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How to sharpen a hoof knife
How to sharpen a hoof knife
(in 5 minutes so that you can shave with it)
Tristan Jubb
Livestock Health Systems Australia
y
May 2010
E: tristan@jubbvet.com; O: 03 5444 0368; M: 0448 403 600
This presentation explains the terminology and This
presentation explains the terminology and
principles of hoof knife sharpening and then shows how to do it
shows how to do it. 2
TERMINOLOGY
3
TERMINOLOGY (cont'd)
TERMINOLOGY (cont
d)
Cross‐sectional view of hoof knife blade
• Hoof knives have a chisel‐shaped blade; one side is beveled, the other flat. 4
PRINCIPLES
Address the bevel side only
• Address the bevel side of the edge only.
• Don’t address the flat side of the edge except to remove burr.
5
PRINCIPLES Understand bevel angles
1
1
1
•
Factory bevel angles range from 10o to 40o depending on brand (20
o
to 30o being the most common).
•
•
Razor sharpness is difficult to achieve with bevel angles greater than 30o 15o, 20o and 30o bevel angles exist when the width of the bevel is 4x, 3x and 2x the thickness of the knife, respectively.
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PRINCIPLES
Maintain a constant bevel angle
Maintain a constant bevel angle
Metal that needs to be removed to regain a sharp edge
g
Blunt edge
• Maintain a constant bevel angle during the entire sharpening process (to create an entire new bevel parallel with the previous bevel).
• By maintaining a constant bevel angle, less metal is removed and the sharpening process becomes quick, efficient and effective.
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PRINCIPLES
Maintain a constant bevel angle (cont'd)
A
B
If a constant bevel angle is not maintained, the edge will become too obtuse (A) or will remain unsharpened (B).
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PRINCIPLES
R
Remove the burr
h b
Burr
•
•
•
A burr forms during the sharpening process. Burr refers to the fine spicules of metal raised along the edge during the sharpening process.
Remove the burr by honing with a leather strop and metal polishing paste.
If not removed, the burr will break off during use causing the edge to ,
g
g
g
blunt.
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PRINCIPLES
Strengthen the edge by honing
g
g y
g
Micro‐burrs
•
•
•
Honing is the final step in the sharpening process and is performed with a leather strop and metal polishing paste (see later). H i
Honing makes the edge sharper, stronger and longer lasting by k th d
h
t
dl
l ti b
removing the jagged edges created by filing during shaping and sharpening stages.
H i
Honing on both the flat and bevel sides of the cutting edge ensures that b th th fl t d b l id
f th
tti
d
th t
any residual micro‐burr is removed.
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PRINCIPLES Use the correct tools
1. A fine (5/32” diameter) round metal file (for shaping the edges of the hook)
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2 A fine
2.
A fine‐grit
grit, tapered
tapered diamond file diamond file
(for sharpening the edges of the hook)
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3. A fine‐grit, oval diamond file (for shaping the straight edges of the knife)
4. A superfine‐grit, oval diamond file (for sharpening the straight edges of the knife)
5. A 10x magnifier (to examine the edge for dull spots)
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6. A 50‐80cm long x 1.5‐2cm wide x 2mm thick leather strop (for honing the edge)
1
2
3
7. An Artline
l 170 permanent ink k
marking pen (to mark the bevel)
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5
8. Metal polishing paste (for honing the final edge with the leather strop)
9. A pencil case (to hold the tools)
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PRINCIPLES
Use the correct tools (cont'd)
10. A vice mounted to a work bench (t
(to secure the hoof knife during sharpening)
th h f k if d i
h
i )
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PRINCIPLES (cont'd)
PRINCIPLES (cont
d)
Sharpen in stages
Stage 1: Shape the bevel ‐ use the fine oval diamond file on the straight edges and the round metal file in the hook. This stage shapes the bevel to the desired bevel angle and provides basic sharpness
to the desired bevel angle and provides basic sharpness.
Stage 2: Sharpen the edge ‐ use the superfine diamond file on the straight edges and the fine tapered diamond file in the hook’s edges. This stage makes the edges very sharp but not sharp enough to cut paper or shave.
Stage 3: Hone the edge ‐ use the leather strop and metal polishing Stage 3: Hone the edge use the leather strop and metal polishing
paste on the straight edges and the hook’s edges. This stage polishes the edges to long lasting razor sharpness.
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HOW TO DO IT
M k th b l
Mark the bevel
•
•
Mark all of the bevel including the hook with a marking pen to help maintain a constant bevel angle during sharpening.
g
g
p
g
Use the progressive wearing away of the pen mark during the sharpening process to ensure that you are removing metal in the p
p
g
g
correct places needed for sharpening the edge.
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HOW TO DO IT
Mark the bevel (cont'd)
•
•
Unless you mark the bevel, it is difficult to judge whether you have chosen Unless
you mark the bevel it is difficult to judge whether you have chosen
the correct sharpening angle. Marking the bevel is a key step toward achieving a razor sharp hoof knife.
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HOW TO DO IT
Use a vice
i
• Secure
Secure the hoof knife vertically in a vice mounted on a work the hoof knife vertically in a vice mounted on a work
bench.
• Securing the knife vertically in a vice helps to maintain a constant bevel angle during sharpening of the straight edges
bevel angle during sharpening of the straight edges.
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HOW TO DO IT
Shape the bevel on the straight edges
•
•
•
Use the fine grit oval diamond file to shape the bevel of the straight edges to the desired bevel angle. Use the black mark on the bevel as a guide to removing metal at the correct angle in the correct places.
Perform two or three test passes with the file to determine the correct sharpening angle.
Once the correct sharpening angle has been found, concentrate on maintaining the same sharpening angle until the black mark along the entire straight edge bevel has been worn away.
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HOW TO DO IT
Shape the bevel of the hook
•
•
•
Use the round metal file to shape the bevel of the hook.
Remove the knife from the vice when using the round or tapered files in g
p
the hook. By shaping the hook on the bench as shown, this allows visualisation of the black mark on the bevel of the hook.
Use the black mark on the bevel in the hook as a guide to removing metal g
g
at the correct angle in the correct places.
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HOW TO DO IT
Mark the bevel again
•
Mark all of the bevel again including the bevel of the hook Mark
all of the bevel again including the bevel of the hook
with a marking pen in preparation for the next stage of sharpening.
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HOW TO DO IT
Sharpen the straight edges
Sharpen the straight edges
•
Use the superfine grit oval diamond file to sharpen the straight edges. •
•
•
•
Secure the hoof knife in the vice again to assist maintaining a constant bevel angle.
Again, use the black mark on the bevel as a guide to removing metal at the correct angle in the correct places
angle in the correct places.
Perform two or three test passes with the file to determine the correct sharpening angle.
Once the correct sharpening angle has been found, concentrate on maintaining the same sharpening angle until the black mark along the entire straight edge bevel has been worn away.
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HOW TO DO IT
Sharpen the hook edge
Sharpen the hook edge
•
Use the fine grit tapered diamond file to sharpen the hook edges
•
•
•
Remove the knife from the vice when sharpening the hook with the tapered Remove
the knife from the vice when sharpening the hook with the tapered
diamond file. Sharpen the hook on the bench as shown to allow visualisation of the progressive removal of the black mark on the bevel of the hook.
The black mark on the bevel in the hook is a guide to removing metal at the correct angle in the correct places.
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HOW TO DO IT
HOW TO DO IT
Use metal polishing paste
• Smear metal polishing paste along the edges in preparation for honing.
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HOW TO DO IT
H
Hone the edges
h d
• Hone the edges with a leather strop and metal polishing paste.
• Pass the leather strop perpendicular to and over the edge away P th l th t
di l t
d
th d
from the knife (in the picture above, the left edge of the knife is being honed, therefore the leather strop is moving from right to left over the edge).
• Stretch the leather strop tight while honing.
p g
g
• Work at maintaining the constant bevel angle of previous stages.
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HOW TO DO IT
H
Hone the edges (cont'd)
h d
(
'd)
• Hone all the edges with the leather strop and metal polishing paste.
• Don’t drag the strop sharply around the edge – maintain the constant sharpening angle of previous stages.
• Long, fast, heat‐generating strokes work best with this method of honing.
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HOW TO DO IT
Hone the hook edges
Hone the hook edges
• Hone the edges of the hook with the leather strop and metal polishing paste.
• Maintain the constant bevel angle while dragging the strop over the edge away from the knife.
• Don’t drag the strop sharply around the edge – maintain the constant sharpening angle of previous stages.
h
i
l f
i
t
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HOW TO DO IT
Remove burr on the flat side
• Burr will have formed on the flat side (back) of the edges which must be removed.
• Strop the flat side of the edge (on the back of the blade) to remove burr.
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HOW TO DO IT
Test for sharpness
Test for sharpness
• A sharp edge should “catch” on the finger print as you drag your thumb across the edge.
th b
th d
• Try slicing strips off the edge of a piece of paper – a razor sharp knife can slice strips off the edge of paper whereas a less than ra or sharp knife will tear the paper
less‐than‐razor‐sharp knife will tear the paper.
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HOW TO DO IT
Test for sharpness (cont'd)
• Examine the edge under magnification and bright light –
a blunt edge will reflect light, a sharp edge will not.
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HOW TO DO IT
Protect the edges
Protect the edges
• Keep edges sharp by protecting your hoof knives in scabbards made from short sections of plastic pipe.
• The ends of the pipe can be split to make a snug fit for the The ends of the pipe can be split to make a snug fit for the
handle of the knife.
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HOW NOT TO DO IT
Common errors
1
1.
Not maintaining a constant bevel angle
Not maintaining a constant bevel angle.
2
2.
N
Not removing the burr. i
h b
3.
Using high speed electric grinders or buffing wheels which may overheat the edge. Overheating the thin metal at the knife edge may soften the metal causing it to blunt easily during use.
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FURTHER INFORMATION
For more information, or if you wish to purchase a hoof knife sharpening kit, contact:
Livestock Health Systems Australia
E: tristan@jubbvet.com, M: 0448 403 600, O: 03 5444 0368
E: tristan@jubbvet.com, M: 0448 403 600, O: 03 5444 0368
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The end
The end