Babbitt Pad Hell 2: The Saga Continues

POST DATE Feb 24, 2016

AUTHOR Udo Jahn

It was Sunday morning after a busy week when I finally sat down to write this blog article. All last week I was thinking about how to write it. Thank goodness we are in an electronic age, otherwise I would’ve had pieces of paper with half written articles on them torn up all over the floor. That would have been a mess. I spent a lot of time last week looking at a sawguide and babbitt pad sample recently sent to me by a new customer. When I opened the package, the first thing out of the box was an aluminum sawguide. I noticed that the back end was rather thin — thinner than I would recommend for an aluminum sawguide, and I wondered why. When I took out the babbitt pad, I realized the answer right away.

It’s time for me to write a sequel, like in the movies, where the characters remain the same but the circumstances are different. Welcome to a special screening of Babbitt Pad Hell 2. (You can catch up on Babbitt Pad Hell 1 over here.)

The babbitt pad from this sample was an impressive 1/2” thick (0.500”). It was pretty heavy and it must have taken a lot of babbitt to pour a set of pads. Needless to say, this sawmill must have a large inventory of babbitt material in order to make all their extra heavy babbitt pads. I wondered why they needed such a thick pad, since normally most babbitt pads are about 0.300” thick before they are ground on the babbitt grinder. These were a full 0.200” (almost a 1/4”) thicker.

As I continued examining the babbitt pad, I noticed that the babbitt pocket was very shallow. It was less than 0.016” after it was put on the babbitt grinder. This quickly indicated to me that this sawmill has some sawing issues. As I have mentioned in previous articles, a shallow babbitt pocket does not allow for the accumulation of coolant to properly cool the saws. This contributes to saws heating up more than normal. Over-heated saws have a tendency to fail because the heat causes them to lose tension. 

Now let’s get back to addressing the extra thick babbitt pad. Because of this extraordinarily thick babbitt pad, the babbitt pad mounting area of the sawguide sample was 0.400” thinner than it should be. Normally it would be thicker, when accompanied by a sawguide paired with a much thinner babbitt pad. On a steel sawguide, this isn’t as much of a big deal than with an aluminum one. Aluminum is not as rigid as steel so the thicker the babbitt pad area, the better. Having a thinner than necessary aluminum babbitt pad area of the sawguide leads to more flexing when side pressure is applied during the cutting of wood. Flexing of the sawguide can lead to sawing problems while cutting lumber. Let me rephrase that: it will definitely lead to sawing problems. 

The more I looked at this babbitt pad combination, the more I began to think about how this thicker than necessary babbitt pad came to be. Assuming that this particular combo of an aluminum sawguide and thick babbitt pad were not designed together, then it’s highly possible that the mold used for this babbitt pad was designed for another sawguide application. Since many sawmills these days are trying to save money, they probably used this existing babbitt pad mold for their new application. This saving of money by reusing parts/equipment/etc can be very good in some circumstances, but in this case it proved to be a very unwise move. 

In the end the logic of trying to save money can sometimes backfire, especially when the outcome causes more losses in time and money than the savings gained in the first place. As with many samples that come my way, there was more than one problem with this sawguide. But if I wrote about all of them, I’d risk turning this simple article into a book, so we’ll leave it at this for now. 

Just remember that an overly thick babbitt pad reduces the rigidity of a sawguide, especially aluminum ones. In the case of this customer, the mold should have been recycled instead of reused. But then what would I have to write about? Oh yeah, only the other 99 problems sawmills go through on a daily basis, right? Stay tuned… Babbitt Pad Hell may turn into a trilogy after all.

 

Author: Udo Jahn

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