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Wear Mechanism
Posted August 22, 2019 - Updated Dec 4, 2019
Wear Mechanism The study of wear is a field called tribology. There is much research on the subject, but little definitive work that can help determine the wear rate of two surfaces in any specific application. The wear mechanism itself is simple to understand. With reference to Figure 38, two rubbing surfaces contact only at […]
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Screw Wear Life
Posted August 22, 2019 - Updated Dec 4, 2019
What is a Screw Wear Life The wear life of Power Screw and nut drive systems are difficult to predict theoretically. The number of variables involved in such a prediction is large; load, speed, screw material, nut material, surface finishes, lubrication, duty cycle, operating temperature, and environmental factors such as the presence of abrasive contaminants, […]
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How to Straighten Screws
Posted August 22, 2019 - Updated Dec 4, 2019
How to Straighten Screws Basics For users who elect to straighten their own screws or who need to straighten a bent screw, we offer the following guide. Straightening methods which are suitable for plain (non-threaded) bars such as roll straighteners or crossed axis roll straighteners do a poor job on lead screws and should not […]
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Preserving Straightness in Screws
Posted August 22, 2019 - Updated Dec 4, 2019
Preserving Straightness Screw shaft straightness is a perishable feature. It is very easy to bend shafts during routine handling, machine loading, during machining and during in-plant transportation. Even inside a wooden crate shaft can be easily bent if precautions are not observed. When transporting screws, it is best if the screws are supported in two […]
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Methods of Achieving Straightness
Posted August 22, 2019 - Updated Dec 12, 2019
Methods of Achieving Straightness Unless special straightening is requested by the customer, Roton will ship screws in “as rolled” straightness condition. For most applications, this level of straightness is sufficient and cost-effective. But some applications have more demanding straightness requirements. Users with applications requiring screw shafts to be straightened beyond “as rolled” condition should specify […]
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Screw Shaft Straightness & Defects
Posted August 22, 2019 - Updated Dec 4, 2019
Introduction to Screw Straightness & Defects A lack of screw straightness can become a critical factor in any application. Bent lead screws can cause noise, premature wear and failure, high drive torque, and excessive heat. But straightness requirements vary widely from application to application, and straightness is an expensive and perishable product feature. For these […]
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End Fixity
Posted August 22, 2019 - Updated Dec 3, 2019
What is End Fixity? Screw end fixity is the engineering term for screw end support. Fixity is an important element in screw and nut drive systems. The rigidity of the screw end support determines the screw drive system’s resistance to column buckling and limit of the speed of rotation to avoid natural frequency vibration. (See […]
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Torsional & Axial Deflection
Posted August 22, 2019 - Updated Mar 24, 2020
What is a Torsional & Axial Deflection? Screw torsional deflection (sometimes called “windup”) may occur when loads are high (resulting in high drive torques) and when the screw is long. Also, screw axial deflection caused by high compression or tension loads may be significant when loads are high and the screw is slender. When rotation […]
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Horizontal Bending
Posted August 22, 2019 - Updated Dec 3, 2019
Horizontal Bending Basics Long screws mounted horizontally may sag due to the weight of the screw. If the sag is significant, the screw threads will be compressed on the top section of the screw and extended on the bottom section of the screw. In severe cases, the nut may actually seize on the screw as […]
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Column Loading
Posted August 22, 2019 - Updated Dec 12, 2019
Column Loading Basics Screws which are loaded in compression may be so slender (long in relation to diameter) that they can fail by elastic instability (buckling) much before they reach their static load limit or compressive strength. A screw system design which undergoes a compressive load must be checked for safe column loading. Basic safe […]