Safety chain and rotatable devices, used on saws or other machines for cutting or abrading material, include a plurality of holding members on which replaceable teeth are retained. Safety lobes prevent the teeth from being dislodged during operation of the saw. The safety lobes may be disposed on a link located in front of the holding member or disposed on a link located in back of the holding member, or both. The teeth can include sharp edges adapted for cutting various materials including wood, plastic and metal and can be formed with abrasive surfaces for abrading materials including brick and concrete. The teeth are quickly removable from the saw without the need for fasteners. While the teeth may be retained by engagement between the teeth and holding member, the chain and rotatable devices may retain the teeth on the holding members using only the safety lobes or safety surfaces. The rotational device can include two blades each including holding members and safety lobes. The blades are positioned and fixed to each other effective to enable the safety lobes of one blade to prevent dislodging the of the teeth of the other blade. The chain and blades can include depth gauges or rakers. Saws or cutting or abrading machines are operated while preventing dislodging of the replaceable teeth. When the device is operated to stop movement of the chain or blades, damaged or worn teeth can be quickly replaced with new or replacement teeth.