Subcontract heat treatment and plating for fastener plants
You make the parts. We run the process to your drawing, keep the lot identity intact, and send the parts back with the measured data.
Thinking about outsourcing your heat treatment or plating?
We are a process subcontractor for plants that already make fasteners. Your screws, bolts, nuts, washers, pins, springs and anchor bolts arrive as your lots, go through heat treatment, trivalent (Cr3+) zinc electroplating, phosphate coating or de-embrittlement baking, and go back to you with a lot report. The plant has run since 1994 under an ISO 9001:2015 quality system and processes up to 2,000 tons per month. Send the drawing and a sample lot; we reply to the quote within 24 hours.
Send a drawing for review- 2,000 t
- Processing capacity per month
- 1994
- Plant in operation since
- ISO 9001:2015
- Certified quality system
- 24 h
- Quote reply
1. What we process, and at what volume
One answer settles most of this conversation: we are a small-parts, bulk-lot plant. Parts run by the lot in baskets, not one at a time on a fixture. If your part fits in a hand, we are probably a fit; if it needs a crane, we are not.
| Item | What we run |
|---|---|
| Part types | Screws, bolts, nuts, washers, pins, springs and anchor bolts — fastener-family parts in production lots |
| Volume | Plant capacity up to 2,000 tons per MONTH across heat treatment and finishing |
| Heat treatment | Carburizing 880–950°C, carbonitriding 820–880°C, through-hardening 800–870°C, quench and temper (150–650°C temper) and stress relief 150–400°C |
| Zinc electroplating | Zinc with trivalent Cr3+ passivation — clear/blue, yellow, black and olive, typically 5–12 µm, with sealer when specified |
| Phosphate coating | Zinc or manganese-containing phosphate as a paint base, oil carrier or run-in surface |
| De-embrittlement bake | Run in-house with logged time and temperature, against the ISO 4042 / ASTM B850 reference window (typically 190–230°C) |
| Laboratory | Hardness (ISO 6507 / ISO 6508), coating thickness (ISO 3497), case depth (ISO 2639), salt spray (ISO 9227 / ASTM B117), microstructure and decarburization review |
| Materials commonly seen | S45C, SWCH cold-heading steels, SCM435, SCM440, 10B21 / 10B33 boron steels, SUP9 / SUP10 spring steels; stainless A2 / A4 for finishing work only |
| Lot size | No fixed number. It is set by geometry, basket loading, the process route and the tests required — send the part and we will tell you what is workable |
Values are typical ranges. The range that applies to your part is confirmed against your drawing and the governing standard; this page replaces neither.
2. How to send parts so the lot stays traceable
Most disputes between a fastener plant and its processor start at goods-in, not in the furnace. A lot that arrives without an identity cannot be given one back.
One container, one identity
- 1One grade, one heat or coil lot, one requested process per container. Two grades mixed in a basket cannot be separated after hardening — the hardness result will not tell you which piece is which.
- 2Label every container with your part number, the grade, the heat or coil lot, the quantity or weight, and the process you are ordering.
- 3Send the drawing revision with the delivery. A lot that arrives without the revision it must be processed to waits until we have it.
- 4Declare the incoming condition: as-headed, as-rolled, threads rolled before or after heat treatment, already plated, previously processed elsewhere, or returned for re-work.
- 5Declare the surface state — drawing lubricant, machining coolant, protective oil, wax or existing rust all change the pre-treatment, and a coating defect usually traces back to what was on the steel before it arrived.
- 6Agree the basis of reconciliation up front: piece count or weight. Small fasteners are normally returned on a weight basis with an agreed allowance for process loss.
- 7Pack for bulk handling — sound bins or crates, no loose foreign objects, and separate packing for long or delicate parts such as anchor bolts.
- 8For a new part, send a sample lot before the first production lot. It is the cheapest way to find out that the geometry, the thread class or the hardness window needs a different route.
What we cannot fix after the fact
- Mixed grades in one basket. A single process window cannot be correct for both.
- Decarburization already present on the incoming wire. Heat treatment does not put the carbon back, and surface hardness will read low.
- A seam or a cold-heading crack. Quenching finds it and opens it, but it did not create it.
- A thread rolled with no allowance for coating thickness. The gauge fails after plating, and the coating is not the cause.
3. What you have to specify
A purchase order that says "harden and zinc plate" is not a specification. These are the fields a quotation needs to mean anything — the same fields you would hand an internal process engineer.
| Field | Why it decides the process | Example |
|---|---|---|
| Material and condition | The steel decides the route. A boron steel, a plain-carbon cold-heading steel and a chromium-molybdenum steel do not respond alike. | SCM435 · cold-headed, as-drawn |
| Property class or hardness | An acceptance window, not a single number. Give the range, the measurement location and the scale. | class 10.9 · 32–39 HRC |
| Process route | Case hardening and through hardening answer different loads. Name the one your part needs, or describe the function and let us propose it. | carburize · effective case depth per drawing |
| Coating and thickness | Coating type, passivation colour, thickness on the significant surfaces, and any sealer or topcoat. | Zn 8–12 µm · Cr3+ yellow · sealer |
| Bake requirement | For electroplated parts above roughly 1000 MPa (about class 10.9 / 320 HV), state that de-embrittlement baking is required and to which reference. | ISO 4042 / ASTM B850 · 190–230°C |
| Corrosion criterion | Hours alone are not a criterion. Name the corrosion type, the surfaces that count and the exposure time. | ISO 9227 NSS · no red rust at 240 h |
| Thread accommodation | A thread gauged to no allowance before plating will fail the gauge after it. State the class and where it is gauged. | 6g / 6H · gauged before plating (ISO 4042) |
| Inspection and report | What is measured, on how many pieces, and what is reported per lot. | ISO 6507 hardness + ISO 3497 thickness, per lot |
| Governing standard | Name the standard and its class, not only its number. The same number can carry very different service conditions. | ISO 898-1 · ASTM B633 SC3 · ISO 4042 |
If a field is missing we will ask, because a guess made here becomes a rejected lot later. To write the whole thing in one pass, the specification builder produces a text block you can paste straight into a drawing note or an RFQ.
4. What comes back with the parts
Parts and paperwork travel together. The report is what lets your incoming inspection release the lot without re-testing it, and what lets you answer your own customer six months later.
- Job and lot identity — your part number, your lot, our job number
- Material and the agreed specification the lot was run to
- Test location, method and instrument
- Measured values against the acceptance limits — not a pass stamp on its own
- Date, inspector and the approval that released the lot
- Images or a hardness profile chart when the specification calls for them
Our laboratory is an in-house works laboratory operating under our ISO 9001:2015 system. We do not hold ISO/IEC 17025 accreditation — if your customer requires an accredited third-party report, plan for an external laboratory and tell us at the quote stage so the sampling matches.
See the report format and factory evidence5. What happens when a lot is out of spec
Any heat-treatment or plating shop that tells you it has never produced a nonconforming lot is either new or not measuring. The question worth asking is what happens in the hour after one is found.
- 1Stop and segregate. The lot is physically held and tagged, and nothing downstream is loaded from it.
- 2Bound the problem. Lot identity is the whole point of the goods-in discipline above — it tells us whether one basket is affected or the whole delivery.
- 3Report the measurement, not an opinion. You get the values, the method and the sample size, so your own engineers can judge it.
- 4Agree the disposition with you before anything is touched: re-process, sort and screen, or return as-is for your decision. We do not quietly re-run a lot and ship it.
- 5Record it. The nonconformance, its cause and the corrective action are recorded under our ISO 9001:2015 system, and we tell you what changed in the process so the next lot is not a repeat.
What can and cannot be re-worked
Usually recoverable
- Coating outside the thickness or colour range — normally stripped and re-plated.
- A part tempered harder than the window — usually re-tempered, where the specification allows a second temper.
- A missed or late bake — it can be run, but the value of a bake falls the longer it is delayed after plating. Declare it, do not hide it.
Not recoverable
- A quench crack. The part is scrap, and the honest job is establishing whether it came from the material, the geometry or the quench.
- Decarburized surface layer. Re-heat-treating does not restore it.
- A second hydrogen charge. Stripping and re-plating a class 10.9 or 12.9 part recharges it, so that decision, the bake and the risk are agreed in writing — never as a silent re-work.
- Distortion beyond the drawing. Another cycle does not correct geometry.
6. How to start
Two things get a real answer: the drawing and a sample lot.
- 1Send the drawing — or a sketch plus the grade, the hardness window and the coating — and tell us the lot size you actually run.
- 2Send a sample lot for a new part. A trial through the real process route tells us more than any phone call.
- 3We review the part, the route, the tests and the packing, and reply to the quote within 24 hours.
- 4We agree the specification in writing: hardness window, coating and thickness, bake, test criterion, report fields and the reconciliation basis.
- 5The first production lot runs to the agreed inspection, and the report comes back with the parts.
The only time commitment on this page is the quote reply: within 24 hours. We will not promise a job-completion date before we have seen the part, the lot size and the tests. A completion date given before that is a guess, and you would be right not to trust it.
We are the wrong supplier if…
Saving you a week is worth more to both of us than winning an enquiry we should not win.
- Your part is a gear, a shaft, a die, a mould or a structural weldment. We are a small-parts, bulk-lot plant; large single components belong in a different kind of shop.
- You need one or two prototype pieces. The line is loaded by the lot, so a hobby quantity is neither economical for you nor representative of production.
- Your drawing calls for hot-dip galvanizing, zinc-flake or other non-electrolytic coatings, nickel, chrome or tin plating, anodizing, nitriding, induction hardening or vacuum heat treatment. Those sit outside the four processes we run in-house.
- Your customer still mandates hexavalent (Cr6+) passivation. We run trivalent Cr3+.
- Your specification requires an ISO/IEC 17025 accredited laboratory report or an IATF 16949 certified processor. We operate an ISO 9001:2015 system with an in-house works laboratory.
- You need a guaranteed completion date before anyone has seen the part. We confirm a schedule after reviewing the part, the lot and the tests — not before.
Questions plant managers ask first
Do you take subcontract work from other fastener factories?
Yes — that is what this page is for. Your part, your drawing, your customer; we run the process and hand the lot back with its report. Drawings and part data you send are used to quote and to process your work.
What is the minimum lot size?
There is no single number. It is set by the part geometry, basket loading, the process route and the tests you require. Send the part data and we will tell you what is workable rather than quote a number that does not fit your part.
Do you issue a report for every lot?
The inspection and the report content are agreed at the quote stage and run per lot. A traceable report carries job and lot identity, the agreed specification, the test method and instrument, the measured values against the acceptance limits, and the approval that released the lot.
Do you bake for hydrogen embrittlement?
Yes. De-embrittlement baking runs in-house with logged time and temperature. ISO 4042 places the threshold at roughly 1000 MPa (about class 10.9 / 320 HV); the reference window is typically 190–230°C, held 4–24 h and started as soon as possible after plating. Your specification prevails.
Are you IATF 16949 or ISO/IEC 17025?
No. We hold ISO 9001:2015 and operate an in-house works laboratory under it. If your customer mandates an IATF-certified processor or accredited third-party test reports, say so before the first lot so we can plan the external testing with you.
Can you re-plate parts that failed at another plater?
Often, but it is discussed rather than simply ordered. Stripping and re-plating a high-strength part adds a second hydrogen charge, so on class 10.9 and 12.9 the decision, the bake and the residual risk are agreed in writing first.
How fast do you quote?
Within 24 hours of receiving the drawing and part data. That is the only time promise we make here — a completion date is confirmed after we have reviewed the part, the lot size and the tests.
Technical reference before you send the first lot
Send a drawing and a sample lot
Tell us the grade, the hardness window, the coating and the lot size you actually run. We reply to the quote within 24 hours.