Typical example using Professor Unwins approximate construction

Gear data:

Pressure angle, 20°. Module, 12 mm: Number of teeth, 25.

Gear calculations:

Pitch-circle diameter = module x no. of teeth

= 12 x 25 = 300 mm Addendum = module = 12 mm Clearance = 0.25 x module

= 0.25 x 12 = 3 mm Dedendum = addendum + clearance = 12 + 3 = 15 mm Circular pitch = n x module = n x 12 = 37.68 mm Tooth thickness = 1 x circular pitch = 18.84 mm

(a) Draw the pitch circle and the common tangent.

(b) Mark out the pressure angle and the normal to the line of action.

(c) Draw the base circle. Note that the length of the normal is the base-circle radius.

(a) Draw the addendum and dedendum circles. Both addendum and dedendum are measured radially from the pitch circle.

(b) Mark out point A on the addendum circle and point B on the dedendum circles. Divide AB into three parts so that CB = 2AC.

(c) Draw the tangent CD to the base circle. D is the point of tangency. Divide CD into four parts so that CE = 3DE.

(d) Draw a circle with centre O and radius OE. Use

Addendum Circle Radius

Fig. 24.17 Unwins construction-stage 1

Typical Engineering Drawings

Fig. 24.17 Unwins construction-stage 1

Addendum Dedendum

Addendum Dedendum

Pitch Circle Pinion
Fig. 24.18 Unwins construction-stage 2

this circle for centres of arcs of radius EC for the flanks of the teeth after marking out the tooth widths and spaces around the pitch-circle circumference.

Note that it may be more convenient to establish the length of the radius CE by drawing this part of the construction further round the pitch circle, in a vacant space, if the flank of one tooth, i.e. the pitch point, is required to lie on the line AO.

The construction is repeated in Fig. 24.19 to illustrate an application with a rack and pinion. The pitch line of the rack touches the pitch circle of the gear, and the values of the addendum and dedendum for the rack are the same as those for the meshing gear.

If it is required to use the involute profile instead of the approximate construction, then the involute must be constructed from the base circle as shown in Fig. 24.14. Complete stage 1 and stage 2(a) as already described, and mark off the tooth widths around the pitch circle, commencing at the pitch point. Take a tracing of the involute in soft pencil on transparent tracing paper, together with part of the base circle in order to get the profile correctly oriented on the required drawing. Using a French curve, mark the profile in pencil on either side of the tracing paper, so that, whichever side is used, a pencil impression can be obtained. With care, the profile can now be traced onto the required layout, lining up the base circle and ensuring that the profile of the tooth flank passes through the tooth widths previously marked out on the the pitch circle. The flanks of each tooth will be traced from either side of the drawing paper. Finish off each tooth by adding the root radius.

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Responses

  • Ceredic
    How to draw gear with unwins method?
    8 years ago
  • amy
    How to finish of engineering drawing using trace paper?
    8 years ago
  • helena sievinen
    HOW TO DRAW GEAR MODULE PROFILE?
    8 years ago
  • SIRJA
    What is pitch circle radius in mechanical drawing?
    8 years ago
  • max
    DOES X REQD IS CORRECT ON ENGINEERING DRAWING OR X PL?
    8 years ago
  • Jo
    How to draw gear teeth by professor unwins method?
    4 years ago
  • PETROS
    How to construct involute gear by unwins method?
    4 years ago
  • pamphila
    How to draw a gear with base circle method on drawing sheet?
    4 years ago
  • olivia
    How to construct spur gear using Unwin's method?
    4 years ago
  • deodato
    How to draw gear tooth in engineering drawing Unwin construction?
    3 years ago
  • tanta
    How to make gear profile trace paper method?
    3 years ago
  • akseli lassila
    How to draw spur gear by professor unwin method?
    3 years ago
  • kenneth moore
    How to draw a gear with approximate method?
    3 years ago
  • Deborah
    How to draw involute gear tooth profile by hand on paper?
    3 years ago
  • ferdinanda
    How to make a gear in drawing sheet,method?
    3 years ago
  • Myley Robertson
    How to draw two meshing gears using prof unwins method?
    3 years ago
  • Geronimo
    HOW TO CONSTRUCT GEAR PROFILE USING APPROXIMATE METHOD?
    3 years ago
  • ren
    How to construst gear using unwins method?
    3 years ago
  • Joel Uosukainen
    How to draw a gear with tracing paper method?
    3 years ago
  • Morgan
    How to draw an involute gear using approximate method?
    3 years ago
  • carmine
    How to construct a spur gear using approximate method?
    3 years ago
  • ralph
    How to draw spur gear approximation method?
    3 years ago
  • Leea Niinist
    How to construct gear tooth profile?
    3 years ago
  • PHILLIPP
    How to draw spar gear in approxi method?
    3 years ago
  • pandora
    How to draw gears on paper?
    3 years ago
  • JUSTIN
    How to draw spur gear profile by prof. onwins method?
    2 years ago
  • FANTINO LOMBARDI
    How to draw a spur gear by approximate method?
    2 years ago
  • Asmarina
    How to make a gear with approximation method?
    2 years ago
  • aiace
    How to draw gear using proffesor?
    2 years ago
  • dominik
    How to construct gear using professor Unwins and approximate method?
    2 years ago
  • Awet
    How to draw gear teeth on paper using approximate metjihdr?
    2 years ago
  • yolando
    How to construct a base circle of a gear?
    2 years ago
  • lassi
    How to construct a spur gear using urwins method?
    2 years ago
  • Torsten
    How to constuct a gear using approximate method?
    2 years ago

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