This professional tool from Homenkol makes unbelievably sharp plastic scrapers in seconds. Precise height-adjustable blade allows for perfect sharpening every time and a 4-sided blade that can be rotated ensures long use before having to re-sharpen. Scrapers are guided along a fence to keep them perfectly flat and straight. Comes with a clamp to solidly anchor it to a bench or table.
Pricey, but worth it.