The Scary Impact of Inaccurate Sawguides to Your Bottom Line

POST DATE Mar 16, 2016


This subject has been on my mind for a long time, stemming from my interactions with new clients. They always wonder why they are experiencing sawing problems. After looking at the problem from a few different perspectives, they still couldn’t figure out what was causing their issues. They saw some or all of the following problems:

  • Increased within-board deviation
  • A hard time starting up their edger, so they needed to increase the clearance between the babbitt pad and the saw. Some needed to use 0.005" or more, when the standard is 0.0015"
  • Saws were heating up and folding over
  • Poor lumber quality
  • Poor saw performance
  • Inconsistent or hard to control gap between the babbitt pad and saw (even when they purchased a new babbitt grinder)
  • Quality control was harassing them

I added the last one because the quality control department is responsible for making sure customers get top quality lumber and if the customers aren’t happy, quality control isn’t happy.

In my case, I usually start off by taking a look at the sawguide.

Since more than 75% of the sawguides being made today are aluminum, let’s start with them. Even without looking at samples, my standard question is to ask if the sawguides are accurate. Inaccurate sawguides will cause many of the problems above. Most people have not checked their sawguides for a long time. Typically, they measure them and discover that their sawguides are varying quite a lot. This is the cause of their problems and it stems from their sawguides being worn out.

The best remedy for this is to buy new ones. Usually this would be the end of the blog post, but not today. The problem is that the industry is experiencing an alarming trend. Sawguides purchased within the last six months to a year are varying more than they should. 

Usually more than 50% of the sawmills that have recently purchased new sawguides did so after approving a drawing provided by the vendor. If this isn’t happening at your sawmill, it’s a good time to start. Checking the drawings of your new sawguides can prevent a lot of problems from occurring, like getting the wrong target size (the critical thickness). The thickness tolerance (or variation allowed) of the critical thickness, which determines the target size, is crucial in setting your babbitt to saw clearance on your babbitt grinder. This is extremely important!

A common process in the manufacturing of aluminum sawguides is to machine them, then anodize them to size. In the past, when steel sawguides were manufactured, you needed to grind them after machining. Getting an unground steel sawguide was unacceptable because straight machining cannot give an accurate steel sawguide. The same holds true for aluminum sawguides. Aluminum sawguides need to be honed in order to get the same accuracy that is achieved in the grinding of steel sawguides. In other words, anodizing sawguides to size yields an inaccurate sawguide which can and will cause sawing problems.

If you look at an aluminum sawguide drawing that gives a tolerance of the following measurements (below), then most likely (okay, very likely!) these sawguides were anodized to size and are not properly finished like ground steel sawguides.

  • +/-0.002" (believe it or not I have seen this one - maybe it should have its own blog post!)
  • +/-0.001"
  • +/- 0.005"
  • +0.000", -0.005"
  • +0.005", -0.000" 

I do realize that you can buy these sawguides a lot cheaper but you would be sacrificing accuracy and they could cause serious manufacturing problems. It’s a decision that you should think about if you have purchased these sawguides in the past. The savings of today may not be worth the costs of tomorrow, especially if you are getting some or all of the problems that were listed above.

Just remember to check the target size tolerance on the sawguide drawings. If you don’t look at the drawings, then start now. It’s critical that you know how a sawguide is being manufactured. The tolerances on your sawguide, otherwise known as the allowed thickness variation, is one good way of knowing how your sawguide is being manufactured. The more you know, the more you’ll save in the long run.


Author: Udo Jahn

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