GlossaryKind of term: Manufacturing termThin wall
What is a thin wall?
A thin wall deflects or vibrates noticeably under cutting or clamping force; whether a wall is thin depends on thickness, height, material and support.
Besides cutting and clamping force, stress released as material is removed can also distort the wall. There is no fixed limit in millimetres. For a wall held along one edge, stiffness grows roughly with the cube of the thickness and falls with the cube of the height, so a wall twice as tall is far more flexible. A floor between pockets machined from opposite sides counts as a thin wall too. There is no drawing symbol for it.
What does the behaviour of a thin wall depend on?
How a thin wall behaves depends on thickness and height, the material and its stiffness, how the wall is supported, the size and direction of the cutting force, and the residual stress in the stock. A wall that flexes causes dimensional error, a poorer finish or chatter. A wall that warps after unclamping may have been within tolerance on the machine and still be rejected. With plastics the heat from cutting adds to the effect.
How does a thin wall work in practice?
Common measures are to keep the wall thick for as long as possible, bring it to size in steps, alternating between both sides, take light radial cuts with sharp tools, rough with allowance and let the part relax before finishing, and support a tall wall with a filler or dedicated workholding. All of these take time that the volume removed does not reveal, and sometimes an extra setup. How much depends on material, height-to-thickness ratio, tolerance and roughness. A question to the customer about thickness or tolerance can achieve more than a different strategy.
What is a thin wall often confused with?
A thin wall is not sheet metal: sheet metal starts as sheet, a thin wall is what remains after machining. Chatter and distortion are consequences, not synonyms: chatter also arises from long tool overhang, and distortion also from residual stress in a thick part.
Frequently asked questions
At what thickness is a wall thin?
There is no fixed limit. It depends on height, material, support and tolerance. Steel deflects less than aluminium but often needs more cutting force. Look at the height-to-thickness ratio and at what is still standing after roughing.
How do I stop a thin wall from warping?
Rough with allowance, let the part relax, then finish to size; keep the wall thick for as long as possible and work in light cuts. Stress-relieved stock and less clamping force in the final setup help too.