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Power Transmission Distributors Association is...

the leading association for the power transmission/motion control industrial distribution channel, bringing together distributors and manufacturers.

Linear Motion

Enhance your employees’ product and industry knowledge with PTDA’s Tech Tips. This library of online tips, hints and techniques may be used to educate new and current employees on power transmission/motion control (PT/MC) products, technologies and concepts and serve as reference and reminder for more experienced staff. Tech Tips are based on the expertise of PTDA member companies, content from Motion Control Made Simple or PTDA’s Power Transmission Handbook®, the definitive resource and training tool on PT/MC products.

Visit the full library of Tech Tips for additional products.
 

What is meant by lead screw accuracy?

The accuracy of a screw is referred to as lead error. Lead error is the deviation from the actual measured screw lead compared to the theoretical mathematical screw lead and is often expressed in inches per foot cumulative.

The Importance of Selecting the Correct Shaft Tolerance for Your Linear Bearing

Selecting the correct shaft tolerance range for round linear bearing applications is essential.  The shaft (which acts as the inner race) must not only meet the linear bearing manufacturer’s specifications for hardness, roundness, straightness, surface finish and depth of hardness, but also have the correct OD tolerance to achieve the optimum running condition without being subjected to any unintentional preload or excessive play.  The tolerance “class” you select for the shaft should also conform to the manufacturer’s recommended tolerance based on the tolerance of the bearing’s ID.  Selecting a shaft with a lower than specified tolerance will result in excess radial clearance and a reduction of precision and position repeatability in the application; conversely, an oversized shaft may result in an unwanted preload condition which will result in increased rolling resistance, premature wear and excessive heat.

Maximize your Linear Bearing Life and Load Capacity

The orientation of your linear bearing in relation to the direction of your primary load can have a dramatic effect on the performance and life of your linear system.  To achieve the maximum dynamic load ratings the ball circuits should be positioned to share the load as equally as possible.  It is best to determine the direction the greatest amount of load is likely to be applied and then ensure that two ball circuits are sharing the load evenly rather than one ball circuit doing a majority of the work.

Determining the Lead of a Ballscrew

Lead is the linear distance the nut or shaft moves in one full 360 degree revolution of the nut or the shaft. The best way to identify the lead is to first mount a dial indicator on the front face of the ballscrew nut. Mark the start point on the ballscrew nut. Rotate the ballscrew nut one full revolution and measure the linear distance travelled by the nut. This will be the lead of the ballscrew.

The information provided in Tech Tips is not meant to be all-encompassing, but rather to draw attention to and provide information about the particular subjects covered. All suggestions and recommendations contained in Tech Tips are based upon information that is believed to be accurate to the best of the experience and knowledge of PTDA’s contributing members, but are made without guarantee or representation as to results. PTDA and Tech Tip contributors expressly disclaim any warranties or guaranties, express or implied, as to the accuracy or completeness of any information published in Tech Tips, and disclaims and makes no warranty that the information in Tech Tips will fulfill any of your particular purposes or needs. PTDA and Tech Tip contributors disclaim liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on Tech Tips.