So I got the aluminum device off ebay. With the Oregon aircut blade pictured and the recess on the back side shown in the picture it locates on the splines but just a tiny bit. Even without the blade the aluminum is thick enough so that the splined piece shown on the chainsaw file that puts real drive to both sides of an attachment can not do that. The other blade is a carbide tipped one that in my usage has made the ones that sharpen with a chainsaw file and benefit from setting the teeth obsolete A small picture and a larger one as a thumbnail
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