Technique for fastening logs and fastener therefor

A technique for fastening together logs and a fastener therefor is directed to a self-drilling/tapping fastener which allows the fastener to be driven through the log to be secured without pre-drilling a bore. Counter-bore fins on the fastener head also form a counter-bore for the head. A lubricious coating applied to a portion of the shank accommodates settling of the logs and facilitates installation.

BACKGROUND OF THE INVENTION 
This invention relates generally to fasteners and fastening techniques for 
fastening logs. More particularly, the present invention relates to 
techniques and fasteners for fastening together the logs of a log home. 
Log homes which are manufactured from pre-shaped logs formed in an 
efficient, mass production process are now commonplace. The pre-formed 
logs are transported to the building site, and the log home is constructed 
in a highly efficient process. The construction process conventionally 
involves fastening together the logs which form the walls of the home. 
Because the logs have a substantial thickness, typically on the order of 6 
inches or more, and because over time there is ordinary significant 
settling and displacement of the connected logs subsequent to 
construction, the fastening process is not entirely straightforward. 
A wide spread conventional log fastening technique involves drilling a hole 
in the log that is to be secured on top of a bottom secured log. A 
counter-sink is also drilled. After the hole and counter-sink are formed, 
a large spiral nail or a common nail is driven through the hole into the 
bottom securing log, or a long screw is inserted through the pre-drilled 
hole and threaded into the bottom log. The fastener head is driven into 
the counter-sink. In log construction a limited free movement of the logs 
must be accommodated since over the lifetime of the log home, the logs 
ordinarily will shrink and will also settle. In addition, the fastening 
technique must be accomplished without splitting the logs. 
SUMMARY OF THE INVENTION 
Briefly stated the invention in a preferred form is a technique for 
fastening together the logs which are used to construct log homes. Rather 
than pre-drill a bore and a counter-bore in the log to be secured, a 
fastener is torqued into the secured log by a self-drilling/tapping 
process which prevents splitting of the log and also, at the same time, 
forms the counter-sink bore. The fastener is configured to allow for 
limited movement of the logs due to shrinkage and settling. 
In accordance with the invention, the log fastener includes a head which is 
adapted to receive a driver for application of a torque. A shank extends 
from the head and terminates in a self-drilling piercing point. The shank 
has a first segment of generally uniform diameter and a second threaded 
section which threads into the secured log. The fastener includes a pair 
of fins under the head which upon torquing the fastener, self-tap the 
counter-bore so that the head may be sunk below the surface of the log. A 
lubricious coating is applied to the shank to allow for settling of the 
logs. The coating also eliminates a significant amount of friction and 
thereby reduces the torque required during installation. 
An object of the invention is to providing a new and improved technique and 
fastener for fastening together pre-formed building logs. 
Another object of the invention is to provide a new and improved fastening 
technique and fastener which allow pre-formed logs to be connected in a 
highly efficient and cost effective manner. 
A further object of the invention is to provide a new and improved 
technique wherein logs may be fastened together in an efficient manner 
which allows for subsequent settling and movement of the logs and does not 
result in splitting of the logs or compromising their structural 
integrity. 
Other objects and advantages of the invention will become apparent from the 
drawings and the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference to the drawings wherein like numerals represent like parts 
throughout the Figures, a log fastener in accordance with the present 
invention is generally designated by the numeral 10. Log fastener 10 is 
especially adapted for fastening together adjacent pre-formed logs such as 
may be employed in constructing a log home. The logs 12, which are 
prototypically illustrated in FIG. 1, may assume a wide variety of shapes 
and configurations. The logs 12 typically have substantial thicknesses 
which may commonly be on the order of 6, 8, 10 inches or even greater 
thicknesses. The logs are formed in an efficient, mass produced process 
which includes a generally uniform shaping so as to produce generally 
uniformly spaced upper and lower planar surfaces 13, 15. The logs also 
typically have various tongues 14, grooves 16, slots 18 and notches (not 
illustrated) which are used in the construction process. 
With reference to FIGS. 2 through 4, fastener 10 includes a hex head 20 
with an integral retainer or flange 22 and a shank 30. The shank 30 is 
comprised of an intermediate segment 32 having a substantially uniform 
diameter. Segment 32 is axially dimensioned to extend substantially the 
entire thickness of the log. The shank also includes a threaded portion 34 
which typically axially extends a distance on the order of 2 inches. The 
shank terminates in a piercing point 36 for self-drilling the fastener 
into the log. A pinch-type drill point is illustrated in the drawings. 
However, other drill tip configurations are also possible. 
In addition, a pair of diametrically opposed fins 40 project downwardly 
until the fins and head engage the top of the log at the underside of the 
head. The fins 40 are configured so that upon torquing the fastener, the 
fins drill a counter-bore. The head 20 may thus be countersunk into the 
secured log as part of the fastener driving process. 
After the fastener has been fabricated, the shank 30 is preferably coated 
with a lubricious coating 50 (partially illustrated). The coating 50 aids 
in the installation by lessening the friction during the installation 
process. In addition, the lubricious coating 50 will allow the logs to 
settle by providing a limited degree of lubricated movement along the 
fastener shank. In the preferred form, the lubricious coating is a 
Xylan.TM. coating which contains Teflon.TM. and is applied via a 
fluorocarbon. 
With reference to FIG. 1, the logs 12 are fastened together by applying a 
torque to the fasteners 10 without initially predrilling either a through 
bore or a counter-bore into the log to be secured. Preferably, a fastener 
holder attachment is used in conjunction with an automatic screw gun 
(neither illustrated). The preferred attachment is the Olympic Speedy Tool 
which is marketed by the assignee of the present invention. The attachment 
supports the fastener so that a sufficient downward force is exerted on 
the fastener for threading the fastener through the secured log and into 
the securing log. The fastener self-drills and self-taps into log 12, and 
as it does so, forms a bore which is dimensioned to receive the shank 
segment 32. As the fastener is driven downwardly, the fins 40 also 
function to form a counter-bore 19 for sinking the head below the top of 
the log. The shank segment 32 and the threaded portion 34 are dimensioned 
so that the fastener only threadably engages the base (bottom) log when 
the fastener is fully driven. The lubricious coating 50 facilitates the 
installation process. 
It should be appreciated that because pre-drilling a bore and counter-bore 
is not required, a significant savings in installation time and labor cost 
is provided by the fastener. 
With reference to FIG. 5, an alternate embodiment of a log fastener is 
generally illustrated by the numeral 60. Fastener 60 primarily differs 
from fastener 10 by virtue of the head 62 which has a rounded 
configuration and a slot 64 for a blade driver (not illustrated). 
Alternately, the head 62 may also include a flat, bugle or truss-type 
configuration. 
In one embodiment of the invention which is adapted for a log having a 
nominal thickness of approximately 8 inches, the length of the shank 30 is 
approximately 8 inches. The length of the threaded segment is 
approximately 2 inches. The diameter of the flange 22 is approximately 
0.400 inches. The diameter of the intermediate shank segment 32 is 
approximately 0.189 inches. The root diameter of the threaded portion is 
0.172 and the thread diameter is 0.240 inches. 
While a preferred embodiment of the foregoing invention is set forth for 
purposes of illustration, the foregoing description should not be deemed a 
limitation of the invention herein. Accordingly, various modifications, 
adaptations and alternatives may occur to one skilled in the art without 
departing from the spirit and the scope of the present invention.