Mold machining normally has two different jobs: remove stock efficiently during roughing, then protect the finished surface and small features during finishing. The correct tool depends on hardness, cavity depth, corner radius, machine rigidity and the amount of stock left for the final pass. A single “mold steel cutter” label cannot describe all of those decisions.
Roughing: control the load and the reach
Start with the material grade, hardness and stock allowance. Choose the largest safe diameter that reaches the cavity without an excessive gauge length. Match substrate toughness and chip space to the engagement, then state the axial depth, radial width and step-over used for the calculation. For deep pockets, a reduced neck can provide clearance, but the cutting length should remain only as long as the feature requires. Monitor spindle load and chip evacuation instead of judging roughing only by sound.
Finishing: protect the geometry
Select flat, corner-radius or ball nose geometry from the surface and internal-corner requirement. A ball nose can follow a 3D surface, while a corner-radius tool can balance edge strength and finish on a shoulder. For HRC50–60 work, confirm the intended hardness window and coating recommendation with the series chart. Use a stable holder, measure runout at the tool and keep the finishing allowance consistent so the toolpath—not a changing stock condition—controls the load.
Feature-driven RFQ data
- Material grade and hardness, including heat-treatment condition.
- Cavity depth, smallest internal radius, wall height and stock allowance.
- Tool diameter, flute count, cutting length, reach, corner form and coating preference.
- Machine model, spindle taper, holder interface, gauge length and runout target.
- Required surface finish, tolerance, quantity and target delivery date.
Send the drawing or model with these fields. BOFA can compare an HRC55 micro ball nose end mill with another series and explain the assumptions behind the quotation in the technical RFQ.
Verify before releasing production
Run a controlled test on a representative feature. Record tool overhang, cutting parameters, machine load, surface finish and the first visible wear. If a small cutter fails, check holder runout, entry motion and the unsupported neck before simply reducing every parameter. The goal is a stable process window that can be repeated on the next cavity.
FAQ
Should roughing and finishing use the same cutter?
Sometimes, but separate tools often provide better control of stock removal, edge strength and surface finish. Decide from the feature and cycle-time target.
What does “HRC55” tell me?
It describes the intended workpiece hardness range; it does not replace the need to specify alloy, feature, reach, coating and cutting conditions.
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