See: Add Rack-Pinion

Use the Rack-Pinion dialog-box to edit parameters for a:

Rack and Pinion and

Open Rack-Pinion dialog-box


Edit the Rack-Pinion:

1.Double-click a Rack-Pinion in the graphic-area or Assembly-Tree.

- or -

The Rack-Pinion dialog-box is now open.

Rack-Pinion / Ball-Screw dialog-box

Rack & Pinion dialog-box [With Ball-Screws tab]

Rack & Pinion dialog-box
[With Ball-Screws tab]

There are three tabs in the Rack-Pinion dialog-box. each with one separator.

General  tab

Gear Tooth tab

Ball-screw tab

General tab :

btn_delkeyword Rack and Pinion Parameters 


Rack Offset

Rack Offset : moves the rack along its pitch-line by a number of teeth.

'# Rack Teeth, N

Rack Tooth, N : the number-of-teeth along the Rack

# Pinion Teeth, N

As you increase the number-of-teeth on the Pinion, the Rack will move to remain in contact with the Pinion.

To correct the Mesh:

When you want to add two Racks to the same pinion, you must do Add Rack-Pinion two times.

You may need to rotate one of the Pinions a fraction of a gear tooth so that the two pinions are appears to be the same. To do this, click one of the options:

Shift Rack, or
Shift Pinion, or
Do not Shift

Select Rack Side

The Rack is one side of the pinion or the other. Select:


- or -


Gear Tooth tab :

btn_delkeyword  Rack and Pinion Tooth Parameters 


Module = P.C.D (mm) ÷  number-of-teeth.

Ratio (degrees / mm) (Read-Only)

The 'degrees of rotation' of the Pinion for each 'mm' travel of the Rack.

P.C.D (Pitch Circle Diameter) (mm) (Read-Only)

The diameter of the Pitch Circle of the Pinion

Pressure Angle (Default = 20º).

The 'standard' Pressure Angle is 20º. Other 'standards' are: 14º, 17.5º (weaker, quieter), 22.5º and 25º (stronger, noisier)

Addendum (Default = Module).

The radial height of the gear tooth from the pitch circle to the tip of the tooth.

Dedendum (Default Value = Module * 1.25 (Module>1)).

The radial depth of the gear tooth below the Pitch Circle to the root of the tooth. It is larger than the Addendum so there is clearance. Then the tip of the tooth is clear of the root of the

Root Radius, or 'Flank Radius' (Default is 0.3 * Module)

The small fillet between the Flank and the Root of the Gear Tooth.

Points along Profile

The number of 'facets' along the gear tooth flank. ':  6 is OK, 8 is Good.

Ball-Screw tab :

btn_delkeyword  Ball Screws Parameters 


Select Type

Rack and Pinion

Ball-Screws - the symbol in the graphic-area changes to a screw, starting at the origin of the sliding-Part.

Ball-Screw Lead (mm) - the distance the Sliding-Part must move to rotate the Rotating-Part one time.
Ball-Screw Diameter (mm) - this simply updates the diameter of the Ball-Screw symbol in the graphic-area.


The length of the Ball-Screw Length is the length of the Line in the sliding-Part - see Add Rack-Pinion.

The Ball-Screw has a Right-Hand Thread when the Rack-Side is set to Right - see General tab

The Ball-Screw has a Left-Hand Thread when the Rack-Side is set to Left - see General tab

Module, in the Gear Tooth tab, changes to a value equivalent to the Ball-Screw Lead


Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd