Subclass 1/28: Working stone or stone-like materials, e.g. brick, concrete, not provided for elsewhere; Machines, devices, tools therefor (fine working of gems, jewels, crystals B28D 5/00; working by grinding or polishing B24; devices or means for dressing or conditioning abrasive surfaces B24B 53/00) by impact tools, e.g. by chisels or other tools having a cutting edge (portable percussive machines B25D) without cutting edge