To solve the problem of deformation caused by pulling and cutting the pocket hole and to lower the line cutting cost we obtain the methods which can prevent the cage from deforming and which can pull and cut the pocket hole successfully. Thus improvement has been made on the process routing and the structure of the pulling knife.

Improvement of routing

Picture one Radial wall thickness of cage, axial wall thickness of pocket hole.
This type of cage can be deformed seriously because line cutting is adopted rather than pulling or cutting. The process accuracy can not be guranteed. After analysis we think that the reason that causes deformation is the soft material(copper) and thin wall of the cage. The radial wall thickness A (difference between the radius of the outer cycle andinner cycle) before the pocket hole is cut or pulled is 3—4 mm as is shown in picture one. The axial wall thickness S (the thickness between the axial ends of the pocket hole and the two ends of the cages) after the pocket hole of the cage is formed is merely 1.3—1.5mm which can not endure the force that occurs when it is cut. According to the experience of pulling and cutting and the results of force analysis A and S should respectively increase to 6mm and 2.5mm thus deformation can be prevented from happening. Methods adopted to improve are: replacing the “finally lathing the second plane” with “fine lathing the second plane”. This increases the width of the retention volume which keeps S around 2.5mm. Then add the process of “lathing the two planes” after pulling and cutting the pocket hole which processes the cage to finished products size; increasing the “ roughly grinding the outer circle” allowance to keep A around 6mm.

Improving the pulling knife

Picture two Gradual type eight square pulling knife.
To lower pulling force and make it stable to keep pulling and cutting force stable we have made a lot of calculation on force analysis and on pulling and cutting allowance to reasonably select design parameter and structure.
(1)Determination of pull knife gear. The increase volume of pull knife should be between a=0.03—0.05mm
(2)Increase the number of calibration teeth: determine the number of calibration as 10. Make sure the cutting and pulling surfacial quality reach the requirement.
(3) Pulling knife used to pull and cut the rectangle pocket hole.
CHG bearing has been processing the pre-made hole to round hole. But for rectangle pocket hole the axial pulling and cutting allowance is comparatively large and the pulling and cutting precision is not stable. Pointing at this feature the pre-made hole is made into elliptic hole. The pulling knife is designed as generating broaching eight square as is shown in picture two. This could decrease the axial pulling and cutting allowance. The position stability can be increased at the same time and the pulling and cutting precision can be guranteed.

Conclusion
It has been tesified by practice that pocket hole processing technic of Thin-section Bearing that CHG research can totally replace line cutting technics. After the thin-section cage has been pulled and cut the processing precision can fully satisfy the drawing requirement. Pulling and cutting stability can be guranteed at the same time. The processing cost can be lowered while products quality can be guranteed and efficiency can be increased. Thus we can increasinglly create comparatively considerable ecomonic benefits for ourcompany.