWN PO?PITCH APEX

$cnoWN

-i?i BACK

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IS : 2458 ( Part 2 ) - 19842.1.40 Crown fo back - The distance in the axial plane from the crown to the locating surface onthe back of the gear blank ( see 2. 1. 39 .2. 1. 41Mounfing distance - The distance along the bevel gear axis from the point of intersectionof the axes of mating gears ( pitch apex in bevel gears ) to the locating surface on the back or frontof bevel gear, in the assembly.2.1;42 Back cone distance - The distance along an element of the back cone from its apex to thepitch circle in the direction normal to the pitch cone ( see 2.1.39 ).2.1.43 Equivalent pitch radius of bevel gear - The radius of curvature of the pitch surface in the

transverse section of bevel gear teeth, at the outer end; and this is equal to back cone distance.

APEX

TRANSVERSE PLANEPITCH CONE

/ -I

EQUIVALENTNUMBER Of TEETH7

DISTANCE)

VIRTUAL CYLINDRICALGEAR

EQUIVALENTPITCH RADIUS(BACK CONE

2.1.44 Equivalenf number of feefh - The number of teeth of the specified module of the bevelgear, contained in the whole circumference of a pitch circle corresponding to an equivalent pitchradius ( see 2.1.43 ).2.1.45 Virtual cylindr ical gear of a bevel gear -The imaginary cylindrical gear of which thetransverse section is having the equivalent number of teeth ( see 21.43 ).

*2.1.46 Crown gear - A bevel gear with straight profile teeth having a pitch angle of 90 and hencea pitch surface at right angles to its axis.CROWN GEAR AXIS

PITCH CONE

*Applicable to bevel gears On!y.

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l S: 245i ( Part 2). 1984*2.1.#7 Basic member -For the family of bevel gears, a bevel gear that can contact both the gearsof a bevel gear pair, at any turning position along the same lines along which the gears contact oneanother.

Note-The basic member for a family of bevel gears is a crown gear ( see 2.1.46 ).

2.1 A8 Complementary basic members - Two basic members are complementary if they can befitted face to face with completely coincident pitch and tooth surface.

*2. 1. 49omplementarymentary basic members.

COMPLEMENTARY BASIC MEMBERS

crown gears -Two bevel gears of 90 pitch angle which are comple-

COMPLEMENTARY CROWN GEARS

2,l.!j9 Conjugate gears - Gears with mating tooth profiles which satisfy the law of gearingexplained below:Law ofgearing -The common ncrmal to the mating tooth surfaces of a pair of gears atevery point of contact passes through the pitch point for gears to transmit uniform motion atconstant velocity ratio.

*Applicable to bevel gears only.8

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IS : 2458 ( Part 2 ) - 19842.1.51 Conjugate crown gear -A crown gear with straight profile teeth which runs with a bevelgear under the law of gearing.

BEVEL PINIO~I BEVEL

70 CROWN GEAR

2.1.52 Corijugate bevel gears - Two bevel gears which are conjugate to a pair of complementarycrown gears.2.153 Interchanaeable bevel aears -The bevel clears within a family, whose basic member (crowngear) is complementary to itself.

2.2 Tooth Characteristics2.2.1 Tooth surface - The surface that forms the side of abounded by the face cone, the root cone and face width of tooth. gear tooth, the area of which is

PLANE NORMAL TOr- PITCH SURFACE

2.2.2surface Tooth profile-The curve of intersection of a tooth surface and a plane normal to the pitch( see 2.2.1 ).2.2.3 Tooth trace-A general term for the curve of intersection of a tooth surface and its pitchsurface ( see 2.2.1 ).

Whole depth - The total depth of a tooth space defined by the distance between the crowncircle and the root circle measured along a back cone element ( see 2.2.5).2.2.4

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IS : 2458 (Part 2)- 19842.2.5 Addendum -back cone element. The distance between the crown circle and pitch circle measured along a

AXIAL SECTIONADDENDUM

DEDENDUM 1 FK CONE DISTANCE

I CIRCULAR \ ,

TOP LAND

SPACE WIDTH/ /BOTTOM LANDT:pcKDN~

SECTION AA2.2.6 Dedendum - The distance between the pitch circle and the root circle measured along aback cone element (see 2.2.5 ).2.2.7 Working depth -The sum of the addenda of the mating bevel gears and this also definesthe depth of engagement of the two gears (see 2.2.5).2.2.6 Clearance- The difference in the dimension of dedendum of a bevel gear and the addendumof its mating gear ( see 2.2.5 ).2.2.9 Circular. thickness - The length of arc of the pitch circle of the bevel gear between the twotooth profiles of a tooth (see 2.2.5 ).2.2.10 Space width -The length of arc of the pitch circle of the bevel gear lying between the twotooth profiles of a tooth space ( see 2.2.5 ).

IO

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IS : 2458 (Part 2 ) - 19842.2.11 Circular pitch -The length of arc of the pitch circle of the bevel gear between corres-ponding profiles of adjacent teeth (see 2.2.5 ).2.2.12 Chordal thickness -The length of the chord subtending a circular thickness arc of a tooth( see 2.2.5 ).2.2.13 Chordaladdendum -The height from the top of the tooth to the chord subtending thecircular thickness arc ( see 2.2.5 ).2.2.14 Toe - The portion of the tooth surface at the inner end of tooth ( see 2. 2. 17 .

. 2. 15Heel-The portion of the tooth surface at the outer end of the tooth (see 2. 2. 17) .2. 2. 16 Top /and-The surface of the top of a tooth ( see 2.2.17 ).2.2.17 Normal top land -The width of the top land measured normal to the tooth lengthwisecurve.

2. 2. 18 nner normal top land - The width of the normal top land at the inner end of the tooth.2. 2. 19Mean normal top land - The width of the normal top land at the middle of the face width.2.2.20 Outer normal top /and - The width of the normal top land at the outer end of the tooth.2.2.21 Bottom /and - The surface of the bottom of a tooth space adjoining the fillets( see 2.2.5 ).2.2.22 Face - The upper portion of the tooth surface ( see 2.2.17 ),2.2.23 Flank - The lower portion of the tooth surface ( see 2.2.17 ).2.2.24 Top side - The upward-facing surface of tooth on the left side of a bevel gear when viewedfrom pitch apex ( see 2.2.17).2.2.25 Bottom side - The downward-facing surface of a tooth on the left side of a bevel gearwhen viewed from pitch apex ( see 2.2.17 ).2.2.26 Concave side -The side of the tooth whose tooth surface is concave in the length-wisedirection of the tooth (see 2.2.17).

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IS : 2458 ( Part 2) - 19842.2.27 Convex side -The side of the tooth whose tooth surface is convex in the length-wisedirection of the tooth ( see 2.2.17 ).2.2.28 Driving side -The side of tooth which is in contact with its mating gear when the pair isin operation.2.2.29 Spiralangle - The angle between the tooth trace and an element of pitch cone at the meancone distance or at the middle of the face width.

--

INNER SPIRALANGLE

,-k

1

.

/

902.3.12 Miter gears - Bevel gears in which each member of the pair has same number Of teeth.

2.4 Terms Connected wifh inspection, Testing and Development Procedure2.4.1 Gear-Of the two gears of a bevel gear pair the one with the larger number of teeth, anddriving member in miter gears.2.4.2 Pinion-Of the two gears of a bevel gear pair the one with the smaller number of teeth,and driving member in miter gears.2.4.3 Pitch -The theoretical distance along the arc of pitch circle between corresponding points,on adjacent teeth.

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IS:2458 (Part 2)-19842.44 Pitch range - The algebraic difference between the longest and the shortest measurementof pitch on the entire gear.2.4.5 Pitch variation - The difference between the theoretical pitch and the measured pitch bet-ween any two adjacent teeth.2.4.6 Tooth spacing - The measured distance between corresponding points on adjacent teeth.

2.4.7 Spacing variation - This is also called tooth-to-tooth spacing and is the difference betweenany two adjacent measurements of spacing.2.4.8 index - The theoretical angular position of teeth about the axis of the pitch cone.2.4.9 Index variation -The displacement of any tooth from its theoretical angular position relativeto a datum tooth.2.4.10 Total index variation - The maximum amount of angular displacement from the theoretical

angular position of any tooth with respect to any other tooth of the complete gear.2.4.11 Concentricity - The degree of coincidence of the axis of the pitch cone with its axis ofrotation.2.4.12 Eccentricity - The perpendicular distance between the axis of pitch cone and its axis ofrotation.2.4.13 Composite variation - The variation in mounting distance of a bevel gear when it rolls intight-mesh with a specified gear on a gear rolling fixture.

2.4.14 Tooth-to-tooth composite variation - The composite variation obtained as the gear isrotated through an increment of 360Number of teeth in gear under inspection *

2.4.15 Total composite variation - The amount of composite variation during one total revolutionof the gear being inspected.2.4.16 Profile wave - The oscillatory displacement of a pinion in the direction perpendicular toits axis, when it rolls in metal to metal contact with its mating gear, as a result of profile modifica-tions introduced on the tooth profiles.

Note - The average value of individual oscillations around one full revolution of the gear is the profile wave forthe gear-pair.

2.4.17 Circumferential backlash - (The backlash in the plane of rotation ). The amount by whichthe spacewidth of a tooth exceeds the thickness of the engaging tooth on the pitch circles.

2.4.18 Normal backlash - (The backlash in normal plane ). The play between mating toothsurfaces at the tightest point of mesh in a direction normal to the tooth surface when the gears aremounted in their specified positions.Note - To obtain circumferentia l backlash, the normal backlash value is divided by cosine of the spiral angleand cosine of the pressure angle.

2.4.19 Backlash variation - The difference between the maximum and minimum backlash occurringin a complete revolution of the larger of a pair of mating bevel gears,20

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IS:2458(Part2)-19842.4.20 Tooth bearing - Also called the tooth contact is the summation of the instantaneous linesof contact on the tooth surface when the gear and pinion roll together cn their specified mountings.

LINES OF CONTACT/- -

/ L_-NE PITCHTOOTH BEARING CONJUGATEOR FULLY MATCHED GEARS

CENTRAL TOE BEARING

TOE BEARINGE3ROSS BEARING

HIGH BEARING

LOCALISED TOOTH BEARING

f@+vFULL LOAD TOOTH BEARINGHEEL BEARING2s

OW BEARING

LAME BEARING2.4.21 Localised foofh bearing - The tooth bearing which results when either or both membersof the gear pair are cut with lengthwise and/or profilewise mismatch ( see 2.4.20 ).2.4.22 Development -The gear cutting procedure through which the tooth surfaces are re-cutwith different machine setting in order to obtain a desired tooth bearing,2.4.23 V and H check -A practical way of accurately measuring, on a testing machine, thoseamounts of relative vertical and horizontal displacements (from the specified mounting positions )which the gears can withstand without the occurence of tooth bearing concentrations at the ends oftheir teeth.

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IS : 2458 ( Part 2 ) - 19842.4.24 Central toe bearing - The tooth bearing, observed on the testing machine under lightload, which extends approximately one-half the tooth length favouring the toe end of the tooths, andalso relieved slightly on the face and flank of the tooth ( see 2.4.20 ).2.4.25 Full load tooth bearing - The tooth bearing observed on application testing which spreadson the whole area of tooth surface but shows slight relief at the ends and along the face and flankof the tooth surface ( see 2.4.20 ). .2.4.26 Toe bearing - The tooth bearing concentrated at the toe end of the tooth ( see 2.4.20 ).2.4.27 Heel bearing - The tooth bearing concentrated at the heel end of the tooth ( see 2.4.20 ).2.4.28 Cross bearing - The tooth bearing concentrated at the toe end on one side and at the heelend on the opposite side of the tooth-( see 2.4.20 ).2.4.29 Low bearing - The tooth bearing on flank on both sides of the tooth ( see 2.4.20 ).2.4.30 High bearing - The tooth bearing on the face or top on both sides of the tooth (see2.4.20).2.4.31 Lame bearing - The tooth bearing towards the top on the side of the tooth and towards.

the flank on the opposite side ( see 2.4.20 ).2.4.32 Wide bearing - The tooth bearing centrally positioned lengthwise, but covering the fulldepth of the tooth profilewise showing very little relief on top and flank of the tooth,

WIDE BEARING

BRIDGED (PROFILE) BEARING

SHORT BEARING

BIAS-IN BEARING FORSPIRALS AND HYPOIDS

2sARROW BEARING

eONG (FULL L ENGTH) BEARING

6RlDGE (LENGTH WISE) BEARING

BIAS-OUT BEARING FORSPIRALS AND HYPOIDS

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IS : 2458 ( Part 2 )- 1984

LONG FLANK, SHORT TOP LONG TOP SHORT FLANKDIAMOND BEARING DIAMOND BEARING

SHORT TOE-LONG HEEL BEARING LONG TOE-SHORT HEEL BEARING(ON V & H CHECK) fON V & H CHECK1

2.4.33 Narrow bearing - The tooth bearing centrally positioned lengthwise and has extremelynarrow profile contact with the concentration of contact in the centre of the working depth( see 2.4.32 ).2.4.34 Bridged ( profile ) bearing - The tooth bearing which shows hard contact on both top andflank of tooth, with lighter contact in between ( see 2.4.32 ).2.4.35 Long bearing ( full length bearing ) -full length of tooth ( see 2.4.32 ). The tooth bearing which shows contact along the

2.4.36 Short bearing - The tooth bearing centrallythe length of the tooth ( see 2.4.32 ).2.4.37 Bridged ( lengthwise ) bearing - The fullmiddle of facewidth.

positioned lengthwise with short contact alonglength bearing with narrower width in the

2.436 Bias-in-bearing - The tooth bearing which always runs from the flank at toe to the top atheel on convex side of pinion tooth, and from top at toe to the flank at the heel on the concave sideof pinion tooth, regardless of the hand of spiral ( see 2.4.32 ).2.4.39 Bias-out-bearing - The tooth bearing which always runs from the top at toe to flank atheel on the convex side and from flank at toe to the top at heel on the concave side of piniontooth, regardless of the hand of spiral ( see 2.4.32 ).2.4.40 Diamond bearing - The tooth bearing with the contact length short at the top and longin the flank or vice versa ( see 2.4.32 ).2.4.41 Short foe-long heel bearing - When V and H check is carried out on a gear pair on atesting machine, the bearing which will be observed to be short at toe and long at heel end of thetooth ( see 2.4.32 ).2.4.42 Long toe-short heel bearing - When V and H check is carried out on a gear pair on atesting machine, the bearing which will be observed to be long at toe and short at heel end of thetooth ( see 2.4.32 ).

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IS : 2458 ( Part 2 ) - 1984SECTION TWO

3. Hypoid Gear Terminology3.1 General Defini t ions

3.1.1 Offset - The perpendicular distance between the axes of pinion and gear.

1FFSEI

t=lNlON

AR

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3.1.2 Pitch surfaces - The surfaces of revolution of hypoid gearscontinuous line of contact which can be either curved or straight.

GEAR PITCH AP XI, -L- GEAR AXISI II.,,.PITCH APEX

PITCH SURFACE

IS: 2458( Part 2)-1984tangent to each other along a

PLANEIMlnhl

OF PIN

WAN POlNl

/v -CRIBED CONESURFACE OFPINION AXIS/GEAR PITCH APEX

I~EV~LUTION OFHYPOIO PAIR7

ONTHE

PlNlONPITCH A

PITCH SURFACE

PINION AMEAN

VIEW AT A3.1.3 Pitch cones - The inscribed cones of the pitch surfaces of the hypoid gears, in their axialplanes, which touch each other at a common point ( see 3.1.2 ).3.1.4 Mean point -The point generally on the middle of face widths of the gear and pinion,where their pitch cones touch each other ( see 3.1.2 ).3.1.5 Pitch plane - The common tangent plane at the mean point which contains the apeces ofgear pitch cone and pinion pitch cone ( see 3.1.2 ).

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IS : 2458 Part 2 ) - 19843.1.6 Pitch normal - The normal at the mean point to the pitch plane and the pitch cones ofhypoid gears.

S OF HELICAL SEGMENI

/__.-EAN POINTMEAN POINT_-

AXIS OF

3.1.7 Limit pressure angle - The unbalance in pressure angle required for a theoretical balanceof tooth action between two sides of a hypoid gear tooth. The value of unbalance is algebraicallyadded to the nominal pressure angle to obtain the concave side pressure angle and algebraicallysubtracted from the nominal pressure angle to obtain the convex side pressure angle.3.1.6 Limit normal - The pitch normal at the limit pressure angle which corresponds to zero

inclination of the line of action.

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IS : 2458 ( Part 2 ) - 19843.1.9 Instantaneous axis - The fine of contact of the pitch surfaces about which the surfacesroll and along which surfaces slide,

PITCH LINES

OFF

3.1 .lO Pitch lines - The lines on the pitch surfaces which are tangent to each other at theirintersection with the instantaneous axis ( see 3.1.9 ).3.1.11 Relative motion -The turning motion of the kinematic pitch surfaces of hypoid gear aboutthe instantaneous axis combined with a translation or sliding motion along the instantaneous axis.3.1 .12 Instantaneous lead -The translation or the relative motion along the instantaneous axisper one turn of relative turning motion about the instantaneous axis of a hypoid pair.3.1.13 Basic member- A surface which has the same instantaneous axis, the same relativemotion and instantaneous lead, as of the gear pair.

Note -The surface that satisfies the above condition is a helical segment ( see 3.1.6).3.2 Types of Hypoid Gears

3.2.1 Hypoid gears -at right angle. Hypoid gears with spiral teeth that are curved and oblique, with their axes3.2.2 Skew hypoid gears -at right angle. Hypoid gears with teeth that are straight and oblique, with their axes3.2.3 Generated hypoid gears - Hypoid gears with tooth, surfaces of both gear and piniongenerated by the same or similar tools.3.2.4 Formate hypoid gears - Hypoid gears with gear tooth surfaces non-generated and themating pinion tooth surfaces generated.

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IS : 2458 ( Part 2 ) - 19843.2.5 Helix form hypoid gears - Hypoid gears with gear tooth surfaces non-generated, but with anadditional helical in feed motion to the cutting tool while forming the tooth surface, the matingpinion tooth surfaces are generated.

3.3 Miscellaneous Terms3.3.1 Shaff angle - The angle between the axes of the hypoid pair in a plane parallel to both the

axes.

OFF

/ MOUNTINGI DISTANCE-PINIONAPEX BEYONDCROSSINGPOINT (-1

MOUNTING-_IISTANCE - GEAR

Note - In hypoid gears, the shaft angle does not have a fixed relation to the pitch angles as in the case of bevelgears.3.3.2 Crossing point - The apparent point of intersection of ,the axes of hypoid pair, whenprojected in a plane parallel to both the axes ( see 3.3.1 ).3.3.3 Mounting distance - The distance from the crossing point of the axes to a locating surfaceof a gear, which may be either at back or front of gear ( see 3.3.1 ).3.3.4 Cone apex beyond crossing point - The distance along the axis of a hypoid gear or pinionfrom the cone apex to a line which is normal to the axis and which passes through the axis of themating member (see 3.3.1 >,

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IS : 2458 ( Part 2 ) - 1984INDEX

The index number is the same as the relevant clause number of the each term in the glossary.

AAddendum 2.2.5

Angle 2.1.24Chordal 2.2.13Modification coefficient 2.2.45Modification coefficient of a bevel gear 2.2.44AnoleAddendum 2.1.24Back 2.1.23Dedendum 2.1.25Face 2.1.21Front 2.1.26Limit pressure 3.1.8Pressure 2.2.41At a point 2.2.40;;;;t2.1. 22Bevel gear 2.1.7Hypoid gear 3.3.1Spiral 2.2.29Inner 2.2.30Outer 2.2.31Angular bevel gear 2.3.9ApexFace 2.1.28Pitch 2.1.27Root 2.1.29Arc of action 2.2.33of approach 2.2.34of recess 2.2.35Axial plane 2.1.9Axis, instantaneous 3.1.9

8Back angle 2.1.23Distance 2.1.34Back cone 2.1 .I3Distance 2.1.42BacklashCircumferential 2.4.17Normal 2.4.18Variation 2.4.19Basic memberBevel gear 2.1.47Hypoid gear 3.1.13BearingBiasin 2.4.38out 2.4.39Bridged

Lengthwise 2.4.37Profile 2.4.34Central toe 2.4.24Gross 2.4.28;$mond 2.4.40length 2.4.35load tooth 2.4.25Heel 2.4.27High 2.4.30Lame 2.4.31Localised tooth 2.4.21Long 2.4.35Long toe-shaft heel 2.4.42Low 2.4.29Narrow 2.4.33Short 2.4.36

Short toe-long heel 2.4.41Toe 2.4.26Tooth 2.4.20Wide 2.4.32Bevel gear 2.1 .IBiasIn bearing 2.4.38

Out bearing 2.4.39Bottom land 2.2.21Bottom side 2.2.25BridgedLengthwise bearing 2.4.37Profile bearing 2.4.34C,e,;trTAltoe bearing 2.4.24

Addendum 2.2.13Thickness 2.2.12CircleCrown 2.1.19Pitch 2.1.11Root 2.1 .I5CircularFitch 2.2.11Thickness 2.2.9Clearance 2.2.8Complementarybasic member 2.1.48crown gears 2.1.49Composite variation 2.4.13Concave side 2.2.26Concentricity 2.4.11ConeApex beyond crossing point 3.3.4Back 2.1 .I 3Face 2.1.16Front 2.1 .I7PitchBevel aear 2.1.4Hypoid gear 3.1.3Root 2.1 .I4Conjugatebevel gear 2.1.52crown gear 2.1.51gears 2.1.50Contact ratio 2.2.36Face 2.2.38Modified 2.2.39Transverse 2.2.37Convex side 2.2.27Cross bearing 2.4.28Crossing point 3.3.2Crown 2.1 .I8Circle 2.1.19Front 2.1.20Gear 2.1.46Crown to back 2.1.40DDedendum 2.2.6Angle 2.1.25Depth-wise taper 2.2.52Development 2.4.22DiameterOutside 2.1.32Pitch 2.1.31Diamond bearing 2.4.40DistanceBack angle 2.1.34Back cone 2.1.42Crown to back 2.1.40Face angle 2.1.33Inner cone 2.1.37

Mean cone 2.1.36MountingBevel gear 2.1.41Hypoid gear 3.3.3Outer cone 3.1.35Pitch apex toback 2.1.39

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IS : 2458 ( Part 2 ) - 1984crown 2.1.38Driving side 2.2.28Duplex taper 2.2.54

EEccentricity 2.4.12Equivalentnumber of teeth 2.1.44

pitch radius 2.1.43External bevel gear 2.3.10FFace 2.2.22Advance 2.2.32Angle 2.1.21Distance 2.1.33Apex 2.1.28Cone 2.1.16Width 2.1.30Flank 2.2.23Formate hypoid gears 3.2.4Frontangle 2.1.26

cone 2.1 .I7crown 2.1 20Full length bearing 2.4.35load tooth bearing 2.4.25GGear 2.4.1Bevel 2.1.1Advance 2.3.9Conjugate 2.1.52External 2.3.10Interchangeable 2.1.53Internal 2.3.11

Left-handskew 2.3.4spiral 2.3.7Right-handskew 2.3.3spiral 2.3.6Skew 2.3.2Spiral 2.3.5Straight 2.3.1Zero1 2.3.8Conjugate 2.1.50Crown 2.1.46Conjugate 2.1.51Generatad hypoid 3.2.3HypoidFormate 3.2.4Generated 3.2.3Helix-form 3.2.5Skew 3.2.2Miter 2.3.12

HHeel 2.2.15Bearing 2.4.27Helix-form hypoid gears 8.2.5High bearing 2.4.30

index 2.4.8Variation 2.4.9Innercone distance 2.1.37normal top land 2.2.18spiral angle 2.2.30Instantaneousaxis 3.1.9lead 3.1 .I2

LLame bearing 2.4.31Left-handskew bevel aear 2.3.4spiral bevel-gear 2.3.7Limit normal 3.1.8Localised tooth bearing 2.4.21Long

bearing 2.4.35toe-short heel bearing 2.4.42Low Bearing 2.4.29MMeancone distance 2.1.36normal top land 2.2.19.point 3.1.4Mismatch 2.2.42Miter gear 2.3.12Module 2.2.43Mounting distanceBevel gear 2.1.41Hypoid gear 3.3.3NNarrow bearing 2.4.33Normal top land 2.2.170gff;lrt 3.1 .I

cone distance 2.1.35normal top land 2.2.20spiral angle 2.2.31Outside diameter 2.1.32PPinion 2.4.2Pitch 2.4.3Angle 2.1.6Apex 2.1.27to crown 2.1.38to back 2.1.39Circle 2.1.11C&Kilar 2.2.11

Bevel gear 2.1.4Hypoid gear 3.1.3Diameter 2.1.31Element 2.1.5Lines 3.1.10~.Normal 3.1.6PlaneBevel gear 2.1.8Hypoid gear 3.1.5Point 2.1.12Range 2.4.4SurfaceBevel gear 2.1.2Hypoid gear 3.1.2Variation 2.4.5PlaneAxial 2.1.9Pitch 2.1.8Transverse 2.1.10Pressure angle 2.2.41at a point 2.2.40Profile wave 2.4.16RReference surface 2.1.3Relative motion 3.1.11Right-handskew bevel gear 2.3.3spiral bevel gear 2.3.6

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IS : 2458 ( Part 2 ) - 1984RootAngle 2.1.22Apex 2.1.29Circle 2.1.15Cone 2.1.14SShaft angleBevel gear 2.1.7Hypoid gear 3.3.1Shortbearing 2.4.36toe-long heel bearing 2.4.41Skew bevel gear 2.3.2Left-hand 2.3.4Right-hand 2.3.3Skew hypoid gear 3.2.2Slot width taper 2.2.51Space width 2.2.10Taper 2.2.43Spacing variation 2.4.7Spiralangle 2.2.29

bevel gear 2.3.5Standardbasic rack tooth profile 2.2.48depth-wise taper 2.2.53Straight bevel gears 2.3.1TTaperDepthwise 2.2.52Duplex 2.2.54Slot width 2.2.51Space width 2.2.49Standard depth-wise 2.2.53Tooth thickness 2.2.50Thickness

Circular 2.2.9Chordal 2.2.12

Toe 2.2.14Bearing 2.4.26ToothBearing 2.4.20Profile 2.2.2Spacing 2.4.6Surface 2.2.1Thickness taper 2.2.59Trace 2.2.3Tooth-to-tooth composite variation 2.4.14Top 2.2.22Top land 2.2.16-Inner normal 2.2.18Mean normal 2.2.19Normal 2.2.17Outer normal 2.2.20Top side 2.2.24 .otal composite variation 2.4.15Index variation 2.4.14Transverse plane 2.1.10

VV and H check 2.4.23Virtual cylindrical gear 2.1.45WWhole depth 2.2.4Wide bearina 2.4.32Width -Face 2.1.30Space 2.2.10Working depth 2.2.7XX-gear 2.2.47X-zero gear 2.2.46ZZero1 bevel gear 2.3.8

EXPLANATORY NOTEThis standard has been prepared for the guidance of manufacturers and users of bevel andhypoid gears to assist them in the correct interpretation of the terms used in the industry.In view of the increasing use of bevel and hypoid gears in automobile industry, a need hasbeen felt to introduce a separate standard on glossary of terms. Subsequently, chapter 3 ofIS : 2458-1965 Glossary of terms for toothed gearing dealing with terminology of bevel andhypoid gears stands deleted. The terms common to parallel axis gears and bevel gears which are

frequently encountered in bevel gear industry are repeated in this standard.Section one in this standard covers the terms connected with bevel gears. Most of the terms inthis section are common to bevel and hypoid gears. Terms which are applicable to hypoid gearsonly appear in section two.In formulation of this standard considerable assistance has been derived from Gleason Bevel