Steel Bar Cutting Plan: How to Calculate Kerf and Scrap?

A steel bar cutting plan shows how many pieces of specific lengths can be obtained from the purchased stock length. For an accurate calculation, simply dividing the stock length by the required part length is not sufficient. The material removed by the saw, end trimming, clamping requirements, and allowances left for subsequent machining operations should also be taken into account. When preparing a cutting plan, it is useful to distinguish between three different lengths:

• Final part length: The finished length of the part specified in the technical drawing
• Cut blank length: The length to be cut, including machining allowance
• Stock length: The length of the steel bar to be purchased

Confusing these values can result in insufficient final part lengths or unnecessary material consumption.

Why Should Saw Kerf Be Included in the Calculation?

When a saw separates the material, it creates a cutting gap known as the kerf. This loss should not be determined solely by looking at the thickness of the saw blade. The actual cutting width of the tool and real operating conditions should also be considered. The value verified by the facility should be used for production planning.

Although each cut may appear to cause only a small amount of material loss, the total difference can become significant when producing a large number of short pieces. For the same reason, if face milling will be performed after cutting, the required machining allowance should be included in the cut blank length.

Simplified Steel Bar Cutting Calculation

In a scenario where each part is separated from the stock by an individual cut and a remnant remains at the end, the following inequality can be used:

• n × (cut blank length + kerf loss) + total end-trimming loss ≤ usable stock length

Here, n represents the number of parts that can be obtained. If a section of the bar cannot be used because of clamping requirements, this length should also be deducted from the usable stock length. In other cutting arrangements where the final part makes use of an existing end, the number of cuts may differ. Therefore, the formula should be adapted to the actual cutting arrangement used on the machine.

How Many Pieces Can Be Cut from a 6-Metre Steel Bar?

The following example is provided only to demonstrate the calculation method. Assume a usable stock length of 6,000 mm, a cut blank length of 395 mm, a kerf loss of 3 mm for each separating cut, and a total initial end-trimming loss of 20 mm. It is also assumed that there is no additional clamping loss.

Under these assumptions, 15 pieces can be obtained. A sixteenth piece would require a total length of 6,388 mm, so the available stock would not be sufficient. The calculation should be repeated whenever the kerf loss or actual stock length changes; a nominal six-metre stock length alone does not guarantee production yield.

Separate Reusable Remnants from Scrap

Not all remaining material should automatically be classified as scrap. Remnant lengths that can be used for another work order should be recorded together with their steel grade, cross-section, length, and heat information. However, storing small and unidentified remnants indefinitely can increase warehouse space requirements and material search time.

A facility can define a minimum reusable remnant length based on how frequently particular sizes are required. Tracking the following categories separately makes the causes of material loss easier to understand:

• Saw chips and kerf loss
• End pieces
• Reusable remnants
• Non-conforming parts

How Can Different Part Lengths Be Planned Together?

Different orders with the same steel grade and delivery condition can be included in a combined cutting plan when traceability requirements allow. Combining long and short parts within the same stock length can reduce the size of the remaining material.

However, the number of setups, delivery schedules, and separation of work orders should also be considered. Cutting efficiency should not be measured solely by achieving the smallest possible remnant. Part yield, on-time production, reusable stock, and total cutting time should be evaluated together. For the commercial implications of material utilisation, you can also review our article on steel procurement costs.

Conclusion

An effective steel bar cutting plan takes the cut blank length, saw kerf, end-trimming allowance, and clamping allowance into account. Performing calculations using the actual stock length and verified kerf loss, recording reusable remnants, and planning compatible orders together can help reduce both material consumption and production time.

To convert planned steel lengths into weight, you can use the Uyar Çelik weight calculator. You can also contact Uyar Çelik through our contact page to learn more about available stock lengths and cutting options.