So repeated several times, until the blade sharp, come together, knife surface bright as a mirror.

如是重复几次，直至刀口锋利、崭齐，刀面光亮如镜。

youdao

Slit with thin blade (about 1 mm thickness), with function of automatic or manual grindstone to keep blade sharp and slit sheet smoothly and tidily.

采用薄刀分切(厚度仅为1毫米)、设有自动、手动砂轮磨削，保持刀刃锋利，使分切的纸板平滑整齐。

youdao

A sharp blade is likely to nick the skin and draw blood.

锋利的刀刃可能会划破皮肤，引起出血。

《柯林斯英汉双解大词典》

The blade is sharp on the inside of the curve, allowing the user to swing it through crops, cutting and gathering them at the same time.

FORBES: No. 6 The Scythe

Prosecuting counsel Karim Khalil QC had told the court Mr Reeve was savagely beaten and his face and torso scored with a sharp blade.

BBC: Kelly, left, and Jodie Barnes

He told the court Mr Reeve "was brutally beaten, cut with a sharp blade and left to die in his home, unable to summon help".

BBC: Barry Reeve