The full course on what’s actually under your feet — why ice is slippery, what a hollow really is, why edges die, and what a real sharpening involves. Short lectures up front. Full deep-dives underneath, if you want to nerd out with The Dude.
The Dude’s one-sentence truth: Sharpening isn’t a number — it’s a result. The entire war between bite and glide is fought over a few ten-thousandths of an inch of steel, which is why who sharpens your skates matters as much as what you ask for.
Start Here (60 seconds)
Tap your situation. You’ll get a fast answer and a pointer to the right lecture.
How this course works: every lecture starts with the bite-size version and a diagram. The “Go Deeper” drawers underneath hold the full science. Read as much or as little as you want — the page works either way.
U1
Unit One
The Science
Why skating works at all, and what a hollow actually is — lectures 1–2
1) Why Ice Is Slippery (The Real Answer)
You’ve been told it’s pressure. It mostly isn’t. Scientists are still arguing about this — that’s how deep this rabbit hole goes.
You don’t actually skate on solid ice. You skate on a microscopically thin, water-like film that sits on top of it — and your blade’s friction adds heat that keeps that film fed. Your edges manage that film. The hollow decides whether they bite through it or ride on it.
Go Deeper: The 170-Year Argument About Slippery Ice
The myth you learned in school: your blade’s pressure melts the ice into water. Plausible — and mostly wrong. Physicists Frank Bowden and T.P. Hughes ran the numbers back in the 1930s: a skater simply doesn’t generate enough pressure to meaningfully move ice’s melting point. On a cold rink, pressure melting can’t come close to explaining why you glide.
What’s actually going on — two mechanisms working together:
The quasi-liquid layer. Ice naturally carries a disordered, water-like film of molecules on its surface — even well below freezing. Surface molecules have fewer bonds holding them in place than molecules deep in the ice, so they stay mobile. Michael Faraday proposed this “premelting” idea in the 1850s, and modern instruments proved him right: the film is real, and it’s nanometers thick.
Friction heating. A moving blade generates heat, which thickens and feeds that lubricating film as you skate. The faster you move, the better it works — one reason skating feels different at speed.
And the argument isn’t over. Researchers were still publishing new models of ice friction in 2025. When the world’s physicists are actively fighting about what’s happening under your steel, “just sharpen them anywhere” starts sounding a little funny.
Why you should care: everything about your sharpening — hollow, edge quality, finish — is about controlling how two thin lines of steel interact with that film. Glide is your blade riding the film. Bite is your edge cutting through it into the solid ice below. The hollow decides how that tradeoff gets made.
2) The Geometry of the Hollow
Every hollow number is just the size of a circle. Small circle, deep valley. Big circle, shallow valley.
When we sharpen, we grind an arc into the bottom of your steel — a slice of a perfect circle, carved up into the blade. ROH (Radius of Hollow) is the radius of that circle. A 1/2" hollow means a circle with a half-inch radius carved the groove. Smaller radius = deeper groove = steeper, grabbier edges. Bigger radius = shallower groove = flatter, faster edges. That’s the entire system.
The number that should blow your mind: on standard hockey steel (about 2.9mm wide), a 1/2" hollow is only about 3 thousandths of an inch deep. The difference between a 1/2" and a 5/8" cut — a change every skater can feel — is about 6 ten-thousandths of an inch. Thinner than a sheet of paper. That’s the margin your sharpener is working in.
Go Deeper: The Actual Math (Depth, Bite Angle, and Why Weight Matters)
The depth formula. For a blade of width w and a hollow radius R, the depth of the groove is d = R − √(R² − (w/2)²). Plug in standard 2.9mm hockey steel and you get numbers measured in thousandths:
3/8" hollow≈ 0.0043" deep · bite angle ≈ 8.7° — maximum grab, maximum drag
1/2" hollow≈ 0.0032" deep · bite angle ≈ 6.5° — the youth/new-skater baseline
5/8" hollow≈ 0.0026" deep · bite angle ≈ 5.2° — the shop standard
1" hollow≈ 0.0016" deep · bite angle ≈ 3.2° — nearly flat, maximum efficiency
Bite angle is how steeply the edge corner meets the ice. Deeper hollow = steeper angle = the edge knifes into the surface harder when you lean. That’s your grip in a tight turn — and your drag in a straight line. You can’t have one without paying for the other.
Why your weight changes everything. Bite comes from your edge penetrating the ice, and penetration is pressure: your weight concentrated on a couple of millimeters of steel. A 70-pound youth player on a 5/8" hollow barely sinks the edge — it feels slippery. A 220-pound adult on a 1/2" hollow buries it — it feels like skating in glue. Same cuts, opposite experiences. This is why “what hollow should I get?” has no one answer — and why the matrices in the next lecture are organized by weight.
And why “sharp” isn’t one thing. The hollow sets the geometry — but level edges and finish quality decide whether that geometry actually reaches the ice. A perfect number with uneven edges feels worse than a “wrong” number done right. More on that in Unit 4.
U2
Unit Two
The Cut
Choosing a hollow, the FBV alternative, and the goalie exception — lectures 3–5
3) Choosing Your Hollow
One ladder, two directions. Everything else is tuning.
Hollows run from 3/8" (deep, maximum bite) to 1" (shallow, maximum glide). Shop standard here is 5/8" — and The Dude pushes most skaters toward the wider end on purpose: less drag, less leg burn, more speed, and edges that still hold when they’re finished properly. Youth and brand-new skaters start at 1/2".
Go Deeper: The Skater Matrix (Weight × Skill → Starting Hollow)
Find your weight row, then your stage. This puts you in the right neighborhood fast — the modifiers below fine-tune from there.
Skater Weight
Beginner / Learning Edges
Intermediate
Advanced / Efficiency
Under 80 lb
3/8–7/16
7/16–1/2
1/2–9/16
80–120 lb
7/16–1/2
1/2–9/16
9/16–5/8
120–160 lb
1/2–9/16
9/16–5/8
5/8–11/16
160–200 lb
9/16–5/8
5/8–11/16
11/16–3/4
200–240 lb
5/8–11/16
11/16–3/4
3/4–7/8
240+ lb
11/16–3/4
3/4–7/8
7/8–1
Read it honestly. Lighter players need deeper hollows to get the same penetration a heavier player gets for free. Stronger, more efficient skaters earn their way shallower — they generate their own pressure and want their speed back.
Go Deeper: The Modifiers — Ice Temperature, Style, and Season
The matrix gets you close. The conditions move you a rung:
Hard / cold ice (17–23°F surface — competitive hockey rinks): edges penetrate less → go one rung deeper.
Soft / warm / snowy ice (24–29°F — figure sessions, busy public rinks, summer): edges sink and drag → go one rung shallower. This is The Dude’s “summer cut” — about 1/8" wider than your winter hollow.
Heavy stop-start style (grinders, penalty killers): one rung deeper.
Most players never connect “the ice felt terrible today” to temperature. Now you can.
The Dude’s honest bias: most recreational players skate too deep. They asked for “sharp,” got a deep hollow, and have been paying the drag tax ever since. If your legs die before your lungs do, your hollow is a suspect. Use the Hollow Finder
4) FBV: The Flat Bottom V
A different answer to the same tradeoff — and an honest take on it.
ROH makes you choose a point on the bite–glide ladder. FBV redraws the blade instead: a flat channel ground up into the middle of the steel, with two fang-like edges left standing at the sides. On the glide, you ride the flat — minimal drag. On the lean, the fangs engage — real bite. Glide of a shallow cut, grip of a deep one. That’s the pitch, and when it’s cut right, it delivers.
Straight talk from the bench: FBV gets mixed reviews for two real reasons. The fang edges are finer than ROH edges, so when they take damage, they can chip in chunks instead of dulling gracefully. And it demands a highly skilled operator — a sloppy FBV is worse than a good ROH. If you try it, get it cut by someone who does it every week. (You know a guy.)
Go Deeper: FBV Numbers, the Official Equivalence Chart, and Who Should Switch
How it’s cut. FBV isn’t dressed onto the wheel with a single radius — the wheel is shaped by a profiled spinner that grinds the flat and the two fangs in one geometry. The numbers (90/75, 100/50…) describe that geometry: the family sets the flat width, the second number the edge profile. More flat = more glide; taller, steeper fangs = more bite.
The official Blackstone ROH equivalents — your translation table if you’re coming from a traditional hollow:
FBV 100/75≈ 3/8" ROH — maximum-bite end of the system
FBV 100/50≈ 1/2" ROH — bite-forward with a glide gain
FBV 90/1≈ 5/8" ROH — the balanced sweet spot, mirrors shop standard
FBV 90/75≈ 3/4" ROH — glide-forward with edges that still show up
FBV 95/50≈ 7/8" ROH — high-glide end of the chart
Who should try FBV: skaters fighting leg fatigue on deeper hollows, players on soft rinks who feel stuck, and anyone whose game lives on long strides and speed. Who should wait: skaters still learning edge control (simpler tuning beats clever geometry), and anyone without reliable access to a shop that cuts FBV consistently — because a half-skilled FBV erases every advantage on this page.
5) Goalies: A Different Course Entirely
Vasilevskiy and Hellebuyck — five Vezinas between them, opposite philosophies. There is no “goalie standard.”
Goalies load edges in two opposite ways. Shuffles and T-pushes want glide — a sticky shuffle ruins tracking. Butterfly pushes want bite — a slipping edge under lateral load is a goal against. And at the very top of the position, the philosophies split completely: Andrei Vasilevskiy attacks the crease on an aggressive deep cut — maximum bite for explosive butterfly pushes — while Connor Hellebuyck rides a shallow cut, trading bite for glide and economy of movement. Two of the best goalies on Earth, opposite ends of the hollow range. That contrast is exactly why goalie hollows start with a conversation, not a default.
Goalie rule of thumb: shuffles feel sticky → go shallower. Butterfly pushes feel weak or slippy → go one rung deeper. Change one rung at a time, same as skaters.
Go Deeper: The Goalie Matrix (Weight × Stage → Starting Hollow)
Goalie Weight
Developing (shuffle/T-push)
Intermediate (mixed)
Advanced (power butterfly)
Under 100 lb
3/4–1
5/8–3/4
1/2–5/8
100–160 lb
3/4–1
5/8–3/4
1/2–5/8
160–210 lb
3/4–1
5/8–3/4
9/16–5/8
210+ lb
7/8–1
3/4–7/8
5/8–3/4
Why developing goalies start shallow: young goalies move by shuffle and T-push, and glide is what makes those mechanics learnable. As the butterfly push becomes the primary weapon — driving hard off the inside edge — bite starts paying for itself, and goalies trend deeper.
Goalie modifiers: sticky shuffles → one rung shallower. Weak pushes → one rung deeper. Hard ice → deeper. Soft ice → shallower. Unstable recoveries → check edge level first, then consider slightly shallower.
U3
Unit Three
The Steel
What your runners are made of, why edges die, and when to come in — lecture 6
6) Steel, Wear & When to Sharpen
Edges don’t “wear out.” They get murdered — slowly by ice, instantly by concrete.
Under a microscope, a fresh edge is a crisp corner of steel. Every stride abrades it; every hard stop rolls it over a little. That’s the slow death: 10–20 hours of ice for a typical player, faster with hard stops, heavy volume, or dirty ice. Then there’s the fast death — one step on concrete, one hit on a goal post, one nick from another blade in the bag. Damage is damage. A skate sharpened yesterday can be dead today.
Go Deeper: Steel Metallurgy — Why Some Runners Hold an Edge Longer
Hardness is the whole story, and it’s measured in Rockwell (HRC). Most stock runners are stainless steel in the 50–55 HRC range — corrosion-resistant, tough, easy to sharpen, but quicker to dull. Premium runners use higher-carbon alloys like 440C (roughly 1% carbon, 16–18% chromium) that heat-treat to 58–60 HRC — measurably harder steel that keeps its corner noticeably longer between sharpenings.
Coatings push it further. Carbon-infused and DLC (diamond-like carbon) coated runners add an ultra-hard skin over the steel — manufacturers claim up to ~30% better surface strength, which shows up as edge retention, corrosion resistance, and a touch more glide. The black runners you see in the NHL aren’t a fashion statement (well, not only a fashion statement).
The tradeoffs nobody mentions: harder steel costs more, takes slightly longer to sharpen, and at the extreme end can be more chip-prone on impact. For most players, the honest math is hours-between-sharpenings: if upgraded steel stretches your cadence and your edges feel consistent deeper into the week, it pays for itself. The Dude stocks and installs upgraded runners — ask at your next sharpening and we’ll fit it to your holder.
Go Deeper: What Actually Kills Edges (and How to Slow It Down)
Abrasion: every stride grinds microscopic steel away against the ice — faster on dirty or artificially hard ice.
Edge rolling: hard stops and explosive starts fold the microscopic corner over sideways. The steel is still there; the corner isn’t.
Impact damage: posts, other blades, the bench gate, that one step across the lobby. Nicks turn a clean glide into a bumpy one and can cause a sudden, mid-stride slip.
Rust: water sitting on steel pits the edge overnight. Pitting is permanent — sharpening can grind past it, but that’s your steel’s lifespan being spent on a preventable mistake.
The care routine that costs nothing: wipe the steel dry after every skate, use cloth soakers in the bag (rubber guards for walking — never for storage, they trap moisture), and walk on mats like your edges depend on it. They do.
Cadence guidance: every 10–20 hours of ice is the working rule. Heavy stop-start players and skaters on cold, hard ice live at the short end. Light-use recreational skaters can stretch toward the long end — but if you can’t remember your last sharpening, it’s overdue.
Bring it to the bench: if your last sharpening is more than ~15 ice-hours behind you — or your steel touched concrete even once — the cheapest performance upgrade in hockey is waiting in a shed in Annandale. Book a Sharpening
U4
Unit Four
The Craft
What a real sharpening involves — and why “same number” doesn’t mean “same result” — lecture 7
7) What a Real Sharpening Involves
The number on your ticket is one step out of six. The feel comes from the other five.
“Getting a 5/8” sounds like one action. It’s actually a process — and every step is a place where a careless shop loses your edge. Here’s what happens to your skates in the shed:
Go Deeper: Each Step, and Where Bad Sharpenings Are Born
1. Inspect. Nicks, rust, edge level, steel height, holder condition. Skipping this is how a damaged blade gets a “normal” sharpening that fixes nothing.
2. Cross-grind (only when needed). A vertical wheel flattens the skating surface to erase deep nicks, rust, or a botched previous cut — a clean slate. Doing this when it isn’t needed wastes your steel’s life; skipping it when it is needed buries damage under a fresh hollow.
3. Dress the wheel. A diamond-tipped dresser carves your exact hollow radius into the spinning grinding wheel. This is the step where your “number” actually lives — a lazily dressed wheel cuts a sloppy hollow no matter what the dial says.
4. Grinding passes. Multiple light passes along the blade. Light matters: pressing hard generates heat, and overheated steel loses its temper — permanently softer, dulls faster forever. If you’ve ever seen blued steel after a sharpening, you’ve seen a blade get cooked.
5. Finish pass. A final featherweight pass with the wheel’s rotation leaves a smooth, consistent surface in the hollow. This is the difference between edges that feel silky and edges that feel grabby on day one.
6. Hand finish + level check. Sharpening raises a microscopic burr along each edge — left on, it makes a fresh cut feel unpredictable, grabby, then suddenly dull. It comes off by hand with a stone. Then the level check: both edges must be exactly the same height. Uneven edges are the single most common reason a sharpening “feels wrong” — one direction turns great, the other washes out, and players blame the hollow.
Why this is the whole ballgame: hand a perfect wheel to a careless operator and you get a bad sharpening. Machines — pro-shop or home units — are tools. Home machines like a Sparx are legitimately good at repeatable maintenance cuts; what they can’t do is steps 1 and 6: diagnose why a skate feels off, fix a leveling problem, or decide your hollow should change because your ice did. That judgment is what you’re actually paying a sharpener for.
U5
Unit Five
The Clinic
Symptoms, safe changes, and the reference desk — lectures 8–10
8) The Troubleshooting Encyclopedia
Find your symptom. Apply the smallest effective change first.
Not enough bite — slipping, washing out
Most common root causes: too shallow for your weight and ice — or a leveling/finishing issue impersonating a hollow problem.
Washes out in turns: go one rung deeper (5/8 → 9/16) and have your edge level verified.
Stops feel sketchy or long: deepen one rung — or you’re simply overdue. Check your hours.
Only the outside edge slips: that’s an edge-level red flag, not a hollow problem. Fix the level before touching the number.
Hard pivots feel unsafe: deepen one rung and confirm finishing quality.
Too much drag — stuck, heavy legs, no glide
Most common root causes: too deep for your weight, or soft ice multiplying your drag.
Feels stuck: go one rung shallower (1/2 → 9/16 → 5/8).
Legs burn before lungs: classic too-deep symptom — shallower, or consider the FBV lecture above.
Unexpected grab on glides: usually a leftover burr — a finishing fix, not a new number.
One skate feels different than the other
This is almost never a hollow problem. It’s leveling, centering, or finish consistency.
Left grips harder than right: verify both blades are level and the hollow is centered on the steel.
One skate chatters: inspect the finish on that blade; re-finish.
Different every time you get them done: your shop has a process problem. Find one with quality control — and a memory.
Damage — nicks, rust, sudden slips
Damage makes a perfect cut feel terrible. Solve the damage first; judge the hollow after.
Sudden slip after a collision or a step off the mats: check for a nick — run a fingernail along the edge. If it catches, sharpen.
Bumpy glide: micro-nicks. Inspect under bright light.
Rust spots: dry your steel after every skate. Pitting permanently shortens your steel’s life.
Goalie-specific — shuffle glide vs butterfly bite
Sticky shuffles: go shallower — the 3/4–1" neighborhood exists for a reason.
Weak butterfly pushes: one rung deeper at a time.
Unstable recoveries: edge-level check first; then consider slightly shallower.
9) Changing Cuts Safely + Your TSD Profile
Tuning is a discipline. Here’s the protocol — and how we keep your answer on file.
One variable at a time. Don’t change hollow, profile, and steel in the same week — you’ll never know what worked.
One rung at a time. 5/8 → 11/16 → 3/4. Skipping rungs tells you nothing and risks a wasted month.
Give it a full skate. A correct change can feel weird for a session. Unsafe (can’t stop) is the only reason to bail early.
Symptoms are signals. Slipping → bite or leveling. Stuck and burning → drag. Inconsistent → process, not number.
The Edge Owner’s Cheat Sheet
Baselines
Shop standard: 5/8" — most skaters belong here or wider
Cloth soakers in the bag — never store in rubber guards
Walk on mats, period
Or skip the homework: every customer gets a TSD profile — your hollow, your steel, your history, what you liked and didn’t. You never have to remember your number again, and your edges feel the same every single visit. Consistency is the real product.
10) Glossary: Pro-Shop Terms → Human
So you can talk edges with anyone — including us.
ROHRadius of Hollow — the radius of the circle ground into the bottom of your steel. Smaller number = deeper cut = more bite.
FBVFlat Bottom V — flat glide channel with two fang edges; glide of a shallow cut with the bite of a deep one. Demands a skilled operator.
BiteHow strongly your edges resist lateral slip when you lean and load them.
GlideHow efficiently the blade rides the ice — low drag, low fatigue.
Bite angleHow steeply the edge corner meets the ice. Set by the hollow; measured in single-digit degrees.
Quasi-liquid layerThe nanometers-thin, water-like film on the ice surface that makes skating possible at all.
Level edgesInside and outside edges at exactly the same height. The hidden driver of how every sharpening feels.
Burr / deburrThe microscopic ragged lip raised by grinding — and its removal by hand. Skipped deburring = grabby, unpredictable edges.
Cross-grindFlattening the skating surface on a vertical wheel to erase damage before cutting a fresh hollow.
DressingShaping the grinding wheel with a diamond to your exact hollow before it ever touches your steel.
You now know more about skate sharpening than 99% of the people in the rink — including some of the people doing the sharpening. Bring the knowledge, or just bring the skates. Call/text (301) 660-7321 or book below.
Sharpening dude is the best he’s been consistent and he is so customer friendly his ability to
Sharpening dude is the best he’s been consistent and he is so customer friendly his ability to work with you and get you. Your custom blade. Sharpening is outstanding. I’ve been going to him for the past two years. He never quits and he is truly a champion.
Ordering process was straightforward. Easy to select options with provided information. Steel runners look and perform great. Only criticism is the notification process from order processing to order shipment.
John is so kind and does such a good and thorough job. He works those blades in a flash but carefully attends to the details and answers questions about his work with confidence and experience. I brought three pair of figure skates today and was in and out quickly and most satisfied. So glad to be a customer.
Thank you so much for squeezing us in last minute! What a difference having my daughter's skates sharpened by a professional made. We appreciate the affordable pricing! We enjoyed meeting you and appreciate your friendly and positive demeanor. We will definitely come again and pass along your name to others.
