Claims
- 1. A roll-threading die for producing a screw on a screw blank, said die comprising a first series of ridges with first valleys therebetween of uniform depth, the bases of said valleys defining a plane, the spacing between said ridges being the pitch of the screw thread, a second series of ridges providing valleys therebetween of varying depth, said depth varying from about 3/4 of the depth of said first valleys to about 1/2 of the depth of said first valleys, and a third series of ridges providing valleys therebetween of varying depth, the bases of said last-mentioned valleys defining an additional plane that forms with said first-mentioned plane an angle of about 20.degree. to 30.degree..
- 2. A roll-threading die for producing a screw thread on a screw blank, said die comprising a first series of ridges with first valleys of uniform depth, a second series of ridges with second valleys of varying depth, which depths are less than the depths of the valleys of the first series, a first plane formed by the bases of the first valleys intersecting a second plane formed by the bases of the second valleys to define a first angle, a third series with at least one ridge and one valley, the base of said last-mentioned valley and the base of the nearest of the valleys of the second series defining a third plane that forms a second angle with the first plane, said second angle being sustantially greater than said first angle.
- 3. A die according to claim 2 in which said first angle is about 5.degree. to 8.degree. and said second angle is about 20.degree. to 30.degree..
- 4. A die according to claim 1 or claim 2 in which said second series of valleys are from two or three in number.
- 5. A roll-threading die for producing a screw thread on a screw blank, said die comprising a first die section with a first series of ridges with valleys between the ridges, the bases of the valleys being substantially in a plane, a second adjacent die section with a second series of ridges and valleys, said valleys in said second series being of a lesser depth than the depth of the valleys in said first section, said second series valleys decreasing in depth in a direction away from said first die section, the second valleys being not more than about three in number and the bases of the second valleys being substantially in a plane that intersects the plane of the bases of the valleys of the first section to form an angle of not more than about 8.degree., and a third die section with at least one ridge and one valley, the base of the last-mentioned valley and the base of the nearest of the valleys of the second series defining another plane that intersects said plane of the bases of the valleys of the first section to form an angle of not less than about 20.degree..
- 6. A roll-threading die for producing a screw thread on a screw blank, said die comprising a first die section with a first series of ridges with valleys between the ridges, the bases of the valleys being substantially in a plane, a second adjacent die section with a second series of ridges and valleys, said valleys in said second series being of a lesser depth than the depth of the valleys in said first section, said second series valleys decreasing in depth in a direction away from said first die section, the second valleys being not more than about three in number and the bases of the second valleys being substantially in a plane that intersects the plane of the bases of the valleys of the first section to form an angle of not more than about 8.degree., and further including a third die section adjacent to said second die section and having ridges and grooves, and a forming ramp which cooperates with a ramp on a companion die to forge a gimlet point on the screw blank.
- 7. A roll threading die couple for producing a gimlet point thread-forming screw, each die comprising a first die section with a first series of ridges and valleys for forming a work-holding thread portion of the screw, a second adjacent die section with a second series of ridges and valleys for forming a step taper thread portion of the screw at which threading action is commenced in a workpiece hole, said second series of valleys having depths that are less than the depths of the valleys in the first section, and a third die section adjacent to the second die section and having means including ridges and grooves forming a ramp on the die, the ramps of the die couple cooperating to forge the gimlet point, number of grooves in the third die section being greater than the number of grooves in the second die section, a plane defined by the bases of the valleys in the third die section forming an angle with another plane defined by the bases of the valleys of the second section that is greater than the angle formed by said other plane and an additional plane defined by the bases of the valleys of the first die section.
- 8. A die couple according to claim 7 in which the greater of said two angles is not less than about 20.degree., the lesser of said angles is not more than about 8.degree., and the second series of valleys being not more than about three in number.
Parent Case Info
This is a division of application Ser. No. 902,098, filed: May 5, 1978, now U.S. Pat. No. 4,194,430.
US Referenced Citations (3)
Divisions (1)
|
Number |
Date |
Country |
Parent |
902098 |
May 1978 |
|