My job as a technician at Dixon Abrasives is to make sanding make sense. This is not as simple a task as most people would think. Every part of the sanding process must work together to accomplish a few simple tasks.
Trouble starts when taking off more than a belt can handle, or taking off more than the scratch pattern of the previous head. These are the most common mistakes in sanding.
Overtaxing a sanding belt will allow the material being sanded to push against the grains and resin coat, heating up and degrading the belt. This not only destroys the belt, but it also starts the heat and compression that destroys the surface of the wood.
When enough material is removed by subsequent heads to get past the existing scratch pattern, the head is driving the grains through solid wood below the original peaks and valleys. Tremendous heat and pressure is the result. This is very important to understanding proper use of abrasives in a wide belt machine.
If a wood surface has been sanded with 120, 150, 180 grit, and the sander was properly set up, the scratch pattern afterward will be very shallow. This scratch pattern only requires about .001” to be removed to get to the bottom of the valleys. If the part is then run back through that same grit sequence and another .010” is removed, .009” of that material is solid wood. This represents a huge amount of mass being removed.
If the surface was sanded to 80 grit, .008” stock removal is required to touch the bottom of the valleys to get rid of the scratch. If the 120, 150, 180 grit sequence is then used to remove an additional .014” (the real depth of the 80 grit scratch) (120/.008”, 150/.004”, 180/.002”) most of the stock removed is just scratch pattern and air…..
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