Prefastenable torque-shear bolt

• US 4,659,267 A
• Filed: 11/29/1985
• Issued: 04/21/1987
• Est. Priority Date: 11/29/1984
• Status: Expired due to Fees

• Current Assignee: Nippon Steel Bolten Co., Ltd. (Nippon Steel Corporation), Nippon Steel Corporation
• Original Assignee: Nippon Steel Bolten Co., Ltd. (Nippon Steel Corporation), Nippon Steel Corporation
• Inventors: Uno, Nobuyoshi, Isa, Takayoshi, Kurata, Eijiro, Tamasaki, Hidetoshi
• Primary Examiner(s): Smith, Gary L.
• Assistant Examiner(s): WILSON, NEILL R
• Application Number:
  US06/803,654
• Time in Patent Office: 508 Days
• Field of Search: 411/2-5, 411/43, 411/410, 411/411, 10/27 R
• US Class Current: 411/5
• CPC Class Codes: F16B 31/021 by means of a frangible part F16B31/025, F16B31/028 take precedence; break members in torque limiters or torque indicators in wrenches or screwdrivers B25B23/1415
• CPC Class Codes: F16B 35/044 Specially-shaped ends
• CPC Class Codes: F16B 35/045 for retention or rotation by a tool specially shaped heads of bolts or screws for rotation by a tool F16B23/00

Abstract

A prefastenable torque-shear bolt has a bolt cut with a thread adapted to engage a nut, and full-fastening and prefastening grips each having wrench-engaging surfaces. One end of the bolt continues to a first transition portion that is tapered like a truncated cone. The full-fastening grip extends from the first transition portion and a full-fastening break-off groove. One end of the full-fastening grip continues to a second transition portion tapered like a truncated cone. The prefastening grip extends from the second transition portion and a prefastening break-off groove. The effective area of the fracture surface of the prefastening break-off groove is smaller than that of the full-fastening break-off groove. A first burr that arises on the threaded portion side when the full-fastening break-off groove is formed by rolling is formed on the first transition portion, and the outside diameter of the first burr is smaller than the diameter of the thread bottom in the threaded portion. A second burr that arises on the full-fastening grip side when the prefastening break-off groove is formed by rolling is formed on the second transition portion.

Claims

1. A prefastenable torque shear bolt comprising:

a bolt head at one end of said bolt;

a bolt section extending from said bolt head and having a thread for engaging with a nut;

a first transition section extending and tapered towards the center of said bolt from said bolt section, a full-fastening break-off groove in said first transition section;

a full-fastening grip section extending from said full-fastening break-off groove, said full-fastening grip section having a plurality of wrench-engaging surfaces along the periphery thereof defining a first polygon around said periphery;

a second transition section extending and tapered towards the center of said bolt from said full-fastening grip section, a prefastening break-off groove in said second transition section, the diameter of said bolt at said prefastening break-off groove being less than the diameter of said bolt at said full-fastening break-off groove for providing an effective fracture surface of said bolt at said prefastening break-off groove that is smaller than an effective fracture surface of said bolt at said full-fastening break-off groove;

a prefastening grip section extending from said prefastening break-off groove and having a plurality of wrench-engaging surfaces along the periphery thereof defining a second polygon around the periphery of said prefastening grip section;

diameters of first circles circumscribed around and inscribed in said first polygon being larger than diameters circumscribed around and inscribed in said second polygon respectively;

a burr on said bolt associated with the formation of said full-fastening break-off groove and comprised of a first burr adjacent the full-fastening break-off groove and between the full-fastening break-off groove and the bolt section, a burr on said bolt associated with the formation of said prefastening break-off groove and comprised of a second burr adjacent the prefastening break-off groove and between the prefastening break-off groove and the full-fastening grip section;

the ratio between the diameters of said second circumscribed circle and said first circumscribed circle and the ratio between the diameters of said second inscribed circle and said first inscribed circle each being between 0.60-0.85 such that said first burr does not extend radially outward of the thread bottom of said thread and said second burr does not extend radially outward of points on said bolt located on said first inscribed circle.

2. A prefastenable torque-shear bolt comprising:

a bolt head at one end of said bolt;

a bolt section extending from said bolt head and having a thread for engaging with a nut;

a first transition section extending from said bolt section and having a taper tapered towards the center of said bolt from said bolt section to a full-fastening grip section, a full-fastening break-off groove in said first transition section;

said full-fastening grip section extending from said first transition section and having a plurality of wrench-engaging surfaces along the periphery thereof;

a burr associated with the rolling formation of said full-fastening break-off groove comprised of a first burr adjacent the full-fastening break-off groove and between the full-fastening break-off groove and the bolt section;

said taper of said first transition section being such that said first burr does not extend radially outward of the thread bottom of said thread.