Measuring the profile and rocker of ice skating blades
Note: This information first appeared as a series
of posts in the Skatingforums.com
website. These were in responses to a thread started by member "Agnes Nitt"
(forum name) in the
Pro Shop section back in December 2015.
The work presented here was an attempt to
carefully measure the rocker, and the entire blade profile, of a figure skating
blade. I tested a new-in-the-box 10-1/2" Jackson Ultima Synchro blade that I
The photo below provides a quick overview of the measurement fixture.
The machined miter slot in my table guides a sliding miter bar (an Incra Miter
Slider) mounted on the underside of the jig to limit motion to one dimension.
The miter bar fit in the slot is adjustable to minimize measurement errors.
I took rocker depth measurements each 1/2" of blade length, and compiled them
into a graphic/regression program (Advanced
Grapher v. 2.2). After the points were plotted and the vertical scale
changed to visually exaggerate the rocker depth, I ran a curve-fitting routine
on it. The resulting curve is a very good fit with an R^2 value of 1.0013. The
resulting formula in case someone wants to duplicate this on a CNC machine is...
You can visually assess the close fit between the two curves overlaid in the
graph below. Blue represents actual blade measurements, and pink is the plot of
the regression formula above.
Standard deviation is only 0.001" - better than most manufacturing tolerances
can be held.
Then I plugged the Cartesian coordinate numbers shown in the table into an
online calculator to find the rocker between the 1" from tail to the 5.5" from
tail section of the blade. The web calculator is found at
The rocker measured 7.5' on the Jackson Ultima Synchro blade.
The advertised rocker is 8'.
These rockers are the primary skating rocker that
is mentioned in the specifications for figure skating blades.
Rockers at various points along the blade
The useable blade ends at the root of
the toe picks at the 10.9" mark, so this starts almost an inch back
from the picks. I just picked the location based upon my own
spinning technique. It arcs upward fairly quickly to the toe picks
beyond that, and we never spin there.
Here's what I found using a 2" "sliding window" along the blade.
Rockers were measured starting from the tail of the blade...
2"- 7.58' rocker near the tail of the blade
6"- 9.25' (the blade flattens out a little here)
7"- 9.81' (still a little flat here too)
8"- 3.08' (rocker shortening toward toe pick as expected)
9"- 1.48' (17.67 inches) rocker approaching the toe picks
I didn't have the data an hand for the rest of it up to the picks,
but by now we are well into the spin rocker and closing in on the
toe picks where blades see little use.
Recognize that with a smaller window comes less measurement
precision. However I believe the flatness evident around 6-7 inches
could be real. If that's the case, it appears that the transition
between glide rocker and spin rocker is not a perfect tangent
between the two arcs. It was probably put there when the blade was
factory sharpened. Of course the next sharpening will change
everything again anyway, so I wouldn't read too much into it.
We page created by
January 31, 2018