The Bottom Line about Sawing Straight - Part 1

by Tim Cook

Tim Cook

It was 1992 and we were selling a lot of thin kerf blades to the portable sawmill industry.   I had a customer in Tomball, TX that had a Cook Sawmill and a LT 40 WM sawmill.  One day he called me and said that he had received some blades that would not cut. He sharpened them and set them and they just would not cut. However he had a box of blades that cut really good from the last order.

I was getting reports equal to his from time to time and I wanted to find out the reason for the variance in saw quality and it led us to believe that there were batches of good steel and bad steel in those days due to these types of results.  But that answer just wasn’t satisfactory and I wanted to solve the mystery. I had spoken to the factory that made the blades, (we welded the blades) and the factory wanted to solve this mystery as well since they felt confident in the material itself. But the fact was they were also getting reports from other distributors.

I asked this customer in Texas to send me all of the bad blades back as well as one that was cutting good.  When I got them I cut them into 12” pieces, labeled them, and sent some of the pieces to the factory for analysis. I got the call from the factory who was very puzzled with the results. They reported that the blades had been put through every test they had – hardness test, chemical analysis, electron microscope (to verify sharpness), and blade flatness test check; the results were that the blades were identical. Regardless of the test results we all acknowledged there was still an issue that had not yet been identified.  I despaired because I had great regard for their ability to test the blades accurately.

I pondered this issue for quite some time hoping to come up with an answer to no avail.  I finally decided to put some of the good cutting pieces on my desk to my right and some bad to my left. I told myself that I would leave them there as a reminder that I would search for the answer until I found it.

I spent a vast amount of time studying the physics of steel and found this action in steel to be what is termed ‘Anticlastic Curvature’.  Now I knew what to call it and what to do about fixing it.  So I designed a machine that would dish the body of the blade to reflect what I saw in the good cutting blade, giving it that slight curvature in the body. I looked over all the pieces and saw that the blades with the crack of daylight dish on the inside ran very good and the blades that were dished on the log side would not cut at all without diving.  I got excited at this point because I felt I had found the solution. I started planning on how to make all the blades saw straight every time.

One day I picked up the good cutting blade piece and for some reason I put a straight edge across the width and was surprised to see that it was not flat as I had presumed.  There was a light ‘dish’ on what would be the inside of the blade if it were on the sawmill.  I quickly reached for the bad cutting piece and put the straight edge on the same side of the blade and found the exact opposite.  I then contemplated and remembered that the factory said that it met factory specs.  So they had a + or – tolerance that they felt was acceptable but these blades represented the extreme of the + and – tolerance.  I believed at this point that I was on to something.

I then took the bad cutting blades that the customer returned and put them through the machine and then sent them back to Tomball, TX.  Not too long after I got a call from the customer and he reported that the blades cut as good as the best he had ever seen!  I knew then that I had discovered the solution to the mysterious problem of blades not cutting good even when they had been sharpened and set properly.  But this was just the beginning of a lot of experimentation.

The blade flattening worked 90% of the time but I was seeing some variation in the field, so I began to hunt for the reasons. Working with several thousand blades and a lot of sweat I found that every sawmill was aligned differently.  I also found that many mills made by major mfgs were set up much different from each other.  Some correct, some a little out of alignment and some grossly out of alignment.  All would cut differently when a good flat blade was installed.  I also found out that people would not believe me if I told them what I was doing to the blades so I started calling the rolling of the blade a MC process, MC standing for Molecule Change.  Over 6 years of experimenting and fine tuning the process we have learned exactly what to do that will work every time and improve production with accurate cuts.  In some cases we have doubled many customers’ production.

We have been sharing this information for several years to help sawyers improve sawing and have been 100% successful when the sawyer is willing to follow the rules; we have it down to a physical science with 5 steps to straight sawing.

We find that there are many people being misled by some of the sawmill mfgs.  Here are some of the Myths being told:

  • Myth #1 - You should never roll a blade, or you should not have to roll a blade
  • Myth #2 -  Steel wheels cause the curvature, that’s why a blade needs rolling
  • Myth #3 - Belted wheels do not cause anticlastic curvature

In the next issue I will address all of these.

In the meantime here is something to consider: Out of all of the people who believe in rolling and do not believe in rolling I have learned how to qualify them as they usually qualify themselves. They usually say something like “I have never rolled a blade or tried to roll or flatten a blade, BUT I don’t think you should have to.”  They just qualified themselves. They know nothing on the issue because they have never been concerned enough to do any research or development.  I on the other hand have been using and perfecting this technology for 20 years and have spent several hundred thousand dollars in research and development concerning flattening and sawing very fast.  Just because a man has been sawing for 15 years or a manufacturer has been in business x number of years does not mean they understands the flatness issues.  However, if a person considers the true facts and uses the knowledge that Cooks Saw has shared he will find that this information is very accurate and will improve production. 

Sometimes it is good to be stubborn, but it is plain foolish to be wrong and stubborn.  I think I am very stubborn but I want to know truth and be accurate with information. We do a lot of experimenting before we share technology because we want to lead people in the correct direction.

If it wasn’t true we wouldn’t promote it and we certainly wouldn’t waste our time rolling blades; we would simply just go with the easy and much cheaper belted wheels.  But we just can’t do that.