A solid carbide rod weighs its cylindrical volume multiplied by the density of its specific grade. Use the starting diameter for raw-material planning and the final diameter for delivered-part mass.
Use the density and weight calculator for the estimate, with the grade density and dimensions identified.
Worked example: a 10 mm rod, 100 mm long
With diameter d and length L in millimeters, and density rho in g/cm3, mass in grams = (pi / 4) x d2 x L x rho / 1,000. The divisor converts cubic millimeters to cubic centimeters. If you use radius instead, the volume is pi x r2 x L; do not halve the diameter twice.
| Step | Calculation |
|---|---|
| Volume | (pi / 4) x 10^2 x 100 = 7,853.98 mm3 |
| Convert volume | 7,853.98 / 1,000 = 7.85398 cm3 |
| Assume density | 14.5 g/cm3, illustrative only |
| Calculate mass | 7.85398 x 14.5 = 113.88 g |
Why oversize stock changes the estimate
A 10.4 mm starting diameter at the same length and assumed density weighs 123.18 g. The 4% diameter increase produces an 8.16% mass increase because diameter is squared. This is material volume, not a prediction of the final quote: setup, finishing and inspection are separate costs.
For a stepped or hollow rod, calculate each section separately and subtract internal volume. A chamfer can be ignored only when its effect is smaller than the precision required for your estimate.
Rod-weight formula in plain language
A carbide rod is a cylinder. The larger the diameter, the faster volume rises. That is why a small change in diameter can affect material cost more than expected. The cleanest workflow is to calculate volume first, then multiply by grade density.
Finished size vs oversize stock
A quote may need both numbers. Finished size helps estimate delivered part weight. Oversize stock helps estimate material consumption before grinding, cutting, or finishing. Do not mix the two in the same calculation.
Where tolerances enter the estimate
Tighter diameter tolerances, h6-style requirements, polish finishes, and straightness requirements do not just affect weight. They affect grinding time, inspection effort, and scrap risk.
Frequently Asked Questions
Why does diameter matter so much?
Cylinder volume uses radius squared, so diameter changes affect volume and weight more strongly than length changes of the same percentage.
Should I calculate with metric or inch units?
Either works if units stay consistent. Convert density and dimensions before calculating final pounds or grams.
Can Extramet estimate rod weight from a print?
Yes. A print with grade, diameter, length, and finish requirements gives the clearest path to an accurate estimate.
For mixed-unit prints, check the density conversion steps before calculating mass.
Check the grind-allowance example when starting dimensions and finished dimensions are different.
Send the drawing, application and quantity through the RFQ form when the requirements are ready for review.
Product questions? Contact Michael Douglas, Extramet Products product expert and Sales and Marketing contact.