Tips to maximize bandsaw productivity: bandsawing is the starting point for many metal fabricating operations, so it can help determine the throughput and profitability of the entire shop. (Sawing).

However, maximizing the productivity and efficiency of your bandsaw takes a coordinated approach to sawblades, sawing machines, and your cutoff process. How do you get the most from your existing bandsaw? Ground-tooth blades, bandsawing analysis software, and good machine maintenance all pay off. So does the insight and assistance of a knowledgeable blade supplier.

Figure Cost-Per-Cut, Not Cost-Per- Blade

The truly accurate measure of bandsaw performance is not "just" the cost of the blade per part. Rather, it is the overall cost-per-cut (see sidebar), including labor, sawing machine burden, and blade costs. The cost-per-cut calculation divides the total cost over the number of good-quality finished pieces. Machine burden consists of the total cost of the machine and labor costs.

Blade costs spread purchase price over the number of pieces cut, and factor in the cost of downtime for blade changes. Together, they provide a meaningful picture of your bandsawing process.

An accurate cost-per-cut calculation can justify the greater price of higher performance sawblades that reduce cost-per-cut. One manufacturer of stainless steel components switched from bi-metal to carbide saw blades that cost about four times as much. The cutting rate accelerated from 1 sq. in/min. to 4 sq. in./min. and there was a 500 to 700% increase in blade life. The carbide blade paid for itself in the first year of operation.

Carbide blades can also open production bottlenecks, providing higher speeds to increase output and meet delivery schedules.

They can also justify themselves on metals too tough for less costly blades and ordinary equipment. Heat-treated alloys harder than Rockwell [45.sub.C] or alpha-case alloys harder than Rockwell [50.sub.C] are nearly impossible to cut with bi-metal blades. Carbide blades readily penetrate such materials and may give you a competitive cost-per-cut in the toughest jobs. One busy aerospace manufacturer switched from bi-metal blades to Bahco triple-set carbide-tipped bandsaw blades to cut tough titanium. The more expensive blades tripled output and lowered cost-per-cut by 90%.

Choose The Best Blade

The right blade for any given job is the one that minimizes overall sawing costs and maximizes productivity. The wrong blade erodes throughput, takes a toll on sawing machines, and risks an expensive workpiece. Even with the same basic construction, not all bandsaw blades are created equal. Ground teeth provide a uniform, precision edge that increases blade life 60% to 70 % compared with milled-tooth blades. Grinding eliminates variations in tooth height so that all the teeth encounter the same cutting forces and contribute to the cutting action. The fewer resulting blade changes reduce replacement costs and unproductive machine downtime. Lower cutting forces reduce machine wear and tear to impact bandsawing machine costs.

Choosing the best blade for your job depends on the machinability and surface condition of the material, and the geometry of the workpiece.

Aluminum and other soft, ductile metals produce low cutting forces and large chips. The most productive blade for such materials has deep tooth gullets to prevent clogging. By comparison, blades with harder teeth, tighter pitch, and smaller gullets best cut harder ferrous metals characterized by higher cutting forces and finer chips. Thin sheet, tube, or pipe is best cut with a uniform fine-pitch blade that resists tooth breakage and wear. Bundled shapes and profiles can be cut smoothly with variable pitch blades that nullify vibration.

Your choice of a sawblade also depends on the power and condition of your bandsaw machine. A coarse-pitch blade in a low-horsepower machine can cause the machine to stall. A 1 1/4" blade is likely to break in a 1" machine. Full-line bandsaw manufacturers can generally suggest the best blades for various jobs on your equipment.

Bahco developed its BandCalc software (patent pending) to help bandsaw operators choose the right blade and determine machining parameters for maximum productivity. The Windows[R]-based software prompts users to enter material properties, workpiece dimensions, and machine characteristics. Unlike simple catalog tables, the BandCalc algorithms select the best Bahco blade and calculate cutting data to optimize productivity.

Don't Coddle Your Blades

In bandsawing, running a blade too slow or at lower feed pressure to reduce wear is false economy. In today's high-productivity shops, a good rule of thumb calls for blades to last a full eight hours. If they last any longer, you can probably increase cutting speed to decrease your cost-per-cut. The key cost factor remains throughput, not blade cost.

To maximize productivity and optimize blade life, bandsaw operators should exploit the full machine feeds and speeds recommended by the manufacturer. Those guidelines define a productive cutting window. The window for a 1.5" blade cutting 4" diameter mild steel is relatively wide. In contrast, the window for the same machine cutting a 30" block of aged Inconel is nearly non-existent. A basic rule of thumb: optimum efficiency is achieved for cutting sizes up to 50% of the machine's maximum capacity.

BandCalc software was designed to define the optimum cutting window for a particular job. Within that window, bandsaw operators need to look, listen, and exercise their judgment to achieve the best productivity.

Look At Teeth, Chips, Workpiece

For an experienced operator, the appearance of the bandsaw blade, cut chips, or finished workpieces tells tales about machining data and machine condition. Blade teeth broken or stripped after a cut are often signs of excess feed or inadequate coolant. Scratches or scorching on the backing of the blade may warn of impending blade failure due to fatigue. They can be a call for blade guide replacement or other machine maintenance.

Chips that form neatly curled "sixes and nines" show a properly chosen blade cutting productively. Chips or cut pieces blue with heat discoloration, or smoke rising from the workpiece tell the operator to either slow the speed, reduce feed pressure or do both. Much as irregular chips can warn of blade wear, a crooked cut on the workpiece can be a clear indicator for blade replacement.

Listen To Your Saw

With your bandsaw blade properly tensioned and your feeds and speeds properly set, your sawing machine should cut without vibration, chatter, or screeching. Unusual noises mean problems. Harmonic sounds like a guitar strumming can signal machine troubles. Either blade tension is too low, or the distance between blade guides is too wide. Harmonics can also indicate problems with workpiece holders or that the blade has the wrong pitch for your workpiece.

Different from the low harmonics of a struggling machine, high pitched squealing warns of problems in chip formation. It signals micro-vibration that may be caused by incorrect cutting data, or by a coolant mixture too lean for the cutting job at hand. For some materials, high-frequency cutting noise is normal, but for others, it's a cue to change machine settings. If your bandsaw makes sounds different from what you heard the last time you cut that material, it may be time to change blades.

Other unusual noises can tip bandsaw operators off to machine or blade trouble. Clicking usually warns of a crack or some other irregularity in a moving blade. By being alert to the sounds and sights of your bandsawing operation, you can catch maintenance problems that compromise productivity.

Keep Blades Tight

Blade tension is one essential part of technically optimum cutting and generally should stay constant throughout the cut.

It is determined both by the bandsaw machine and the selected blade. Bahco field specialists typically specify 30,000 psi tension on machines using bimetal blades 1 1/4" or wider. The manufacturer usually specifies the right tension for narrower blades. While higher-than-usual tension may be appropriate for some hard-to-cut workpieces, it can reduce blade life. Inadequate blade tension can result in a crooked cut. Like all bandsaw parameters, the right blade tension is the one that provides the best combination of throughput, cut quality, and blade life.

Keep Machine In Shape

A properly maintained bandsawing machine is essential to quality cuts and optimum sawblade life. Carbide blades require a rigid machine with variable blade speed and variable feed rate and pressure. Bahco technical specialists routinely conduct a 12-point machine inspection. The process includes examining idler and drive wheels, guides, blade tracking, chip brushes, coolant, clamps, and feeds and drives. Regular attention to those items ensures the machine is up to the job.

Put Good Coolant Where You Need It

Recent Bahco tests showed D2 and D6 tool steels can be sawed equally well with and without cutting fluids. However, high quality coolants in the right concentration are essential to most cutting jobs. Cutting fluids contain lubricants. anti-weld additives, and wetting agents to reduce heat, extend blade life, and prevent thermal distortion of workpieces. While straight cutting oils may be necessary for some difficult-to-cut materials, fluid manufacturers of water soluble or synthetic oils recommend specific dilutions to optimize performance.

Putting your cutting fluid in the right spot is just as important as the right fluid mix. To maximize lubrication and heat dissipation, coolant nozzles have to flood the cut. Splashing fluid all over the saw does little to lubricate the workpiece. Likewise, popular mist cooling systems that fog small quantities of fluid on the blade may provide a cleaner workplace, but they do not dissipate heat. Sawing heat can warp thin workpieces. The optimum coolant solution depends on the sawing job, and like other process parameters, may require expert assistance.

Look For Help

Bandsaw users seeking maximum productivity and minimum cost-per-cut face bewildering choices in blades and cutting parameters. A working partnership between bandsaw users. and their blade suppliers can identify and implement process improvements.

For a major lift truck manufacturer, a comprehensive bandsawing analysis addressed not only blades, but also machine maintenance and sawing practices. The coordinated fixes effectively doubled throughput per workshift and slashed blade costs about 60%. With the new blade running, bandsaw output increased from about 300 pieces to nearly 600 pieces a day. Cutting speed nearly doubled, and the new blade lasted more than twice as long as its predecessor. Projected blade savings alone topped $15,000 over a full year.

By taking a coordinated approach to sawblades and sawing machines, you can make your handsaw operation more productive and competitive. The trick is to ask for help from a knowledgeable supplier. Bahco Tools, Inc.

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RELATED ARTICLE: Cost-Per-Cut Calculation

The Cost-Per-Cut calculation used by Bahco field representatives adds comprehensive sawing machine costs to blade costs. It divides the total cost over the number of finished pieces.

Machine Cost includes:

Capital cost of machine

Cost of workspace

Cost of power

Cost of labor

Blade Cost includes:

Cost of blade

Cost of blade change

Total Cost Per Piece = Machine Cost + Blade Cost