What is cost per cutting edge?

Cost per cutting edge is the insert price divided by the number of usable edges on that insert. A square insert with four edges at 8 EUR costs 2 EUR per edge, a triangle with three edges at the same price costs 2,67 EUR per edge. It is the fair way to compare inserts of different shapes and prices, instead of comparing sticker price alone.

How do you calculate tool cost per part?

Divide the tool life per edge (in minutes) by the cutting time per part to get parts per edge, then divide the cost per edge by parts per edge. Tool cost per part = (insert price / edges per insert) / (tool life per edge / cutting time per part). This is the number that actually drives your part cost, not the insert's unit price.

Why does a cheaper insert sometimes cost more per part?

Because unit price ignores edge count and tool life. A cheaper insert with fewer edges or shorter tool life can produce fewer parts per edge, so its real cost per part is higher than a pricier insert that lasts longer and cuts faster. Cost per edge and cost per part are the numbers to compare, not the price tag.

What operating hours should I use for an annual tooling-cost projection?

Use your actual annual spindle-on time for that machine or operation, not a generic default. A single eight-hour shift, five days a week, roughly 48 weeks a year, is close to 1,900 to 2,000 hours; two shifts roughly doubles it. If you do not know the real figure, your production or scheduling data will have it, and using the real number is what turns this from a rough estimate into a decision-grade one.

Does this calculator account for machine downtime or scrap cost?

No. This calculator isolates tooling economics only: cost per edge, cost per part, and an annual tooling-cost projection from insert price, edge count, tool life and cycle time. It does not model machine hourly rate, scrap, rework, or changeover time, which belong in a full part-cost model.

MATERIAL CROSS-REFERENCE · P CASE-HARDENING STEEL

20MnCr5 / AISI 5120: one material, every designation.

20MnCr5 is the same material your supplier may list as AISI 5120 or JIS SCr420. This page maps the designations across standards and gives the ISO P-group machining starting point, brand-neutral.

EN · W.-Nr. · AISI/ASTM/UNS · JIS ISO 513 group P Free, no signup

01 · DESIGNATIONS

20MnCr5 / AISI 5120 across the standards

System	Designation
EN (EU)	20MnCr5
Werkstoffnummer	1.7147
AISI / ASTM / UNS (US)	AISI 5120 (nearest)
JIS (Japan)	SCr420 (nearest)

Compiled from the public standard designation systems (EN 10027, SAE/AISI, ASTM, UNS, JIS). Entries marked “nearest” are the closest commonly-cited counterpart, not a drop-in equivalent. Always verify against the material certificate.

NEAREST MATCH, NOT A TWIN

At least one designation on this page is a nearest commonly-cited counterpart rather than a same-composition equivalent (structural and cast grades are specified by properties, not chemistry). Confirm suitability against the material certificate and the drawing requirement, not this table alone.

02 · MACHINING

How 20MnCr5 machines

Same story as 16MnCr5 with a touch more carbon. After case-hardening, the machining problem changes entirely and becomes H-group work on the case.

ISO group	Starting Vc (coated carbide, turning)	Feed fn
P P · Steel	150–350 m/min · 490–1150 sfm	0.1–0.5 mm/rev · .004–.020 ipr

Group-level starting range from our speeds & feeds guide; convert to RPM with the speeds & feeds calculator. Condition, subgroup and operation shift the number — the material page has the detail: ISO P · Case-hardening steel.

Related materials: 16MnCr5 / AISI 5115

03 · FAQ

Common questions

What is the US equivalent of 20MnCr5?

20MnCr5 (Werkstoffnummer 1.7147) corresponds to AISI 5120 (nearest) as the nearest commonly-cited counterpart — check the certificate before substituting. In JIS terms the counterpart is SCr420 (nearest).

Which inserts and cutting data for 20MnCr5?

It is an ISO P-group material, so the starting window is 150–350 m/min · 490–1150 sfm at 0.1–0.5 mm/rev · .004–.020 ipr for coated-carbide turning, adjusted for condition and operation. For a grounded, brand-neutral pick — grade, geometry and cutting data across 13 brands — ask the advisor.

Are 20MnCr5 and 5120 interchangeable on a drawing?

Not automatically: this pairing is nearest-by-properties, and structural or cast grades are specified by mechanical requirements. The drawing standard and the material certificate decide, not the cross-reference table.

Designation solved. Now the tooling question.

Knowing the material is half the job; picking the grade and cutting data for the operation is the other half. That is what the advisor does, grounded in catalog data and honest when there is no verified match.

Ask the advisor about 20MnCr5 → ISO P material guide All material cross-references