WO2007113510A1

WO2007113510A1 - Tool holding jig

Info

Publication number: WO2007113510A1
Application number: PCT/GB2007/001168
Authority: WO
Inventors: David Thomas Seear
Original assignee: David Thomas Seear
Priority date: 2006-03-31
Filing date: 2007-03-30
Publication date: 2007-10-11
Also published as: GB0606517D0

Abstract

The present invention relates to a tool holding rig (1) for use in sharpening tools and blades (28) using a bench grinder (30). The tool holding rig (1) comprises a complete power tool which is powered separately from the bench grinder (30) and can be used in conjunction with any conventional bench grinder (30).

Description

TOOL HOLDING JIG

FIELD OF THE INVENTION

The present invention relates to a tool holding jig for a grinding apparatus.

BACKGROUND OF THE INVENTION

Hand tools such as chisels require regular sharpening to maintain a good cutting edge. Conventionally such hand tools are sharpened by hand-honing on an oiled sharpening stone. However, hand-honing will not be sufficient to sharpen blades which have incurred numerous nicks. Instead, it is necessary to grind the outer surface of metal to sharpen the blade. To do this, it is known to use either a bench grinder or a stationary sander. In order to sharpen a blade on a bench grinder, the operator presses the flat side of the bevel of the tool gently against the grinder wheel. However, the operator has to be skilled if he is to provide the tool with a straight sharpened edge in the minimum time without overheating the steel so that the tempering of the steel is lost.

US 5,301,473 discloses a grinding apparatus including a tool holding jig. The tool holding jig includes parallelogram linkages mounted on the grinding machine by respective parallel swivel rods for uniaxial pivoting about the axes of the rods. Pivoting of the linkages causes the tool to rock across the flat end face of a grinding wheel. The apparatus includes drive means connecting a shaft driving the grinding wheel to the tool holding jig via a gear train. The drive means causes the tool face being sharpened to rock back and forth across the flat end face of the grinding wheel whilst the grinding wheel rotates.

The tool holding jig of US 5,301,473 requires the grinding machine to have a suitably geared output shaft to which the tool driving apparatus can be connected. Consequently, the tool holding jig can not be used with all conventional portable grinding machines. Furthermore, the tool holding jig must be sized specifically for the grinding machine to which it is attached so that when the driving apparatus is connected to the output shaft, the face of the tool to be sharpened is capable of being positioned against the face of the grinding wheel.

Consequently, a need exists for an improved tool holding jig which can be used in conjunction with any conventional grinding apparatus. The tool holding jig should be capable of being used to accurately position the tool relative to the grinding surface, and should also be capable of being used to sharpen the tool surface without overheating the tool.

SUMMARY OF THE INVENTION

The present invention provides a tool holding jig comprising: attachment means for attaching the tool holding jig to a tool rest of a bench grinder; a tool holder slidably connected to the attachment means; and a motor for effecting back-and-forth slidable movement of the tool holder relative to the attachment means.

By sliding the tool holder back-and forth relative to the attachment means, a tool supported by the tool holder can be caused to slide back-and forth across the outer surface of a grinding wheel of the bench grinder. The extent of the back-and-forth motion can be chosen so that the tool being sharpened is intermittently moved into contact with the grinding wheel such that the tool does not overheat and lose its tempering.

The attachment means may comprise a mount and a clamp mechanism for clamping the tool holding jig onto the tool rest of a bench grinder.

The motor may comprise a DC motor. The speed of the motor may be variable to enable the operator to set the speed at which the tool is moved back-and-forth across the grinding surface according to requirements. The motor may be powered by the mains, via a transformer. The speed of the motor may be controlled by a variable transformer or a variable resistor. By incorporating the motor into the tool holding jig to provide a complete power tool, the tool holding jig can be used in conjunction with any conventional bench grinder irrespective of whether the bench grinder is provided with a separate output shaft.

The tool holder may be slidably connected to a support. The tool holder may be connected to the support via at least one slide, for example at least one ball bearing slide.

The tool holder may be suitable for holding a tool or a blade to be sharpened, such as a chisel, a plane blade or a plane iron.

The tool holding jig may further comprise an adjustment mechanism for moving the tool holder relative to the attachment means in a second direction substantially transverse to the first direction. The adjustment means can be used to move the tool to be sharpened into contact with the grinding surface of the bench grinder such that the pressure with which the tool is pushed against the grinding surface can be controlled. By controlling the pressure with which the tool is pushed against the grinding surface, overheating of the tool being ground can be prevented.

When the tool holding jig includes a support, the support may be slidably connected to the attachment means such that the support can be slidably moved relative to the attachment means in the second direction. The adjustment means may comprise a threaded means. The threaded means may be connected to a threaded insert provided in the support and a first end of the threaded means may act against the attachment means.

By rotating the threaded means within the threaded insert, the support and tool holder can be moved in the second direction relative to the attachment means. Consequently, the operator can have strict control over the amount of pressure applied to the grinding wheel by the tool being sharpened. A spring may be provided between the support and the attachment means to bias the adjustment means against the attachment means, and prevent the tool holder from being pushed away from the grinding wheel.

The motor may be connected to the support. The drive shaft of the motor may be connected via a plurality of links to the tool holder such that rotation of the drive shaft of the motor causes the tool holder to slide in a back-and forth motion in the first direction. The plurality of links may comprises a first crank arm connected to the drive shaft, and a second driving arm having a first end connected to the first crank arm and a second end connected to the tool holder. Rotation of the drive shaft causes the first crank arm to rotate which, in turn, causes the first end of the driving arm to follow a circular motion and the second end of the driving arm to follow a straight back-and-forth, periodic motion.

The tool holder may include a first surface and a second surface. The first surface may be connected to the support means and the second surface may be inclined at an angle relative to the first surface. The second surface may include support means for holding a tool. The support means may comprise at least one clamp. The at least one clamp may be connected to the second surface via a slot in the second surface. The slot may be arranged such that its longest dimension extends in the first direction. Using a combination of at least one clamp positioned in a slot in the second surface, the tool being sharpened can be accurately positioned relative to the grinding wheel. For example, the tool can be centralised relative to the grinding wheel prior to commencing grinding.

The present invention also provides a method of sharpening a blade comprising: attaching the tool holding jig of the present invention to the tool rest of a bench grinder; attaching the blade to the tool holder of the tool holding jig; positioning the blade in contact with a grinding surface of the bench grinder; and activating the motor of the tool holding jig to effect back-and-forth slidable movement of the blade relative to the grinding surface.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described with reference to the drawings in which: figure 1 shows a side plan view of a tool holding jig according to the present invention when attached to a bench grinder, and figure 2 shows a perspective view of the tool holding jig of figure 1. DETAILED DESCRgTION OF THE DRAWINGS

Figures 1 and 2 show an embodiment of the tool holding jig 10 of the present invention when attached to a conventional bench grinder 30.

The tool holding jig 10 is attached to the tool rest 32 of the bench grinder 30 via attachment means. The attachment means includes a mount 11 and a clamp mechanism 12 for fixedly connecting the mount 11 to the tool rest 32. The clamp mechanism 12 comprises a threaded bolt which engages with an opposite thread in the mount 11. A support 13 is connected to the mount 11 and a tool holder 14 is connected to the support 13. The tool holder 14 is slidably connected to the support 13 via a pair of ball bearing slides 15 which allow the tool holder 14 to slide in a direction shown by arrows 50 in figure 2.

The support 13 is slidably connected to the mount 11 such that the support 13 can slide relative to the mount 11 in a direction shown by arrows 52. The tool holding jig further includes an adjustment mechanism for moving the support 13 and the tool holder 14 relative to the mount 11 in the direction of arrow 52. The adjustment mechanism includes a threaded screw 17 which engages with a threaded insert 29 in the support 13. A first end of the threaded screw 17 acts against the mount 11 and a second end of the threaded screw 17 is provided with a rotation knob 16. The second end of the threaded screw 17 passes through an elongated slot 19 provided in the tool holder 14. Rotation of the rotation knob 16 in a first direction pushes the first end of the threaded screw 17 against the mount 11 and causes the support 13 and the tool holder 14 to move away from the mount 11 in the direction of arrow 52. Rotation of the rotation knob 16 in a second direction opposite to the first direction pulls the first end of the threaded screw 17 away from the mount 11. A spring 18 biases the support 13 towards the mount 11 such that the support 13 and tool holder 14 are moved towards the mount 11 in the direction of arrow 52.

A D. C. motor 20 is attached to the support 13. A drive shaft 21 of the motor 20 extends towards the tool holder 14 and is connected to a crank arm 22. The crank arm 22 is connected to a first end of a driving arm 23. A second end of the driving arm 23 is connected to the tool holder 14. Rotation of the drive shaft 21 causes the first crank arm 22 to rotate which, in turn, causes the first end of the driving arm 23 to follow a circular motion and the second end of the driving arm 23 to follow a straight back-and-forth, periodic motion. Consequently, rotation of the drive shaft 21 of the motor 20 causes the tool holder 14 to slide in a back-and forth motion relative to the mount 11 in the direction shown by arrows 50 in figure 2. The speed of the motor 20 is variable.

The tool holder 14 includes a first surface 24 and a second surface 25. The first surface 24 of the tool holder 14 is connected to the support means 13 via the slides 15.

The second surface 25 of the tool holder 14 is inclined at an angle relative to the first surface 24. A slot 26 is provided in the second surface 25 with its longest dimension parallel to the arrows 50. A pair of clamps 27 are mounted in the slot 26. The clamps 27 are provided to hold a tool 28 in a fixed position relative to the tool holder 14. By sliding the clamps 27 along the slot 26 before tightening, the tool 28 can be positioned accurately relative to the bench grinder 30. For example, the tool 28 can be centralised relative to the grinding wheel 33 prior to commencing grinding. The clamps 27 are individually movable so that the tool holder can hold tools or blades of different sizes.

In operation, a tool or blade 28 is attached to the second surface 25 of the tool holder 14 and placed in a position corresponding to the centre of the grinding wheel 33 using the clamps 27. The rotation knob 16 is then rotated to move the edge of the tool 28 to be sharpened towards the grinding wheel 33. The rotation knob 16 allows the operator to have strict control over the amount of pressure applied to the grinding wheel 33 by the tool 28. The motor 20 is then turned on and the tool holder is caused to slide in a back- and forth motion relative to the mount 11, such that the tool 28 supported by the tool holder 14 is caused to slide back-and forth across the outer surface of the grinding wheel 33 of the bench grinder 30. The extent of the back-and-forth motion is chosen so that the tool 28 being sharpened is intermittently moved into contact with the grinding wheel 33 such that the tool 28 does not overheat and lose its tempering. The speed at which the tool 28 moves back-and-forth is chosen by altering the variable resistor provided on the motor 20. The back-and-forth motion of the tool across the grinding wheel ensures grinding of the tool is carried out at a consistent level against the extent of the tool. Accordingly, the present invention provides a tool holding jig for improving the ease and consistency with which blades and tools can be sharpened using a standard bench grinder. The quality with which tools are sharpened using the tool holding jig of the present invention in conjunction with a standard bench grinder does not rely heavily on the experience of the operator. The tool holding jig of the present invention allows the blade or tool to be presented to the rotating grinding wheel at a controlled pressure and with only intermittent contact.

It will of course be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of the invention as defined by the claims.

Claims

1. A tool holding jig comprising: attachment means for attaching the tool holding jig to a tool rest of a bench grinder; a tool holder slidably connected to the attachment means; and a motor for effecting back-and-forth slidable movement of the tool holder relative to the attachment means.

2. The tool holding jig of claim 1 wherein the attachment means comprises a mount and a clamp mechanism for clamping the tool holding jig onto the tool rest of a bench grinder.

3. The tool holding jig of claim 1 or claim 2 wherein the motor comprises a D.C. motor.

4. The tool holding jig of any preceding claim wherein the speed of the motor is variable.

5. The tool holding jig of any preceding claim wherein the tool holder is slidably connected to a support.

6. The tool holding jig of claim 5 wherein the support is slidably connected to the attachment means such that the support can be slidably moved relative to the attachment means in a second direction substantially transverse to the first direction.

7. The tool holding jig of claim 5 or claim 6 wherein the tool holder is connected to the support via at least one slide.

8. The tool holding jig of any preceding claim further comprising an adjustment mechanism for moving the tool holder relative to the attachment means in a second direction substantially transverse to the first direction.

9. The tool holding jig of claim 8 wherein the adjustment means comprises a threaded means acting against the attachment means.

10. The tool holding jig of any preceding claim wherein a drive shaft of the motor is connected via a plurality of links to the tool holder such that rotation of the drive shaft of the motor causes the tool holder to slide in a back-and forth motion in the first direction.

11. The tool holding jig of claim 10 wherein the plurality of links comprises a first crank arm connected to the drive shaft, and a second driving arm having a first end connected to the first crank arm and a second end connected to the tool holder.

12. The tool holding jig of any preceding claim wherein the tool holder includes a first surface and a second surface, wherein the tool holder is slidably connected to the attachment means via the first surface and the second surface is inclined at an angle relative to the first surface.

13. The tool holding jig of claim 12 wherein the second surface includes support means for holding a tool.

14. The tool holding jig of claim 13 wherein the support means comprises at least one clamp.

15. The tool holding jig of claim 14 wherein the at least one clamp is connected to the second surface via a slot in the second surface.

16. A tool holding jig substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

17. A method of sharpening a blade comprising: attaching the tool holding jig of any preceding claim to the tool rest of a bench grinder; attaching the blade to the tool holder of the tool holding jig; positioning the blade in contact with a grinding surface of the bench grinder; and activating the motor of the tool holding jig to effect back-and-forth slidable movement of the blade relative to the grinding surface.