| 摘要 |
PURPOSE: To suppress the fall of a signal level and to improve the SN ratio by forming ruggedness sized >=1μm in desired positions between the gap forming surface of an I core and the edge on an opposite side. CONSTITUTION: A mask 5 having holes 6 is brought into contact with or is adhered to the I bar 30 of a GB bar 3 consisting of a U bar 31 and the I bar 30 and thereafter, the GB bar 3 is fixed to a working surface plate (not shown in Fig.). Next, an opening 8 of a nozzle 7 is set above these holes 6 and a cutting agent 4 is blown toward the holes 6 from the aperture 8 of the nozzle, by which the cutting agent 4 past the holes 6 of the mask 5 forms plural pieces of the ruggedness only in the desired positions of the I bar 30. Sand blasting or powder beam processing, etc., are used as the method of blowing the cutting agent 4 toward the holes 6. The cutting agent 4 is silicon carbide of mesh #400 to #3000 or is a mixture composed of abrasive grains of alumina, etc., and gas or liquid. The surface roughness of a work is made into about 2μm with mesh #1000 and into about 1μm with mesh #2000 if the work is ferrite.
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