Gear Racks

Welcome to the widest range of standard racks & pinions in the World!  Consisting of both helical & straight (spur) tooth versions, in an assortment of sizes, materials and quality levels, to meet almost any axis drive requirements.

These drives are perfect for a wide range of applications, including axis drives requiring precise positioning & repeatability, traveling gantries & columns, pick & place robots, CNC routers and material handling systems.  Heavy load capacities and duty cycles can also be easily handled with this drives.  Industries served include Material Handling, Automation, Automotive, Aerospace, Machine Tool and Robotics.

Typical delivery time for these standard components is 2 to 3 weeks, which is ideal for OEM's requiring just-in-time delivery schedules.  Special and/or modified components are always possible - please consult the factory.  For harsh environments, stainless steel rack & pinions are available, as well as coatings such as black oxide and chromium (Armoloy ®).

For information on replacing Diametral Pitch (DP) rack & pinions, please follow this link.

NEW Article:  Separating Rack & Pinion Myths From Reality

Rack and pinion drives are an age-old mechanism widely used for converting rotary motion into linear motion.  However, myths and misconceptions abound regarding the use and application of rack & pinions in this age of servo-driven machinery.  In this article, we debunk some of those fallacies.

NEW StrongLine Racks utilizes an innovative carburized case-hardening process to increase the strength of the rack, including the tooth flanks and root, which maximizes its power density, stiffness and performance.

NEW Ultra-High-Precision DIN 4 & 5 Hardened & Ground Racks, which are precision manufactured in a controlled environment with pitch accuracies down to 0.012 mm per 1,000 mm length.

Quality Levels  |  Range  |  Selection  |  Lubrication  |  PDF Files  |  Operating Manual

There are four basic gear rack styles available (click on style for PDF catalog pages):

Helical	Straight	Integrated	Round
These racks have the teeth at an angle (19º 31' 42") to rack length for increased load capacity and quiet operation.	These racks have the teeth perpendicular to rack length, and are traditionally known as "spur".	These racks were designed for mounting directly to most common linear guides.	These racks have a round cross-section and use bushings for support.

Helical versus Straight:  The helical style provides several key benefits over the straight style, including:

• They run quieter than the straight, especially at high speeds

• They have a higher contact ratio (the number of effective teeth engaged) than straight, which increases the load carrying capacity

• Their lengths are nice round numbers, e.g. 500.0 mm and 1,000.0 mm, for easy integration with machine bed lengths; Straight racks lengths are always a multiple of pi., e.g. 502.65 mm and 1005.31 mm.

• In most cases, they cost the same as the straight racks!
  

Rack Quality Levels Overview:

There are four classes of gear racks available and eight different quality levels, each of which is well suited for certain types of applications.  Click on Series Numbers for PDF catalog pages. 

Rack Class:	Rack Type:	Tooth Quality:	Pitch Accuracy:	Typical Applications:	Helical:	Straight:
Basic (BR)	Induction Hardened	DIN 10 (~AGMA 8)	< 0.200 mm per meter	Heavy Loads Low Accuracy	39-Series	27-Series 34-Series
	Soft	DIN 9 (~AGMA 9)	< 0.150 mm per meter	Light Loads Medium Accuracy	47-Series	25-Series 36-Series (Stainless)
Precision (PR)	Quenched & Tempered	DIN 8 (~AGMA 10)	< 0.100 mm per meter	Medium Loads Medium Accuracy	38-Series	33-Series
	Hardened & Ground	DIN 8 (~AGMA 10)	< 0.060 mm per meter	Heavy Loads High Accuracy	39-Series	34-Series
High Precision (HPR)	Hardened & Ground	DIN 7 (~AGMA 11)	< 0.060 mm per meter	Heavy Loads High Accuracy	29-Series	28-Series
		DIN 6 (~AGMA 12)	< 0.048 mm per meter		29-Series	28-Series
Ultra-High Precision (UHPR)	Hardened & Ground	DIN 5	< 0.030 mm per meter	Heavy Loads Ultra-High Accuracy	29-Series	28-Series
		DIN 4	< 0.012 mm per meter		48-Series	46-Series

The quality levels denote the accuracy of the teeth, which affects the positioning accuracy, backlash and noise level of the rack & pinion set.  We always recommend a hardened & ground pinion regardless of the rack type used.

When talking about rack & pinion accuracy, it can be broken down into three components:  Backlash, Pitch Deviation and Tooth Quality.

• Backlash is the amount of clearance between the rack & pinion tooth flanks, and will depend on the type of rack selected and alignment accuracy between the rack and pinion.  The backlash can be eliminated completely by using a Preloaded Split-Pinion or Dual Pinion Drive System.
  

• Pitch Deviation is the difference between the theoretical rack length and its actual length.  This varies depending on the rack quality selected and is shown in the catalog as GTf.  Some servo systems can compensate for this error by using a laser interferometer to map out the errors.  Zero cumulative pitch deviation for long travels is available - please consult the factory.
  

• Tooth Quality is the accuracy that the tooth flanks are manufactured to, which affects the running precision, smoothness, backlash and noise level of the axis drive.  Soft racks have a quality level of ~AGMA 9 (DIN 9).  Induction-hardened racks have a quality level of ~AGMA 8 (DIN 10), due to deformation from the heat treatment process.  Quenched & Tempered racks have a quality level of ~AGMA 10 (DIN 8).  Finally, Hardened & Ground racks have a quality level of ~AGMA 12 (DIN 6), since the teeth are precision ground.  For high accuracy applications, a Precision Hardened & Ground Rack should be used.
  
  *AGMA quality level numbers increase with higher precision; DIN quality level numbers decrease with higher precision.
  

Selecting the right gear rack and pinion depends on many things, including accuracy and load requirements, design constraints, and cost.  Sometimes it is possible that two different racks would work for the same application, but each having it's own advantages and disadvantages.

Rack & pinions are typically selected based on the peak cycle forces, which usually happen during accelerations and decelerations.  These cycle forces depend on the weight being moved, the speed vs. time profile for the cycle, the friction of the axis bearings, and any other external forces acting on the axis.

Tangential force ratings for the various racks can be seen in the following table:

* Ratings are based on helical rack with a 25 tooth hardened & ground pinion; using smaller pinions would reduce rating.  The ratings are based on fatigue strength with adequate lubrication; breaking strength ratings are much higher.  Service factors need to be applied to these ratings to make a proper selection.  The rack mounting screw holding force may also need to be checked.

Helical Rack Ratings  |  Straight Rack Ratings

What is a Module?  Module is a metric pitch, inversely related to diametral pitch, e.g. Module = 25.4 / Diametral Pitch.

For application & selection assistance, please call us or fill out our Application Sheet.  Your application data will be reviewed by our engineers, who will recommend the best solution for your application.

Rack & Pinion Selection Procedure  |  Application Sheet

To view the rack dimensions, please click on the "Series" in left column.

Series	Style	Rack Description	Modules Available	Tooth Heat Treatment	Quality Level
25	Straight	Soft (Without Holes)	1, 1.5, 2, 2.5, 3 4, 5, 6, 8, 10	None	~AGMA 9
26	Straight	Plastic (Without Holes)	1, 1.5, 2, 2.5, 3	-	~AGMA 8
27	Straight	Induction Hardened (Without Holes)	1, 1.5, 2, 2.5, 3 4, 5, 6, 8, 10	Induction Hardened	~AGMA 8
28	Straight	Hardened & Ground	2, 3, 4, 5, 6 8, 10, 12	Case-Hardened	~AGMA 12
28a	Straight	Hardened & Ground	2, 3, 4, 5	Case-Hardened	DIN 5
28b	Straight	Hardened & Ground	2, 3, 4, 5, 6, 8	Induction-Hardened	DIN 7
29	Helical	Hardened & Ground	2, 3, 4, 5, 6 8, 10, 12	Case-Hardened	~AGMA 12
29a	Helical	Hardened & Ground	2, 3, 4, 5	Case-Hardened	DIN 5
29b	Helical	Hardened & Ground	2, 3, 4, 5, 6, 8, 10	Induction-Hardened	DIN 7
33	Straight	Quenched & Tempered	2, 3, 4, 5	Quenched & Tempered	~AGMA 10
34	Straight	Induction Hardened	2, 3, 4, 5, 6 8, 10, 12	Induction Hardened	~AGMA 8
35.0	Straight	Round & Soft	1, 1.5, 2, 2.5 3, 4, 5	None	~AGMA 9
35.1	Straight	Round Quenched & Tempered	1, 1.5, 2, 3, 4	Quenched & Tempered	~AGMA 10
36	Straight	Stainless (Without Holes)	1, 1.5, 2, 3	None	~AGMA 10
36.9	Straight	Round Stainless	1, 1.5, 2, 3	None	~AGMA 10
37.0	Straight	Soft (Without Holes)	5 & 10 mm Circular Pitch	None	~AGMA 9
37.9	Straight	Round & Soft	5 & 10 mm Circular Pitch	None	~AGMA 9
38	Helical	Quenched & Tempered	2, 3, 4, 5	Quenched & Tempered	~AGMA 10
39	Helical	Induction Hardened	2, 3, 4, 5, 6 8, 10, 12	Induction Hardened	~AGMA 8
39a	Helical	Induction Hardened	2, 3, 4, 5	Induction Hardened	~AGMA 8
46	Straight	Hardened & Ground	5, 6, 8, 10, 12	Induction Hardened	DIN 4
47	Helical	Soft	1.5, 2, 3, 4 5, 6, 8, 10	None	~AGMA 9
48	Helical	Hardened & Ground	5, 6, 8, 10, 12	Induction Hardened	DIN 4
49	Straight &  Helical	Integrated Racks	Module 2, 3, 4 & 5, 10 & 13.33 mm Circular Pitch	Soft & Induction Hardened	~AGMA 9 & AGMA 12

 

With open gearing such as rack & pinions, lubrication is critical!  A thin film of grease or oil should always be on the contacting tooth flanks to ensure there is no metal-to-metal contact, which can damage the teeth.

It is recommended to use our Automatic Lubrication System, which pumps grease through a felt gear applicator and meshes directly to the pinion or the rack.  This provides continuous lubrication at the tooth flanks, extending the lifetime and maintaining the quality of the gearing.

For more information on our Automatic Lubrication Systems, please follow this link.

Pinion Gears, consisting of both helical & straight (spur) tooth versions, in an assortment of sizes, materials and quality levels, to meet almost any axis drive requirements.

ISO Flanged Pinions, are provided with ISO 9409-1 flanges to mount directly to our High-Torque (HT) Servo-Worm Reducers and popular planetary gearboxes, such as Alpha TP, Stober PH, Apex AD and Neugart PLF.  This interface provides a tight integration of the pinion to the gearbox output, reducing overhung loading and backlash between the components.  The pinions are easily mounted and replaceable if future repair is needed.

Integrated Racks mount directly to most standard linear guides (HIWIN, IKO, INA, NSK, SKF, Star, THK, etc.), eliminating the need for additional machining and alignment, saving time and money.


Servo Reducers are available in five levels of precision to meet any application needs.  Perfect for use in applications that demand high performance, precise positioning and repeatability.  Angular backlash levels down to less than 1 arc-minutes are available as standard.  Optional integral pinion shafts are also available to mount directly to hollow output shaft.