My Oster A-5 motor runs normally, but when I engage the blades they do not function... ie. they do not go back and forth. I have used this clipper for several years and am familiar w/ its function. I do not think I am using it wrong.

All clippers run hot. Motor is enclosed, gearbox and friction all add to the heat.

ok the blade latch only holds the blade into place.

the hinge assembly which the latch sits behind needs to be open, there is a silver piece with two ridges on, place a flat bladed screwdriver behind the hinge and this will lever open you can then slot the blade onto the hinge and close shut with the clipper running.

the clipper must be running when you try to fit a blade, if its all pf your blades your having trouble with then the problem is with your clippers, its possible the black latch which you need to depress to release a blade is bocken, loock at the end and make sure there is a hook which catches the blade, look at the picture.

Check the two screws either side of the hinge assembly make sure they are tight, the problem appears to be with the clipper if all blades do the same.

There is a small gun-metal colored bar at the very rear, just below the back of the blade. It pushes inward, in the direction of the blade. Push it firmly in and pull up on the teeth of the blade. It should pop upward. You can then remove the blade from the tongue that it sits upon. When you want to put it back, slide the blade back on the tongue, then, WITH THE MOTOR TURNED ON, push the blade down to its seated position. It will click into place.

If the blade mover is going when you turn the clipper on than all you need to do is take the blades apart and clean them well with a Oster spray and then oil them. I would recommend cool lube.

ensure the blades are snapping onto the clippers if, they are the blade socket on the blade may be bent you can try replacing it yourself but they can be tricky.

If the power lever (the tab that moves the blade back and forth) is not moving with the blade off, chances are that you have a stripped bakelite gear. Take the two screws out of the cover plate and remove it. Remove the lever. Remove the link (the metal part that the lever connects with). Remove the bakelite gear (the part that the link fits down over). You should then be able to see if the teeth are chewed or worn off to the point that the armature gear will not turn the bakelite gear. If that is the case, replace the gear. Amazon carries both single speed and 2 speed gears under Oster A5 clipper parts.
Good luck.

You can get a wide varity of oster clipper heads at Sally's Beauty Supply. I am not sure where you live but they are in most citys.

Found another web site where some one had posted the information I needed. I just used Google search and found the information.