GB2278305A

GB2278305A - Grinding rest

Info

Publication number: GB2278305A
Application number: GB9326503A
Authority: GB
Inventors: Michael O'donnell
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-12-24
Filing date: 1993-12-29
Publication date: 1994-11-30
Anticipated expiration: 2013-12-29
Also published as: GB2278305B; GB9326503D0; GB9227008D0

Abstract

A grinding rest has a support means 2 for locating an article adjacent to a grinding surface 3. The support means are in the form of two orthogonal elongate members 5, 6 and permit adjustment of the position of the article relative to the grinding surface 3 along the two axes of the elongate members. A first axis is tangential to the grinding surface 3 which is in form of a grinding wheel 4. <IMAGE>

Description

GRINDING JIG This invention relates to a grinding jig.

Rotating grinding wheels are used to hand shape and sharpen woodturning and woodworking tools, for example, chisels, gouges and plane blades. Similarly, such wheels are used to grind other metal edged tools, for example, metal turning tools and masonry chisels. In order to obtain an accurate grinding angle the tools must be held at a constant angle to a grinding wheel.

Rests are normally provided for use with vertical wheel grinders where tools are sharpened and shaped on the circumferential periphery of the wheel. However, these rests are often difficult to use. In the past, jigs have been used to provide a rest in the form of a support platform, the platform usually being located squarely on the jig shaft forming a constant angle with a grinding wheel. Such jigs cannot be varied to provide different exact grinding angles. Although some variation of position is possible as the jig shaft may be rotated and the shaft length adjusted, a jig of this form cannot cover the most important range of grinding angles for woodworking and is not safe and easy to regularly adjust.

According to the present invention there is provided a grinding jig comprising a support means for locating an article adjacent to a grinding surface, the support means being such to permit adjustment of the position of the article relative to the grinding surface along at least two axes.

Preferably, the grinding surface is a grinding wheel and the first axis is substantially tangential to the grinding wheel.

Preferably, the second axis is substantially at right angles to the first axis.

Preferably, the support means is formed of two elongate members arranged along the two axes.

Most preferably, the support means has an angled platform at an end of the support means proximal to the grinding surface.

Preferably, the platform is angled at a constant angle of 300 to the support means.

Preferably, the two elongate members are orthogonally arranged.

Most preferably, the second elongate member is linearly slidable in a longitudinal direction.

Preferably, the second elongate member has a plurality of predetermined slidable portions in order to allow the platformzto-be positioned at a set angle to the grinding surface.

Preferably, the platform is disposed at the end of the second elongate member and is positioned tangentially in relation to the grinding wheel.

Preferably, the first and second elongate members are orthogonally joined by a boss member.

Preferably, a first elongate member is fixed via a clamp means to a work surface or other fixed surface.

Preferably, the first elongate member is linearly slidable allowing adjustment to compensate for wear of the grinding surface.

Preferably, the articles are woodworking tools, woodturning tools, metal turning tools, masonry chisels or other tools requiring angular grinding.

Embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig 1 is a side view of a jig in accordance with the present invention with a bench grinder; Fig 2 is a side view of a jig in accordance with the present invention with a wet stone grinder; and Fig 3 is a side view of a tool with a bevel angle produced by the use of a jig in accordance with the present invention.

Referring to the drawings, a grinding jig 1 has a support means in the form of two elongate members 5, 6.

The jig 1 is arranged to enable the support means to locate a tool for grinding adjacent to the grinding surface 3 of a grinding wheel 4.

The first elongate member 5 is a steel rod or square/rectangular bar, one end 12 of which is slidably held in a clamp 8. The clamp 8 is held in a fixed position on a worksurface 9 or support for the grinding wheel 4. Two different arrangements of clamp 8 are illustrated in Fig 1 and Fig 2 for use with an 8" bench grinder and a 10" wet stone grinder respectively. The first elongate member 5 is held in the clamp 8 at a fixed angle to the horizontal. The second end 13 of the first elongate member 5 terminates in a boss 7 or other form of receiving means.

The second elongate member 6 is a steel rod or square/rectangular bar, slidably mounted in the boss 70r other form of receiving means in a position orthogonal to the first elongate member 5 such that a first end 14 of the second elongate member 6 is positioned substantially above the clamp 8 and adjacent to the grinding surface 3 of the grinding wheel 4.

The first end 14 of the second elongate member 6 terminates in a platform 2 angled at a fixed angle to the second elongate member 6 such that the platform 2 is angled at a constant 300 angle to the second elongate member 6.

The platform 2 has a slot (not shown) to accommodate guide mechanisms for specific angles or shapes of the tool end. For example, 900 for square chisels and plane blades, 60C for skew chisels or curved.

The first elongate member 5 can be slidably adjusted in the clamp 8 and the adjustment is relayed to the attached second elongate member 6. The second elongate member 6 can be independently slidably adjusted in the boss 7. The second elongate member 6 has three set positions within the boss 7 corresponding to specific resultant angles of grinding of tools supported on the platform 2. The predetermined set positions correspond to grinding at angles of 15O, 300 and 450. The second elongate member 6 is a steel rod with the predetermined set positions achieved by counter sinks located on the steel rod into which a locking screw is tightened through the boss 7.

The second elongate member 6 can also be adjusted to infinitely variable positions between the predetermined set positions within the boss 7 by a second screw in the boss 7 which locates in a key way which can lock the steel rod in any slidable position.

The platform 2 remains at a constant angle to the second elongate member 6 regardless of the linear adjustment of the first and second elongate members 5 and 6. This angle of the platform allows a comfortable working position for holding tools on the platform.

Adjustment of the first elongate member 5 in the clamp 8 results in the platform 2 moving parallel to the radius of the grinding wheel 4 at a fixed point on the circumference of the griding wheel 4. This adjustment can compensate for wheel wear and maintain accuracy in the grinding angle as the grinding wheel 4 reduces in size.

For ease and accuracy of setting, a slip gauge (not shown) is hooked over the platform 2 and adjustment of the platform 2 position is obtained by adjusting the clamp 8 until the platform touches the grinding wheel 4. This adjustment can made while the platform 2 is set, by the slidable position of the second elongate member 6, for a specific grinding angle.

In use, tools can be accurately and repeatably hand ground at particular angles. The tools are supported on the platform 2 which is large enough and at a comfortable angle for a person to hold the tools easily close to the grinding wheel. School children should also be able to sharpen their own tools using a jig of this form.

Woodturners sharpen most of their tools with bevel angles between 150 and 450. These angles need to be repeatedly accurately ground. A tool 22 with a bevel angle 20 is illustrated in Fig 3. The ground surface 21 forms a cutting edge 23 at the point of the bevel angle 20. The bevel angle 20 is defined as the angle at a defined point along the ground surface 21 and the tool axis in this case the top surface 24 of the tool 22. The ground surface 21 is slightly concave from grinding on the grinding wheel 4.

In practice, the platform 2 is angled, and positioned relative to the circumferential surface of the grinding wheel 4. This is first approximately achieved by selecting a datum diameter of the grinding wheel 4 which is usually the mid-point of the full wheel diameter at which the wheel is discarded due to wear.

For example, a 6" diameter wheel is discarded when the diameter is worn to 5", and a datum diameter is taken as 5.5". A datum grinding angle is selected, usually as a mid-point of the working range. The platform 2 is angled and positioned to give the datum grinding angle at the datum diameter point on the circumference of the grinding wheel.

The platform 2 is then adjusted to be as close to the wheel 4 as possible and this is set with the slip gauge as mentioned above. The working angle of the tool for a particular type of grinder is selected which then sets the attitude of the platform which remains constant. The working angle is usually set for specific applications, for example, 300 below horizontal when a standard bench grinder is used (see Fig 1), 100 above horizontal when a wet stone grinder is used (see Fig 2).

The fixed grinding angle (in this embodiment, 150, 300 or 450) at a distance above the platform surface, which distance is usually the thickness of the average tool, is set by slidable adjustment of the second elongate member 6 in the boss 7 and engagement of the locking screw in the counter sink. This movement of the platform 2, to change the grinding angle, is parallel to a tangent of at this point of contact on the grinding wheel 4.

Compensation for grinding wheel 4 wear can be made by adjustment of the first elongate member 5 in the clamp 8.

The working range of grinding of the jig 1 can be increased by pivoting the platform 2 about the datum point on the wheel surface 3. However, the predetermined positions increase repeatability and accuracy.

The jig 1 is formed of steel or cast iron or a similar suitable material.

Modifications and variations of the above described embodiment can be adopted without departing from the scope of the invention.

Claims

1 A grinding jig comprising a support means for locating an article adjacent to a grinding surface, the support means being such to permit adjustment of the position of the article relative to the grinding surface along at least two axes.

2 A grinding jig as claimed in Claim 1 wherein the grinding surface is a grinding wheel and the first axis is substantially tangential to the grinding wheel.

3 A grinding jig as claimed in Claim 1 or Claim 2, wherein the second axis is substantially at right angles to the first axis.

4 A grinding jig as claimed in Claim 1, 2 or 3, wherein the support means is formed of two elongate members arranged along the two axes.

5 A grinding jig as claimed in any one of the preceding Claims, wherein the support means has an angled platform at an end of the support means proximal to the grinding surface.

6 A grinding jig as claimed in Claim 5, wherein the platform is angled at a constant angle of 300 to the support means.

7 A grinding jig as claimed in Claim 4, 5 or 6, wherein the two elongate members are orthogonally arranged.

8 A grinding jig as claimed in any one of Claim 4, 5, 6, or 7, wherein the second elongate member is linearly slidable in a longitudinal direction.

9 A grinding jig as claimed in Claim 8, wherein the second elongate member has a plurality of predetermined slidable portions in order to allow the platform to be positioned at a set angle to the grinding surface.

10 A grinding jig as claimed in any of the Claims 5 to 9, wherein the platform is disposed at the end of the second elongate member and is positioned tangentially in relation to the grinding wheel.

11 A grinding jig as claimed in any one of Claims 4 to 10, wherein the first and second elongate members are orthogonally joined by a boss member.

12 A grinding jig as claimed in any one of Claims 4 to 11, wherein a first elongate member is fixed via a clamp means to a work surface or other fixed surface.

13 A grinding jig as claimed in any one of the Claims

4 to 12, wherein the first elongate member is linearly slidable allowing adjustment to compensate for wear of the grinding surface.

14 A grinding jig as claimed in any of the preceding Claims, wherein the articles are woodworking tools, woodturning tools, metal turning tools, masonry chisels or other tools requiring angular grinding.

15 A grinding jig substantially as hereinbefore described with reference to the accompanying drawings.