Apparatus for cold forming recesses in the heads of screw fasteners

In a heading machine having a die for holding a screw blank, a ram reciprocably movable toward and away from the die, the ram being constructed and arranged to carry a pair of punches including a first punch for forming an upset bloom and a second finishing punch, the ram being mounted to move the punches in sequence toward the die first to form the upset bloom and then to impact the upset end of the screw blank held in the die, an improved finishing punch for forming a head with a driver-engageable recess therein in the bloom of the upset blank comprising:

• a punch pin
• a punch pin carrier slidably mounted to the ram;
• means biasing the carrier in a forward position in the ram;
• impact means carried by the ram behind the punch pin carrier;
• the punch pin carrier having a bore formed fully therethrough and being open at its forward and rearward ends, the forward end of the bore opening into the forward end of the carrier the forward end of the bore being smaller in diameter than the diameter defined by the upset bloom;
• the punch pin being disposed within the carrier bore and having a recess forming nib at its forward end, the length of the pin as measured from its rear end to the tip of the nib being greater in length than the carrier bore by an amount at least equal to the intended depth of the recess to be formed, whereby when the ram is advanced forwardly toward the upset bloom, the impact means will engage the rear end of the pin to drive the pin into the upset bloom while the carrier is biased toward the die under the influence of the biasing means;
• the rear end of the pin being of substantially smaller area than that circumscribed by the rear end of the carrier whereby the contact area between the impact means and the rear end of the pin may be minimal;
• and
• the pin being loosely disposed within the carrier bore and being dimensioned with respect to the bore so that the pin may slide, rotate freely and cant within the bore.

In a heading machine having a die for holding a screw blank, a ram reciprocably movable toward and away from the die, the ram being constructed and arranged to carry an upset punch and a finishing punch successively toward the die to successively form the end of the screw blank held in the die by first forming an upset blank and then forming a finishing head with a driver receptive recess thereon, an improved punch combination for forming the head with the recess therein comprising:

• the finishing punch including a punch pin having a main portion and having a recess forming nib at the end of the main portion, the recess forming nib including a plurality of wings extending generally radially from the axis of the pin, the main portion of the pin, at least at said end thereof, being of a diameter smaller than that of the screw head to be formed;
• means mounting the punch pin to the ram for movement toward the upset bloom supported in the die to impact the nib into the upset bloom to simultaneously form the recess, reduce the upset bloom height to that of the finished screw head while causing outward radial cold flow of the metal of the upset bloom to enlarge the diameter of the bloom to that of the intended finished screw head, the finishing punch being substantially free of any other shaping members for forming the exterior shape of the screw head;
• the upset punch being constructed and arranged to form the upset bloom to a selected predetermined configuration which will enable the metal of the upset bloom to cold-flow to the finished screw head shape solely in response to the impacting of the punch pin during operation of the finishing punch.

In a heading machine for cold forming a screw head having a recess formed therein, the improvement comprising, in combination:

• first punch means for forming an upset bloom on an end of a screw blank;
• second punch means including a punch member having a recess forming nib on the forward end thereof;
• means for carrying the punch member so that is nib engages the upset bloom;
• means for driving the punch member from its rear end along its axis and along the axis of the upset bloom to impact the nib of the punch into the upset bloom, the driving means including an impact member mounted to be driven against a small contact area at the rear end of the punch member and along the axis of the punch,
• the punch carrying means being constructed and arranged to enable the punch member to rotate and cant with respect thereto at least during the impacting of the nib to the upset bloom whereby the punch may be supported primarily at small contact areas at its opposite ends thereby to enable the nib to seek the path of least resistance through the metal of the bloom.