Flattening Force Calculator
Estimate the elevated tonnage required for flattening, hemming, coining, and bottoming operations.
Using this calculator responsibly
The Flattening Force calculator is an engineering aid for checking a shop-floor estimate before a setup, quote, or process review. Enter values in the units shown, confirm material properties against the applicable specification, and keep a record of the assumptions used. Calculator output does not override machine capacity, tooling limits, part requirements, or a qualified engineer's approval.
Before using a result in production, repeat the calculation with the extreme values allowed by the print or process window. Check that the selected material, thickness, geometry, and safety factor reflect the actual job. If a result approaches a press, die, fastener, or machine limit, stop and verify it with the equipment manufacturer or responsible engineer.
Inputs and results
Read every field label before entering data and avoid mixing inch and metric values. A useful result should be traceable to the job number, revision, material certification, and machine or tooling record. Treat warnings, invalid ranges, and unusual outputs as reasons to inspect the inputs rather than as values to work around.
Flattening, hemming, bottoming, and coining force the material against the die instead of just bending it in air. That demands far more tonnage than air bending — but it sets the form and kills springback.
Formula: Bottoming/coining tonnage ≈ Air-bend tonnage × (3 to 10)
Worked example
- A bend that air-forms at 9 tons/ft may need 30–90 tons/ft to coin.
- Confirm the press and tooling can handle the multiplied load before bottoming.