Multi-stepped power drill bit having handle chuck adaptor

A power drill bit having a stepped construction, referred to as a cone drill, and a quick change capability provided by a shank having a non-circular cross-section and a circumferential groove for quick connect-disconnect in a power tool or drill. The preferred embodiment includes a hexagonal shank which is at least one-half of the axial length of the drill bit in order to provide a better engagement to the power chuck.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to drill bits and power bits having a stepped, 
cylindrical coaxial construction for drilling holes of different diameters 
and more particularly to drill bits having a shank which provides for 
quick release securing of the bit to the chuck of a handle. 
2. Background Art 
Drill bits of a stepped construction have been used for providing holes of 
different sizes. The diameter hole desired depends on the depth of 
penetration of the drill bit into the material. For example, Oakes U.S. 
Pat. No. 3,758,222 and Korb et al. U.S. Pat. No. 4,582,458 each disclose 
drill bits having coaxial cylindrical surfaces with bevelled portions 
which extend between the cylindrical surfaces helically to provide axial 
clearance for the drill. At least one flute extends axially along the 
length of the cutting portion of the drill bit for providing a cutting 
surface. 
Known disclosures of such drill bits have been mainly for use in fixed or 
portable drills. These drill bits usually have a shank that is cylindrical 
or cylindrical with up to three flats, the flats being spaced apart 
equally in order to prevent slippage. Such shanks are appropriate for use 
in a standard chuck to use with these drills. The chuck is tightened 
around the shank to hold the drill bit within the tool during use and the 
shank helps avoid slippage. 
The connection into and tightening of the chuck around the drill bit shank 
is an unnecessarily time-consuming procedure and is occasionally prone to 
accidental misalignment of the drill bit from the axis of rotation of the 
drill chuck. This may result in further lost time in untightening the 
chuck, realigning the drill bit and retightening the chuck. Furthermore, 
if the misaligned drill bit is used in drilling, the workpiece may be 
damaged or the drill bit may break, which may result in serious injury to 
the operator. 
More recently, hand tools and power tools have been manufactured utilizing 
a quick-change capability allowing swift, efficient and essentially 
error-proof insertion of tool bits without misalignment. For example, 
screwdriver tips or hexagonal bolt tips having a construction generally 
able to be quickly changed are known. Other tools have been used for quick 
change which are known in the industry as power bits. The term "power bit" 
refers to elements typically used for driving fastener devices such as 
screws, nuts, and bolts. To facilitate the quick change of these types of 
bits within power tools, such as hand held power tools that are driven by 
electric or air driven tools, various quick change devices have been 
utilized. For example, one type of a quick release device having a quick 
change capability is found in U.S. Pat. No. 4,184,692. This patent 
describes a quick release chuck similar in principle to most quick release 
chucks of power tools in present use. The American National Standards 
Institute has provided a specification for quick change tools, known as 
ANSI B107.4-1973, to standardize the shape, dimensions and other features 
of the shank of the tool bits to provide easy interchangeability of tool 
bits. 
The known use of quick change devices in present use requires that the 
chuck for which these tools are intended for use have a specific 
construction. An example of such construction is taught by U.S. Pat. No. 
4,692,073. The specific chuck construction is not of overriding importance 
to this discussion other than as an explanation of the use of the 
inventive drill bits within the context of hand held power tools. 
What is not shown in the prior art and what is necessary for providing a 
quick change ability to drill bits of the conical shaped drill bits. 
SUMMARY OF THE INVENTION 
The invention herein described and claimed is a multipurpose drill bit 
having a capability of a quick change within a chuck for a power bit use, 
which further eliminates the requirement for adjustment to hold the tool. 
Additional advantages derive from the capability provided by the present 
invention to ascertain the axial position of the multi-purpose drill bit 
relative to the rotating chuck and to maintain that position invariably. 
This capability ensures that the drill height or distance from the 
workpiece is constant during repeated use for drilling identical 
workpieces. This capability is especially useful in automated drilling 
operations where the drill can be programmed to penetrate the workpiece to 
the proper depth in order to provide a hole drilled to the required 
diameter. 
Accordingly, there is provided a power drill bit of stepped construction 
having a shank at one end and a series of generally cylindrical outer 
surfaces of incrementally decreasing diameter from the shank end to a tip 
end, the power drill bit comprising a beveled conical surface 
interconnecting each adjacent pair of cylindrical surfaces, at least one 
flute, each of the flutes having at least one essentially radially and 
axially extending surface, each one of the flutes being machined into the 
drill bit to provide at least one cutting edge for each diameter defined 
by the intersection of said one surface of each of said flutes, each of 
said cylindrical surfaces and each of said conical surfaces, and said 
shank having a non-circular cross-section and a groove extending 
circumferentially about the shank, said groove including an essentially 
flat center portion and at least one radius portion intersecting the 
non-cylindrical surface of said shank. 
In a preferred embodiment, two flutes are machined in opposite sides of the 
power bit and the relative lengths of the shank portion to the drill 
portion is about one to two, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is an elevational front view of the power bit according to this 
invention. The power bit 10 includes a drill bit portion 12 and a shank 
portion 14. These elements may be integrally connected to each other to 
ensure that rotation of the shank 14 will result in simultaneous rotation 
of the power drill bit portion 12. 
Referring now to both FIGS. 1 and 2, the drill bit portion 12 comprises a 
base 16 and a plurality of axially spaced essentially cylindrical surfaces 
18, 20, 22, 24, 26, and 28. For convenience, these cylindrical surfaces 
are sometimes referred to as steps. The base 16 provides a connecting 
bridge between the shank portion 14 and the drill bit portion 12. The 
shank portion 14 is either integral or integrally joined to the base 16 by 
welding or other essentially permanent means in the preferred construction 
of the power bit 10. 
The drill bit portion comprises a plurality of cylindrical surfaces 18, 20, 
22, 24, 26, 28 having a progressively decreasing diameter, with largest 
diameter being at the base portion 16 and the smallest being at the tip 
end 30. Conical transition surfaces 32, 34, 36, 38 and 40 are provided 
between pairs of adjacent stages of the cylindrical surfaces 18, 20, 22, 
24, 26 and 28, respectively. The power bit 10 also has at least one 
axially extending flute 46 and preferably has a second axially extending 
flute 48 as shown in FIG. 2. 
The shank portion 14 may comprise a hexagonal shank having axially 
extending surfaces 50 and radially inwardly extending circumferential 
groove 52. The groove 52 is of a predetermined width and of a 
predetermined depth, preferably in accordance with the ANSI standards 
described above. The groove 52 includes a pair of radius portions 54,56 
and a bottom flat 58 between the radius portions 54,56 which are best seen 
in FIG. 3. 
The shank portion 14 must have a sufficient axial length for engagement 
into a number of tools, such as a power chuck adaptor or a standard 
cordless screwdriver. A length of the shank portion 14 at least one-half 
the length of the drill bit portion 12 is considered adequate, and a ratio 
of about 1 to 2 is considered preferable. The longer axial length of the 
shank portion 14 enables the power bit 10 to remain true in rotation about 
the longitudinal axis, labelled CL in FIGS. 1 and 3. A hexagonally shaped 
shank portion 14, as shown in cross-section by FIG. 4, is thus preferable 
for use in a power bit, to provide a better engagement of the power chuck 
to the shank portion 14. 
The axial length of the circumferential groove 52 is dictated by the ANSI 
standards and will enable an operator to accurately position and retain 
the tool within a power chuck to high enough tolerances thereby enabling 
precise formation of a hole in a workpiece. The precise axial disposition 
of the circumferential groove 52 relative to the axial positions of the 
various cylindrical surfaces 18, 20, 22, 24, 26 and 28 allows the bit to 
provide a hole having a desired diameter strictly as a function of the 
depth of penetration of the workpiece by the drill portion 12 of the power 
bit 10. 
The precise relationship of axial distance from the groove to the hole 
diameter gives rise to several advantages which are useful to most 
drilling operations but most efficiently suited to take advantage of the 
increasing trend toward automated and programmed operations. The efficacy 
of a multi-stepped drill bit has been understood since the introduction of 
such drill bits. One drill bit may be used to drill holes of different 
diameters without necessitating the change of drill bits and wasting 
valuable time. 
By using a power bit 10 according to the present invention, however, the 
depth of penetration into a workpiece can be now correlated to the hole 
size and the precise axial movement of the drilling tool. In an automated 
operation, for example, holes of different sizes may be made simply by 
programming the drill to move axially a shorter or longer distance, 
depending on the hole diameter desired. The programming instructions 
themselves may be standardized, thus further gaining a savings in 
programming time. 
Use of the present invention may enable an operator to drill all of the 
holes on a workpiece by using a single power bit, where before each drill 
bit could only be used to drill a hole of one size, requiring several bit 
changes during the operation if holes of different diameter were desired. 
Conversely, if a known multi-step drill having a conventional shank 
portion were used, the operation would have to be carried out manually to 
ensure that the operator would stop penetration of the drill bit into the 
workpiece at the right depth. This last procedure is prone to errors 
because the manual operation requires counting the number of cylindrical 
surfaces which have penetrated. 
Although not generally a problem with six such cylindrical surfaces, as 
shown in FIG. 1, when a greater number of steps, such as the thirteen 
steps shown in U.S. Pat. No. 3,758,222 issued to Oakes. As shown in the 
alternative embodiment 110 in FIG. 5, ability to provide a greater number 
of steps on a multi-stepped power bit is further enhanced by the precise 
positioning of the circumferential groove 52 relative to the steps 18, 20, 
22, 24, 26 and 28. The definite and precise relationship permits 
cylindrical surfaces to have much shorter axial lengths, on the order of 
one-eighth inch (1/8") or less. Thus, a greater number of hole diameters, 
in excess of ten and even more, may be accommodated by a single power bit. 
A thirteen step power bit 112 made according to the present invention is 
shown for clarity, wherein the drawing FIG. 5, wherein like elements are 
identified by identical reference numerals as in the embodiment of FIG. 1. 
Preferred embodiments of the invention are described and one is shown in 
the illustrated drawing to illustrate the underlying principles of the 
invention. It is to be understood that various modifications and 
adaptations may be made thereto without departing from the broad spirit 
and scope of the invention which is only limited by the following claims 
and equivalents thereof.