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By Mike Wheat

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The Number 1 Factor Affecting Blade Performance is Coolant, Coolant, Coolant!

Here's a Top Ten List of why blades break: 
Number 10: Coolant. 
Number 9:   Really bad coolant.
Number 8:   No coolant to speak of.
Number 7:   Right coolant mixed wrong.
Number 6:   Wrong coolant mixed right.
Number 5:   Old coolant.
Number 4:   Good coolant mixed too thin.
Number 3:   Poor quality coolant.
Number 2:   Poor quality coolant mixed wrong.

  And the Number 1 reason why blades break is: 
See Number 10.

Really! In exhaustive tests performed at HE&M Saw Headquarters in Pryor, Oklahoma, we've shown that coolant quality has a direct effect on blade life.

Simply by using high quality, properly mixed coolant saw owners can extend blade life substantially.  Too many saws are operating with coolant designed (and mixed) for other 

machines.  While a particular kind of coolant may work miracles in a turning center, it could be disastrous when used in a band saw.

Let's look at it in another way.  In a lathe you have a fairly large tool removing fairly small amounts of material from the work piece. In effect, the tool is larger than the chip.  The tool and the work piece are directly exposed to flood coolant. The chips that are being removed are not as big as the tool. And the instant the chip is removed it is flushed away from the cutting action. The role of "coolant" in this application is largely just that - to keep the tool and the material cool.  In band saw cutting, the tool is very small.  Only the very tip of the tooth does much work. The rest of the tooth is designed simply to hold the tip in place. The chip remains curled up in the blade during the cut.

The chip being removed is larger than the tooth itself.  After the chip is removed from the work piece we still have the problem of getting the chip out of the cut and off the saw blade.  So we have a very small tool doing very heavy work.  The tooth has to work BURIED in the work piece away from much benefit of flood coolant. The role of "coolant" in band saw cutting is as much lubrication as it is cooling. Note that not all cutting fluids are suitable for all materials. 

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Cutting fluid also prevents chip welding to either the blade or the parent material by chemical and/or thermal interface.  When chips weld to the blade, the tooth form is changed resulting in cut deviation or lack of penetration. If the chips weld to the parent material, the usual result is a stripped blade.  

Cutting fluid lubricates the blade and, more importantly, the chips as they pass up into the gullets of the blade.  Cutting fluid tends to cool the blade and the material being cut by absorbing heat.  Heat is always generated because “work” has occurred from the cutting action as well as from friction.

Note that when wide material is being cut, the blade gets much hotter than when narrow material is cut.  This happens even when both materials are cut at the same rate in square inches per minute.

Cutting fluid is so important it cannot be over stressed.  A good quality cutting fluid in a band saw is one of the most important factors in straight cutting.  If cutting fluid is unable to cool the blade teeth, they will soften and become dull.  If the cutting fluid is distributed to only one side of the blade, the opposite side will become dull.  This will cause the blade to cut toward the side that has the most cutting fluid and the cut will be crooked.

 If we compare sawing to milling, we immediately see that in sawing there is much less room for the chip.  The chip must lodge in a small place between the teeth and be carried smoothly out of the cut.

In selecting a cutting fluid, pick one which is of high quality.

Without proper cutting fluid one of two things

 will happen.  First, the chip may become welded to the tooth.  This will change the form of the tooth, which, in turn, will change the amount of force required for the blade to cut. The result is an unbalanced blade that will produce a crooked cut.  

The second possibility is that the chip will wedge in the cut.  Since the chip is work-hardened and harder than the stock from which it came, the blade will cut into the stock beside the chip.  Again, the result is a crooked cut and a dull blade.

In selecting a cutting fluid, pick one that is of high quality.  Avoid thinly mixed soluble oils.  Some of the new synthetic oils are highly satisfactory in difficult operations.

If optimum cutting and blade life are the desired result, before selecting a cutting fluid and mixture for your saws, ask yourself the question, “Would I tap this material with this fluid?”  

Saw owners and operators may believe that we are over stressing the importance of coolant as a factor in good blade life.   But it is a fact that we have learned from more than 30 years of band saw experience, in the field, in our own shop, and in tests that we perform regularly

If you have additional questions about this topic, call or e-mail us today.