Removing the drive belt in a Bridgeport Milling machine can be a difficult process, but following the correct steps, you can have access to this belt for replacement in a relatively short time. Once you replace the belt, it will be even easier to reassemble the mill and you will have a stronger, more accurate response from the machine. Maintenance on a Bridgeport is essential due to the length of time these machines can last.
Adjust the Bridgeport to the low setting. Turn the machine on and switch it into low gear and lower the RPMs to the lowest possible rate. This will allow you to get to the belt easier and will make removing the belt easier as well.
Disconnect the power to the machine. Although these machines run on 220 volts, they are usually plugged into the wall and can be easily unplugged before starting the drive belt removal and replacement.
Remove the three screws and the plate on the bottom of the main drive head. You can use Allen wrenches for this, but make sure you place each set of screws in a special place and use the same screws when you reassemble the machine.
Compress the spring on the bottom of the head with thescrews that you have just removed and carefully rotate the speed changer. This will allow you to remove the belt housing.
Disconnect the screws on the top of the housing. Lift the drive belt mechanism up and place it on the rest area to the left of the housing. This will allow you to remove the old belt and replace it without completely removing the belt drive mechanism.
Remove the old drive belt by pulling it over the lower drive plate. Remove the entire motor at this point to get to the other end of the belt.
Remove the screws located above the other drive spindle and insert them into the threaded holes to lift up that bearing. This holds the other drive disc in place.
Remove the two large bolts holding the housing together. Also, remove the smaller screw located on the bottom underneath the motor housing, which you removed in Steps 3 through 5.
Remove the housing to expose the other drive disc and slip the drive belt over the top to remove. Place the new belt over the top of the drive disc and repeat the steps in reverse order to reassemble your Bridgeport mill.