Drill
AssigneeM. A. Ford Mfg. Co., Inc.
InventorLee A. Schneider
Life of this patent
Estimating the term…
Abstract
The drill invention relates to forming holes in circuit boards and the like. Smoother holes may be formed faster by reducing tendencies of drills to chip. The drill (11) employs primary and secondary reliefs (28,29) behind cutting lips (27) to provide lesser and greater clearances, thereby strengthening the cutting lips' outer edges. The margins (10) having lengths variable in width (20,21) and variable in helix angle (22,23) facilitate the foregoing.
Claims4
A drill bit having a shank, a cutting end with a chisel edge, and a flute length connecting the shank and cutting end, the flute length having at least one land forming at least one flute and defining the periphery of the drill, characterized in that,
- cutting lip means is formed on the cutting end and extends from the chisel edge to the periphery;
- and
- strengthening means is connected to said cutting lip means adjacent the periphery and includes clearance surface means formed on the cutting end, extending back from said cutting lip means, providing a first clearance angle adjacent the periphery, and providing a second clearance angle greater than said first clearance angle adjacent the chisel edge whereby the outer edge of the cutting lip of the drill has a reduced tendency to chip due to its greater thickness, and further includes margin means formed on the land, having a first width length adjacent said cutting lip means, and having a second smaller width length contiguous with said first width length and disposed away from said cutting lip means.
A drill bit having a shank, a cutting end with a chisel edge, and a flute length connecting the shank and cutting end, the flute length having at least one land forming at least one flute and defining the periphery of the drill, characterized in that,
- cutting lip means is formed on the cutting end and extends from the chisel edge to the periphery;
- and
- strengthening means is connected to said cutting lip means adjacent the periphery and includes clearance surface means formed on the cutting end, extending back from said cutting lip means, providing a first clearance angle adjacent the periphery, and providing a second clearance angle greater than said first clearance angle adjacent the chisel edge whereby the outer edge of the cutting lip of the drill has a reduced tendency to chip due to its greater thickness.
A drill bit having a shank, a cutting end with a chisel edge, and a flute length connecting the shank and cutting end, the flute length having at least one land forming at least one flute and defining the periphery of the drill, characterized in that,
- cutting lip means is formed on the cutting end and extends from the chisel edge to the periphery;
- and
- strengthening means is connected to said cutting lip means adjacent the periphery and includes margin means formed on the land, having a first width length adjacent said cutting lip means, and having a second smaller width length contiguous with said first width length and disposed away from said cutting lip means.
Dependencies are inferred from the claim text.