An Improved Screw-nail.
Year: 1890

page_text: COMPLETE SPECIFICATION.
An Improved Screw-nail.
I, SYLVANUS EUGENE GROFF of Marietta in the county of Lancaster and State of
Pennsylvania, United States of America, Carpenter do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the foliowing statement:-
This invention relates to improvements in screw-nails; and the object of my
improvement is to produce a spiral grooved nail which shall rotate as it is driven
into the wood, forming a corresponding thread therein to prevent it from being
withdrawn.
My invention consists in cutting or otherwise forming a number of parallel spiral
grooves in nails formed of cylindrical wire the entire length of the nail from a short
distance below the head to the point, which should be conical.
My invention is illustrated in the accompanying drawing, forming a part of this
specification, in which-
Figure 1 is a vertical sectional view of a block of wood on the line y-y, figure 3,
sbowing the nail in place.
Figure 2 is a similar view, but with the nail removed to show the threads formed
in the wood.
Figure 3 is a transverse section on the line x-x of Figure 1.
In the drawing, A represents one of my nails driven into a block of wood, B.
Care spiral grooves cut in the surface of the nail, and extending from a point, a,
near the head of the nail to the point of the nail.
The effect of this construction is, that as the nail is driven into the wood the
grooves CC form threads d in the wood, which causes the nail to revolve as it is
driven in, so as to preserve the continuity of the threads and thus offer as much
resistance to the withdrawal of the nail as though it was a screw.
When the point of the nail is driven into the wood the lower ends of the grooves
receive the parts opposite to them without crushing or forcing the fibres thereof apart.
The nail progressing, this action continues, the fibres of the wood being received in
the ends of the grooves as they are successively brought opposite to them by the
advance of the point of the nail, so that each groove forms a continuous and unbroken
thread, which remains engaged therein. The grooves are of such number that the
threads formed by them have the strength necessary to produce a continuous rotary
movement of the nail as it advances.
I have been in the habit of cutting four grooves in each nail, as giving good results,
but this number may be varied, though it is somewhat doubtful whether a less number
would be certain to produce the necessary screw motion.
The pitch of the grooves is about two inches; though the amount of pitch may
also be varied. To withdraw the screw-nail from the wood into which it has been
driven, a screw-driver is used, as in the case of any ordinary screw.
Figure 2 in which the nail is removed, fully shows the spiral threads or ribs d,
formed by the grooves in the nail as it is driven into the wood.
I am aware that there are nails having a single groove or rib; these do not turn,
but push through the wood, depending upon the elasticity of the wood to fill in the
groove or about the rib and hold the nail in place.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
A screw-nail having conical raint and nervided with parallel spiral grooves
D

page_text: extending from the head to and terminating in the point, the grooves being of such
number and so elongated as to rotate the nail and form threads in the wood as the
nail is driven into the same, substantially as and for the purpose specified.
"
Dated this 26th day of March 1890
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.