Heat Treating Services
Resolute Precision Manufacturing coordinates heat treating of precision machined components through our qualified outside heat treat network. From quench and tempering to stress relieving, annealing, carburizing, and through-hardening, we manage the complete process and deliver heat treated parts with certification documentation. One purchase order covers machining and heat treatment. Request a QuoteWhy Heat Treatment Matters for Precision Parts
Heat treatment changes the mechanical properties of metal components by increasing hardness and strength, relieving internal stresses, or establishing a specific microstructure for the application. The right heat treatment is as critical to component performance as the geometry itself. For example, a 4140 steel shaft can reach very different strength and hardness levels depending on its heat treatment and final condition.
The challenge with heat treating CNC machined parts is managing dimensional distortion. Quenching, in particular, can cause shafts to bow, bores to change diameter, and thin sections to warp. Controlling distortion requires an understanding of how part geometry, material, heat treatment process, and later grinding or finishing requirements interact.
Our team coordinates heat treatment with your machining requirements, helping plan stock allowances and finishing operations so parts reach the required final dimensions.
Heat Treatments for CNC Parts: Processes We Coordinate
We coordinate the following heat treatments for CNC components through our qualified supplier network:
- Quench and temper (Q&T): hardening followed by tempering to reach the specified hardness, strength, and toughness.
- Stress relieving: a controlled thermal cycle that reduces machining-induced residual stresses while limiting changes in hardness.
- Annealing: heating and controlled cooling to soften material, improve machinability, or prepare components for later processing.
- Normalizing: heating above the critical temperature followed by air cooling to refine grain structure and improve uniformity.
- Carburizing and case hardening: enriching the surface with carbon and then hardening it to give a wear-resistant case over a tougher core.
- Through-hardening: hardening the full cross-section for applications that need hardness throughout the material.
Machined Parts With Heat Treatment: One Source, One Purchase Order
Splitting machining and heat treatment between suppliers adds handoffs, shipping, and finger-pointing when a part comes back out of tolerance. With RPM, machined parts with heat treatment are managed under one purchase order. We plan the sequence, machine the parts, send them to the right qualified processor, and inspect them when they return, so the person accountable for your tolerances is the same person who arranged your heat treatment.
A typical sequence looks like this:
- Rough machine the part with stock left for distortion and finishing.
- Heat treat to the specified hardness, case depth, or condition.
- Finish machine or grind the critical dimensions.
- Inspect and document the result, with certification and test reports provided with the parts.
Design Considerations for Heat Treated Parts
Our engineers can advise on important design and manufacturing considerations during quoting:
- Material selection: choosing the steel grade that meets your hardness, strength, wear resistance, and toughness requirements.
- Stock allowance: planning machining allowances for post-heat-treat grinding and finishing on critical dimensions.
- Masking and selective hardening: protecting threads, precision bores, or other specified areas from hardening where required.
- Drawing callouts: clearly defining hardness range, case depth, heat treatment process, and applicable standards on the drawing.
- Geometry: avoiding sharp internal corners and abrupt section changes, which concentrate stress and raise the risk of distortion or cracking during quench.
Planning these requirements early reduces the risk of dimensional problems and extra finishing operations when heat treating CNC machined parts.
Specifications
| Materials | All hardenable steels — 1045, 4140, 4340, 8620, D2, H13, 17-4 PH stainless steel, and others |
| Hardness Range | Rc 20–65 depending on material, process, and specification |
| Specifications | AMS 2759 series, ASTM A255, MIL-H-6875, and customer-proprietary specifications |
| Case Depth (Carburize) | 0.010″ to 0.060″ effective case depth, per drawing specifications |
| Documentation | Heat treatment certifications, hardness test reports, and case depth reports provided with finished parts |
| Turnaround | Typically 1–2 weeks for standard processes; expedited service available upon request |
| Certifications | ISO 9001:2015 |
Common Applications
Heat treatment is essential in parts that carry high loads, wear against other surfaces, or must hold dimensions in service:
- Shafts and axles: 4140 and 4340, quenched and tempered for strength and fatigue resistance
- Gears and splines: carburized 8620 for a hard, wear-resistant case and a tough core
- Tooling and dies: D2 and H13, through-hardened for edge retention and wear resistance
- Hydraulic components: hardened rods, pistons, and valve parts
- Fasteners and pins: high-strength bolts, studs, and dowel pins
Frequently Asked Questions
How much dimensional change should I expect after heat treatment?
Distortion from quench hardening is geometry and material dependent. Thin sections and long slender parts distort more. As a general rule, allow 0.003″ to 0.010″ stock on OD diameters that require grinding after heat treat. We advise on stock allowance as part of the quoting process.
Can RPM selectively harden only certain surfaces on a part?
Yes. Through masking with copper plating or mechanical shields, we can protect specific features from case hardening threads, precision bores, and ground surfaces are commonly masked during carburizing and nitriding processes.
What documentation does RPM provide with heat treated parts?
We provide the heat treater’s certification of conformance, hardness test records (Rockwell or Brinell), case depth measurements for carburized parts, and temperature charts for critical processes. All documentation is referenced to the specific lot and part number.
Can RPM handle stainless steel heat treatment?
Yes. We coordinate 17-4 PH stainless heat treatment to H900, H1025, H1075, and other aging conditions per AMS 5604. We also coordinate solution annealing of 316 and 304 stainless for stress relief and corrosion resistance optimization.