Codger_64
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The use of modern fine blanking greatly reduced the secondary surface finishing required on blades and springs by eliminating the tear and break out on the sides of the blanks. But there were side effects of the fine blanking that required changing other processes. The fine blanking process caused the blank to have a lot of "roll" on one side (or somewhat of a radius), and a burr on the other. With the older blanking methods, if they did need to size their blanks to thickness, they could use a double disk grinder which would take the same amount of material off both sides of the blade. With fine blanking, they needed differential grinding, different stock removal on each side. A dual table flat grinder, Berger DRG (or DRS), was the machine Schrade chose. First, the blade would be run through a “Timesaver” flar belt sander to reduce the burr, then typically, they would put the burr side up on the first table and just take off enough to remove the burr and clean up the surface. On the second side, they would be grinding to the finished size. Fine blanking required the blade stock material to be thicker than conventional blanking because you needed enough stock to grind off all of the radius. It also was complicated by making sure they weren't grinding off the tang stamp. Schrade had 1 DRS (plc logic) and 2 DRG's (CNC). The CNC's with unique wheel sensing. I am told that these may have been the only two made this way. All the others before, and also since, had to have a sensor adjusted to each grind thickness manually and then they would grind until the sensor was reached. Schrade’s would sense after each grind and then grind to a set point based on thickness and wheel wear. With this difference it was a much quicker machine to change over.
There were several other reasons for surface grinding the blanks. First, with the advent of CNC equipment it became more and more important to put higher quality / consistant parts (thickness tolerance) into these machines. And second, often the coil stock would come in with tiny pits that were not noticed until after blade grinding and vibratory finishing. At first, they thought was caused by rust. But, after poring over the data, it was determined that mostly those blades that were not surfaced were having that problem. Going back through the processes, it was determined that the coil stock did contribute to the problem. Consistant stock material is important for consistant finished products.
Codger
There were several other reasons for surface grinding the blanks. First, with the advent of CNC equipment it became more and more important to put higher quality / consistant parts (thickness tolerance) into these machines. And second, often the coil stock would come in with tiny pits that were not noticed until after blade grinding and vibratory finishing. At first, they thought was caused by rust. But, after poring over the data, it was determined that mostly those blades that were not surfaced were having that problem. Going back through the processes, it was determined that the coil stock did contribute to the problem. Consistant stock material is important for consistant finished products.
Codger