Forging Part Family Input Weight and Yield Worksheet
Material is the largest cost on most forgings, and it is set by how much steel has to be heated to make a pound of finished part. This worksheet applies flash, scale and bar-end losses to each part, then rolls up annual pounds, yield and cost for the whole family.
| Part number | Material | Finished forging weight (lb) | Annual quantity (pcs) | Flash and trim allowance (% of forging) | Scale loss (% of heated billet) | Saw kerf and bar-end loss (% of billet) | Bar price ($/lb) | Billet weight (lb) | Stock weight per piece (lb) | Material yield | Finished pounds per year | Stock pounds per year | Annual material cost | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
4.8 | 4.92 | 85.4% | 75,600 | 88,560 | $69,077 | |||||||||
8.7551 | 8.9302 | 87.3% | 70,200 | 80,371.84 | $49,831 | |||||||||
3.051 | 3.1426 | 82.7% | 104,000 | 125,702.04 | $93,020 | |||||||||
13.2692 | 13.5346 | 85% | 34,500 | 40,603.85 | $95,419 | |||||||||
2.2533 | 2.3209 | 81.9% | 47,500 | 58,021.61 | $107,340 |
Flash percentages and scale loss in the example rows are illustrative only. Take flash from the die design, scale from your heating method (induction usually gives less than gas fired) and bar-end loss from your sawing practice. Flash is usually remelted by the mill as scrap, not returned to you, so treat it as a real cost.
Compute billet requirements from your BOMs
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How to use the worksheet
Enter the finished forging weight, annual quantity and bar price for each part. Then add the losses specific to that part: flash and trim allowance as a percentage of the forging weight, scale loss as a percentage of the heated billet, and saw kerf and bar-end loss as a percentage of the billet. The worksheet computes billet weight, stock weight per piece, yield, annual stock pounds and annual cost. Use it to compare designs, to set purchase quantities with your mill, or to see how a switch from gas to induction heating changes yield.
The method
The forging must be heavier than the finished part by the flash that is trimmed away, so the forging weight including flash is the finished weight times one plus the flash fraction. Scale forms during heating and falls off, so the billet that goes into the furnace must be heavier by dividing by one minus the scale fraction. Bar-end and saw kerf add a final percentage on the billet. Material yield is the inverse of the combined factor. Annual cost is stock weight times quantity times bar price.
- Billet weight = finished weight x (1 + flash) / (1 - scale)
- Stock weight = billet weight x (1 + bar-end loss)
- Yield = finished weight / stock weight
Reading the result and common mistakes
Yields in the 70 to 85 percent range are typical for closed die work on steel, and lower for complex shapes with heavy flash. Check any part far from the family average. Common errors include applying scale to the finished weight instead of the billet, forgetting bar-end loss when bars are cut to exact multiples, and using the same flash allowance for every shape. Another is ignoring that stainless and titanium lose less to scale but cost much more per pound, so a small yield gain has a big dollar effect.
Frequently Asked Questions
What is a normal scale loss for steel forging?
Scale loss depends on temperature, time in the furnace and atmosphere. Induction heating generally gives lower loss than gas fired furnaces because of shorter heating time. Many shops use a figure of a few percent of billet weight; measure it from your own weigh-backs.
How is flash allowance determined?
Flash is set by die design: the gutter and land geometry control how much material escapes at the parting line. The die designer or process engineer should give the expected flash weight, which you convert to a percentage of the forging weight.
Can I use this for aluminum or titanium?
Yes. Set lower scale loss values and adjust the bar price. Aluminum and titanium have different flash and trim behavior, so use your own die data. The same formulas apply to any hot forged material.
Why is yield not the same as one minus scrap?
Yield here describes material that ends up in the finished part, so flash, scale and bar ends all count as loss. It is not the same as quality scrap, which is parts rejected after forging and should be added separately in costing.
If you want billet requirements and yields calculated from your BOMs and mill orders, we can connect this to your ERP on your own servers.
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