Owner-confirmed machining process case

4340 Bushing Machining: Allowance for Heat-Treatment Distortion

A Jinhua batch-order project using 4340 material, with outsourced quenching and tempering followed by in-house external-diameter grinding.

Evidence note: This account is based on manufacturing facts confirmed by the Project Owner. The supplied process description was organized with AI assistance from process information. Original manufacturing, material and inspection records have not been independently reviewed for this candidate.

Project and material responsibility

The Project Owner identifies this as a batch-order project that started in 2020. Jinhua purchased the 4340 raw material. The application is not specified in this account, and no order quantity or current delivery status is stated.

Heat treatment was outsourced. The Owner confirms that the remaining processing and inspection were carried out by Jinhua. This project account does not identify machine models or establish general equipment ownership or capability.

The confirmed manufacturing route

Cutting: Cut the raw material for machining.
Turning: Machine the component before heat treatment.
Outsourced heat treatment: Quench and temper the part.
External-diameter grinding: Finish the outside diameter after heat treatment. The Owner describes a chuck-and-center support arrangement, referred to as “一夹一顶”. Detailed locating features are not specified here.

Addressing heat-treatment distortion

The Owner confirms that heat-treatment distortion occurred on this project. The process left machining allowance before heat treatment, with material subsequently removed during external-diameter grinding to address the dimensional change.

The account concerns this project’s allowance and finishing sequence. It does not specify an allowance value, a universal process rule or a quantified improvement. It makes no claim about removing cracks or grinding burn.

Inspection scope and production status

The Owner reports 100% inspection coverage using air gauging and confirms that the project reached volume production.

The measured features and numerical readings are not published. Inspection coverage is not a statement of 100% conforming output or a claim that every dimension was checked. No lot-acceptance dataset or current production status has been independently verified for this account.

Historical process-confirmation attribution

The Project Owner identifies He Zhou (周贺), Technical Manager, as having confirmed the process in May 2024. That historical attribution is owner-confirmed; the underlying sign-off has not been independently inspected. May 2024 is not a review date for this article.

Scope of this case

This account omits customer identity, drawing numbers, specific dimensions, tolerances, hardness and surface-roughness values. It does not claim a material-performance guarantee, a verified inspection PASS, zero defects or quantified gains in yield, cost, cycle time or service life.