GB2271948A

GB2271948A - A bit

Info

Publication number: GB2271948A
Application number: GB9222858A
Authority: GB
Inventors: Peter Roy Rogers
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-10-31
Filing date: 1992-10-31
Publication date: 1994-05-04
Also published as: GB9222858D0

Abstract

A drill bit 10 designed for drilling or rebating 2-diameter holes has a flat head 11, which comprises a lead point 12, a first set of cutting edges 13 and a second set of cutting edges 14. The cutting edges 14 are longitudinally displaced from cutting edges 13 and are of greater diameter. <IMAGE>

Description

A Bit This invention relates to drill bits designed for drilling rebated or 2-diameter holes.

Drill and counter sink bits, and indeed drill and counter bore bits, are well known for drilling holes having portions of different diameter. However these bits have always had to be machined from a single piece of metal because of their very complex construction. The result is that even at trade prices they may cost 25 a bit and this makes them uneconomi;c except in extremely repetitive jobs.

From one aspect the present invention consists in a spade or flat bit having a first set of cutting edges for forming a hole of a first width and a second set of cutting edges longitudinally spaced from the first set for forming a hole of a second greater width.

It will be understood that spade bits are much cheaper to manufacture and so this arrangement provides the advantages of the previous bits but at a considerably reduced cost. Indeed it is possible to form the bit of the invention by appropriate milling of an existing spade bit.

Despite this ease of manufacture and the considerable cost saving, the Applicants' arrangement has not previously been proposed and it will be understood that it fulfils a long felt need.

Typically, as with most spade bits, the bit would also be provided with a lead point which may be grooved to allow for the passage of swarf.

From another aspect the invention consists in a method of locating a device having a generally circular bit portion and a wider generally circular seat or end on one end of the bit, the method comprising drilling a rebated hole with the bit as defined above and inserting the device in the hole.

Whilst the arrangement could obviously be used with screws, the bit also provides a useful way of locating any generally circular object such as a magnetic detector for use in an alarm system and it could be extremely appropriate for door locks if they were designed on a circular configuration.

Although the invention has been defined above it is to be understood it includes any inventive combination of the device set out above or in the following description.

The invention may be performed in various ways and a specific embodiment will now be described with reference to the accompany drawings which is a plan view of a drill bit.

A drill bit 10 has a flat head 11, which comprises a lead point 12, a first set of cutting edges 13 and a second set of cutting edges 14. It will be seen that the cutting edges 13, which are nearest the lead point 12, have a width D1 and create a hole of that diameter, whereas cutting edges 14 define a width D2 and cut a hole of that diameter.

The longitudinal spacing between the cutting edges 13 and 14 defines the depth of the first portion of the hole cut. Normally this would be designed to receive the body of a device, such as a magnetic catch or detector. Further drilling will then cut into the wood or plastics with the cutting edges 14 for a sufficient depth to provide a rebate for a flange mounted on the main body of the detector.

It will be appreciated that the dimensions D1 and D2 can be varied in manufacture to achieve different combinations of the dimensions D1 and D2 and of the longitudinal spacing between cutting edges 13,14. Cutting edges 14 may be inclined to provide a counter sink rather than a flat rebate if that suits the particular use, e.g. if the bit is to be used to form screw holes.

In an alternative embodiment the drill bit may consist of a shaft on which flat bit heads can be mounted at different longitudinal positions and a set of different width heads may be provided. In this way the user could make up a drill bit in accordance with the desired characteristics for any particular job. For example the drill bit may consist of a shaft having a bifurcated end between which the drill bit heads could be slid. The ends may have holes or slots for receiving releasable fasteners which can be passed through the ends and the heads lying between them.

Claims

1. A spade or other flat drill bit having a first set of cutting edges for forming a hole of a first width and a second set of cutting edges longitudinally spaced from the first set for forming a hole of a second greater width.

2. A bit as claimed in Claim 1 further including a lead point.

3. A bit as claimed in Claim 2 whether or not the lead point is grooved to allow for the passage of swarf.

4. A spade or other flat drill bit substantially as herein before described with reference to the accompanying drawings.

5. A method of locating a device having a generally circular portion and a wider generally circular seat or end at one end of the circular portion the method comprising drilling a rebated hole with a bit as claimed in any one of the preceding Claims and inserting the device in the hole so formed.