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Ron Chisholm's Skate Sharpening

Flat Bottom Skate Sharpening

Presented by:   Ron Chisholm - a dedicated hockey fan, parent of four players, past player and coach of many years, and expert skate sharpener since 1983.

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Flat Bottom Form Dressing

The hollow of a skate blade is not limited to a radius.  There is an infinite number of shapes that can be transferred to the bottom of a skate blade.  The idea of applying different types of shapes to the bottom of the skate blade was actually patented in July 1983 (US Patent No. 4,392,658).  One of these shapes incorporated a flat surface in the middle of the hollow, rather than just a circular hollow in the blade.  To the best of my knowledge, these shapes were never used on skates until recently.  Flat bottom sharpening is very different from standard radius of hollow (ROH) sharpening.  Essentially, a flat bottom with slightly higher edges is ground into the skate blade.  When skating, the blades don't cut as deeply into the ice, but sit on the flat profile giving increased glide and speed with less drag using less energy in the process.  When cutting, pushing off or stopping, the edges dig into the ice as they would with a standard hollow.

In the Fall of 2008, Blackstone began using what they call the Flat Bottom V (FBV).  This process has been incorporated into their spinner dressing system.  Each shape uses a separate (changeable) 1-1/4" spinner wheel to dress the sharpening stone.  Blackstone is currently marketing many different FBV shapes.  A few of these are shown below.


The numbers are meant to identify the width of the flat and the height of the edge.  For example, a 90/75 would have a flat width of 90 thousandths (.090 inches) and an edge height of 75 ten thousandths (.00075 inches).  Blackstone also sells a stand alone adapter (shown above) which can be used on other manufacturer's sharpening machines.  This adapter has no vertical height adjustment and is set for the standard wheel height of 4-1/2".  I feel that this is a deficiency as the actual wheel height varies slightly on different machines and I would like to get the wheel dressing as close to the center of the grinding wheel as possible.

Centering of the skate blade to the center of the grinding wheel along the entire length of the blade is critical.  Blade widths typically vary from .108" to .121", which means that an error as little as .004" could result in not having an edge on the blade.  This is only the thickness of a human hair.  In the worst case, there is no room for error at all, and you must be aware that the individual blades on a pair of skates may vary in thickness by as much as .005".  This makes the height adjustment of the skate holder much more critical for form dressing than it is for the standard hollow grind.

Blademaster has also created their own Blademaster Form Dressing (BFD) system which is independent of the finishing head and thus is available for almost all existing table top skate sharpening machines.  This dressing system can be used interchangeably with the conventional single point dressing arm on existing machines.  This option became available in September 2009.  The BFD system uses large 3 inch diameter diamond rolls to dress the sharpening wheel.  Blademaster has various Flat Bottom shapes available, 4 of which are shown below.  Also shown is the BFD dressing arm and the stand alone Multi Purpose Form Dresser (MPFD) for use with almost all sharpening machines.  Both of these dressers can be used for either Flat Bottom or standard Radius of Hollow (ROH) dressing.  Individual diamond rolls are available for each standard ROH as well as for each of the Flat Bottom shapes.  It should be noted that the MPFD does have a height adjustment to allow for the slight differences in the wheel height of various machines.  Follow this link to see a short video showing the use of the Blademaster dresser.



The flat bottom dressing is intended to increase the glide (and speed) of the skater without sacrificing cutting ability.  With a standard ROH, you must compromise between speed and grip/bite.  A shallow hollow gives better speed, but the deep hollow enhances maneuverability.  Flat bottom sharpening gives maximum bite with maximum speed/glide.

I offer the Blademaster Flat Bottom Form Dressing in addition to the standard ROH sharpening.  With the Blademaster BFD, all options X5, X6, X7, and X8 have enhanced glide - with different choices for bite, with X5 the most and X8 the least.  The most preferred option is the X7 cut, but it is still a matter of personal preference.  While it is impossible to correlate directly to a standard radius sharpening, the X5 cut will feel like a 3/8" to 7/16" hollow; the X6 will have a bite similar to 1/2" to 9/16"; the X7 feels like 5/8 to 11/16; and the X8 will feel more like a 3/4" ROH.  Radiused edges, when used in conjunction with a "flat bottom" will feel like a progressive bite and give the skater more control over the bite angle.  The enhanced glide that is achieved with the flat bottom sharpening will provide more speed with less effort as the friction is less and drag is reduced.  Speed is not lost as rapidly while gliding and, most importantly, because less effort is required to skate, there will be less muscle fatigue in the legs.  The most noticeable results are achieved by players who change from standard ROH cuts of 5/8" or less.

The beauty of the Flat Bottom Form Dressing is that you do not have to make a compromise between speed and maneuverability.  Adjusting to flat bottom is quick for most skaters.  In a matter of minutes, you will enjoy the benefits of increased speed and endurance while having the bite needed for quick turns.  Flat bottom sharpening does not alter the contour of the skate blade and probably removes less steel than a conventional ROH sharpening.  However, the choice is still up to the skater.  Standard ROH's are still offered as well as the options that are available for the Flat Bottom Dressing.

Additional Sharpening and Skate Information

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The information on this site has been collected from official scoresheets and from on ice observations.  As such, the final statistics are not to be construed as official or sanctioned by the Salem High School Athletic Department or by the NHIAA.  However, much of this information is not available from any other sources.

2020 Ron Chisholm & Associates
Salem, NH

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