Dental instrument sharpening guide

Apparatus for manually sharpening dental instruments which require honing at a specific angle, comprising a planar base member having flat parallel sides and an elongated slot, a planar honing stone having flat parallel honing surfaces disposed within the slot of the base member perpendicularly to the plane of the base member and a spring clip positioned between one end of the slot and the honing stone for providing a biasing force to maintain the honing stone in pressure contact with the other end of the base member slot.

The present invention relates to manual tool sharpening devices and more 
particularly to a hand held hone and guide combination for the sharpening 
of dental instruments. 
BACKGROUND OF THE INVENTION 
In an earlier U.S. Pat. No. 4,821,462, issued Apr. 18, 1989 for Dental 
Instrument Sharpening Hone, by the same inventor, a hone for 
reconditioning dental instruments is disclosed that is characterized by a 
planar abrasive surface supported upon a base alongside of which a 
protractor element is mounted for rotation. The protractor element 
displays one or more straight lines whose angular relation to the abrasive 
surface can be changed by rotation of the element with respect to the 
abrasive surface so that the line or lines can be set to have the same 
angle with respect to the abrasive surface as the handle of the instrument 
has to the cutting surface of the tool which is carried by the handle. 
In operation, the protractor element is adjusted to the desired rotation 
and fixed therein so as to position and maintain the indicia lines at a 
desired angle to the hone, depending on what instrument is being 
sharpened. The cutting edge of the dental instrument is then laid upon the 
hone with the angle of the instrument's handle positioned parallel to the 
indicia reference lines on the protractor element. As the cutting edge is 
manually drawn across the abrasive surface the handle is maintained at its 
initial angle to the hone, that is parallel with the line or lines on the 
protractor element. 
The foregoing device is well suited to its intended purpose, however the 
infinite adjustability of the reference lines with the circular protractor 
element does not lend itself to compactness and simplicity. 
Therefore, the primary purpose of the present invention is to provide a 
tool sharpening guide with non-movable parts and a more simplistic and 
economical construction, albeit with several fixed angles of reference 
lines rather than the infinitely variable selection of the former 
invention. 
Another object of the present invention is to provide an instrument 
sharpening tool that can withstand being sterilized in a customary 
autoclave at soak temperatures in the vicinity of 275 degrees fahrenheit. 
A further object of the invention is to provide a manual sharpening hone 
containing a reference angle guide which doubles as a hand steadying rest 
throughout the sharpening stroke. 
Other and further objects, features and advantages of the invention will 
become apparent upon a reading of the following detailed description of a 
preferred form of the invention, taken in connection with the accompanying 
drawings:

DESCRIPTION OF PREFERRED EMBODIMENT 
The tool sharpening guide 2 comprises a rectangular, double faced abrasive 
sharpening stone 4 disposed in a slot 6 of the reference guide base 8 and 
perpendicular thereto. The sharpening stone may be constructed of a 
ceramic material such as aluminum magnesium silicate. Preferably, the 
reference guide base 8 bisects the top and bottom sharpening planes of the 
stone so as to provide four equally sized sharpening surfaces 10, 12, 14 
and 16. Accordingly, upper and lower sharpening surfaces are then disposed 
on each side of the reference guide base. 
A stainless steel spring clip 20 interacting between one end 22 of the slot 
6 and the end surface 24 of the stone 4 maintains the abrasive sharpening 
stone in its position in the slot. The spring 20 is a substantially "U" 
shaped leaf spring with one stem, or upright stroke, 25 of the "U" being 
approximately twice the length of the shorter stem 27. The longer stem 25 
lays flat against one end edge surface 24 of the stone 4, terminating in a 
bent over end 26 which wraps around the comer of the stone and lays 
against its lateral longitudinal edge 30. The main body portion of the 
spring clip 20 lies on one side of the reference guide base with the short 
stem 27 of the spring projecting through the slot 6 and having the end 28 
of the short stem bent at a right angle so as to wrap around the end of 
the slot and lay against the face of the reference guide base which is 
opposite to the side of the base on which the main body portion of the 
spring is disposed. The clip spring arrangement as described retains the 
stone within the slot through the bias of the spring, forcing the stone 
against the end of the slot opposite to the end which is in contact with 
the spring. The bent ends 26 and 28 of the spring 20 prevent lateral 
movement of the stone 4 in one direction but permit it under firm pressure 
in the opposite direction for removal of the stone from the reference 
guide base. 
The faces of the reference guide base are etched or otherwise marked with 
indicia guide lines 35, each having an angle to the sharpening surfaces of 
the hone 4 which is identical to the angle of a particular dental 
instrument's handle to the planar surface of its cutting tool. To sharpen 
a dental tool, the correct angle of the handle to the sharpening surface 
is first determined by reference to the information which may be printed 
on the guide base, as shown in FIGS. 2 and 3, or obtained elsewhere. When 
the proper angle is known the tool is laid upon the abrasive surface of 
the sharpening stone with the handle of the instrument positioned in 
alignment with or parallel to the appropriately angled one of the guide 
lines 35. If the handle of the instrument is kept parallel to the proper 
reference line as the cutting surface of the tool is drawn across the 
hone, the tool will be reconditioned with the proper angle. 
It should be appreciated that the slot 6 in the guide base is not located 
exactly midway between the upper and lower edges of the base. For the 
lower handle angles of, for example, 10 and 20 degrees it is more 
appropriate to position the flat upper edge of the guide base closer to 
the surface of the hone. This positioning provides a proper hand rest, or 
railing, for supporting the hand while holding the instrument handle at 
these lower angles as the instrument is drawn across the sharpening 
surface. However, on the opposite side of the stone 4 the edge of the 
guide base is somewhat more elevated from the abrasive surface, thus 
providing a similar railing for the continuous support and steadying of 
the hand as the higher angle instruments are sharpened. Additional timing 
of the support for the instrument can come from maintaining the instrument 
in contact with the side face of the guide base as it is moved across the 
stone. 
Because the reference guide base 8 is substantially reduced in size from 
the large rotatable protractor reference guide of the prior invention, it 
is economically feasible to use the more expensive high temperature 
plastic that can withstand the high temperatures of sterilizing 
autoclaves. One such material is a plastic made of polysulfone, by "Amoco" 
having a tolerance for continuous temperatures of at least 300 degrees 
fahrenheit. By the use of such materials the sharpening device can be 
placed with other instruments into an autoclave for sterilization without 
fear of damage to the apparatus.