GB1589293A

GB1589293A - Hole-saws

Info

Publication number: GB1589293A
Application number: GB3678076A
Authority: GB
Original assignee: Daley F A
Current assignee: Daley F A
Priority date: 1977-10-06
Filing date: 1977-10-06
Publication date: 1981-05-13

Description

(54) IMPROVEMENTS IN OR RELATING TO HOLE-SAWS (71) I, FRANK ARTHUR DALEY, of 4 Leicester Road, Upper Hill Lane, Southampton, a British Subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to hole-saws and is concerned with hole saws of the type comprising a body rotatable in a clock-wise direction, and forming a mounting for a cylindrical saw blade, whereby a hole can be formed by cutting a disc out of material.

According to the invention a hole-saw of the type hereinbefore described is provided with a conical spring comprising a left-hand helix, the helix being wound so that, when the spring is compressed fully, the height of the helix corresponds to substantially no more than the thickness of one coil, wherein the spring operates to eject material cut out by the hole-saw.

The conical spring may be of single of double conical form.

In the case of a spring of double-ended form, the helix of each cone is wound so that, when the spring is compressed fully, the height of the helix corresponds to substantially no more than the thickness of one coil thereof.

When a hole has been cut with a hole-saw blade of tubular form, the disc of material which is formed has a diameter corresponding to the inner diameter of the hole-saw blade.

This disc is often trapped within the holesaw blade and it becomes difficult to remove.

Some hole-saw blades are formed with a hole in the wall of the blade which provides access for a tool used to push the disc from the blade, but the pushing operation is timeconsuming. Alternatively, some operators tend to prise the disc from within the blade, using the teeth of the blade as a fulcrum, but this can result in damage to the teeth.

The present invention seeks to provide a hole-saw wherein the above-mentioned disadvantages are avoided.

The various aspects of the present invention will now be described, by way of example only, with reference to: a) the drawing accompanying Provisional Specification No. 36780/76, which is a side view, partly in section, of a hole-saw provided with a single-ended spring, b) the drawing accompanying Provisional Specification No. 6406/77, which is a similar view of a hole-saw provided with a doubleended spring and c) the drawing accompanying the complete specification, which are side views of modified forms of double-ended conical (or substantially conical) springs for use with hole-saws according to the invention.

Like reference numerals used in the present disclosure correspond to like components.

With reference to the drawing accompanying Provisional Specification No. 36780/ 76, a hole-saw 1 comprises a rotatable body 2 formed with a pair of end-bosses 2a, 2b, separated by a flange portion 3 and with a central hole 4 locating a pilot (twist) drill 5.

The pilot drill is secured to the body 2 by a pinch-screw 6 located in the end-boss 2b. The pinch-screw 6 bears on a flat formed on the drill 5. A cylindrical hole-saw blade 7 is mounted on the end-boss 2a and is secured thereto by the usual fixing screws, not shown.

The hole-saw 1 is designed so as to cut holes in material when rotated, (by a hand or power drill - not shown), in a right-hand, i.e.

clockwise direction, when viewed from behind the saw blade 7. The direction of rotation is here indicated by arrows 8.

The hole-saw 1 is shown in combination with a conical spring 10 of single conical form comprising a left-hand helix of wire 11. The arrow 12 indicates the direction of winding.

Preferably, the helix is formed so that, as the spring 10 is compressed fully, the overall height of the spring corresponds to substantially no more than the thickness of one coil.

It is also preferred that the spring 10 is formed so that, when fully compressed, its lower or larger end presents as large a surface areas as possible to the disc of metal to be ejected.

The upper end of the spring 10 is formed so that it is a tight (push) fit on the shank of the pilot drill 5.

In use, when cutting a hole 15 in sheet material 16, with the spring 10 fitted to the drill 5, the hole-saw 1 is rotated, as indicated by the arrows 8, so as to cut a pilot hole (17) in the material, using the drill 5. Obviously, some axial pressure has to be applied to the drill 5 in order to get it to cut.

some axial pressure has to be applied to the drill 5 in order to get it to cut.

Once the drill 5 has broken through the material 16, further axial pressure is applied to the hole-saw/pilot drill combination, whereby the teeth 7a of the hole-saw blade 7 start to cut the hole 15. At the same time, the further axial pressure causes the spring 10 to be compressed, between the end-boss 2a and the material 16. Compression of the spring 10 offers substantial resistance to shock loadings caused by impact of the rotating teeth 7a in the material 16. It also tends to prevent the spring from rotating with the drill 5.

As the hole-saw blade 7 cuts the hole 15, a disc 20 is formed within its wall. Normally, when the hole-saw blade has broken through the material 16, the disc 20, which is sharpedged and which is now of elevated temperature, would tend to lodge within the blade 7. In the present case, however, once the blade 7 has broken through the material 16, resilience in the spring 10 causes the disc 20 to be ejected from the blade, as indicated by the arrows 21.

The hole-saw 1 is now available for immediate re-use, with no time wasted in prising the disc 20 out of the blade 7.

The drawing accompanying Provisional Specification No. 6406/77 illustrates a modified hole saw which makes use of a conical spring of double conical form.

The hole-saw 1 is now shown provided with a conical spring 1 0a of double-conical form with the smaller diameters of the spring at the ends 30, 31 thereof, and further comprising a (single) left-handed helix of wire 1 la. As before, the arrow 12 indicates the direction of winding.

Preferably, the helix is formed so that, as the spring 10a is being compressed, its coils progressively overlap so that, when compressed fully, the overall height of the spring corresponds to substantially no more than the thickness of two coils.

The ends 30, 31 of the spring 1 0a are formed so that at least the upper end is a tight (push) fit on the shank of the pilot drill 5.

However, the internal diameter of the lower end of the spring 10a is preferably made slightly larger (e.g. 0.020") than the drill diameter. Ifit were a push fit on the drill, the lower end may remain compressed after use. To avoid mistakes, the enlarged lower end may need some kind of ready identification, for example, it may be coloured.

Once the drill 5 has broken through the material 16, further axial pressure is applied to the hole-saw/pilot drill combination, whereby the teeth 7a of the hole-saw blade 7 start to cut the hole 15. At the same time, the further axial pressure causes the spring 1 0a to be compressed, between the end-boss 2a and the material 16, whereby the large-diameter coil at the spring centre bears on the material. As before, compression offers substantial resistance to shock loadings caused by impact of the rotating teeth 7a in the material 16, and also tends to prevent the spring from rotating with the drill 5.

The spring 10a also reduces loads caused by the blade 7 breaking through the material 16, as the free length of the spring is substantial.

(Twice that of spring 10 shown in the drawing accompanying Provisional Specification No.

36780/76. Accordingly, the spring 1 0a has a better ejection performance also).

Other advantages of the spring 10a are that both ends of the spring are accurately located on the axis of drilling, and that the view of the pilot drill 5 is not obscured.

With reference to the drawings accompanying the complete specification, which show various modifications of conical springs of double conical form: Figure 1 illustrates a spring 10b substantially like that illustrated in the drawing accompanying Provisional Specification No. 6406/77, but possessing a larger number of turns, Figure 2 illustrates a conical spring 10c of double-conical form, wherein the larger di-' meters are at the ends, and Figures 3 and 4 illustrate springs 10d and 10e basically similar to those illustrated by Figures 2 and 3 respectively, but of substantially conical form.

The springs 10b, 10c, 10d, 10e each comprise a left-hand helix and each may incorporate any of the features referred to above.

Furthermore, each spring may be employed in combination with a hole-saw of the kind shown in Application Nos 36780/76 and 6406/77. The size, rate, etc. of the springs 10-lOe will vary, according, inter alia, to the size of the hole-saw with which they are to be used, and to discejection requirements.

WHAT I CLAIM IS: 1. A hole-saw of the type hereinbefore described provided with a conical spring comprising a left-hand helix being wound so that, when the spring is compressed fully, the height of the helix corresponds to substantially no more than the thickness of one coil, wherein the spring operates to eject material cut out by the hole-saw.

2. A hole-saw as claimed in Claim 1, wherein the spring is of double conical form, the helix of each cone being wound so that, when the spring is compressed fully, the height of the helix corresponds to substantially no more than the thickness of one coil thereof.

3. A hole-saw of the type hereinbefore described provided with a conical spring, substantially as hereinbefore described with reference to the drawing accompanying Provisional Application No. 36780/76.

4. A hole-saw of the type hereinbefore described provided with a conical spring, substantially as hereinbefore described with reference to the drawing accompanying Provisional Application No. 6406/77.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

some axial pressure has to be applied to the drill 5 in order to get it to cut.

Once the drill 5 has broken through the material 16, further axial pressure is applied to the hole-saw/pilot drill combination, whereby the teeth 7a of the hole-saw blade 7 start to cut the hole 15. At the same time, the further axial pressure causes the spring 10 to be compressed, between the end-boss 2a and the material 16. Compression of the spring 10 offers substantial resistance to shock loadings caused by impact of the rotating teeth 7a in the material 16. It also tends to prevent the spring from rotating with the drill 5.

As the hole-saw blade 7 cuts the hole 15, a disc 20 is formed within its wall. Normally, when the hole-saw blade has broken through the material 16, the disc 20, which is sharpedged and which is now of elevated temperature, would tend to lodge within the blade 7. In the present case, however, once the blade 7 has broken through the material 16, resilience in the spring 10 causes the disc 20 to be ejected from the blade, as indicated by the arrows 21.

The hole-saw 1 is now available for immediate re-use, with no time wasted in prising the disc 20 out of the blade 7.

The drawing accompanying Provisional Specification No. 6406/77 illustrates a modified hole saw which makes use of a conical spring of double conical form.

The hole-saw 1 is now shown provided with a conical spring 1 0a of double-conical form with the smaller diameters of the spring at the ends 30, 31 thereof, and further comprising a (single) left-handed helix of wire 1 la. As before, the arrow 12 indicates the direction of winding.

Preferably, the helix is formed so that, as the spring 10a is being compressed, its coils progressively overlap so that, when compressed fully, the overall height of the spring corresponds to substantially no more than the thickness of two coils.

The ends 30, 31 of the spring 1 0a are formed so that at least the upper end is a tight (push) fit on the shank of the pilot drill 5.

However, the internal diameter of the lower end of the spring 10a is preferably made slightly larger (e.g. 0.020") than the drill diameter. Ifit were a push fit on the drill, the lower end may remain compressed after use. To avoid mistakes, the enlarged lower end may need some kind of ready identification, for example, it may be coloured.

Once the drill 5 has broken through the material 16, further axial pressure is applied to the hole-saw/pilot drill combination, whereby the teeth 7a of the hole-saw blade 7 start to cut the hole 15. At the same time, the further axial pressure causes the spring 1 0a to be compressed, between the end-boss 2a and the material 16, whereby the large-diameter coil at the spring centre bears on the material. As before, compression offers substantial resistance to shock loadings caused by impact of the rotating teeth 7a in the material 16, and also tends to prevent the spring from rotating with the drill 5.

The spring 10a also reduces loads caused by the blade 7 breaking through the material 16, as the free length of the spring is substantial.

(Twice that of spring 10 shown in the drawing accompanying Provisional Specification No.

36780/76. Accordingly, the spring 1 0a has a better ejection performance also).

Other advantages of the spring 10a are that both ends of the spring are accurately located on the axis of drilling, and that the view of the pilot drill 5 is not obscured.

With reference to the drawings accompanying the complete specification, which show various modifications of conical springs of double conical form: Figure 1 illustrates a spring 10b substantially like that illustrated in the drawing accompanying Provisional Specification No. 6406/77, but possessing a larger number of turns, Figure 2 illustrates a conical spring 10c of double-conical form, wherein the larger di-' meters are at the ends, and Figures 3 and 4 illustrate springs 10d and 10e basically similar to those illustrated by Figures 2 and 3 respectively, but of substantially conical form.

The springs 10b, 10c, 10d, 10e each comprise a left-hand helix and each may incorporate any of the features referred to above.

Furthermore, each spring may be employed in combination with a hole-saw of the kind shown in Application Nos 36780/76 and 6406/77. The size, rate, etc. of the springs 10-lOe will vary, according, inter alia, to the size of the hole-saw with which they are to be used, and to discejection requirements.

WHAT I CLAIM IS: 1. A hole-saw of the type hereinbefore described provided with a conical spring comprising a left-hand helix being wound so that, when the spring is compressed fully, the height of the helix corresponds to substantially no more than the thickness of one coil, wherein the spring operates to eject material cut out by the hole-saw.
2. A hole-saw as claimed in Claim 1, wherein the spring is of double conical form, the helix of each cone being wound so that, when the spring is compressed fully, the height of the helix corresponds to substantially no more than the thickness of one coil thereof.
3. A hole-saw of the type hereinbefore described provided with a conical spring, substantially as hereinbefore described with reference to the drawing accompanying Provisional Application No. 36780/76.
4. A hole-saw of the type hereinbefore described provided with a conical spring, substantially as hereinbefore described with reference to the drawing accompanying Provisional Application No. 6406/77.
5. A hole-saw of the type hereinbefore

described provided with a conical spring, the spring being substantially as hereinbefore described with reference to Figure 1 of the drawings accompanying the Complete Specification.
6. A hole-saw of the type hereinbefore described provided with a conical spring, the spring being substantially as hereinbefore described with reference to Figure 2 of the drawings accompanying the Complete Specification.
7. A hole-saw of the type hereinbefore described provided with a conical spring, the spring being substantially as hereinbefore described with reference to Figure 3 of the drawings accompanying the Complete Specification.
8. A hole-saw of the type hereinbefore described provided with a conical spring, the spring being substantially as hereinbefore described with reference to Figure 4 of the drawing accompanying the Complete Specification.