Tool handle and method of attaching a handle to a percussive tool head

A tool handle includes a tapered shaft retainer which is dimensioned for insertion into the eyehole of a tool head, a high strength handle shaft bonded within the shaft retainer, and a grip which ensheathes the handle shaft. The shaft retainer includes an outer surface portion generally corresponding to a portion of the eyehole, an upper enlarged portion which is incapable of passing through the eyehole, and a slightly tapered inner cavity. The shaft retainer is inserted into the eyehole from the top end thereof, a measured adhesive is placed into the inner cavity, and then the handle shaft is pressed therein through a lower end of the eyehole. In order to improve the bond between the shaft retainer and the upper end of the handle shaft, keyways are provided on the upper end of the shaft and within the inner cavity of the shaft retainer. The grip may be molded directly onto the handle shaft prior to assembly of the shaft retainer to the handle shaft, or the grip may be slidably received onto the handle shaft afterwards and then attached thereto. In such a case, in one preferred method of assembly, an adhesive compound is placed within the grip prior to its being slid onto the handle shaft. In another preferred method of assembly, a mechanical attachment is utilized between the girp and the handle shaft.

BACKGROUND OF THE INVENTION 
This invention relates generally to hand tools. More particularly, the 
present invention relates to an improved composite handle and means for 
attaching the handle to the heads of percussive tools, such as hammers, 
hatchets, axes and the like, in such a manner that the union will be 
strong and invariable during the normal useful life of the tool, and which 
may be utilized equally well during the original manufacture of the the 
tool or while replacing the handle in the field. 
Until recent years the only material used for handles in percussive tools, 
i.e., striking, cutting and/or prying tools such as hammers, sledges, 
peaveys, axes, etc., has been wood. For this reason, the method of 
attaching the handle to the tool head, whatever type it might have been, 
was dictated by the property characteristics of wood. It is generally 
recognized that, other than being strong enough to withstand handle abuse 
the tool would regularly take, there are two conditions which must be 
accommodated when inserting a wood handle into a tool head: to keep the 
tool head attached to the handle under all working conditions; and to 
maintain the head tight to the handle. 
Traditionally, in percussive tools such as sledge hammers, the tool head 
includes an aperture or eyehole through its body which has a single or 
double taper. In both cases, the taper expands at the top of the tool head 
or that portion which is normally directed away from the user when the 
tool is in use. When a wooden handle is driven through the eyehole from 
the bottom side of the tool head, the excess wood protruding from the top 
side is cut off, and some wedging device, such as an ordinary wedge, is 
driven into the wood so that the upper end thereof is expanded to provide 
an inverted frustum which, theoretically, is tightly expanded into the 
tool eyehole. The expanded section of wood must fit within the upper 
tapered portion of the eyehole tightly so that the head cannot fly off 
during use. This is a very elemental assembly which has been in use for 
many years. 
The use of wedges and the like to expand the upper section of the wood 
within the eyehole inherently involves damage to the handle which 
adversely affects many of the physical properties which are desired to be 
retained. Further, the wedges that are driven into the end of the wooden 
handle often tend to work loose, due most frequently to changes in 
humidity which cause alternate swelling and contraction of the wood with a 
gradual decrease in tightness. Many expedients have been employed in an 
attempt to overcome these faults, including the provision of metal sleeves 
to hold the tool handle in place, the use of adjustable wedges which must 
be periodically driven by the owner of the tool to compensate for 
loosening of the joint, the use of metal handles, the casting of wedges in 
position in the tool, and the provision of rubber sleeves interposed 
between the handle and the head. None of these aforementioned expedients 
have proven to be entirely satisfactory. 
The primary reason why prior handles are typically inserted from the bottom 
and wedged at the top of the tool head is that there are very few tools 
which have an eyehole large enough to provide an opening through which the 
grip of the handle can pass. In prior handles, if the handle were small 
enough to pass through the eyehole, the grip would be much too small for a 
man to properly grasp it, and the wood would be too small to resist the 
abuse that the tool would take. Notably, there is one category of 
percussive tools that does not require the handle to be inserted from the 
bottom and then affixed within the eyehole as described above. This 
category includes the pick or pick-mattock style of tool in which the 
eyehole is so massive that even a large grip can be passed through the 
eyehole. Traditionally the handles for such pick or pick-mattock style 
tools are shaped so that the upper end has a reverse taper allowing the 
pick to be dropped over the grip onto the end farthest away from the user 
so that the expanded end of wood is large enough to lock the tool head in 
place and prevent it from ever sliding off the upper end. Of course, the 
tool head can always be removed in the same manner it is placed on the 
handle, by removing it from the butt or grip end. 
Recent years have seen the development of extremely strong composite tool 
handles formed of reinforcing fibers cured within a resin composite. Such 
reinforcing fibers may include fiberglass, polyester, boron, kevlar or 
graphite, and suitable resin composites include polyester, epoxy, 
phenolics, etc. With the development of these composite materials, the 
shaft underneath the tool head can now be made with a cross-section small 
enough to pass through the conventional eyehole of percussive tool heads, 
yet have sufficient strength to withstand the tremendous impact forces to 
be applied. 
As advanced materials have been introduced to replace wood, the materials 
have been either bonded into the eyehole of the tool, substituting the 
bond for the old traditional wedge, and/or welded such as metal to metal. 
Whereas these techniques are suitable to some degree for the manufacture 
of original tools in which the handle is installed with appropriate 
machinery and equipment at a factory, the techniques are not suitable when 
practiced in the field. In the case of bonding, composite shafts have been 
attached to tool heads primarily by means of adhesives in the epoxy field. 
When utilizing such adhesives, despite the continued development of these 
materials, it takes care, precision and good workmanship to properly 
install a replacement handle in a tool head, reliably in the field with no 
secondary tools to assist. Even in factories where the tool head is 
installed on a production basis, high levels of quality control must be 
practiced in order to insure that the head is secured to the handle under 
all anticipated working conditions. Further, since the high strength 
composite shafts are usually inadequate in cross-sectional size to be 
comfortable for a user's hands, a grip of rubber or some other plastic 
material is usually molded onto the shaft or subsequently bonded thereto 
in a manner which guarantees that the grip will not accidentally slide off 
the shaft. 
Accordingly, there has been a need for a highly reliable, simplified method 
by which a handle can be installed onto a percussive tool head, in which 
the handle is permitted to pass through the eyehole from the upper end in 
a manner which effectively prohibits the tool head from flying off the 
handle unintentionally. A handle for use in such method must include a 
minimum number of separate parts in order to greatly simplify assembly of 
the handle to the tool head, and also permit attachment of a grip which 
comfortably fits a user's hands. Further, an improved method of attaching 
a handle to a percussive tool is needed which facilitates use of 
reinforced composite tool handles as field replacements for older tools, 
which overcomes drawbacks associated with fixing such handles within the 
eyehole of the tool head solely by means of an epoxy. Moreover, an 
improved tool handle and method of attaching the handle to a percussive 
tool is needed which simplifies the manufacture and assembly of tools for 
both a field user and original equipment manufacturers. The present 
invention fulfills these needs and provides other related advantages. 
SUMMARY OF THE INVENTION 
The present invention resides in an improved tool handle and method of 
attaching the handle to a percussive tool in such a manner that the union 
will be strong and invariable during the normal useful life of the tool, 
and which may be utilized equally well during the original manufacture of 
the tool or while replacing the handle in the field. The improved tool 
handle comprises, generally, a shaft retainer dimensioned for partial 
insertion into a tool head through its eyehole from the top end thereof, 
and a high strength handle shaft which has its upper end fixed within an 
inner cavity of the shaft retainer. The shaft retainer is configured so 
that it is incapable of passing completely through the eyehole, and thus 
provides an anchor point against which the tool head is rigidly 
positioned. 
In a preferred form of the invention, a percussive tool manufactured 
utilizing the improved tool handle typically comprises a tool head having 
a body and an eyehole through the body, wherein the eyehole includes a 
taper expanding towards the top of the tool head. The shaft retainer, 
which is dimensioned for partial insertion into the tool head through the 
eyehole from the top end thereof, forms a tapered, generally 
frusto-conical slug. The shaft retainer includes an outer surface portion 
generally corresponding to a portion of the eyehole adjacent to the top of 
the tool head, an upper enlarged portion incapable of passing through the 
eyehole, and an inner cavity having an opening opposite to the upper 
enlarged portion. The inner cavity is slightly tapered so as to expand 
towards an upper end of the cavity opposite to the opening thereof. 
Further, the surfaces of the inner cavity include keyways which extend 
generally perpendicularly to the longitudinal axis of the shaft retainer. 
The high strength handle shaft has an upper end thereof inserted into the 
inner cavity of the shaft retainer. The upper end of the handle shaft is 
bonded by means of an adhesive within the inner cavity such that the shaft 
extends substantially the length of the eyehole and downwardly from a 
lower aperture thereof. In order to increase the strength of the bond 
between the handle shaft and the shaft retainer, at least one of the 
surfaces of the upper end of the handle shaft includes keyways similar to 
those keyways provided within the inner cavity of the shaft retainer. 
The shaft retainer includes means within the inner cavity for rigidly 
aligning the longitudinal axis of the handle shaft with the longitudinal 
axis of the shaft retainer. The aligning means includes a plurality of 
longitudinal ribs which protrude into the inner cavity. These ribs 
frictionally engage the handle shaft as it is inserted into the inner 
cavity. The frictional engagement between the ribs and the handle shaft is 
such that the handle shaft may be lifted without a separation of the shaft 
retainer from the handle shaft, even when the shaft retainer supports a 
tool head. 
Means are provided for bonding the upper end of the shaft within the inner 
cavity of the shaft retainer. Preferably, the bonding means comprises a 
measured adhesive which is placed into the inner cavity of the shaft 
retainer prior to insertion of the handle shaft. As the shaft is inserted, 
the adhesive evenly spreads between the handle shaft and the shaft 
retainer, and after it cures, a rigid bond between the two members is 
formed. 
A grip ensheathes a lower end of the handle shaft, and is preferably 
positioned so that one end of the grip is situated adjacent to a lower 
portion of the tool head. Preferably, the grip is molded directly onto the 
lower end of the handle shaft prior to assembly of the handle shaft to the 
shaft retainer. However, the grip may be slidably received onto the handle 
shaft after assembly of the handle shaft to the shaft retainer, and then 
the grip can be attached securely to the handle shaft. If it is desired to 
attach the grip to the handle shaft after the shaft retainer is bonded to 
the handle shaft, in one preferred form of the invention, a measured 
adhesive is deposited into the grip so that as the grip is slid over the 
handle shaft, the adhesive evenly spreads between the grip and the handle 
shaft to form a bond therebetween. In another preferred form, the handle 
shaft is provided with one or more strips of barbs. These barbs permit the 
grip to be slid onto the handle shaft in one direction, but prevent 
removal of the grip from the handle shaft in another. 
The handle shaft has a generally uniform cross-sectional dimension when 
taken perpendicular to its longitudinal axis. This cross-sectional 
dimension generally corresponds with the cross-sectional dimension of the 
inner cavity when taken perpendicular to the longitudinal axis of the 
shaft retainer. This helps insure that a uniform, rigid and strong bond is 
formed between the handle shaft and the shaft retainer. 
The tool handle of the present invention greatly facilitates the rehandling 
of tools in the field. In the case where it is desirable to provide an 
existing tool head with a new handle, the method simply comprises the 
insertion of the tapered shaft retainer into the tool eyehole from the top 
end thereof. A measured adhesive is then placed into the inner cavity, and 
the handle shaft is pressed into the inner cavity. The adhesive uniformly 
spreads between the handle shaft and the shaft retainer to form a bond 
therebetween. If the grip has already been molded directly onto the handle 
shaft, the rehandling assembly process is completed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in the drawings for purposes of illustration, the present 
invention is concerned with an improved tool handle, generally designated 
in the accompanying drawings by the reference number 20. The improved tool 
handle 20 comprises, generally, a tapered slug or shaft retainer 22 which 
is configured for insertion into an eyehole 24 of a tool head 26, which 
receives and is bonded to a high strength handle shaft 28. A grip 30 is 
preferably molded onto a lower end of the handle shaft 28 to ensheathe the 
handle shaft and to position an upper end of the grip adjacent to a lower 
portion of the tool head 26. 
Tool heads which may be advantageously utilized in connection with the 
improved tool handle 20 of the present invention comprise most of the 
broad range of percussive-type tool heads. Such tool heads typically 
include a body portion 32 and either a single-taper or double-tapered 
eyehole 24. In both instances, the eyehole 24 has a tapered portion which 
expands toward a top 34 of the tool head 26. The handle of the tool 
typically extends downwardly and away from a lower or bottom portion 36 of 
the tool head 26. 
In accordance with the present invention, and as illustrated best in FIGS. 
1 through 9 and 13 through 15, the shaft retainer 22 comprises a generally 
frusto-conical slug which is dimensioned for at least partial insertion 
into the eyehole 24 of the tool head 26. Preferably, the shaft retainer 22 
is molded of a glass-reinforced nylon material for high strength and 
durability. The shaft retainer 22 includes an outer surface body portion 
38, an upper enlarged portion 40 which is dimensioned so as to be 
incapable of passing through the eyehole 24, and an inner cavity 42 which 
has an opening 44 opposite to the upper enlarged portion 40. 
As illustrated in FIGS. 4 and 8, the inner cavity 42 is slightly tapered so 
as to expand towards an upper end of the cavity opposite to the opening 
44. This taper is on the order of three degrees. As illustrated in FIGS. 8 
and 9, the surfaces of the inner cavity 42 include keyways 46 which extend 
generally perpendicularly to the longitudinal axis of the shaft retainer 
22. The purpose of these keyways is to provide supplemental, anchoring 
channels into which an adhesive may flow for purposes of bonding the shaft 
retainer 22 to the portion of the handle shaft 28 inserted therein. 
The high strength handle shaft 28 may be manufactured of any suitable 
material, including metal, but is preferably formed of a fiberglass-resin 
composite material. The handle shaft 28 is manufactured so that it has a 
generally uniform cross-sectional dimension taken generally perpendicular 
to its longitudinal axis, and is of sufficient length to extend 
substantially the entire intended length of the tool handle 20. The handle 
shaft 28 includes an upper end 48 configured for insertion into the inner 
cavity 42 of the shaft retainer 22. When the shaft retainer 22 is securely 
positioned within the eyehole 24, the upper end 48 of the handle shaft 28 
extends substantially the length of the eyehole and downwardly from the 
bottom edge 36 of the tool head 26. As illustrated in FIGS. 12 and 13, at 
least one of the outer surfaces of the upper end 48 of the handle shaft 
28, includes keyways 50 which extend generally perpendicularly to the 
longitudinal axis of the handle shaft 28. Like the keyways 46, the keyways 
50 provide channeled anchoring slots for an adhesive 52 which is utilized 
to bond the upper end 48 of the handle shaft 28 within the inner cavity 42 
of the shaft retainer 22. 
Extending longitudinally within the inner cavity 42 of the shaft retainer 
22 are a plurality of ribs 54. These ribs 54 provide means within the 
inner cavity 42 for rigidly aligning the longitudinal axis of the handle 
shaft 28 with the longitudinal axis of the shaft retainer 22. The ribs 54 
are dimensioned so as to frictionally engage the upper end 48 of the 
handle shaft 28 as it is driven into the inner cavity 42. Since the outer 
dimension of the handle shaft 28 may vary, depending on manufacturing 
tolerances, the ribs 54 are likely to be coined to some degree as the 
handle shaft 28 is driven into the shaft retainer 22. This tends to create 
a frictional engagement between the ribs 54 and the handle shaft 28 which 
permits the handle shaft to be lifted immediately after being driven into 
the shaft retainer 22, without a separation of the shaft retainer 22 and 
the tool head 26, from the handle shaft 28. Further, the ribs 54 also 
ensure sufficient space between the upper end 48 of the handle shaft 28 
and the walls of the inner cavity 42 of the shaft retainer 22, to provide 
sufficient clearance for the adhesive 52 to flow between the two members 
and into the keyways 46 and 50. Once the adhesive 52 is allowed to cure, a 
rigid, high strength bond is formed between the shaft retainer 22 and the 
handle shaft 28. The slight taper of the inner cavity 42 acts to 
strengthen the bond between the shaft retainer 22 and the handle shaft 28. 
Specifically, cured adhesive between the handle shaft 28 and the walls of 
the inner cavity 42 creates an incompressible wedge which cannot be 
removed under normal circumstances from the shaft retainer 22. 
If the grip 30 has been previously molded directly onto the handle shaft 
28, then after the handle shaft 28 is mated with the shaft retainer 22, 
assembly of the tool handle 20 to the tool head is complete. It may be 
preferable in some circumstances, however, to assemble the grip 30 to the 
handle shaft 28 after assembly of the handle shaft to the shaft retainer 
22. If such further assembly of the grip 30 to the handle shaft 28 is 
necessary, the grip 30 is slid over a lower end 56 of the handle shaft 28 
(FIG. 14). An upper end 58 of the grip 30 may be situated adjacent to the 
bottom surface 36 of the tool head 26. The grip may be of any suitable 
length, however. The grip 30 is preferably molded into a desirable shape 
from any material which is strong and yet comfortably handled by a user. 
It should be understood, however, that the grip 30 itself primarily serves 
as a convenient surface and mass for which the user can grasp the tool 
handle 20. It does not provide the strength characteristics of the tool 
handle 20. Rather, the inherent strength of the tool handle 20 is provided 
by the shaft retainer 22 and the handle shaft 28. 
In either a rehandling operation or during construction of a tool by an 
original equipment manufacturer, in the case where one handle is suitable 
for several different tool heads 26, wherein the tool heads are not 
necessarily of the same height or thickness between the upper and lower 
surfaces 34 and 36, a ferrule may be added to the tool handle 20. The 
ferrule would typically be provided between the upper edge of the grip 58 
and the lower edge 36 of the tool head 26. Preferably, the ferrule would 
be permitted a limited adjustable sliding range relative to the grip 30 to 
accommodate various tool head thicknesses. 
Following assembly of the grip to the handle shaft as shown in FIG. 14, 
means are provided for securely attaching the grip 30 to the handle shaft 
28. This can be accomplished in many different fashions, however two 
preferred forms of attaching the grip 30 to the handle shaft 28 are 
illustrated. In one embodiment, illustrated in FIGS. 14 and 15, an 
adhesive 60 is placed within a cavity 62 of the grip 30 prior to its being 
slid over the lower end 56 of the handle shaft 28. This adhesive 60 tends 
to become uniformly dispersed between the inner surface of the cavity 62, 
and the outer surface of the handle shaft 28, and when allowed to cure, 
forms a strong bond between the two components. 
An alternative means for securely attaching the grip 30 to the handle shaft 
28 is illustrated in FIG. 17. In this embodiment, the securing means 
comprises a mechanical lock which is illustrated as a rack of 
unidirectional spring-steel barbs 64 fixed to at least one surface of the 
handle shaft 28 below the bottom edge 36 of the tool head 26. The barbs 64 
are constructed so as to allow the grip 30 to be slid onto the handle 
shaft 28, but prevent removal of the grip from the handle shaft. The 
design of the barbs 62 permits the surfaces of the cavity 62 of the grip 
30 to slide over the sharp edges thereof, but these same sharp edges dig 
into the relatively soft material of the grip 30 if the grip is pulled in 
an opposite direction. 
As mentioned previously, the handle shaft 28 is provided with a generally 
uniform cross-sectional dimension taken perpendicular its longitudinal 
axis. This cross-sectional dimension generally corresponds with the 
cross-sectional dimension of both the inner cavity 42 of the shaft 
retainer 22, and the cross-sectional dimension of the cavity 62 of the 
grip 30, when each is taken perpendicular to its longitudinal axis. This 
helps to insure that the handle shaft 28 will not be permitted to twist or 
turn relative to the shaft retainer 22, and further that the grip 30 will 
not be permitted to twist and/or turn relative to the handle shaft 28. 
The assembly of the tool handle 20 is illustrated best in FIGS. 2, 10-12, 
14 and 16. Whether the tool handle 20 is being utilized by an original 
equipment manufacturer in a factory, or by a field user in re-handling a 
tool, the present invention provides a highly reliable, simplified method 
by which a handle can be installed onto most types of percussive tool 
heads, in a manner which effectively prohibits the tool head from flying 
off the handle unintentionally. First, as illustrated in FIG. 10, the 
shaft retainer 22 is banged or thumped into the eyehole 24 from the top 34 
of the tool head 26. Since the upper portion 40 of the shaft retainer 22 
is incapable of passing through the eyehole 24, there is no danger that 
the tool head 26 will ever fly off the tool handle 20. Further, since the 
outer surface 38 of the shaft retainer 22 is configured to generally match 
the taper of the eyehole 24, there is typically a solid area of contact 
between the shaft retainer 22 and the body 32 of the tool head 26 within 
the eyehole 24. It has been found that the tool handle 20 performs 
satisfactorily so long as a minimum of twenty-five percent of the body 32 
surrounding the eyehole 24 is in direct contact with the outer surface 
body portion 38 of the shaft retainer 22. 
Next, a measured quantity of the adhesive 52 is placed within the inner 
cavity 42 of the shaft retainer 22. This is but a preparatory step which 
is done prior to driving the upper end 48 of the handle shaft 28 into the 
inner cavity 42. 
As the upper end 48 of the handle shaft 28 is driven into the inner cavity 
42, the adhesive 52 flows into the keyways 46 and 50, and spreads 
generally uniformly between the handle shaft 28 and the shaft retainer 22. 
The ribs 54 tend to align the handle shaft 28 with respect to the shaft 
retainer, and further to provide enough frictional force between the 
handle shaft 28 and the shaft retainer 22, that the lower end 56 of the 
handle shaft 28 can be grasped and lifted, before the adhesive 52 has been 
allowed to bond the handle shaft 28 to the shaft retainer 22, without any 
separation of those two components. This is often desirable in a 
manufacturing operation. 
In many instances the grip 30 will have been previously molded directly 
onto the handle shaft 28 (FIG. 1). In this case, after the adhesive 52 has 
been allowed to cure, assembly of the tool handle 20 to the tool head 26 
is complete. However, it is sometimes preferable to ensheathe a lower 
portion of the handle shaft 28 with a grip 30 of a selected length after 
the upper end 48 of the handle shaft 28 is bonded within the inner cavity 
42 of the shaft retainer 22. Two methods are illustrated in the 
accompanying drawings for attaching the grip 30 to the handle shaft 28. In 
a first of these embodiments, an adhesive 60 is placed within the cavity 
62 of the grip 30 in much the same manner as the adhesive 52 is placed 
within the inner cavity 42 of the shaft retainer 22. As the grip 30 is 
slid over the handle shaft 28, the adhesive 60 becomes generally uniformly 
dispersed between the walls of the cavity 62 and the handle shaft 28. Once 
this adhesive 60 has been allowed to cure, the handling of the tool is 
complete, and the completed tool handle 20 may be used for all intended 
purposes. 
In a second preferred method of attaching the grip 30 to the handle shaft 
28, a rack of barbs 64 is attached by any suitable means to the handle 
shaft 28, and then the grip is simply slid over the barbs 64 to abut 
against the tool head 26. The barbs 64 prevent removal of the grip 30 in 
much the same manner as the adhesive 60 does. 
From the foregoing it is to be appreciated that the present invention 
provides a highly reliable, simplified method by which a handle can be 
installed onto a percussive tool head, which effectively prohibits the 
tool head from flying off the handle unintentionally. The tool handle 20 
of the present invention includes a minimum number of separate parts which 
greatly simplifies assembly of the handle to the tool head 26. Moreover, 
the grip 30 may be molded so that it will comfortably fit a user's hands. 
The tool handle 20 of the present invention facilitates use of reinforced 
composite tool handles as field replacements for older tools, and the 
present method overcomes drawbacks associated with fixing such handles 
within the eyehole of the tool head solely by means of an epoxy. 
Although a particular embodiment of the invention has been described in 
detail for purposes of illustration, various modifications may be made 
without departing from the spirit and scope of the invention. Accordingly, 
the invention is not to be limited, except as by the appended claims.