Importance

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Abstract

An improved punch retainer is disclosed in which a backing plate extends over a relatively large surface area to dissipate force from a punch. A punch retainer body and the tacking plate are permanently connected to each other and include passages which are finally ground after the two have been permanently connected. With this arrangement, it is ensured that passages within the backing plate and retainer body are all properly aligned during formation of the punch retainer. Since the backing plate dissipates force over a relatively large surface area, the punch retainer may be used in heavier applications than prior art punch retainers. A spring passage may be closed off by a seal received in the backing plate, allowing the use of standard springs. In a method according to the present invention, a dowel passage in the backing plate is finally ground such that it is centered on the center line of the punch within the retainer. The punch is of a slightly smaller outer diameter than the inner diameter of the punch retainer passage and has a center line which is slightly offset from the center line of the punch retainer passage. Thus, by ensuring that the dowel passage in the backing plate is finally ground such that its center line is coaxial with the center line of the punch, it is ensured that the punch is more accurately positioned on a punch die shoe. Parts formed by the inventive punch retainer are more accurate than those formed by prior art punch retainers.

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First Claim