Note: Descriptions are shown in the official language in which they were submitted.
212 ~12 i 4
TITLE: JIG FOR HAND~GRINDING EDG -TOC)LS
TECHNICAL FIELD
This invention relates to jigs for grinding edged cutting tools, particularly hand-held
tools, including turning, carving gouges, ~lat and curved chisels and the like for use
5 with relatively soft materials such as wood and plastics. It can also be used for
many forms of hand-held metal-cutting tools for use with watch-maker's, hobby and
other light metal-turning lathes, as well as for engraving, piercing, shaping, scraping
and carving.
10 BACKGROIJND TO THE INVENTION
Many grinding jigs are known in the art, some being adapted for the sharpening of
hand cutting-tools and others being designed for sharpening tool-bits, blades, drill-
bits and the like for use on machine tools. In general, these jigs aim to present the
tool to th~ grind-stone or wheel at precise pre-set angles in two or more axes or
15 planes. Some allow the operator to move the tool against the stone and to control
the pressure manually to determine lhe depth of cut. Others autornatically move the
tool with respect to the stone after the depth of cut has been set. Such jigs are
generally poorly suited to the grinding of hand-turning and carving gouges of various
shapes because either a special jig is neéded for each tool shape or a an expensive
20 'universal' tool grinder is required which requires a long time to set up if the tool to
be sharpened differs from the last one.
Examples of such jigs are provided by the following prior patents or applications: WO
A 84103246 to Wolff, French patent No, 1,446,463 to Fombouze, US patent No. ~ 9
25 4,936,053 to Shanelec, US patent No. 1,858,297 to United Shoe Machinery Corp,
-. ; .
European application No 225806 (1987) by Temtool Sales, German patent Nos.
803401 to Genkinger and 801,497 to Burkert, and UK patent No 507,371 to Norman.
In general grinding jigs like these aim to allow tools to be effectively sharpened by
persons having little manual skill on the grinding wheel or stone but, in so doing,
30 become cumbersome and frustrating to use by, say, skilled wood-turners or carvers.
The result is that such tradesmen or craftsmen almost invariably attempt to sharpen
theirtools free-hand, but with indifferent results--especially with curved gouge-form -
tools. ~ ;
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In the special case of bevelled straight-edge tools, a number of jigs are available
which are simple and convenient and, in the hands of a moderately skilled person,
yield good results. An example of such a jig is that disclosed in UK patent No.
795,157 to Hampton. This jig is a simple frame in which the blade is clamped and5 which includes a single central hardened ball to support it for movement on a flat
grind-stone, the ~ngle of bavel being set by the amount by which the blade projects
from the jig to meet the stone. The jig, with the attached blade, is then held and
moved by hand over the sufface of the stone. Though the critical angle (for a simple
flat blade with a straight edge) is set in this manner, some skill is necessary to
10 ensure an even pressure across the blade. It will be evident, however, that such jigs
cannot used with any other form of cutting blade--for example, with curved gauge-
form chisels and with relieved knife-type tools having straight or curved edges.
In this specification, the front of the grinding jig is taken to be the end or portion
15 nearest the grinding wheel when the jig is in use. Thus, the cutting edge of a tool
being ground is at or to the front and the handle of the tool is at the back or to the
rear.
OE3JECTIVES OF THE INVENTION
20 It is therefore an object of the present invention to provide a simple but effective jig
for use in the hand-sharpenin~ of a variety of edged cutting-tools.
OUTLINE OF INYENTION
This invention is based upon the realisation that a wide variety of hand cutting-tools
25 can be sharpened in a near-freehand manner, but with significantly reduced skill
requirements, if a jig is provided which holds the tool at a substantially fixed distance
from the grinding stone or wheel (so that the tool cannot be moved bodily to or ~rom
tha wheel) but which otherwisa allows the tool to be freely manipulated with respect
to th~ stone or wheel. Thus, the jig may simply comprise: (i) a support adapted to
30 be secured to a fixture, (ii) means for holding a tool and (iii) universal joint means
connecting or locating the support with respect to the tool holding means so as to
allow substantially free hand-controlled multi-axis angular mov0ments of the holding
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,~ means (and any tool held therein) vvith respect to the support (and, therefore, with
respect to the ~ixture and the ~rinding wheel).
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: The universal joint means may conveniently be a ball-and-socket joint which
r!~i 5 connects or locates the tool holder to the support, the ball of the joint being carried
by the support or by the holder. The balljoint allows the tool to be tilted (in
elQvation), swung (in azimuth) and rolled about axes which pass through the centre
of the ball. It also permits the point of intersection of the axes to be positioned both
close to the tool itself and close to the front end of the tool holder (ie, the grinding-
10 wheel end) of ths jig. The ball may fit in~o a hemispherical socket or it may be
located in a groove of arcuate section so that its position along the groove can be
adjusted to bring the pivot point toward or away from the tool tip. The ball-joint
. . arrangement has been found to suit most types of turning gouges, whether of flat or
curved section, square, rounded or bevelled ends.
~, 15
The support rneans may be adjustabie (eg, by including pivoting or extensible
elements in the support) so that the height of the tool holder means and/or its
position with respect to the grinding wheel can be adjusted. This assists in
generating the desired bevel angle on the tool being sharpened when the tool and20 its holder are moved with a tilting and/or swinging motion. The tool holder may
!~ include a tool clamp for firmly holding the tool in place. Adjustment means may also
be employed so that longitudinal position of the tool holder and/or clamp may beadjusted with respect to the universal joint. This assists in forming a curved end of
the desired uniform radius on the tool being sharpened when the tool is swung
25 and/or rolled. The combination of tilting, swinging and rolling motion allows a
uniform bevel and end-curve to be easily ground by hand on a wood-turning gouge
of concave section, a task that would be most difficult otherwise.
Instead of a balljoint, the universal joint means may be formed by ssparate pivotal
30 or rotary joints of any other suitable design. For example, the universal joint may be
of the crossed-pivot type, it being preferabl~ (but not essential) that the axes of the
separate pivots intersect at a single point or are arranged in close proximity to one
another. It is envisa~ed that one element of the universal joint (referred to below as
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the first joint element) may be formed by supporting the tool olamp and/or holder for
i rolling motion about an axis which is parallel to or coincident with the axis of the tool.
;~ This may be achieved by providing the tool holder with an external cylindrical surface
so that it may rest and turn freely within a cylindrical-form shoe, the shoe being
! 5 pivoted to the support and said pivot forming the second joint element and providing
for movement of the tool/tool-holder in elevation (ie, providing ~or tilting motion).
;~, Conveniently, the tool holder and the first and second joint elements mzy be
?t' arranged to rotais with respect to the support by means of a third joint element
providing for movement of the tool/tool holder in azimuth (ie, providing for swinging
10 motion). In such an arrangement, it is desirable that meàns be provided to axially
locate the tool-holder with respect to the shoe so that the tool cannot be moved to
and from the grinding wheel relative to the shoe. ~-
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In another form of universal joint envisaged, the shoe bearing of the above-described
15 joint can be replaced by a pivot pin or bearing arranged below the tool holder and
substantially parallel with the axis of a tool held in the holder. In yet another form,
the universal joint may simply be formed by engaging a conical-form post on the
support means (or the tool holder) with a larger conical-form recess in the lower face
of the tool holder (or in the upper face of the support means). Provision may be20 made to secure thc two parts together in this relationship, or they can be manually
engaged when in use and manually disengagscl when not in use.
As indicated, the universal joint means may include a variety of ball, sliding, pivotal
and rotary connections or joint-elements which act togsther to effectively permit free
25 arcuate movement of the tool holder means (and its tool) with respect to the support
about at least three mutually orthogonai axes within a defined solid angle of use.
There may be one or more joint elements in the universal joint means, one element
usually being sufficient if it is a ball or cone bearing and three elements usually being
sufficient if they ars pivotal or rotary bearings. However, universal joints are30 envisaged in which ball-joint elements are combined with pivot-joint elements, or in
which there are more than three joint elements.
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The jig may include adjustment means whereby the position of the universal joint~ relative to the holder may be adjusted along the axis of a tool in the holder, so that
;.. ~i the distance of the joint from edge of the tool and/or from the grinding wheel can be
set without adjustment of the tool in the holder or of the support. It is also envisaged
5 that the support may include adjustment means permitting the distance of the joint
and/or the tool holder means to be adjusted with respect to the tixture or grinding
. wheel.
DESCRIPTIOM OF EXAMPLES
10 Having broadly portrayed the nature of the present invention, a number of examples
will now be described by way of illustration. In the following description, reference
will be made to the accompanying drawings in which: -
'i 1 -
Figures 1A, 1B and 1C are (respectively) a side eievation, a sectional end
: 15 elevation and a plan view of the grinding jig which forms the ~irst example of
the invention. Figure 1C shows the tool and its holder in the horizontal
position, rather than angled as in Figures 1A and 1 B.
Figures 2A and 2B are end and side sectional elevations of the second ~ ~
example of a grinding jig formed in accon~ance with the invention. : -
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Figures 3A and 3B are perspective views of the grinding jig of the third ~ ~1
example showing alternative forms o~ clamping and joint means.
Figure 4 is an exploded perspective of the jig which forrns the fourth example.
Figures 5A and 5B are side elevations of two variants of a form of jig
comprising the fifth example of the invention, Figures 5C and 5D being details
of the joints of the variants of Figures 5A and 5B respectively.
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Figures 6A, B and C are respectively end, plan and side views of the sixth ~ `
example ofthis invention.
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sl. 7
. Fj9UFeS 7A, B and C are respectively end, plan and side views of the seventh
:~ example of this invention.
Figure 8 depicts a variety of hand tools which can be sharpened by the jig of
~;~. 5 this invention.
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Referring to Figures 1 A to 1 C, the grinding jig 10 of ~he first example of the invention
is shown fitted to the wheel-guard 12 of a bench-grinder having a grinding wheel 14.
Jig 10 comprises a tool holder 16 (which in turn includes a tool clamp 18 and a tool-
10 support base 20) a support rnember comprising a threaded rod or post 22 and a~;j balljoint comprising a ball 24 affixed to the top of post 22, the ball 24 fitting into a
hemispherical socket 25 formed on the under-side of the front end of base 20. Ball
24 is retained in socket 25 by means of a keeper plate 26 which is attached to the
bottom surface of base 20. As shown, threaded post 22 is secured to a standard
15 slotted mounting bracket 28 by nuts 30 threaded thereon, nuts 30 allowing thevertical position of post 22 to be adjusted. The distanca between post 22 and wheel
14 can also be adjusted by loosening nuts 30 and moving the post backwards or
~' forwards in a horizontat slot (not shown) formed in the upper flange 28a of bracket
28. Bracket 28 is attached to guard by bolts 32 which pass through verRcal slots 34
~! 20 formed in the vertical flange 28b of bracket 28, providing further means for the
vertical adjustment of post 22.
As shown in Figures 1A to 1 C, a curved, bull-nosed, wood-turning gouge 36 is inposition for sharpening, being aligned with and supported by base 20 and being held
25 against movement with respect thereto by a thumb-screw 38 which forms part of tool
clamp 18. Tool 36 is positioned on base 20 so that its cutting edge 36a extends
forward beyond ball 24 by approxirnately the radius of the tool nose or somewhatrnore. As will be seen from Figure lA, the diameter of wheel 14, the positioning of
post 22 with respect to bracket 28, tha vertical adjustment of post 22 by means of
30 nuts 30 and the distance which tool 36 extends beyond bas~ 20 substantially
determine lhe bevel angle ground on the tool. However, the double-curved and
bevelled edge must be ground by a combination of tilting, rolling and swinging
movements as respectively indicated by arrows T, R and S in Figures 1A, 1 B and
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~:~i 1 C. All these movements (separately or in combination) are permitted by the ball-
joint formed by ball 24 and its socket 25.
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~;,' The grinding jig of the second example of the invention, shown in Figures 2A and
5 2B, also employs a ball-joint as the univarsal joint but the fore-and-aft position of the
ball along the tool-holder base is adjustable. Referring to the Figures, the tool-holder
again comprises a clamp 40 and a base 42, but a central lon~itudinal groove 44 is
formed along the underside of base 42 and has an arcuate section of substantially
the same radius as ball 46. The ball (46) is formed on the upper end of a pin 4810 which is held coaxially within a pin-chuck 50 that forms the upper end of a support
post 52. The lower end of post 52 terminates is supported by a pivot bolt 54 by
r~j~ which it is attached to a base p1ate 56 that is secured by bolts 58 to a suitable flxture
(not shown), pivot bolt 54 being capable of tightened (or loosened) by a lever 60 to ::
~! permit angularadjustment of post 52.
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Clamp 40 consists of a rectangular box-frame 62 that encircles base 42 so that its
upper plate 62a may hold a tool 64 for sharpening between it and the top surfaceof base 42. A thumb-screw 66 is threaded into the lower plate 62b of box-frame 62,
has a hemispherical end 68 of the same diameter as ball 46 that engages groove
20 44. Ball 46 is held within groove 44 by a spring-steel retaining strip 70 which has
a hole formed in its front end to capture ball 46 and another formed in its rear end
through which the threaded portion of thumb-screw 66 is passed, strip 70 beiny
retained against hemispherical end 68 by a spring 72. Alternatively, strip 70 may be
retained against end 68 by a nut (not shownJ. `~
In operation, the height and position of ball 46 relative to the grinding wheel is
adjusted by the use of the pin-chuck 50 and clamping lever 60. Thumb-screw 66 is ~1~
loosened off and the gouge 64 (or other tool) to be sharpened is entered into box ~ ~ -
member 62 and laid on base 42 so as to be aligned with it anci ~o project slightly
30 beyond the front end thereof. While holding tool 64 in position on base 42 with the
fingers, clamp member 40 is pushed forwards or pulied rearwards to position bali 46
within groove 44 as desired and then thumb-screw 66 is tightened to fix (i) the clamp
40 with respect to the tool-holder base 42, clamp the tool 64 on the tool-holder base
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42 and (iii3 locate the ball 46 at the desired fore-and-aft position. Longitudinal
alignment of tool 64 on base 42 can be assisted by the use of a U or V-section
~J.~/ elastomeric material secured to the upper face of base 42.
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i 5 The third example ~shown in Figures 3A and 3B) illustrates the use of a different
.5 form of tool-holder/clamping means and universaljoint. In this example, the tool
holder 90 is formed from pressed steel to provide a curved semi-cylindrical base 92
which is internally lined with ribbed elastomeric material 94 and has a series of holes
,~1 or indentations 96 formed on it under surface along its centre-line. Indentations 96
10 form alternative sockets for a tapered support pin 98 that is slidably located in a
support post 100 for vertical adjustment by a grub-screw 102 so that the height of
the tool holder 90 can be adjusted. The tapered end of pin 98 and the correspond-
ing indentation form the universal join~. While indentations 96 and the end of pin 98
can be of semi-spherical form and have essentially the same diameter (thereby
15 forming a ball and socket joint), its is also envisaged that they may be of conical
~i form, the mouth of the indentation being substantially larger than ~he diameter of the
end of the pin.
,,!j Tha tool clamp of holder 90 is formed by two wings 104 and 106 which extend
20 upwards and outwards from the rear of base 92 and which carry a clamping plate
108. One end of plate 1 0S is attached to the end of wing 104 by a hinge 110. Plate
108 carries a plung~r 112 which is biased downwards by spring 114. The other endof plate 108 carries a toggle-clip assembly 116, which is shown closod in Figure 3A
and open in Figure 3B. This clip assembly may be of any suitable form known in the
25 art. As illustrated, it comprises a hinged clip-plate 118 curved upwardly at one end
~o ~orm a raised finger-hook 120 and hinged at the other end to the top of plate 108,
clip-plate 118 carrying a wire fastening loop or strap 122 which can be engaged with
a hook 124 formed at the tip of wing 106.
30 In operation, clip 116 is opened and a tool to be sharpened (not shown) is laid in
basa 92 to project the desired distance beyond the front end thereof. The clip is
then pressed toward the closed position to bring the lower end of plunger 112 into
contact with top of the tool, further closure of plate 108 against the pressure of
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spring 114 being effected by engaging strap 122 with wing-hook 124 and pressing
finger-hook 120 down against plate 108 to lock it in position against wing 106. The
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appropriate indentation 96 in the base of tool holder 90 is then fitted over pin 98 and
'j the tool is manipulated against the grinding wheel to sharpen it as before described.
,~ 5
In the fourth example, shown in Figure 4, the tool-holder 130 is a hollow cylinder 132
.'. cut away at the front 132a and fitted with a thumb-screw 134 in its upper surface
toward the rear. The thumb-screw 134 serves to clamp a tool (not shown) onto an
appropriately shaped pad 136 within the cylinder 132 so as that its cutting edge10 projects the desired distance beyond front face 1 32a. With larger tools, pad 136 can
be omitted. Cylinder 132 is provided with an annular lip or ridge 1 38a at its rear end :
and a similar ridge 138b at its front end to form a pair of square, upstanding
shoulders or abutments that serve to locate the tool holder 130 longitudinally (fore-
and-aft) within a semi-cylindrical shoe 140 that is pivo~ed about a horizontal pin 142
15 to the head 144 of a post or support 146. Post head 144 is arranged to turn in or
on the rest of post 146 about a substantially vertical axis (indicated by arrow 148).
It will be seen, therefore, that a tool clamped in holder 130 can be moved freely and
simultaneously about three orthogonal axes--namely the generally horizontal roll-
axis of cylinder 132, the generally horizontal pitch-axis of pin 142 and the generally
20 vertical yaw-axis of post 146--it being easy and preferable to arrange that the yaw-
axis passes through both the pitch and the roll axes. It will also be seen that the
holder and tool can be quickly removad from the shoe to allow inspection of the tool
tip, then returnad to the shoe for further grinding. -
25 A number of variants of the fou~lh example are possible. Shoe 140 can be formed
as a tube within which a tubular holder like 132 is a close sliding and turning fit. In
that case, ridge 138b is omitted (so that the holder can enter the shoe-tube) and
ridge 138a is moved to a position just ahead of clamp screw 134 so that the screw
does not foul the rear end of the shoe. As before, the tool and holder can be quickly
30 removed for inspection and then returned for further work. The latter arrangement
can be further varied by using a locating groove rather than a ridge around the
tubular holder ahead of screw 134 and providing a releasable catch or finger-screws
on the shoe which enter the groove and axially locate the holder tube in the shoe-
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. tube. Finally, the pivot joints between the shoe (140) and the support (146) can be
replaced by a ball joint.
,.:. .
The fifth example, illustrates two variants (Figures 5A and 5B~ of a simple jig (200a5 and 200b) comprising an elongate, cu~ed-section and clampless tool-holder (202a,
202b) having a row of holes (204a, 204b) along its bottom for engagement by a
short spigot (206a,206b) which is supported on the top of a rod-like support member
.;~. (208a, 208a). To use the jig, the user snaps the spigot (which is fitted with a snap-
,J' ring [21 Oa, 21 Ob]) into a selected hole (204a, 204b), lays the tool to be sharpened
:~l 10 (not shown) on holder (202a, 202b) in the desired fore-and-aft position, holds the
tool in that position by gripping it and the holder between the thumb and the fingers,
and then manipulates the tool and holder to bring the edge of the tool against the
grinding wheel (not shown). If desired, a simple tool clamp of the type shown inFigure 7A can be employed.
In the variant of Figures 5A and 5C, the universal-joint is simply a slack-joint formed
between spigot 206a and a hole 204a. As shown in the detail of Figure 5C, the
upper and lower openings of holes 204a are opened-out by chamfering or bevellingto maximise the d~gree of angular movement in all directions while minirnising the
20 amount of slack between the spigot and the hole. Spigot 206a is conveniently
formed integrally with support rod 208a, a spring-loaded sleeve 212 being fitted to
the top of support rod 208a to further reduce the feeling of slack in the joint (the
spring being shown at 213).
25 Tho joint of the variant of Figure 5B, detailed in Figure 5D, is a double bal! joint.
Spigot 206b fits snugly in holes 204b so that holder 202b moves as one with it, the
lower end of spigot 206b terminating in a ball 214 which rests on a second ball 216
that, in turn, is supported for rotation in a socket formed in the end of support rod
208b. The joint assembly is held together by a flexible casing 218. The double ball
30 joint thus formed allows a much greater range of movement of the holder 202b than
would be possible in a single balljoint or, of course, than is offered by the slack-joint
of Figure 5A. It will be appr~ciated that, spigot 206b can be screwed into the front
hole of the holder (or fixed permanen71y therein), the other holes then not being
2 'i ~
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required or provided. In that event (as in the case of the examples shown in Figures
;; 1, 3, 4, 6 and 7), adjustment for tool nose radius is made simply by adjusting ~he
distance by which the tool projects from the front of the holder. ~ ~ -
:i,r;
., 5 The sixth example is shown in Figures 6A-C and comprises a hollow triangular-
~,j section tool holder 250 which has a V-shape bottom 252 and a flat top 254. A
thumb-screw clamp 256 is threaded through top 254 so that a tool inserted into the
holder ~50 can be clamped therein. A ball-headed rod 258 is fitted into a curveddepression formed on the under side of holder ~52 at its front end, the ball being i
10 held in place by a keeper plate 260 fixed to the underneath of holder 252. ~ ~
: :.
The jig of the seventh example, shown in Figures 7A-C is essentially the same asthat of the sixth example except that the lower part of the holder is curved rather ``~
,l than angled. The same reference numerals are therefore employed to designate
15 parts with the same function as those of the sixth example.
Turning now to Figure 8, the variety of wood-turning and wood-working hand toolswhich can be sharpened using the jigs of the examples is illustraited. The various
tools comprise, an angled flat knife-edge turning tool 270, a shallow-curved bull-nose
20 turning gouge 272, a flat chisel 274, a flat bull-nose turning tool 276, a large deeply
fluted turning gouge 278, a flat-bit wood-auger 280 and a small deeply-fluted turning
goug~ 282.
i' While it will be appreciated that the examples provided herein meet the objectives
25 of the invention and offer simple but effective grinding jigs for hand tools, those
skilled in the art will appreciate that many modifications can be made to these jigs,
and many other forms of jig can be devised, without departing from the spirit orscope of the present invention. For example, it is convenient to provide a simple
detachabla joint within the support means, or between the tool-holder and the
30 support means, so that the tool-holder with a tool in place can be simply detached
from and replace on ths support to allow for tool inspection and re-grinding. The
detachable joint can form part of the universal joint or be separate therefrom.
