Why can I bench more on machine than I can on free-weight benching?!

Best Answer - Chosen by Voters

Machines have gears and pulleys and it doesn't necessarily take 120 pounds of force to lift the 120 pounds of weights.
Also, machines limit the range of motion so that you don't have to use any supporting muscles to balance and control the weight.
Free weights give you a superior exercise. I suspect your main problem is that you're not used to the motion and your supporting muscles are weak. If you stick with it, I'll bet you can get up to 120 lbs on the free weights within six weeks.

When you use the machine, your muscles have full focus on moving in once plane of motion. When you to the bar, some of your muscles must stabilize and cannot contribute as much to lifting the weight.

Think of it like your car. You have an engine with a lot of power, but not all of that power gets to the wheels. Some of it is used to power the power steering pump that helps you control the car. If the engine didn't have power steering (because you were only going in a straight line), more power would go to the wheels.

The machine controls the direction of the weight, forcing you to move only one way, this is harmful because everyones body is built differently and has slightly different form.

Free weights have a different range of motion and can be more difficult.

Its like a 35lb dumb bell and a 35lb kettle bell are very different, for example.