What is backlash in machining?

Question

somebody said about backlash when using a miling machine. What's that suppose to mean?

thanks.

Answer 1

Its to do with the gears. When you set the dial to move something you must be already going in the direction you intend to move. If you change direction, there is a certain amount of movement on the handle that actually does nothing until the backlash is taken up.

The manufacture tries to minimize gear backlash but its unavoidable so you have to understand that it is there for accurate machining.

Answer 2

Backlah comes from the space between the gear teeth. If the gears wear there is a larger space. When you turn the head back and forth when the machine is off you can hear where the gears make contact. That is the lash in the gears. Some people will quickly turn the machine in reverse to stop it quicker and this will increase wear and cause backlash.

Also if you have a motor that moves backward and forwards all the time the backlash will increase over time with wear until it start to be noisy like the motor and gearbox we changed on Friday.