Forged/machined transformer: calculate the minimum stock removal

16 September 2025
Blog

During the production of forged blocks of special steel, physiological surface defects may occur: marks left by forging, deformations due to the production process, oxidation, decarburization or imperfections from oxy-cutting.
If not removed, these defects can compromise the quality of the part, subsequent machining and the performance of the component in service.

To ensure quality and reliability, it is essential to accurately calculate the minimum stock removal.
Our forged/machined transformer was created precisely to meet this need.

Forging process of a special steel block — Forging process

Defects in forged blocks: why they should not be overlooked

A raw block is never ready for immediate use:

it may show oxidation and surface decarburization
it undergoes deformations and cracks during forging
it carries traces of thermal cutting

To eliminate these defects, a mechanical stock removal process is required, ensuring a block suitable for the production of reliable mechanical components.

Preheating phase during steel block processing — Preheating phase

Example of surface defects on a forged steel block — Surface defect

Surface imperfections to be removed on a raw steel block — Surface defect

Reference standards and good practices

There are technical standards that support users, such as DIN 17350:1980 – Tool Steels – Technical Conditions of Delivery, which specifies delivery conditions for tool steels (cold work, hot work, high speed), indicating tolerances and minimum stock to be removed from the raw block.

Using dedicated formulas, it is possible to determine the minimum machined dimensions to which the raw block must be brought, ensuring it is free from physiological defects.

How the Bonomi Acciai transformer works

Our digital tool allows you to calculate quickly and reliably:

the minimum stock removal on thickness (per side),
the associated weight of the block in the three states: raw, machined, finished.

Just enter the data of thickness, width and length for one of the states, and the calculator returns the key values, avoiding manual calculations and possible errors.

Practical applications and benefits

The transformer is useful in many contexts:

to eliminate forging defects and deformations
to define the correct amount of material to be removed, avoiding waste
to guarantee quality and uniformity in the manufacture of molds and mechanical components
to obtain reliable and immediate values in the workshop

In many cases, the weight difference between raw and machined blocks can reach 15%, with significant impacts on costs, time and material management.

Difetti e deformazioni da correggere su blocchi di acciaio forgiato — Deformazioni

Example of deformations in a forged steel block — Deformations

Preliminary measures for toolmakers

Correct management of stock removal is part of a broader set of good machining and heat treatment practices.
As explained in our article on preliminary measures for toolmakers, it is essential to:

properly prepare the blocks,
remove residual stresses,
ensure defect-free surfaces before further treatments.

The forged/machined transformer is therefore a key step for toolmakers and mechanical workshops aiming for consistent, high-quality results.

Why choose Bonomi Acciai tools

The transformer is part of the Bonomi Acciai tool suite, developed to support customers with practical digital solutions in addition to the supply of high-quality special steels.

As the Italian partner of Swiss Steel Group, we provide know-how, innovation and concrete tools that simplify the daily work of those operating in the steel sector.