The whale-noko needs frequent sharpening, thankfully its quick. Perhaps you can hear that some of the teeth in the center are harder than the others? I start with a small square file to form both facets of the chone-gake. At the moment I’m using a 100mm yasuri to file the top bevel that forms the edge. This is a normal sharpening, only some of the chone-gake need adjustment, there’s enough set for many sharpenings, and the top bevel haven’t become too wide to require cutting down of the major tooth angles. I use a coarse diamond plate for jointing the tooth line. Soon to come, video of the saw at work.