MRO Magazine

Answers: Bandsaw productivity quiz

1. (D) An accurate measure of bandsawing cost-effectiveness is more than the cost of the sawblade spread over the number of cut parts. Blade manufacturers calculate overall cost-per-cut, including labour, sawing machine burden and blade cos...


February 1, 2004
By MRO Magazine

1. (D) An accurate measure of bandsawing cost-effectiveness is more than the cost of the sawblade spread over the number of cut parts. Blade manufacturers calculate overall cost-per-cut, including labour, sawing machine burden and blade costs. The result amortizes the total cost of the job over the number of good-quality finished pieces.

2. (B) The choice of bandsaw blade pitch is generally based on workpiece size. Rule-of-thumb calls for a pitch that keeps at least three teeth in contact with the workpiece at all times to dissipate chip loading forces and prevent tooth breakage.

Thick-walled pipe greater than 2 in. dia calls for relatively coarse pitch blades with few teeth per inch. By comparison, thin-walled tubes or pipes are better cut with fine-pitch blades packing more teeth per inch to prevent tooth breakage and wear. Bundled tubes or pipes call for variable pitch blades that nullify vibration in stacked workpieces.

3. (C) High-quality cutting fluids in the right concentration are usually essential to most bandsawing jobs. Like other sawing operations, bandsawing aluminum typically requires water-soluble or synthetic cutting oils diluted around 10-to-one.

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Cutting fluid specially formulated for aluminum contains anti-weld additives that keep chips from adhering to blades and extend blade life. Abrasive aluminum particles also promote blade wear, so cutting fluids must be changed more frequently than those used to cut steel.

4. (D) While bandsaws might cut free-machining steel productively at around 300 sfpm, the recommended speed cutting wrought aluminum shapes is 500 to 1,000 sfpm. Cutting speeds of only 40 to 50 sfpm with bimetal blades or 60 to 70 sfpm with carbide blades maximize throughput and blade life when cutting superalloys.

At too high a feed rate, blade teeth can chip as they enter hard workpieces. Feed rates per tooth are consequently less with cutting superalloys versus mild steel. However, with insufficient feed pressure, both superalloys and titanium work-harden.

Bandsaw operators should seek a uniform chip load to keep the blade from sliding unproductively through the cut. Actual settings inevitably vary with the alloy and the workpiece, but feed speed and pressure should be adjusted to “pull a chip” at all times.

5. (D) Trick question. Any of the remedies might increase blade life. However, running a blade slower or at low feed pressure to reduce wear is a false economy.

In high-productivity shops, a good rule of thumb calls for blades to last about eight hours. If blades last longer than a work shift, you can probably increase your cutting speed to decrease your cost-per-cut. The key to productivity remains throughput, not blade cost.

6. (C) Harmonic sounds like a guitar strumming can signal trouble. They can warn that the blade tension is too low, or the distance between blade guides is too wide. Blade manufacturers typically specify 30,000 psi tension on machines using bimetal blades 1-1/4 in. or wider. Low frequency sound can also warn of incorrect blade pitch or cutting data, or a coolant mixture too lean for the cutting job.

7. (B) Aluminum and other soft metals produce low cutting forces and large chips, and are best cut with bimetal blades having deep tooth gullets to prevent clogging.

Carbide-tipped blades provide the best abrasion resistance for high-speed cutting, however not all bandsawing machines and operations can use them effectively or economically. Blades with harder teeth, tighter pitch and smaller gullets are best suited for cutting harder ferrous metals characterized by higher cutting forces and finer chips.

8. (C) Ground bimetal blades with precise, uniform knife-edge teeth increase blade life 60% to 70% compared with milled bimetal blades. They also reduce cutting forces to improve the quality of the finished work and reduce wear-and-tear on sawing machines.

When cutting relatively soft titanium, for instance, sharp, ground bimetal blades can provide higher cutting speeds and greater productivity than milled blades.

9. (A) Blade manufacturers’ technical representatives can help define a window for efficient tube and pipe cutting.

Bandsaw operators sawing tube and pipe can estimate cutting data from catalog charts. However, chart data is based on cold-finished, fully annealed solid bar stock. Generally, optimum cutting rates for tube or pipe stock will be less than those quoted for solid shapes.

Proprietary software is available to help bandsaw operators choose the right blade and determine machining parameters for maximum productivity cutting pipe and tube. The most advanced programs prompt users to enter material properties, workpiece dimensions and machine characteristics. More than simple catalogue tables, today’s sophisticated algorithms select the best blade and calculate cutting data to optimize productivity.

If you scored 8-10 out of 10, congratulations, you are getting the best productivity out of your blades. Keep up the good work.

If you scored 5-8, you are doing okay, but don’t overlook opportunities to improve productivity in your operation. If you want help, ask a knowledgeable saw blade supplier.

If you scored 0-4, you are not realizing the full productivity potential of your bandsaw blades. Ask your blade supplier for help — there’s a lot to be gained.