Band Saw Blade for Aluminum: TPI, Material, and Cut Compatibility
You need to cut aluminum bar stock, angle, and tube on your band saw. You tried using your wood blade and it loaded up immediately, smearing aluminum across the teeth. You tried a metal cutting blade and it cut but left a rough finish. You need to understand what blade and technique will give you clean cuts in aluminum.
Aluminum is a soft, gummy metal that presents unique challenges for band saw cutting. The soft chips tend to weld to the blade teeth, loading the gullets and stopping the cut. The right blade, speed, and technique can prevent this and produce clean, efficient cuts.
Why Aluminum Is Difficult to Cut
Chip welding. Aluminum chips are soft and sticky. Under pressure and heat, they weld to the blade teeth and fill the gullets. Once the gullets are loaded, the blade stops cutting and starts rubbing, generating more heat and making the problem worse.
Heat buildup. Aluminum conducts heat well, but the cut zone can still overheat. Heat softens the aluminum further, making chip welding worse. The blade must clear chips fast and the cut must be lubricated.
Gummy material. Some aluminum alloys (especially pure aluminum and soft alloys like 1100 and 3003) are gummier than others. Harder alloys like 6061 and 7075 cut more cleanly. The alloy affects blade selection and cutting technique.
Blade Material for Aluminum
Bi-metal M42: The standard for aluminum cutting. The M42 edge is hard enough to cut aluminum cleanly, and the flexible backing withstands the blade flexing around the wheels. Bi-metal blades are available in all common band saw lengths.
Carbon steel: Can cut aluminum but dulls faster than bi-metal. Acceptable for occasional use on a woodworking band saw with speed reduction. Not recommended for production cutting.
Carbide-tipped: Overkill for aluminum. Carbide cuts aluminum very well but the cost is not justified unless you are doing high-volume production. For most users, bi-metal is the better choice.
TPI Selection for Aluminum
6 to 8 TPI: Thick aluminum bar (1 inch and up). Coarse teeth produce large chips that clear the gullets before welding. The aggressive bite prevents rubbing.
10 to 14 TPI: Medium thickness (1/4 to 1 inch). The most common TPI range for aluminum cutting. Handles bar, angle, and tube in most common sizes.
14 to 18 TPI: Thin material (under 1/4 inch). Fine teeth prevent grabbing in thin stock. Must use lubrication to prevent chip welding.
18 to 24 TPI: Very thin sheet and small tube. Fine teeth produce a clean edge but are prone to loading. Use with cutting fluid and slow feed.
Variable pitch (10/14 or 14/18): Good for mixed thicknesses. The variable pitch breaks up the cutting rhythm and reduces the tendency for chips to weld. A good all-around choice for aluminum work.
Tooth Profile for Aluminum
Hook tooth (positive rake): The aggressive bite shears aluminum chips before they can weld to the teeth. The best profile for aluminum cutting. Most aluminum cutting blades use a hook tooth profile.
Skip tooth (0 degree rake): The large gullet clears chips well. A good alternative to hook tooth, especially in softer alloys where the aggressive hook might grab.
Regular tooth (negative rake): Too conservative for aluminum. The negative rake resists feeding and promotes rubbing, which causes chip welding. Avoid for aluminum.
Speed Requirements
Woodworking band saws (3000 SFPM): Too fast for aluminum. The high speed generates excessive heat and promotes chip welding. You need a saw with speed reduction to cut aluminum effectively.
Metal cutting band saws (100 to 350 SFPM): The right speed range for aluminum. Most portable band saws and horizontal metal saws run in this range.
Variable speed saws: Set the speed to 200 to 300 SFPM for aluminum. Start at the low end and increase if the cut is clean and the chips are not welding.
If your saw only has one speed (woodworking speed): You can cut aluminum with a bi-metal blade and lots of lubrication, but the cut quality will be poor and the blade life will be short. For regular aluminum cutting, invest in a saw with speed reduction.
Lubrication
Lubrication is critical for aluminum cutting. It prevents chip welding, reduces heat, and extends blade life.
WD-40: The most accessible lubricant. Spray or brush it on the blade and cut zone during cutting. It works well for occasional use. Not ideal for production because it evaporates quickly and leaves a residue.
Cutting fluid (water-soluble): The best choice for production cutting. Flood the cut zone with cutting fluid using the saw’s coolant system. The fluid cools the cut, flushes chips, and prevents welding.
Wax sticks: Rub a wax stick on the blade during cutting. The wax provides lubrication without the mess of liquid. Good for portable saws without a coolant system.
Cutting oil: Works but is messy and can stain the workpiece. Better for steel than aluminum.
Cutting Technique
Feed rate. Feed steadily and consistently. Do not pause mid-cut, as this lets the blade rub and generate heat. Do not force the cut, as this overloads the teeth and promotes chip welding.
Break-in. Run the first few cuts at half feed pressure to let the blade teeth wear evenly. This is especially important for aluminum because a sharp blade with a feather edge is more prone to chip welding.
Clear the chips. If you notice the cut slowing down, stop and clear the chips from the blade teeth with a brass brush. Do not continue cutting with a loaded blade.
Support the work. Aluminum bar and tube can vibrate during cutting. Clamp the work securely to prevent vibration, which causes blade wandering and poor cut quality.
Aluminum Alloys and Cut Quality
6061 (structural aluminum): Cuts cleanly with 10/14 TPI bi-metal. The most common alloy for fabrication. Good chip formation, minimal welding.
6063 (extrusion aluminum): Slightly softer than 6061. May need more lubrication. 10/14 or 14 TPI works well.
7075 (aircraft aluminum): Harder and stiffer than 6061. Cuts very cleanly. 10/14 TPI bi-metal is ideal.
3003 (soft sheet): Gummy and prone to chip welding. Use 14/18 TPI with lots of lubrication. Slow feed rate.
1100 (pure aluminum): Very soft and gummy. The most difficult to cut. Use 14/18 TPI, slow speed, and continuous lubrication. Consider a circular saw with a carbide blade instead.
Cast aluminum: Brittle and abrasive. Cuts easily but dulls blades faster than wrought aluminum. Use bi-metal and expect shorter blade life.
FAQ
What TPI blade should I use for cutting aluminum?
For material 1/4 to 1 inch thick, 10/14 TPI variable pitch bi-metal. For thicker material (1 inch and up), 6 to 8 TPI. For thin material (under 1/4 inch), 14 to 18 TPI.
Can I cut aluminum on a woodworking band saw?
Only if the saw has speed reduction. Woodworking speed (3000 SFPM) is too fast for aluminum and will cause chip welding and poor cuts. For regular aluminum cutting, use a metal cutting saw.
Why does my blade load up when cutting aluminum?
Aluminum chips are soft and sticky. Under heat and pressure, they weld to the blade teeth and fill the gullets. Use lubrication, the right TPI, and a steady feed rate to prevent this.
What lubricant should I use for cutting aluminum?
WD-40 for occasional use. Water-soluble cutting fluid for production. Wax sticks for portable saws. Apply lubrication continuously during the cut.
What speed should I cut aluminum at?
200 to 300 SFPM. Start at the low end and increase if the cut is clean. If the chips are welding, reduce speed and add more lubrication.
Can I use a wood blade to cut aluminum?
No. Wood blades are carbon steel with tooth geometry designed for wood, not metal. Use a bi-metal blade with a hook or skip tooth profile for aluminum.
References
- LENOX Tools. “Aluminum Cutting Blade Selection Guide.” LENOX Industrial Division.
- MK Morse. “Cutting Non-Ferrous Metals on Band Saws.” MK Morse Company.
- Starrett. “Bi-Metal Blade Performance on Aluminum.” L.S. Starrett Company.
- The Aluminum Association. “Aluminum Alloy Properties and Machining Data.”
- Practical Machinist. “Band Saw Cutting Aluminum Tips and Techniques.” practicalmachinist.com.
