Bit for removing damaged screws
AssigneeAlden Corporation
InventorPeter J. Bergamo
Life of this patent
Estimating the term…
Abstract
This bit has an axis and a tip end with an obtuse angle. There are multiple scraping surfaces, each facing counter-clockwise into a longitudinal recess in the tip end. Each scraping surface has a scraping edge at an angle of about 55° to 70° to the axis. Behind each scraping surface the outer surface of the tip end curves down to a rearward edge adjacent another of the longitudinal recesses, the rearward edges each being disposed at a sharper angle to the axis than the scraping edge so that there is some relief, allowing the scraping edge to be more pronounced and enhance its ability to dig into the metal of a deformed screw at points removed from the axis to get a good purchase on the screw.
Claims27
For removing damaged screws, a bit having an axis and a tip end formed with a point and a rear end formed in hexagonal cross-section adapted for installation in a chuck of a variable speed reversible drill, the tip end having a plurality of longitudinal recesses uniformly disposed about the tip end, each bordered by a longitudinal surface facing in a counter-clockwise direction, the surface formed with a distal straight scraping edge, the scraping edges of the recesses each being in a plane including the axis and being at an acute angle less than 70° to the axis, and a support portion behind each scraping edge, the support portions each defined by a relief surface curving away from the scraping edge down to a rearward edge bordering one of the longitudinal recesses, each rearward edge also lying in a plane including the axis and being disposed at more acute angle to the axis than the scraping edge angle.
A method for unscrewing threaded fasteners installed in an object and having a head with a deformed end surface, the method comprising the steps of:
- a. providing a bit having an axis and a tip end formed with a point, the tip end having a plurality of longitudinal recesses uniformly disposed about the tip end, each bordered by a longitudinal surface facing in a counter-clockwise direction and being in a plane including the axis, and formed with a straight scraping edge, the scraping edges of the recesses each being at acute angles to the axis and a support portion behind each scraping edge, the support portions at the tip end each defined by a relief surface curving away from the scraping edge down to a rearward edge bordering one of the longitudinal recesses, each rearward edge also lying in a plane including the axis and being disposed at more acute angle to the axis than the scraping edge,
- b. engaging the head with the tip end with the scraping edges engaging the end surface of the fastener,
- c. rotating the bit in a counter-clockwise direction.
In combination:
- a. a threaded fastener having an axis, a threaded section and a head section, the head section being formed with a generally radial end surface having a damaged cross slot having sloping sidewall portions defining a first angle to the axis, and
- b. a cylindrical extraction bit having an axis aligned with the axis of the fastener and a tip end formed with a point, the tip end having a plurality of longitudinal recesses about the tip end, each bordered by a longitudinal scraping surface facing in a counter-clockwise direction and having a scraping edge, the scraping edges each lying in a plane including the axis of the bit and disposed at a second angle to the axis, the second angle being less sharp than the first angle, the scraping edges engaging the end surface of the fastener at the margin of the cross slot.
A tool for removing damaged screws comprising:
- a bit having an axis and a tip end formed with a point and a rear end formed in hexagonal cross-section adapted for installation in a chuck of a variable speed reversible drill, the tip end having a plurality of longitudinal recesses uniformly disposed about the tip end, each bordered by a scraping surface facing in a counter-clockwise direction, the scraping surface formed with a distal straight scraping edge, the scraping edges of the recesses each being disposed at a scraping edge acute angle to the axis less than about 70°, and a support portion behind each scraping edge, the support portions each defined by a relief surface curving away from the scraping edge down to a rearward edge bordering one of the longitudinal recesses the rearward edge being disposed at a more acute angle to the axis than the scraping edge acute angle.
A tool for removing damaged screws comprising:
- a bit having an axis of rotation extending between a tip end and rear end, the rear end being formed with a cross-section adapted for installation in and rotation by a chuck of a reversible drill, the tip end having a plurality of longitudinal recesses uniformly disposed about the tip end, each recess bordered by a scraping surface facing in the counter-clockwise direction of rotation, the scraping surface being formed with a distal scraping edge, each of the scraping edges being disposed at a scraping edge acute angle relative to the axis of the bit, and a support portion behind each scraping edge, the support portions each defined by a relief surface leading away from the scraping edge to a rearward edge bordering one of the longitudinal recesses, the rearward edge being disposed at an angle relative to the axis of the bit more acute than the scraping edge acute angle.
A tool for removing damaged screws comprising:
- a. a bit having an axis of rotation extending between a tip end and a rear end,
- b. the roar end being formed with a cross-section adapted for installation in and rotation by a chuck of a reversible drill,
- c. the tip end having a plurality of longitudinal recesses uniformly disposed about the tip end, each recess bordered by a scraping surface facing in the counter-clockwise direction of rotation,
- d. the scraping surface being formed with an associated scraping edge at the tip end of the bit,
- e. the associated scraping edge when viewed perpendicular to the axis being disposed at a first acute angle relative to the axis,
- f. a support portion being located behind the associated scraping edge in the direction of rotation, the support portion being defined by a relief surface loading away from the associated scraping edge to a rearward edge,
- g. the rearward edge when viewed perpendicular to the axis being disposed at a second acute angle relative to the axis, the second acute angle being more acute than the first acute angle.
A tool for removing damaged screws comprising:
- a. a bit having an axis of rotation extending between a tip end and a rear end,
- b. the rear end being formed with a cross-section adapted for installation in and rotation by a chuck of a reversible drill,
- c. the tip end having a plurality of longitudinal recesses disposed about the tip end, each recess bordered by a scraping surface facing in the counter-clockwise direction of rotation,
- d. the scraping surface being formed with an associated scraping edge at the tip end of the bit,
- e. the associated scraping edge being disposed at a first acute angle to a first plane passing through the axis of the bit,
- f. a support portion being located behind the associated scraping edge in the direction of rotation, the support portion being defined by a relief surface leading away from the associated scraping edge to a rearward edge,
- g. the rearward edge being disposed at a second acute angle to a second plane passing through the axis of the bit, the second acute angle being more acute than the first acute angle.
Dependencies are inferred from the claim text.