Dremel makes a line of ergonomic power tools for grinding, drilling and routing. The Dremel 770 is a cordless model with a rechargeable battery pack. Drill bits install quickly on the Dremel 770. Although it may seem like an involved procedure, the steps are actually simple but must be done in the correct order. The Dremel will not run if the bit is not seated and locked correctly.
Press the shaft-lock button on the front end of the tool on the same side as the sliding on/off switch.
Turn the metal collet nut counterclockwise on the tip of the tool.
Remove the housing cap (about the size of a nickel with a hole in the center) behind the metal collet nut by unscrewing it.
Pull the collet straight out from the shaft. The collet is a metal tube that holds Dremel bits securely when the collet nut is screwed in place and locked.
Choose a collet to fit the new Dremel bit you wish to install on the tool. The Dremel 770 comes with four sizes of collets. It's important to choose a collet and bit that fit well, but do not force the bit into the collet.
Set aside the new bit for a moment.
Slip the collet into the collet nut until it is flush against the nut.
Push the new Dremel bit through the collet and collet nut assembly.
Place the housing cap over the end of the tool and thread it loosely on the housing.
Insert the collet into the Dremel tool drive shaft and slide the collet nut over the threading on the end of the drive shaft.
Press the shaft-lock button on the side of the Dremel tool, turning the collet nut until it locks into place.
Release the shaft-lock button when it clicks.
Tighten the housing nut by screwing it onto the Dremel tool.