These are the top five sawing mistakes that can cost you blades.
When we sat down to write this article we set out to identify a handful of sawing mistakes, and we came up with almost 60. And for each problem, there are as many as ten causes. Mistakes are common and predictable, but they’re also preventable; with the economy recovering and factories coming back to life, this is no time for slip-ups. So let’s sink our teeth into the top five sawing mistakes that waste material, time and destroy blades.
Saws are very much like the people who use them; they don’t react well to heat, shock, abrasion, stress or tension. Here are some tips and advice to extend blade life, make better cuts and improve productivity.
1.FEELING PRESSURE TO PERFORM? We all feel the need for speed but your blades can really feel the heat when you run them too hard or fast. Excessive feed rate, pressure and speed can damage or destroy your blades. Running a blade too fast or pushing material too hard can dull blades, break teeth, snap welds or crack the blade’s back edge. Chip welding can also be a problem. A blade works by removing chips from the material being cut; if the blade runs too hard, heat from friction welds those chips into blade gullets, filling the indented space between blade teeth. When the gullets circle back around there’s no place for the chips to go and that leads to bad cuts, stripped teeth and cracked gullets.
SOLUTION – Know the material you’re cutting and set your machine to the correct blade speed and cut rate. As a general rule, slow the blade for tough materials and increase speed for softer material. Check your operator’s manual or the feed rate chart on your machine for specific information. Ask your bandsaw blade sales representative if their company offers free, online educational resources and calculators that can help determine correct cutting procedures.
2. KEEP YOUR COOL. When a blade overheats, its teeth wear faster, materials chips weld into blade gullets and it all leads to worn out bandsaw blades and poor cuts. Cutting fluid is a critical part of the operation because it cools the blade, lubricates the teeth and washes away chips. Cutting fluid needs to be mixed with water, and it has its own special formula when to use it for sawing versus grinding and general machining. You will need a richer cutting fluid mix when you use it on bandsaws. A rich solution does a better job coating and lubricating the blade throughout the entire cut.
SOLUTION – Coolant should wash over the blade as the bandsaw blade enters and exits the cut. Coolant is re-circulated and used continuously throughout the cutting process, but be sure to replace water that evaporates from the mixed solution. You should also be on guard for chips that fly into the system and block coolant flow. Watch for system leaks, which can also be a problem.
3. GIVE YOUR BLADE THE BRUSHOFF. Most machines have a rotating wire brush that sweeps material chips out of blade gullets while the bandsaw blade is making its cut. These chips could get welded into the gullets if the blade runs too hard, hot or fast. The brush should be positioned close to the drive wheel so it can continually whisk away debris. When we make shop visits, quite often we see poorly adjusted brushes that are set too far from the blade to do any good — the brush tips don’t reach far enough into the gullet. We’ve also seen machines with no brushes at all, which is a big and all-too-common problem.
SOLUTION – The brush needs to be close enough to the blade for the filaments to effectively remove chips from gullets. But don’t set the brush too close to the blade because the hard-hitting filaments could prematurely dull bandsaw teeth. A brush set too close to the blade could also wear itself out and quickly become useless. The brush should reach in and touch, but not go beyond the deepest part of gullets.
4. DON’T BE TENSE. Hypertension isn’t good for anyone or anything, especially your bandsaw. Blades that are either too tense or too loose can cause problems, so make sure your blade is in a nice state of equilibrium. Most bandsaws work best with blade tension set to a minimum of 25,000 pounds per square inch (p.s.i.) or a maximum of 32,000 p.s.i. Anything less than 25,000 leads to poor beam strength, band fatigue or crooked cuts; more than 32,000 and you could break the band, crack the gullets or wear out machine bearings.
SOLUTION – Use a gauge to measure and properly set blade tension. If you don’t have a gauge or don’t know how to use it, give us a call and we’ll give you a free check and help you correctly set blade tension.
5. APPLY THE BREAKS. Just like a new car or pair of shoes, you need to break-in your blade. This will “hone” the teeth and extend blade life. Think of brand new blade teeth as freshly sharpened pencil tips. If you press down too hard on a pencil, you’ll break off its tip. A bandsaw tooth reacts the same way. Excessive feed pressure breaks pointed edges of bandsaw teeth.
SOLUTION – The best way to break-in new bimetal blades is to reduce the normal feed rate by half during the break-in period. Band speed isn’t what breaks teeth during blade break-in; pressure from excessive feed rate is the most damaging dynamic. You will greatly improve the life of your blade if you take the time to break it in properly.
A handy formula for breaking in bimetal blades:
– Break-in rate: 50% of recommended blade feed rate
– Break-in formula: multiply the recommended blade speed by 25% and cut that number of square inches
Recommended blade feed rate: 200 feet per minute
– Break-in for 50 square inches
Recommended blade feed rate: 100 feet per minute
– Break-in for 25 square inches
For long life, make sure your blade tension is right – usually between 25 k.p.s.i. and 32 k.p.s.i. But check with your blade manufacturer to confirm the values for your blades.
Once you approach the end of the break-in period, you can gradually bring your bandsaw feed rate back to normal. It is true that some blades are broken in at the factory, but we recommend that you still use our break-in formula to make sure your blade is honed to perfection.
As the economy begins to improve, factories are under increasing pressure to perform. But even as you work hard to keep pace, there are no shortcuts to optimal performance – yours or the blade’s. Take time to get the information you need to do the job right, and cut out those mistakes.