GB2382854A - Countersink screw - Google Patents

Abstract

A countersink screw comprises a body portion (2) and a head (3), one or more grooves (4) extend along the underside of the head in which the leading edge (7) of the grooves are adapted to cut the material in which the screw is used. The grooves may extend at an angle from the top of the head to the bottom in the direction of the turn of the screw and are such that as the screw is turned the material cut is forced up the length of the grooves and out the top of the head. Preferably, the grooves have a V-shaped cross section and are used on a self tapping screw.

Description

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Countersink Screw This invention relates to a screw which provides its own countersink into the material with which it is used.

The countersinking of a hole in a material, for example wood, involves the enlarging of the upper part of the hole to allow a screw or bolt fitted into it to sink below the surface. Such an arrangement is desirable because it leaves a flush finish to the surface of the material.

However, to countersink a hole a three stage process is required. First the pilot hole must be created using a drill, then the countersink must be formed using another broader drill bit or specially adapted tool, then the screw is driven into the hole to the desired depth.

This process is time consuming when it has to be repeated many times during the construction of an item. The object of the present invention is to overcome this problem.

According to the present invention a countersink screw comprises a body portion and a head provided with one or more troughs extending along the length of its underside, in which the leading edges of troughs are adapted to cut the material with which the screw is used.

Preferably the troughs are formed at a negative angle to the body so that when the screw is driven into the material the lower face of the trough forces the cut material up and out of the top of the screw head, where it can be disposed of.

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In a preferred construction the body is provided with a close screw thread so an adequate fastening is provided to operate the cutting mechanism.

In one construction the screw is a self-tapping screw so that it can be driven into the material with which it is to be used and countersunk in one action. In another construction for use with harder materials the screw requires a pilot hole to be drilled into the material before it is screwed in.

The invention can be performed in various ways but one example will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a side view of a screw according to the present invention; and, Figure 2 is a top view of the screw shown in Figure 1.

In Figures 1 and 2 a screw 1 comprises a body portion 2 and a head 3. Troughs 4 extend along the underside of the head 3. The troughs 4 are formed with a V-shaped cross section, with an upper surface 5 and a lower surface 6. The leading edge 7 of the trough 4 is sharpened into a cutting blade. The body portion 2 is provided with a close self-tapping thread 8. As shown in Figure 2 the head 3 is provided with a driving socket 9 for co-operation with a screw driver. Driving socket 9 is for a Philips style screw driver, but it will be appreciated that any known screw driving socket can be used.

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When screw 1 is driven into the material with which it is to be used (not shown) the self-tapping thread 8 and the driving force of the screw driver brings the head 3 into contact with the surface of the material. As the screw 1 is turned the leading edges 7 of the troughs 4 cut into the material and form a countersink hole. The waste material is forced up through apertures 10 by the lower surfaces 6 of the troughs 4, and is disposed of by the user. The force required to drive the body of the screw into the material will be similar to the force required to drive the leading edges 7 into the material to cut it, but the user can apply more force to the screw driver if necessary.

While the screw 4 is shown with four troughs it will be appreciated that one or more troughs can be provided to perform the same function. It has been found for example, that a screw provided with 12 troughs works effectively with soft woods. In addition while screw 1 is a self-tapping screw for use with softer materials, it will be appreciated that the invention can also be applied to screws which require a pilot hole.

Thus a screw is provided which forms its own countersink, and can be applied to a material in one step.

Claims (5)

1. Claims 1. A countersink screw comprising a body portion and a head provided with one or more troughs extending along the length of its underside, in which the leading edges of troughs are adapted to cut the material with which the screw is used.
2. 2. A countersink screw as claimed in Claim 1 in which the troughs extend at an angle from the top of the head to the bottom in the direction of the turn of the screw.
3. 3. A countersink screw as claimed in Claim 2 in which the troughs are adapted to force the material cut from the material with which the screw is used up their length and out of the top of the head as the screw turns.
4. 4. A countersink screw as claimed in Claim 3 in which the troughs are of a V-shaped cross section.
5. 5. A countersink screw as claimed in any of the above Claims in which the screw is self tapping.