Ball Screw
Accessory Parts

Ball screw accessory parts are the structural components that mount and support a ball screw assembly in a linear motion system. The main parts: End support blocks (BK/BF) — hold the ball screw shaft at fixed (BK, with angular contact bearings) and floating (BF, with deep groove bearings) ends. Nut flange / nut housing — bolts the ball screw nut to the moving carriage or table. Bearing housing — larger block for heavy-duty ball screws. Coupling adapter — connects the servo motor to the ball screw shaft end.

BK (fixed-end) support block: holds the ball screw shaft with two back-to-back angular contact bearings — supports both radial and axial loads, fixes the ball screw axial position. Used at the motor end of the screw. BF (floating-end) support block: holds the screw shaft with a single deep groove bearing — supports radial load only, allows axial movement. Used at the non-motor end to accommodate thermal expansion of the screw shaft. Most ball screw installations use one BK + one BF block; short ball screws sometimes use BK at both ends if thermal expansion is small.

HXC machines custom end blocks and nut flanges for all major ball screw brands: THK, NSK, Hiwin, PMI, TBI, ABBA, and other metric-standard ball screws. We require the screw shaft diameter, shaft end dimensions, nut flange bolt pattern, and bearing specification. We can also match existing OEM end block dimensions for replacement applications — provide the end block drawing or physical part for copying.

Ball screw end block bearing bores: H7 for deep groove bearing (floating end — clearance fit, bearing OD can slide for thermal expansion). K6 or M6 for angular contact bearing (fixed end — slight interference fit to prevent bearing outer race spin). Bore roundness ≤ 0.005 mm. Bore-to-bore parallelism (if two bearings in same block) ≤ 0.008 mm. These tolerances are achievable with CNC boring and verified by CMM. All critical bores are 100% CMM measured on HXC end block production.

For a ball screw installation, the two end block bearing bores must be coaxial within the ball screw manufacturer's alignment specification — typically 0.05–0.1 mm over the block separation distance. Misalignment introduces a bending moment in the screw shaft and increases bearing load. When both end blocks are machined by HXC from the same job, we machine a reference datum (ground surface) on both blocks that allows the installer to shim to coaxiality using a precision straight edge. For the highest accuracy, we recommend using a reference rail or the machine bed as the mounting datum.

Yes — HXC regularly machines custom nut flanges, nut housings, and carriage plates for non-standard or discontinued ball screws where OEM replacement parts are unavailable. Provide the ball screw nut OD, flange bolt pattern, and the mating carriage interface dimensions. We machine the nut flange from Al 6061 (anodized) or C45 steel, with the nut register bore to H6 for accurate nut centring and the carriage mounting face precision-ground flat.

Key dimensions: shaft diameter at the bearing journal (typically d_s on the ball screw datasheet); bearing type and size (manufacturer's recommendation); block mounting face dimensions (must suit your machine bed or linear guide rail spacing). HXC engineers will calculate the block dimensions from your ball screw part number and installation envelope.

Al 6061-T6 (anodized black): standard for CNC machine and gantry end blocks — lightweight and adequate for most servo motor drives. C45 steel (zinc or black oxide): for heavy-duty ball screws with high axial preload forces. SUS304 / 316: for medical and cleanroom systems. Al 7075: for lightweight aerospace or robot linear axes.

HXC supplies end blocks as machined parts. Bearing installation is typically performed by the customer or a local bearing distributor. We specify the correct bearing type and size for your ball screw, provide the preload value, and supply the lock nut and end cap drawings if required. For high-volume orders, we can also supply end blocks with bearings pressed in — contact us for this option.

Standard Al 6061 BK/BF blocks (prototype): 5–7 days. Production (50–500 pcs): 8–14 days. Heavy C45 steel blocks: 7–12 days. Custom nut flanges: 5–10 days. Full end block sets (BK + BF + nut flange): 7–12 days.