Woodworking Techniques and Advice
There are several factors that affect a wide belt sander’s ability to hold a close thickness tolerance. When a sander is new, with proper operating procedures, any rigid orifice-type machine should reasonably hold plus or minus .005” tolerance. If a machine has been specifically designed and has the right characteristics to hold a close tolerance, thickness tolerances of plus or minus .0025” are achievable. However, within a short period of time (less than one year), certain wear factors require machine maintenance procedures along with proper operating procedures in order to continue to obtain tight thickness tolerances.
In previous issues, we have addressed the following questions:
Table A allows you to compare abrasive belt mineral sizes based on several different grading systems. Please note that the P-designated belts (European grades) are a different mineral size than the X-designated belts (U.S. grades] except for 180 grit.
My first two articles provided depth of scratch and material removal information. Based on the depth of scratch, material removal data and the machine that you have, you can now determine what grit sequence should be used.
The biggest operating problem that I witnessed during countless plant visits was the use of excessive feed speeds. This resulted in abrasive belt loading, burning, streaking and shortened belt life, along with poor sanding quality. There were no guidelines provided by abrasive belt or machinery manufacturers.
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