U.S. patent number 3,802,130 [Application Number 05/248,972] was granted by the patent office on 1974-04-09 for diamond and like grinding wheels.
This patent grant is currently assigned to Edenvale Engineering Works (Proprietary) Limited. Invention is credited to Dirk-Alfred Lindenbeck.
United States Patent |
3,802,130 |
Lindenbeck |
April 9, 1974 |
DIAMOND AND LIKE GRINDING WHEELS
Abstract
A peripheral grinding wheel wherein the peripheral grinding
portion contains diamond or cubic boron nitride abrasive particles
and is characterised in that it consists of two co-axial sections,
the one section being a coarse section and containing coarse
particles of between 60/80 mesh and 100/120 mesh and the other
being a fine section containing fine particles of between 170/200
and 300/350 mesh, or in that it consists of a fine section
sandwiched between two coarse sections, in each case the
concentration of abrasive particle in the fine section preferably
being greater than the concentration of abrasive particle in the
coarse section.
Inventors: |
Lindenbeck; Dirk-Alfred
(Randburg, ZA) |
Assignee: |
Edenvale Engineering Works
(Proprietary) Limited (Johannesburg, Transvaal,
ZA)
|
Family
ID: |
25563397 |
Appl.
No.: |
05/248,972 |
Foreign Application Priority Data
|
|
|
|
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May 12, 1971 [ZA] |
|
|
71/3105 |
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Current U.S.
Class: |
451/544 |
Current CPC
Class: |
B24D
5/14 (20130101) |
Current International
Class: |
B24D
5/14 (20060101); B24D 5/00 (20060101); B24d
005/14 () |
Field of
Search: |
;51/207,204,26R,206.4,29R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kelly; Donald G.
Attorney, Agent or Firm: Young & Thompson
Claims
I claim:
1. A peripheral grinding wheel having an effective grinding portion
containing abrasive particles selected from diamond and cubic boron
nitride abrasive particles, characterised in that the effective
grinding portion comprises two co-axial sections, the one section
containing coarse particles, from 60/80 mesh to 100/120 mesh in
size, and the other section containing fine particles, from 170/200
mesh to 300/350 mesh in size, and the concentration of abrasive
particle in the section containing the fine particles being greater
than the concentration of abrasive particle in the section
containing the coarse particles.
2. A wheel according to claim 1 wherein the effective grinding
portion consists of two and only two sections.
3. A wheel according to claim 1 wherein the effective grinding
portion consists of a central section containing fine particles
sandwiched between two outer sections containing coarse
particles.
4. A wheel according to claim 1 wherein the ratio of the
concentration of abrasive particle in the section containing the
fine particles to the concentration of abrasive particle in the
section containing the coarse particles is 3:1.
5. A wheel according to claim 1 wherein the matrix of the effective
grinding portion is a cured synthetic resin and the concentration
of the abrasive particle in the section containing the fine
particles is 100 to 150 and the concentration of the abrasive
particle in the section containing the coarse particles is 50 to
100.
6. A wheel according to claim 1 wherein the matrix of the effective
grinding portion is a matrix metal and the concentration of
abrasive particle in the section containing the fine particles is
100 to 300 and the concentration of abrasive particle in the
section containing the coarse particles is 50 to 100.
7. A wheel according to claim 1 wherein the abrasive particles are
metal coated.
Description
This invention relates to peripheral grinding wheels incorporating
as abrasive particles diamond or cubic boron nitride.
Peripheral grinding wheels include a hub portion having a central
bore therein adapting the hub portion to be mounted on a shaft or
spindle. The hub portion is itself formed from some suitable
support material commonly used in the art such as steel, bakelite
or a light metal. Carried on the periphery of the hub portion in a
position to make effective contact with a workpiece, is the
effective grinding portion. This portion commonly has a thickness
of the order of either one-fourth inch or one-eighth inch
(approximately 6 mm and 3 mm respectively). This peripheral portion
has abrasive particles such as diamond embedded in a cured
synthetic resin or metal matrix.
Peripheral grinding wheels which incorporate abrasive particles
such as aluminum oxide or silicon carbide can be suitably dressed
both for good grinding efficiency, i.e. high stock removal, and for
relatively low grinding efficiency, i.e. good surface finishing or
polishing. When good grinding efficiency is first required then
good polishing for a given workpiece, it is possible to dress the
same wheel to achieve both effects. However, dressing a peripheral
grinding wheel incorporating diamond or cubic boron nitride is not
easily achieved and hence different wheels have in the past
generally been required to achieve both high stock removal and good
surface finish.
It is an object of the present invention to provide a peripheral
grinding wheel incorporating diamond or cubic boron nitride
abrasive particles which minimises the abovementioned shortcomings
of similar wheels of the prior art.
According to the invention, there is provided a peripheral grinding
wheel having an effective grinding portion containing diamond or
cubic boron nitride abrasive particles, characterised in that the
effective grinding portion comprises two co-axial sections, the one
section having coarse particles and providing, in use, a high stock
removal (hereinafter referred to as the "coarse section") and the
other section having fine particles and providing, in use, a good
surface finish (hereinafter referred to as the "fine section").
In one form of the invention, the effective grinding portion
consists of two such co-axial sections.
In another form of the invention, the effective grinding portion
consists of a central fine section sandwiched between two outer
coarse sections.
The coarse section is preferably wider than the fine section the
width in any given case being influenced by the amount of crossfeed
during grinding. The widths of the sections will preferably be 20
percent or more greater than the amount of crossfeed.
It has been found that particularly good results are achieved if
the concentration of abrasive particle in the fine section or
sections is greater than, preferably three times greater than, the
concentration of abrasive particle in the coarse section or
sections. As is known, concentration is determined by taking the
weight of abrasive particle per unit volume of the finished
grinding element. The grinding element in this case is the
effective grinding portion. The concentration is expressed relative
to a standard of 100 where the weight of abrasive particle is 72
carats per cubic inch.
The preferred concentrations of abrasive particle in the fine
section will vary with matrix being used. In the case of a cured
synthetic resin matrix, the preferred concentration of abrasive
particle in the fine section or sections is 100 to 150. In the case
of a metal matrix, the preferred concentration of the abrasive
particle in the fine section or sections is 100 to 300.
The preferred concentration of abrasive particle in the coarse
section or sections is 50 to 100, irrespective of the matrix
material.
The fine abrasive particles preferably have a size between 170/200
mesh and 300/350 mesh and the size of the coarse particles is
preferably between 60/80 mesh and 100/120 mesh.
To ensure good retention of the abrasive particles in the matrix of
the wheel it is preferred that the particles are metal coated.
Two embodiments of the invention are described with reference to
the accompanying diagrammatic drawing which show, in end view, the
effective grinding portions of two peripheral grinding wheels
according to the invention.
Referring now to FIG. 1, there is shown the effective grinding
portion 10 of a peripheral grinding wheel which consists of two
co-axial sections 12 and 14. Section 12 is the fine section and
contains fine diamond grit of size 170/200 mesh while the section
14 is the coarse section and contains coarse diamond grit of size
60/70 mesh. The grit concentration of the fine section is 150 (i.e.
108 carats per cubic inch) while the grit concentration of the
coarse section is 50. The matrix material for both sections is
cured synthetic resin and the diamond grit is metal coated grit
known as DX DA - MC.
In the wheel 20 of FIG. 2, there are three sections, 22, 24 and 26.
The sections 22 and 26 are the coarse sections with grit size and
concentration as for the section 14. The section 24 is the fine
section, with grit size and concentration as for the section 12.
The matrix material is again synthetic resin and the grit is DX DA
- MC.
In use, the wheels are used for grinding workpieces such as metal
workpieces. Considering first the wheel according to FIG. 2, a
grinding process can be carried out with cross-feeds from opposite
directions. As the grinding progresses, so the sharp edges 28
(shown in dotted lines) of the effective grinding portion will be
worn away and become rounded, as indicated in solid lines in the
drawing. The outer sections 22, 26 will remove most of the material
being ground whereas the central section 24 will polish the surface
left by the outer sections.
Because of the curved profile of the wheel 20, a waviness may be
left on the workpiece surface. In order to reduce this waviness,
the grinding wheel 10 of FIG. 1 may be used for grinding with the
crossfeed being applied in only one direction i.e. the crossfeed of
the workpiece in the direction of the arrow 16. The profile of this
wheel, in use, will have less curvature than that shown in FIG. 2,
the curvature being indicated by solid lines in FIG. 1. This will
have the effect of considerably reducing the waviness. Furthermore,
such a grinding process is more efficient as a greater amount of
the diamonds are used during grinding. Therefore, lower wheel costs
and better surface finish are obtained when an abrasive wheel, as
shown in FIG. 1 is used with crossfeed in only one direction.
The illustrated embodiments have been described using metal coated
diamond grit, but cubic boron nitride abrasive particles may also
be used.
* * * * *