I have a Nicholson #50 rasp that I've had for many years and used it to the point that it became almost worthless. I sent it off to Boggs Tools and they re-sharpened it so well that it's better than it was when new. I'm impressed since they only charged $8:50 for the work. The bad news is that the postage totaled up to $20 + change. A new #50 is around 70 to 80 bucks so it's still a good deal.
https://boggstool.com/
https://boggstool.com/