Bi-Metal Band Saw Blades for RC60 Steel: TPI, Material, and Cut Compatibility
You need to cut RC60 hardened steel on a band saw. You have been using bi-metal blades for mild steel and they work fine, but RC60 is a different animal. You are not sure if bi-metal blades can handle it, what TPI to use, or what blade life to expect. You need a guide that tells you what bi-metal blades can and cannot do with RC60 steel.
RC60 steel has a Rockwell C hardness of 60. This is harder than mild steel (typically RC 20 to 30) and harder than most stainless steel (RC 25 to 35). Bi-metal blades can cut RC60 steel, but with significant limitations. Understanding these limitations is essential for getting acceptable results and not wasting money on blades that dull after a few cuts.
What RC60 Steel Is
RC60 (Rockwell C 60) is a hardness rating, not a specific steel alloy. Steel can reach RC60 through heat treatment, case hardening, or through-alloying. Common RC60 materials include:
Tool steel: A2, D2, O1, and S7 tool steels heat-treated to RC 58 to 62. Case-hardened steel: Low-carbon steel with a carburized surface layer at RC 60. Spring steel: 1095 carbon steel hardened to RC 55 to 60. Bearing race: Hardened bearing steel at RC 58 to 64.
RC60 is hard enough that standard carbon steel blades cannot cut it. The blade edge is softer than the workpiece and will dull immediately.
Bi-Metal Blade Edge Hardness
Bi-metal blades have an M42 high-speed steel edge hardened to 67 to 69 HRC. This is harder than RC60 steel, so the blade can cut it. But the margin is small.
M42 edge: 67 to 69 HRC. Can cut material up to about RC 38 to 40 efficiently. Above RC 40, cutting is possible but blade life drops significantly.
M51 edge: 69 to 70 HRC. Slightly harder than M42. Better for RC60 but still limited. Expect 20 to 30 percent longer life than M42 in RC60.
The problem: At RC60, the blade edge is only 7 to 9 HRC harder than the workpiece. The blade can cut, but the edge wears fast because the hardness margin is small.
TPI Selection for RC60 Steel
10/14 Variable Pitch (Bi-Metal M42 or M51)
Best for: Solid bar and thick stock (1/2 to 2 inches). The variable pitch breaks up vibration, which is critical in hard material. Vibration causes edge chipping, which destroys the blade quickly.
14 TPI (Bi-Metal M42 or M51)
Best for: Medium thickness (1/4 to 1 inch). Finer teeth engage more teeth in the cut, distributing the load. This reduces the force on each tooth and helps prevent chipping.
18 to 24 TPI (Bi-Metal M42)
Best for: Thin material (under 1/4 inch). Fine teeth prevent grabbing in thin hardened material. But expect very short blade life.
Rule for RC60
Use a finer TPI than you would for mild steel. More teeth in the cut means less force per tooth, which reduces chipping. For 1-inch RC60 bar, use 14 TPI instead of the 10 TPI you would use for mild steel.
Tooth Profile for RC60
Hook tooth (positive rake): Not recommended for RC60. The aggressive bite can chip the edge in hard material.
Skip tooth (0 degree rake): Better. The straight-up tooth engages the material with less force, reducing chipping risk.
Regular tooth (slight negative rake): Best for RC60. The negative rake scrapes rather than bites, which is gentler on the edge. Slower cutting but longer blade life in hard material.
Blade Life in RC60 Steel
| Blade Type | Expected Cuts in 1-Inch RC60 Bar |
|---|---|
| Bi-metal M42, 14 TPI | 5 to 15 |
| Bi-metal M51, 14 TPI | 8 to 20 |
| Carbide-tipped, 14 TPI | 50 to 150 |
| Carbide-grit | 30 to 80 |
Compare this to mild steel, where a bi-metal M42 blade might make 50 to 100 cuts in the same material. RC60 reduces bi-metal blade life by 80 to 90 percent.
Cutting Technique for RC60
Speed
Run at the slowest speed your saw allows. For RC60, 30 to 60 SFPM is ideal. If your saw’s minimum speed is 100 SFPM, use it. Higher speed generates more heat, which softens the blade edge.
Feed Pressure
Use light, steady feed pressure. Do not force the cut. Forcing the cut in RC60 will chip the blade edge immediately. Let the blade cut at its own pace, even if it is slow.
Lubrication
Use cutting fluid or sulfurized cutting oil. Flood the cut zone if possible. Lubrication reduces heat and helps prevent chip welding, which is a major cause of blade failure in hard material.
Blade Break-In
Break in the blade with 2 to 3 very light cuts in mild steel before cutting RC60. This rounds the feather edge and helps prevent chipping. Skipping break-in in RC60 will reduce blade life by 50 percent or more.
When Bi-Metal Is Not Enough
If you are cutting RC60 steel regularly or in production quantities, bi-metal blades are not cost-effective. The blade life is too short.
Carbide-Tipped Blades
Carbide teeth are 90+ HRC, which is 30 points harder than RC60. Carbide cuts RC60 efficiently and lasts 5 to 10 times longer than bi-metal.
Cost: 60 to 200 dollars depending on size. When to switch: When you cut RC60 more than once a week, or when the cost of bi-metal blades exceeds the cost of one carbide blade.
Carbide-Grit Blades
Carbide-grit blades have no teeth. The edge is coated with carbide grit that grinds through the material. They are ideal for very hard or abrasive materials.
Cost: 40 to 100 dollars. When to use: When the material is too hard for toothed blades, or when the surface finish does not matter.
Alternative Methods
If band saw cutting of RC60 is too slow or too expensive, consider:
Abrasive saw: Cuts RC60 with a grinding wheel. Fast but rough cut. Generates heat that can affect the heat treatment.
EDM (Electrical Discharge Machining): For precision cuts in hardened steel. Slow but produces excellent surface finish with no heat-affected zone.
Annealing: If the application allows, anneal the steel to RC 30 to 35, cut it with bi-metal, then re-harden. This is only practical if you have heat-treating equipment.
FAQ
Can bi-metal band saw blades cut RC60 steel?
Yes, but with significant limitations. Blade life is 80 to 90 percent shorter than in mild steel. Use M51 bi-metal, fine TPI, slow speed, and cutting fluid.
What TPI should I use for RC60 steel?
Use a finer TPI than for mild steel. For 1-inch RC60 bar, use 14 TPI. For thinner material, use 18 to 24 TPI. More teeth in the cut means less force per tooth and less chipping.
How long do bi-metal blades last in RC60 steel?
Expect 5 to 15 cuts per blade in 1-inch RC60 bar with M42 bi-metal. M51 bi-metal gives 8 to 20 cuts. Carbide-tipped blades give 50 to 150 cuts.
What speed should I use for cutting RC60?
30 to 60 SFPM is ideal. If your saw’s minimum speed is higher, use the lowest available speed. Higher speed generates more heat and shortens blade life.
Should I use carbide-tipped blades for RC60?
If you cut RC60 more than once a week, yes. Carbide blades last 5 to 10 times longer than bi-metal in RC60 and are more cost-effective for regular use.
What is the best tooth profile for RC60?
Regular tooth (slight negative rake). The negative rake scrapes rather than bites, which is gentler on the edge and reduces chipping in hard material.
References
- LENOX Tools. “Cutting Hardened Steel with Bi-Metal Blades.” LENOX Industrial Division.
- MK Morse. “Master Cobalt Blade Performance on Hardened Steel.” MK Morse Company.
- Starrett. “Bi-Metal Blade Specifications for Hard Materials.” L.S. Starrett Company.
- Sandvik. “Band Saw Blade Technology for Hard Materials.” Sandvik Materials Technology.
- Practical Machinist. “Cutting RC60 Steel on a Band Saw.” practicalmachinist.com.
