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SYMBOLS FOR RULES & FORMULAS a Addendum tr Tooth Thickness Tolerance ac Chordal Addendum tt Transverse Circular Thickness anc Normal Chordal Addendum tx Axial Thickness

B Backlash Vap Total Accumulated Pitch Variation b Dedendum Vapk Total Accumulated Pitch C Center Distance Variation within a sector of k Pitches c Clearance Vcq Total Composite Variation D Reference Standard Pitch (double flank) Diameter VcqT Total Composite Tolerance Db Base Diameter (double flank)

Dc Datum Circle Vp Pitch Variation

Di Internal Diameter VpA Allowable Pitch Variation

DR Root Diameter Vpn Normal Pitch Variation

Dt Throat Diameter Vq Tooth-to-Tooth Composite Variation (double flank) Do Out side diameter VqT Tooth-to-Tooth Composite dp Operating Pitch Diameter Tolerance (double flank)

F Face Width Vr Radial Runout

Fe Effective or Active Face VrT Radial Runout Tolerance Width Ft Total Face Width Vs Spacing Variation hk Working Depth Vx Index Variation ht Whole Depth(tooth depth) VΦ Profile Variation

L Lead VΦT Profile Tolerance m Module Vψ Tooth Alignment Variation mc Contact Ratio VψT Tooth Alignment Tolerance mF Face Contact Ratio Z Length of Action mG Ratio α Addendum Angle mn Normal Module Γ Pitch Angle mo Modified Contact Ratio ΓR Root Angle mp Transverse Contact Ratio Σ Shaft Angle mt Total Contact Ratio ε Involute Roll Angle

N Number of teeth or threads θ Involute Polar Angle

Ne Equivalent Number of teeth θN Angular Pitch

Pd Diametral Pitch (transverse) λ Lead Angle

Pnd Normal Diametral Pitch λb Base Lead Angle

P Circular Pitch λo Outside Lead Angle

Pb Base Pitch λp Pitch Lead Angle

Pm True Position Pitch p Profile Radius of

Pn Normal Circular Pitch Φ Pressure Angle

PN Normal Base Pitch Φn Normal Pressure Angle

Pt Transverse Circular Pitch Φt Transverse Pressure Angle

Px Axial Pitch Φx Axial Pressure Angle

PX Axial Base Pitch Ψ Angle, Angle

Q Quality Number Ψb Base Helix Angle

Qa Arc of Approach ------

Qr Arc of Recess

Qt Arc of Action A Allowable Variation

Rr Test Radius G Features on a gear

rf Fillet Radius,(when constant) k A Variable

rt Throat-form Radius n Normal plane

rr Tip or Edge Radius of Tool P Features on a Pinion

t Circular Tooth Thickness T Tolerance

tb Base Circular Thickness t Transverse Plane

tc Chordal Thickness W Features on a Worm

tn Normal Circular Thickness

tnc Normal Chordal Thickness

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