“Hardened steel” on an RFQ without a number is how projects buy hope: a coating name standing in for missing HRC, rigidity, and coolant facts.
This page frames a hardness window gate for solid carbide drilling: what must be true before carbide is even on the table, what “hardened” must specify, when to stop and change process, and which RFQ fields keep Cost per Good Part honest—no universal HRC success charts.
Hardness as a gate, not a marketing badge
Treat hardness as an entry gate. Undefined “hardened” is not a tool SKU. Confirm whether solid carbide drilling is realistic for the stated hardness band, hole depth, and machine—or whether another process belongs upstream.
Materials: steel · series context: Choose carbide drill series by material · product: Carbide Drill for Hardened Steel.
Rigidity, runout, and coolant prerequisites
Even inside a plausible hardness window, long stickout, soft fixtures, and poor coolant make edges chip. Measure assembled runout and stickout—Stickout, runout & toolholders. Breakage patterns: Why solid carbide drills break.
What “hardened” must specify
On the RFQ, write:
- Steel grade / designation
- Hardness with scale (HRC or HB) and where measured
- Hole diameter/depth, blind/through
- Machine, holder, stickout, measured runout
- Coolant route
- Current scrap mode (chip, size, break)
Without the number and scale, quotes stay provisional.
Window talk without publishing a fake HRC chart
Shops often ask for a single HRC number that “carbide can drill.” This article will not publish one. The workable window depends on grade, heat treatment uniformity, hole depth, interrupted cuts, machine condition, and coolant. XRZ will discuss application fit from your measured hardness and setup—not from a blog table that pretends every 50 HRC part is identical.
If two lots of the same grade measure different hardness, treat them as different RFQ cells.
When to stop and change process (not just coating)
Stop promising a solid carbide drill when:
- Hardness is unknown or far outside a discussed window
- Rigidity/runout cannot be stabilized
- The operation is really a different process (e.g., needs prior soften, alternate method)
Coating and point tweaks do not replace a missing gate. Geometry vocabulary only after the gate: Solid carbide drill geometry.
RFQ fields → Cost per Good Part realism
Gated applications burn money on broken tools and scrap. Count tooling + breakage + downtime into cost per accepted hole, then send a complete hardness packet via Custom Cutting Tool RFQ · Solid Carbide Drill.
Frequently Asked Questions
Can XRZ quote from “hardened ~50 HRC” alone?
Better with exact grade, measured hardness, depth, and setup.
Will a premium coating open any HRC?
No—coating is not a hardness gate.
What to send?
Grade, HRC/HB, depth, machine/holder/runout, coolant, scrap mode → RFQ.
Why no published HRC success chart?
Workable windows depend on grade, heat-treat uniformity, depth, interruption, machine, and coolant—treat different measured lots as different RFQ cells.