Ball screw nut flange bolt patterns are not universal, and the exact hole count, spacing, and thread size vary by nut series and manufacturer [S2].
The engineering decision starts with the screw diameter: Thomson lists standard flanged metric assemblies from 16 to 50 mm, while other catalogs include smaller 6–10 mm flanged nuts and 12–25 mm ground screws [S1][S5][S6].
Standard Flange Patterns Depend on Nut Series
Flange type describes how a ball nut mounts, while circulation type describes how its balls return, and preload describes axial-clearance control; these are independent design attributes, so one flange nut can also use internal circulation and preload [S2]. A round, cut-flat, square-like, or custom flange can therefore share the same general mounting role without sharing the same bolt pattern [S2].
Thomson specifies flanged styles for nominal diameters of 16, 20, 25, 32, 40, and 50 mm, with available leads listed as 2, 3, 5, 10, 20, 25, and 40 mm by diameter [S1]. Smaller assemblies occupy a different dimensional envelope: PBC lists flanged ball screws from 6 to 10 mm in diameter and 150 to 500 mm in length, with six metric diameter-and-lead combinations [S6].
This size split matters because a bolt circle cannot be selected from screw diameter alone. A 16 mm screw can have several lead options, and the flange drawing still controls hole location, flange thickness, pilot diameter, counterbore, and thread engagement. The installation process should treat the manufacturer dimension drawing as the controlling document [S1][S8].
How to Read a Flange Drawing
A usable flange drawing should identify at least the nominal screw diameter, lead, flange outline, mounting-hole count, and bolt-circle diameter. It should also state whether the mounting holes are threaded or clearance holes, their nominal thread or diameter, the counterbore or counter-sink condition, and the flange thickness [S8].
The RS062 example is a useful illustration of why visual copying is unsafe: its metric mounting entries use M6 threads, while the flange table also includes inch conversions such as 0.500 inch, 0.375 inch, and 0.50 inch, plus a 34.92 mm dimension and a 66.80 mm vertical bracket dimension [S8]. These values belong to that specific RS062 family, not to a general ball screw standard.
For procurement, request a dimensioned drawing tied to the exact assembly number, nominal diameter, lead, accuracy class, preload arrangement, and circulation system. If the drawing lists only a series table, verify the revision before releasing the machine frame. A 2 mm change in bolt-circle diameter can shift load into bending, while incorrect thread specification can prevent assembly [S1][S8].
DIN 69051 Has a Defined Scope
Thomson states that its 10–12 mm miniature metric ball screws are precision rolled to T7 accuracy class standard. The 16–50 mm range is listed separately, so its accuracy class must be verified for the selected assembly rather than assumed to be T7.
For Thomson’s 16–50 mm metric assemblies, the screw material is listed as Cf53 or SAE 1045 with tensile strength of at least 610 N/mm², while the nut material is listed as 16MnCr5 or SAE 8620 with tensile strength above 800 N/mm². These construction details help identify the intended series, but they do not replace the flange outline or mounting-hole drawing.
The operating envelope provides another cross-check during component selection. A nut selected for a higher-temperature axis must be matched to a documented flange drawing as well as to the thermal rating.
Flange, Cylindrical, and Custom Nut Comparison
Flanged nuts are the practical choice when the moving table, nut housing, or machine structure can provide a flat interface and discrete mounting holes [S2]. Cylindrical or compact nuts suit restricted radial spaces, custom housings, narrow-profile modules, or applications where the nut must fit inside a dedicated housing [S2]. Neither arrangement removes the need to prevent nut rotation and transmit axial load into the surrounding structure [S2].
Across the four main decision criteria, flange mounting provides a direct bolted interface and simple replacement, cylindrical mounting reduces radial envelope but requires a suitable housing, and custom flanges can satisfy special interfaces at the cost of manufacturer-specific drawings. Preload changes stiffness and backlash rather than fixing a mounting pattern, and the selected preload method must remain compatible with the nut geometry [S2][S3].
For standard machine frames, a catalog flange is usually the lower-risk route because its drawing, thread callout, and load path are defined. For retrofit work, an adaptor can be engineered around the existing hole pattern, but the adapter must retain adequate material around every hole and provide a direct load path into the carriage. The broader ball screw nut mounting types framework helps separate those structural choices from preload and ball-return decisions.
Metric and Inch Nuts Do Not Share One Pattern
Metric flanged assemblies may cover 6–50 mm across the cited catalogs, but the product families remain distinct: Thomson's standard flanged metric range begins at 16 mm, isel lists 12, 16, 20, and 25 mm ground diameters, and PBC offers 6–10 mm flanged products [S1][S5][S6]. A nominal diameter appearing in one catalog does not establish that another manufacturer's nut has the same flange geometry.
Rockford's inch catalog includes standard, preloaded, and keyway configurations across several dozen sizes, with custom flanges, adaptors, UNJ or metric mounting threads, trunnion mounts, and special coatings available [S3]. Such customization reinforces the procurement rule: specify nominal diameter, lead, accuracy, preload, flange form, mounting thread, and interface drawing rather than relying on a diameter-only search term.
Metric machine builders should not substitute an inch clearance hole for an M6 threaded hole, and inch assemblies should not be adapted from an M-series drawing without a complete fit, strength, and corrosion review. The crossed roller guide page covers a different guided-motion architecture, but the interface principle remains comparable: machine-frame hole geometry has to be established before the component is released.
Application and Failure-Mode Checks
Flange bolts carry preload, shear, and repeated cyclic loads while keeping the nut fixed against rotation; loose fasteners can therefore produce axial play, uneven loading, and unintended movement [S2]. The mounting surface must be flat, adequately stiff, and prepared to avoid distortion. A washer arrangement or manufacturer-specified mounting method should be retained where specified by the nut documentation.
Three checks deserve explicit review. First, compare every drawing dimension: 34.92 mm, 66.80 mm, 0.500 inch, and M6 appear in the RS062 example, but they are not transferable to another series [S8]. Second, verify bolt strength against the calculated axial load, preload, and cycle demand rather than selecting by nominal thread size alone. Third, confirm that the selected lead and accuracy fit the axis duty; the cited catalogs cover leads from 2 to 40 mm and accuracy grades down to C0 [S1][S4].
Long-axis performance can limit the required screw before flange strength does. A related analysis of ball screw buckling limits for long travel axes is useful when a mechanically sound flange pattern would still produce excessive screw deflection. Likewise, speed limits must be checked against screw diameter, lead, support arrangement, and critical resonance rather than copied from the nut catalog [S4].
Specification Checklist for Procurement
A purchase specification should include screw diameter, lead, accuracy class, preload method, ball-return type, flange shape, number of mounting holes, bolt-circle diameter, hole type, thread designation, counterbore geometry, flange thickness, pilot dimensions, and required drawing revision. For the Thomson 16–50 mm flanged family, DIN 69051 compliance, the listed screw accuracy class, and the stated temperature limits provide useful identification points [S1].
Before machining, compare the released assembly drawing against a physical sample or a supplier-confirmed dimensional report. Check bolt access for the socket or hex head, wrench clearance, edge distance, thread engagement, and possible interference with the screw, coupling, support bearing, or cable management. The flange may be the visible interface, but the screw and support arrangement determine the stiffness and speed of the finished axis [S1][S4].
The traceable specification record is the finished drawing plus the exact manufacturer part number. If either is missing, the hole pattern remains unresolved; for a complete axis review, combine it with the ball screw buckling limits for long travel axes and the ball screw maximum speed before critical resonance checks before machine release.