The History of Thin Kerf Bandsaw Blades

by Tim Cook

TimThe thin kerf blade is a relatively young industry having its roots beginning around the 1970’s. During this time period most narrow blades being produced were for the metal bandsaw industry.  So as wood sawing blades were being developed, the technology was borrowed from these metal cutting blades. However, much of the terminology used to describe the wood sawing blades came from the wide band saw industry.

The wide band by that time had been perfected for many years with its swaged tooth technology.  So many people were looking at other ways to improvements. This led to industry leaders experimenting with using metal cutting bandsaw blades and merging that with the knowledge they had of wide band blades.  The ones who were able to make this transition possible were the wide band sawfilers, and through them many of the questions that were met in the transition were answered. It was also during this time when I was a young sawfiler myself that I came to have a good understanding of what did and didn’t work from the merger of these two industries.

Later into the 80’s and early 90’s when the first thin kerf sawmills were built they were very low in horsepower and using 1-1/4” wide blades with 3/4” tooth spacing.  25hp was about the largest mill produced and 19” band wheels were the common wheel of the day.  Many believed that 25hp was the most you could use without busting the thin kerf blades in two.  Of course, there were many things that weren’t exactly done right at that point like untrue band wheels, roller guides that were not true, rigid tension guides, and softer ‘flexback’ blades just to name a few.  All these things were the real culprits to breaking the narrow blades in two.

What the sawfilers knew was that in wide bands the blade that used a full configuration tooth (swaged tooth with no set) that it put 3 times the tooth load per square inch on the tooth compared to one with teeth that had set in them. The set teeth had no side load while the full tooth had load on both sides which contributed to the stretch of the blade. The set we now have in narrow blades is what makes them successful – left, right, and middle raker tooth setup.

While manufacturers began to understand the need for true wheels and guides the blades started running longer and faster, and as a result horsepower was increased.  Then, as the demand for more horsepower increased there was a need for wider blades so we could saw faster.

Keep in mind that the wider the blade the more surface area there is to control and therefore it is naturally easier to run a 1” wide blade than it is to run an 1-1/2’ wide blade for example. However, there is more performance potential in a wider blade as it can be pushed harder. 

What we discovered in the early 90’s through many, many hours of experimenting is that the trick is making the body of the wider blade as flat as possible.  To make this work we designed a roller machine that would flatten the blades.

 At that time it was believed that a person could not tension roll a narrow blade.  However, the wide band saw blades were rolled and tensioned every time they were serviced. This meant they were tensioned as a new blade before they were run and retentioned again after 2hrs of run time, and at that point it could run another 4hrs.  If a sawyer decided to run them 6 to 8 hours the blade would still be cutting straight but it would develop cracks in the gullet and fail.  The reason was because it was run too dull, and that caused too much tension in the blade – a recipe for cracking blades every time.

So at Cooks Saw we explored rolling and tensioning the narrow blades (this was unheard of in the thin kerf industry) which proved to be excellent for more production.  It took several years to perfect the exact method for these blades.  At first we tried to dish the blade .001 to .003 and lengthen the back of the blade; some worked great and some did not.  What we found was that it was different sawmill machine setups that caused this 50/50 success.  

We then concentrated on just getting the blade flat, and as a result we discovered something we didn’t expect, which turned out to be our key to success in making these blades perform; it is still something we hold as proprietary information to this day.

Later what we discovered with this perfectly tuned blade was that most of the sawmill machines out there were out of adjustment. They were out of adjustment because they were tuned to run imperfect blades.  When we started teaching people how to tune their sawmills then we had success we could repeat consistently.  Even with this success there were other issues in the thin kerf industry that had to be addressed as more people made the move from wide bands to narrow bands.

One of these issues was micro cracks in that would form in the gullet.  Many believed that it was a result of friction/heat caused by sawdust going through the gullet making micro cracks that ultimately caused blade breakage.  So the answer in the industry was to grind the gullets to get rid of these micro fractures.  This belief came from the wide band industry, however, this was found to be incorrect.  The theory was to grind the gullet to remove the damage that the heat had caused.  The obvious problem with this theory was that sawdust doesn’t get hot enough to cause that kind of damage, as a matter of fact if sawdust did get that hot it would combust in the cut. Another thing to consider is that grinding sparks are much hotter than sawdust being cut so if something is going to cause micro cracks it is grinding too much in the gullet. The theory had no real scientific grounding. 

One benefit that came from this thinking was that it made sawyers pull their blades before being stressed too much due to dull teeth and get them sharpened.  But the reason given was they were doing it to grind the supposed micro cracks in the gullet rather than for what they really needed to be pulled for; to sharpen the tooth. We have proved through numerous test that not grinding the gullet and simply sharpening the tooth improves blade life.  But we still hear this saying today about the gullets needing to be ground and people still follow it today, but many sawyers have overcome it and now concentrate on sharpening the tooth and let the gullet alone as much as possible. It is often hard to change our belief system when we have done it a certain way so long.

As many of these hurdles continued to be overcome the thin kerf industry also continued to increase in size and popularity with not only more thin kerf manufacturers but also sawmill manufacturers.  This has turned thin kerf blades into a major market in the wood industry. As a result more and more advancements have been made over the last few years with the introduction of wider blades and wider tooth spacing.  And like anything new these newer wider blades have issues of their own as the old school wide blade sawfilers know that the wider the blade the flatter the body must be. So the old adage holds true – ‘what comes around, goes around’ as we now see the wider ‘thin kerf’ blade becoming more popular.

With all that said, these thin kerf blades have come a long way since the 1990’s and we at Cook’s Saw will continue to push the envelope with blade performance innovation as we have done with introducing both the patented Turbo Tooth™ in the early 2000’s and the now the patent pending Super Sharp™. 

We hope that you will give us a try. We are continually growing and learning more as we strive for perfection in quality, service and price. We know there is always room to improve and we believe we are always improving. If you haven’t tried us in a while please consider us again. If you like a company that has leading edge technology,  will be honest with you, and tries to help you make more money, you will enjoy working with us.