I just received an email from a friend who recently visited a troubled sawmill. This sawmill has unfortunately been experiencing a lot of problems with their saws getting very hot and underperforming. Underperforming is not an accurate description of what is really going on. In reality, this sawmill’s saws are losing tension and folding over on a regular basis. This has been going on for years without a remedy in sight. I cannot even imagine the level of frustration of the people working at this sawmill. I suppose it becomes a normal occurrence after awhile and people just learn to live with it.
My friend told me that the mill has tried everything to solve the problem. The solution they ended up implementing was to use a large amount of coolant at a very high pressure in an attempt to prevent the saws from heating up. This helped a bit, however the saws still eventually lost tension and folded over from the heat.
After examining the sawguides, my friend discovered something that seems to be a recurring theme in many sawmills that have experienced this problem: a wonky babbitt pad. Right off the bat he noticed that the babbitt pad had a very narrow deep slot, otherwise known as a coolant pocket, with only two small coolant holes in it. Since the pocket was very deep, it could never properly fill up and cool the saws. Having only two coolant holes did not help either. Most babbitt pads and sawguides have 3 coolant holes to fill the pocket. But in this case, even if the pocket had been the right depth with the 3 coolant holes, it was still too small and therefore ineffective at cooling the saw.
A small pocket area indicates that the balance of the babbitt pad is solid babbitt, which is the large surface that comes in contact with the saw. The higher the area of babbitt contact with the saw, the more friction generated. This increased friction causes a lot more heat to be generated than a babbitt pad with a small contact area.
The big picture of this situation is that the saw was experiencing higher heat from the increased contact friction, and also experiencing poor cooling due to the ineffective babbitt pocket.
This theme in sawmills seems to be becoming a bigger problem than I had originally thought. Very few companies are addressing these poor babbitt pad designs. It seems that the more sawmills are trying to increase speeds and feeds in lumber cutting, the worse this problem gets. It is obvious that babbitt pads need to be addressed more than ever today. Higher speeds and feeds will cause even more heat. Poor babbitt pad design and ineffective cooling is going to cause saws to fail more often due to the increased heat as sawmills try to run higher feeds and speeds.
My friend suspects he will be encountering more and more of this issue in regards to poor babbitt pad design moving forward. He is also having a hard time convincing many sawmills that this babbitt pad problem is the source of their issues. I would like to say that most of the incidents are being caused by older sawguide designs with mold-on babbitt pads. However, we are also seeing it in newer installations where the sawmill has been adjusting target sizes by using spacers to increase it, or by milling off portions off the sawguide to decrease the target size. If this is not properly done, then the coolant pocket may become ineffective.
If your saws are heating up and folding over, then one of the areas to look at is definitely your babbitt pad. The pocket might be ineffective in cooling your saws, or your babbitt area surface is too large and causing unnecessary friction. This Babbitt Pad Hell ends up causing nothing but problems for a sawmill if not corrected, so keep your eyes as sharp as your saws and watch out for this issue in your mill.
Interested in more about babbitt pads? Check out Babbitt Pad Hell 2: The Saga Continues.
Author: Udo Jahn
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