Method for making a ball-nut and method for making a ball-screw

1. A method for making a ball-nut comprising the steps of:

a) obtaining a ball-nut body including a substantially-cylindrical inner-circumferential wall portion having a longitudinal axis;

b) obtaining a whirling-type internal-diameter cutting machine; and

c) cutting at least one 360-degree closed-loop surface groove in the inner-circumferential wall portion using the cutting machine, wherein the at-least-one 360-degree closed-loop surface groove surrounds the longitudinal axis, is adapted for receiving a plurality of ball bearings, includes a helical-grooved portion substantially coaxially aligned with the longitudinal axis, and includes a crossover-grooved portion.

2. The method of claim 1 , wherein the helical-grooved portion has a first groove depth, and wherein the crossover-grooved portion has a second groove depth which is deeper than the first groove depth.

3. The method of claim 2 , wherein the whirling-type internal-diameter cutting machine has a tool-head cutting angle and has a tool-head eccentricity, wherein the tool-head cutting angle and the tool-head eccentricity are fixed as step c) is cutting the helical-grooved portion of the at-least-one 360-degree closed-loop surface groove, and wherein the tool-head cutting angle and the tool-head eccentricity are dynamically changed as step c) is cutting the crossover-grooved portion of the at-least-one 360-degree closed-loop surface groove.

4. The method of claim 2 , wherein the helical-grooved portion is a substantially 300-degree helical-grooved portion.

5. A method for making a ball-nut comprising the steps of:

a) obtaining a ball-nut body including a substantially-cylindrical inner-circumferential wall portion having a longitudinal axis;

b) obtaining a whirling-type internal-diameter cutting machine; and

c) cutting a plurality N of longitudinally-spaced-apart, 360-degree closed-loop surface grooves in the inner-circumferential wall portion using the cutting machine, wherein each surface groove surrounds the longitudinal axis, is adapted for receiving a plurality of ball bearings, includes a helical-grooved portion substantially coaxially aligned with the longitudinal axis, includes a crossover-grooved portion, and includes a transition-grooved portion disposed between the helical-grooved portion and the crossover-grooved portion, wherein longitudinally-adjacent crossover-grooved portions are circumferentially staggered, and wherein a narrower groove is cut in the helical-grooved portion and the crossover-grooved portion than in the transition-grooved portion.

6. The method of claim 5 , wherein each crossover-grooved portion has a midpoint, and wherein longitudinally-adjacent midpoints are circumferentially staggered by substantially 360/N degrees.

7. The method of claim 6 , wherein each helical-grooved portion has a first groove depth, and wherein each crossover-grooved portion has a second groove depth which is deeper than the first groove depth.

8. The method of claim 7 , wherein the whirling-type internal-diameter cutting machine has a tool-head cutting angle and has a tool-head eccentricity, wherein the tool-head cutting angle and the tool-head eccentricity are fixed as step c) is cutting each helical-grooved portion of the 360-degree closed-loop surface grooves, and wherein the tool-head cutting angle and the tool-head eccentricity are dynamically changed as step c) is cutting each crossover-grooved portion of the 360-degree closed-loop surface grooves.

9. The method of claim 8 , wherein each helical-grooved portion is a substantially 300-degree helical-grooved portion.

10. The method of claim 7 , wherein each helical-grooved portion is a substantially 300-degree helical-grooved portion.

11. A method for making a ball-screw comprising the steps of:

a) obtaining a ball-screw body including a substantially-cylindrical outer-circumferential wall portion having a longitudinal axis;

b) obtaining a whirling-type external-diameter cutting machine; and

c) cutting at least one 360-degree closed-loop surface groove in the outer-circumferential wall portion using the cutting machine, wherein the at-least-one 360-degree closed-loop surface groove surrounds the longitudinal axis, is adapted for receiving a plurality of ball bearings, includes a helical-grooved portion substantially coaxially aligned with the longitudinal axis, and includes a cross-under-grooved portion.

12. The method of claim 11 , wherein the helical-grooved portion has a first groove depth, and wherein the cross-under-grooved portion has a second groove depth which is deeper than the first groove depth.

13. The method of claim 12 , wherein the whirling-type external-diameter cutting machine has a tool-head cutting angle and has a tool-head eccentricity, wherein the tool-head cutting angle and the tool-head eccentricity are fixed as step c) is cutting the helical-grooved portion of the at-least-one 360-degree closed-loop surface groove, and wherein the tool-head cutting angle and the tool-head eccentricity are dynamically changed as step c) is cutting the cross-under-grooved portion of the at-least-one 360-degree closed-loop surface groove.

14. The method of claim 12 , wherein the helical-grooved portion is a substantially 300-degree helical-grooved portion.

15. A method for making a ball-screw comprising the steps of:

a) obtaining a ball-screw body including a substantially-cylindrical outer-circumferential wall portion having a longitudinal axis;

b) obtaining a whirling-type external-diameter cutting machine having a cutting tool; and

c) cutting a plurality N of longitudinally-spaced-apart, 360-degree closed-loop surface grooves in the outer-circumferential wall portion using the cutting machine, wherein each surface groove surrounds the longitudinal axis, is adapted for receiving a plurality of ball bearings, includes a helical-grooved portion substantially coaxially aligned with the longitudinal axis, includes a cross-under-grooved portion, and includes a transition-grooved portion disposed between the helical-grooved portion and the cross-under-grooved portion, wherein longitudinally-adjacent cross-under-grooved portions are circumferentially staggered, and wherein the cutting tool is angled to cut a narrower groove in the helical-grooved portion and the cross-under-grooved portion than in the transition-grooved portion.

16. The method of claim 15 , wherein each cross-under-grooved portion has a midpoint, and wherein longitudinally-adjacent midpoints are circumferentially staggered by substantially 360/N degrees.

17. The method of claim 16 , wherein each helical-grooved portion has a first groove depth, and wherein each cross-under-grooved portion has a second groove depth which is deeper than the first groove depth.

18. The method of claim 17 , wherein the whirling-type external-diameter cutting machine has a tool-head cutting angle and has a tool-head eccentricity, wherein the tool-head cutting angle and the tool-head eccentricity are fixed as step c) is cutting each helical-grooved portion of the 360-degree closed-loop surface grooves, and wherein the tool-head cutting angle and the tool-head eccentricity are dynamically changed as step c) is cutting each cross-under-grooved portion of the 360-degree closed-loop surface grooves.

19. The method of claim 18 , wherein each helical-grooved portion is a substantially 300-degree helical-grooved portion.

20. The method of claim 17 , wherein each helical-grooved portion is a substantially 300-degree helical-grooved portion.