Sumitomo AC420K: the maker lists AC4125K as its successor
Sumitomo Electric puts Sumitomo AC4125K against AC420K in its own catalogue material. We publish the pair only because the maker printed it; the source and page are below.
What the maker's document shows
AC420K → AC4125K · K / cast iron turning (CVD)
The table has a "Grade" column and an "Old Grades" column. AC4125K is in the Grade column; AC420K is in its Old Grades column.
Source: Sumitomo Electric, General catalogue 2025–2026, coated carbide grade table, printed page A27 (PDF page 27). Open the maker's PDF at that page →
Text line as extracted from the PDF (table columns run together)
AC4125K 91.1 2.5 ABSOTECH 12 · Especially effective for stable long life in roughing of parts like AC420K
What this does and does not mean
It means the maker positions AC4125K as the newer grade for the work AC420K was used for. It does not say AC420K is discontinued, and it does not say every insert shape and chipbreaker you buy in AC420K exists in AC4125K.
Before you switch:
- Check that your exact insert designation and chipbreaker are offered in AC4125K in the maker's current catalogue.
- Start from the maker's recommended cutting speed for AC4125K, not the numbers you ran with AC420K.
- Run both grades until the edge is worn out on the same part and compare parts per edge. One part is not a result.
Grade lineage in the same document
AC700G → AC420K → AC4125K. AC420K itself is listed as the newer grade for AC700G.
Other Sumitomo successor pairs
AC230 → ACP100 · AC304 → AC630M · AC405K → AC4010K · AC610M → AC6020M · AC700G → AC420K · AC8015P → AC8115P · AC810P → AC8015P · AC830P → AC8035P · ACP100 → ACP2000
Tell the advisor your insert, material and operation. It answers brand-neutral, including options from other makers. To check a whole tool list for older grades, use the free coverage check.