Skate
Sharpening Information for freestyle and dance skaters.
I have listed below often
asked questions and their answers with the goal to take some of the mystery out
of skate sharpening and help skaters make knowledgeable decisions about the
sharpening of their skates.
Besides needing to have a
very good and accurate sharpening machine, the sharpener needs to be a skilled
craftsperson with a method that makes the sharpening consistent and with a “feel” for the actual sharpening.
The answers below come from
over four years of sharpening or working with very good sharpeners. As one of the very few sharpeners that
actually currently skates and competes I have a good understanding of many of
the concerns and anxieties of having ones skates sharpened. Technical information was taken from Sidney
Broadbent’s book “Skateology” and many of the questions and answers came from a
list by Charles Wright.
When reading the
questions and the answers, you have a question that is not answered or a comment
or suggestion on any of the responses, please email them to me. Send
Email Question or Comment.
Often asked questions:
How
does the blade move or slide over the ice?
Why
does the blade turn when I lean?
What
is the correct hollow for me?
What
is the difference between a dance and freestyle blade?
How is
a skating blade sharpened?
Is
the toe pick ever sharpened?
Why
does the area behind the toe pick not have a hollow?
Why
are some blades not flat on the sides?
How
often should I have my skates sharpened?
Are
new blades ready to skate on?
How
can I tell if the edges are level or square?
Should
I be concerned with nicks in the blade?
What
does a sharp edge look like?
What are templates and how are they used?
How
should I deal with my skate sharpener?
How
long should it take to break in newly sharpened skates?
My
blades feel and look sharp but they don’t feel secure?
How
can I check or monitor the quality of my sharpening?
Why
use guards or soakers on my blades?
What
are common sharpening flaws?
How does the blade move or slide over the ice?
If you apply pressure to
ice, it melts. When the blade presses
against the ice, it creates a thin film of water, which acts as lubricant to
allow the blade to slide. When you are
skating, you actually are skating on a thin film of water.
Why does the blade turn when I lean?
Next time you skate, glide
straight ahead on the blade. Using your ankle and nothing else, tilt the skate
to the right or left, and feel how it turns you in that direction. View the
blade from the side and notice how it curves up at the front and back (it has
"rocker"). Pressed into the ice, a short length of it is actually in
contact with the ice. As it is tilted onto an edge, you can probably envision
that this length of contact is slightly curved. As the blade moves along the
ice, it will follow this curve. The
curve will be deeper if you lean your ankle more. It will also be deeper if
your blade has more of a rocker, as most blades are toward the front. As
you glide on an edge, press slightly forward on it, and feel how it tries to
curve more.
What is the hollow?
You probably know that your blade has two edges, inside and outside, and that there is a "hollow" between the edges. You may also know that the hollow can be "deep" or "shallow", and be able to feel the difference by running your finger across the blade. Refer to the following figure showing a cross section of a blade. The blade is made of a piece of steel of some thickness (a typical freestyle blade is about 0.15" thick). The bottom of the edge is ground out with a circular cross-section (see "how is a blade sharpened", below). The radius of the circle is called the Radius of Hollow (ROH). The shorter the ROH, the "deeper" the hollow. A blade with a deep hollow will hold the ice better, but will also be grabbier and slower.
What is the correct hollow for me?
This is a very individual matter. I
will state some facts, and then some opinions. An important thing to note is that
the ROH (see question "What is the hollow") does not tell the whole story about how a blade feels. The blade touches the
ice only along the edges, so what's really important is the angle between the
side of the blade and the bottom of the blade at the edge. Some blades are
wider than others. For example an MK Phantom is 0.155" wide, an MK Dance is
only 0.11" wide. If you have a geometric mind, you can probably see that,
given the same ROH on the two blades, the wider blade will have a sharper angle
at the edge. So, to give the same strength of edge, narrower blades will need a
shorter ROH.
A more acute edge angle (deeper
hollow) makes the blade less likely to slide sideways, so a deeper hollow gives
more secure edges. There is more to it than that, though. It also makes the
blade more determined at going where IT wants to go, so it will be harder to
control (more likely to grab or "catch an edge"). And, the deeper cut
into the ice causes more drag, so the blade will be slower. Given these
tradeoffs, one could state that the optimum ROH is one which is just deep
enough to give the skater the required edge security.
Learning proper use of the ankle to
control edges is important, and a shallower hollow facilitates this. As the
skater becomes more advanced, they are likely to use a deeper hollow to gain
security of the edge. This may be especially important to advanced freestylers
desiring edge confidence on jump takeoffs and landings. On freestyle
blades, I see ROHs varying
from 7/16" to 5/8". The
following graph shows bite angle versus ROH for various blade widths (The MK
Dance is 0.11" wide, Wilson Dance is 0.14" wide, most skates are
0.15" wide, Phantoms are 0.155" wide at their widest part). Given a
desired bite angle and the width of your blade, you can look up the radius of
hollow required to give that bite angle. A 10-degree bite angle is pretty deep,
and a 7-degree is fairly shallow.
Note that on side-honed blades,
(Phantom, Gold Seal and Gold Star) the side of the blade where it meets the ice
is cut at an angle to the plane of the blade, so the bite angle is effectively
increased by this amount. On side-honed blades this angle varies between
blades, but appears to be between 2 and 3 degrees. An exception is the Phantom
Special, on which the side is cut at an angle of about 9 degrees! Note that the
geometry is slightly different for this case, so the blade will behave
differently than one that simply has a very deep hollow.
What is the rocker?
If
you look at the blade from the side, you will see that it curves from front to back. This is
the rocker. Blade companies generally specify the "rocker
radius" for their different blades. If you draw a circle of this radius
(typically 7 or 8 feet), approximately the back 2/3 of the blade will have a
fairly circular contour that matches the arc of the circle with a 7 or 8-foot
radius. The radius of curvature decreases toward the front (there is more
curve), giving the blade a complex shape.
The
increased curve toward the front of the blade has an interesting effect. If you
move your weight forward on the blade while on an edge, it will want to turn on
a deeper edge. You may know that you spin on this part of the blade. You
probably have also felt how the blade can grab if you rock back on it while
spinning. A
long radius of curvature gives a faster, more stable blade. This is why speed
skates have very little rocker. It also gives less maneuverability, which is
a reason why figure skates curve more at the front. MK
blades are mostly specified to have a 7-foot radius and John Wilson blades have
an 8 radius specification. A
recent check of many new blades indicated that the MK blades were pretty close
to their specified 7-foot radius, while Wilson blades were closer to 6.
Of
more concern is the considerable deviation that is seen, in the form of local
"humps" in the rockers at various points on the blade, of both
brands. Their specified radius is not precisely controlled. A good sharpener can detect these “humps”
and usually correct the rocker. Of course, it is also quite possible that
careless sharpening can introduce such problems as well.
What is the difference between a dance and freestyle blades?
First,
dance blades are shorter. Dancers tend to do a lot of tight footwork, and the short heel
gives less to get tangled up (step on, lock with your partner's blades or your
own, etc.). Secondly, they don't tend to curve up as quickly on the front, so
they are not particularly good for jumps and spins. Also, they do not have the
pronounced toepick that is seen on freestyle blades, since they are not
expected to be used for jumping. Dance
blades are less forgiving than freestyle blades. Many dancers have experienced
getting their weight too far back and falling over backwards. Some styles or brands of dance blades are
narrower than freestyle blades.
What does the toe pick do?
There
are two parts of the toepick, the part that hangs down (the drag pick), and the
part that sticks out in front (the master picks). The drag pick is the last
thing to leave the ice on an axle, the first thing to touch on a jump landing,
and it just touches the ice on most spins.
If
you rock forward on the blade, you can only go so far before hitting the drag
pick. This forward most point is called the "Forward Balance Point".
When you spin, you are skating on this point, with the drag pick just touching
the ice. Because
of the drag pick, you cannot skate on the length of blade between the
forward balance point to the drag pick.
How is a skating blade sharpened?
The
skate is sharpened with a rotating grinding wheel. Prior to sharpening, the
wheel is "dressed" (using a special diamond-tipped tool) in such a
way that it has a circular cross-section (whose radius is the Radius of
Hollow). The skate blade is clamped into a holder, which holds its bottom surface
perpendicular to the grinding wheel. Your friendly skate sharpener moves the
clamped blade along the rotating grinding wheel to refresh the hollow in the
bottom of the skate. The sharpening machine has a special guide to keep the
blade perfectly aligned with the grinding wheel.
The
goal of the sharpening is to remove just enough metal from the bottom of
the blade to renew the edges. A steady hand is required, so that no part of the
blade is ground more than another.
Is the toe pick ever sharpened?
Yes.
You can see that after a blade has been sharpened many times, the profile of
the edge should be the same, but closer to the boot. If the drag pick (see question "What does the toepick do?)
has been
left untouched, the drag pick will be at a different relative position than
when the blade was new, and the skater's technique will change to accommodate
this. It is therefore desirable to occasionally remove tiny amounts of material
from the pick, so that the profile is retained.
Why does the area behind the toe pick not have a hollow?
This
area between the toe pick "drag pick" (see question "What does the toepick do?) and the forward balance point is a
non-skating zone that does not come in contact with the ice. Most new blades are not sharpened in this
area and thus no hollow. Large wheel
sharpening machines cannot sharpen in this area without hitting the toe pick
(drag pick). Sharpeners with small
wheel machines usually start their cutting in this non-skating area and even
the pressure as they move along the blade.
This is also less likely to cause a flat spot on the blade at the
forward balance area.
Why are some blades not flat on the sides?
Generally,
less expensive blades are of constant thickness, with flat sides. As you get
into the more expensive blades, you may see two features: they may be tapered
from front to back (wider at front, narrower toward back), and they may be
"side honed" (material ground from the sides so that instead of being
flat, they are concave).
Depending
on the blade design, side honing may create a sharper bite angle at the edge.
It definitely makes a blade harder to sharpen with level edges.
A
blade design variation worth noting is the "Coplanar" and “Ultma”.
These blades have the high quality steel and stronger construction of high-end
blades, but are of constant thickness throughout, thus easy to sharpen well. In
addition, they have a unique mounting geometry with certain claimed advantages
(because of their flat mounting plates, they can be repositioned on the boot
without changing the blade angle.).
How often should I have my skates sharpened?
"Before
they need it". It depends on how much you skate and how hard you skate. If
your edges are damaged or no longer feel secure, then it's certainly time to
get them sharpened. I try to remember that nice feel of freshly sharpened
skates, and when they don't feel that way, it's time. Generally, to keep the sharp feel all the time, and not have to
get use to just sharpened skates, have them sharpened between 20 to 30 hours of
skating. If you stay with the same
sharpener, sharpening often will be more like a touchup and, if done correctly,
the blade will still last five to eight years.
If
you examine the bottom of the blade right after sharpening, the bottom of the
blade will have a uniformly satin sheen. With more skating, the blade bottom
near the edge, under different light conditions, will begin to appear dull.
These lines along the edge of the blade are the starting of “flat spots” or a
“dull” blade.
Are new blades ready to skate on?
Figure
skate blades generally come from the factory already sharpened. My observation
is that this sharpening job is generally of low quality, unlevel edges and the
factory ROH (see question "What is the hollow") may or may not be appropriate for the particular skater. Always
sharpen new blades before skating on them or at least have them checked by your
skate sharpener.
How can I tell if the edges are level or square?
Ideally,
the centerline of the hollow is halfway between the two sides of the blade. If
it is not, one edge will be higher than the other and will have a sharper bite
angle. If too far off, the effect will be asymmetrical edge strength (for
example, inside edge grabby, outside weak), and flats that want to turn. Your
skate sharpener should always check that your edges are level after
sharpening. A common way to make a
rough check is to balance a coin (or other straight edge) on the bottom of the
blade and "eyeball" it. I think that this method is really too
imprecise to detect any but really gross errors. I use a miniature, precision
machinist's square to check that edges are square with the side of the blade.
Other devices for checking this are also made. Note that side-honed blades are
much more difficult to check, because the side of the blade is not flat.
Should I be concerned with nicks in the blade?
Not
really. It is extremely important that any deformation of the metal on the side
or bottom of the blade, next to the nick be ground away. I observe that a slight
"hole" in the edge is generally not noticeable, and, in the interest
of prolonging blade life, large nicks are generally not completely removed.
What does a sharp edge look like?
If you examine a sharp edge
in a strong light, you should see no reflection from the edge, even looking
with a strong magnifier.
What are templates and how are they used?
Templates
are like patterns or outlines of a blade to the manufacturers original
specifications. Templates are most
often used to restore a flattened rocker, damaged from bad sharpening.
How should I deal with my skate sharpener?
I
suggest that, once you find a skate sharpener that you like, stick with them.
The reason for this is simple. Every skate-sharpening machine has slight
differences. A blade can be resharpened on the same machine with minimal metal
removal, protecting your blade investment.
Each sharpener also has his own touch or feel for the sharpening.
You
should be prepared to interact a little with the person who sharpens your
skates. Hopefully, they will be willing to discuss any problems that you
perceive.
For
the first sharpening, find out how far off, if any, the blades are. Decide if you want them corrected in one
sharpening or over several sharpenings, or have your coach talk with your
sharpener and make these decisions.
Always leave your name and phone number with your skates to be sharpened,
in case the sharpener has questions for your sharpening.
Your
sharpener should keep detailed records of your skate sharpenings and be willing
to review them with you. After your
first sharpening, your sharpenener should be able to match exactly what you have
each time.
When
you buy new blades, take a few minutes to trace their contour on a piece of
paper. Occasionally, after sharpening,
compare each blade to this contour and note any visible changes to the rocker. In particular, if the same person has been
sharpening your skates, visible changes are something he would want to know
about.
How long should it take to break in newly sharpened skates?
Most
skaters are conditioned to expect a bit of an adjustment period after having
their skates sharpened. The common symptom is that skates feel
"grabby"; edges catch, and stopping is difficult. Skaters with newly
sharpened skates are often seen doing things like dragging their skates
sideways on the ice, running blocks of wood along their blades, etc., to dull
them into skateability. The correct
expectation is that properly sharpened blades should have little or no
adjustment period. They should never feel grabby. They should simply feel more
secure. (exceptions are those cases in which changes are made to a blade, such as
correcting previous sharpening errors or changing the depth of hollow, or
sharpening an exceptionally dull blade).
The
edge of a well sharpened blade should feel very smooth as a finger is run along
the edge; proper edge finishing will have removed the metal burrs that can
cause grabbiness, and give the edge a smooth, non draggy feel. Be careful: a
sharp blade can cut (though a well-finished blade is less likely to do so).
My blades feel and look sharp but they don’t feel secure?
This insecure feeling on sharp
blades can have several causes and possible solutions. Maybe you need a deeper hollow or the hollow
was made shallower on the last sharpening.
Talk with your coach and skate sharpener. It may be that you are ready for a deeper hollow. There are many pro and cons about using polish
on the last pass of the grinding wheel when sharpening skates. Many figure
skaters do not like the feel of a polished hollow. Decide on the use of polish for yourself, based on how it feels
when you skate and not on what others say.
How can I check or monitor the quality of my sharpening?
First,
you should be alert to any differences in the feel of the blade after
sharpening. Are your jumps or spins different?
Do the edges grab, especially one more than another? Discuss any feelings or differences with
your skate sharpener. This is where
having a sharpener, who also skates, will be a big plus.
Why use guards or soakers on my blades?
Guards should be used only when you
need to walk around when not on the ice.
Guards should not be on the blades any longer than necessary. Blades will start to rust in a very short
time when wet with the guards on.
Soakers should be on the blades anytime the skates are not on your
feet. Even though rinks have rubber
mats and various other materials around the rink to protect blades from damage
– NEVER walk on these materials with your blades. There is a lot of dirt from street shoes, etc. that will quickly
dull your blades.
How long should blades last?
If
I have previously sharpened a blade, I find that each sharpening removes only
about 0.001" of metal (a typical piece of paper is about 0.004"
thick) on a resharpening. If there is 0.1" of sharpenable depth on the
blade when new, this means that you might get as many as 100 sharpenings out of
a blade. With monthly sharpenings, this would give a blade life of up to 8
years. Sharpenings to restore edge level will take off much more metal. So will
sharpenings to change radius of hollow. I believe that skaters typically get a much shorter blade life, for various reasons. Still, a careful sharpener can do
much to prolong blade life and protect the skater's investment.
What are common sharpening flaws?
While
the goals for good sharpening are quite easy to quantify, skate sharpening is a
manual operation and as such is very much a "craft". The most often
seen flaw is unlevel edges. If the centerline of the grinder is not aligned
with the centerline of the blade, one edge will be higher (and
sharper/grabbier) than the other. The effect of this is that one edge will grab
while the other will feel weak. If really bad, the blade will pull to the right or
left.
To
achieve an even grind, the sharpener must move the blade along the rotating
wheel with constant force and speed. With time and repeated sharpenings, it is
possible that errors will accumulate and show up as uneven rocker. The degree
to which this happens is a measure of the skill of the sharpener. Sometimes a
particularly heavy hand in sharpening can alter this curve in one sharpening.
If when reading the
questions and the answers you have a question that is not answered or a comment
or suggestion on any of the responses, please email them to me. Send
Email Question or Comment.