Page 9 of catalogue Ball screws of SKF Linearsysteme GmbH

Recommendations for selection

Manufacturing precision
Generally speaking, the precision indication given in the designation denes the lead precisions see page 12 - lead precision according to ISO - (ex. G5 G7…). Parameters other than lead precision correspond to our internal standards (generally based on ISO “class 7”). If you require special tolerances (for example class 5) please specify when requesting a quotation or ordering.

Materials and heat treatments
Standard screw shafts are machined from steel which is surface hardened by induction (42CrMo4-NF EN10083-1 for diameters > 16 mm and C45E for diameters ≤ 16 mm). Standard Nuts are machined in steel which is through hardened (100 Cr6 - NFA 35.565 or equivalent for diameters ≥ 20 mm and carbon steel for diameters < 20 mm). Hardness of the contact surfaces is 56-60 HRc, depending on diameter, for standard Screws. Most assemblies made of stainless material have a surface hardness in the range 50 to 58 HRc, depending on the type. The load rating of the catalogue are given only for standard screws.

Number of circuits of balls
A nut is dened by the number of ball turns which support the load. The number is changing, according to the product and the combination diameter/lead. It is dened by the number of circuits and their type.

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Recirculation inserts
The standard products have been tted with composite ball recirculation inserts. System performance is improved because of the smoother ball recirculation. This results from the improved precision of the moulded insert when compared to the former steel insert. If the product is used in severe applications, or the insert is used to prevent collapse (especially in vertical applications), a steel version is available. In such cases, the specier should consult SKF Linear Motion to obtain the optimum solution.

Working environment
Our products have not been developed for use in an explosive atmosphere, consequently we cannot take any responsability for the use in this eld.

NOTE: 42 CrMo4, an AFNOR reference is similar to AISI 4140; 100Cr6 is similar to AISI 52100.

(1) SKF can help you to define this value in relation with the actual conditions of service.

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