Sprue Bushing Manufacturer & OEM Supplier for Precision Injection Mold Components
GUNRI manufactures high-precision sprue bushings to ISO 10072, JIS B 5112 and DIN design standards — produced under your brand or to your drawings. Repeatable quality, clear technical communication and flexible production volumes for distributors, mold makers and OEM customers worldwide.
What is a sprue bushing?
Simply put, it is the gate between the machine nozzle and the mold.
A sprue bushing (also called a sprue bush) is the component that connects the injection molding machine nozzle to the mold’s runner system. Typically made of hardened tool steel, it guides molten plastic from the nozzle into the sprue and runners in a controlled, leak-free flow.
Because every shot passes through the bushing at high temperature and pressure, precision matters: the bore must stay concentric to the nozzle, the spherical radius must seal properly, and the polished finish must allow smooth flow across the entire production run.
Sprue bushings come in two families. Cold sprue bushings (covered by ISO 10072 and JIS B 5112) are unheated — the sprue solidifies each cycle and is removed and reground. Hot (heated) sprue bushings build a heating element into the bushing to keep the melt molten, eliminating the cold sprue; they are used in hot-runner systems or to retrofit existing molds and are custom parts made to the customer’s drawing. GUNRI supplies standard cold sprue bushings and accepts custom orders for heated types on request.
Common challenges when sourcing sprue bushings
Companies looking for a stable supply of precision injection mold components often run into the same problems.
Inconsistent quality between batches
Dimensional variation or surface finish problems appear after the first few shipments, creating end-customer complaints and costly rework.
Slow or unclear technical communication
Drawings are misunderstood, questions take days to answer, and simple changes turn into long email chains.
Difficulty getting true private label
Some factories prefer to push their own brand or set minimum quantities that do not match your market needs.
Unreliable lead times
Promised dates slip, making inventory planning and commitments to your own customers difficult.
How GUNRI supports sprue bushing OEM partners
We focus on contract manufacturing of precision mold components so you can strengthen your product line and serve your customers with confidence.
Production under your brand
We manufacture sprue bushings to your requirements and support private label packaging and marking. You keep the brand relationship with your customers.
ISO / JIS / DIN standard dimensions
Parts can be produced to ISO 10072, JIS B 5112 (Types A–F) and DIN design dimensions for interchangeability, or fully customized to your drawings.
Process-focused quality control
Material selection, heat treatment, grinding and inspection follow defined procedures aimed at repeatable results across production batches.
Clear technical communication
We work from technical drawings and 3D models and provide structured feedback. English communication is standard for international projects.
Flexible order volumes
Prototype and small-batch orders are accepted. Ongoing production can be arranged once samples have been approved.
Long-term partnership approach
Our goal is stable, repeatable supply that supports your business in Europe, North America and Southeast Asia.
Sprue bushing standards we manufacture to
GUNRI produces sprue bushings to internationally recognized dimensional and material standards — so you get interchangeable, reliable parts.
ISO 10072
International standard for sprue bush dimensions and tolerances (Types A & B), used mainly in injection moulds for plastics and rubbers.
JIS B 5112
Japanese industrial standard with Types A–F, covering head styles, spherical radius and body dimensions widely stocked by Asian mold component distributors.
DIN design dimensions
German-series dimensions (DIN ISO 10072) and related mold component geometries common in European markets.
We can also manufacture to your own drawings or samples. If a dimensional interchange is needed, please provide the reference dimensions or a sample part — we will confirm feasibility before quoting.
Precision sprue bushings & related mold components
We produce both standard-dimension and fully custom parts for plastic injection molds.
Standard-dimension series (ISO 10072 / JIS B 5112 / DIN)
- Common sprue bushing styles, head types and dimensions
- Designed for interchangeability across widely used systems
- Suitable for distributors needing reliable stock items
Private label & custom production
- Manufactured to your drawings or sample parts
- Special dimensions, materials, bores and features
- Packaging and marking options available
Cold sprue bushings (ISO 10072 · JIS B 5112)
A cold sprue bushing is the unheated standard type: the sprue solidifies with every cycle, is separated from the part and then reground. This is the product family covered by ISO 10072 and JIS B 5112. Types A and B are the corresponding ISO 10072 types, and the JIS range extends this to A–F. The type code defines both the nozzle seat and the body series: A, C and E carry a spherical (SR) seat that mates with a radius-tipped machine nozzle; B, D and F carry a flat seat for flat-tip nozzles. A/B are supplied with material by agreement and hardness 50±5 HRC, C/D are the widely stocked pre-hardened-steel series (40±3 HRC), and E/F are the SKD61-or-equivalent series (50±2 HRC).
Type A — Spherical Seat
Spherical (SR) seat that matches a radius-tipped machine nozzle. Material by agreement between buyer and supplier; hardness 50±5 HRC. Dimensions per JIS B 5112 Table 1.
ISO 10072 A · JIS B 5112 AType B — Flat Seat
Flat seat for flat-tip machine nozzles. Material by agreement between buyer and supplier; hardness 50±5 HRC. Dimensions per JIS B 5112 Table 1.
ISO 10072 B · JIS B 5112 BType C — Spherical, Pre-hardened
Spherical (SR) seat on a pre-hardened steel body, hardness 40±3 HRC. The widely stocked cost-efficient series for medium workloads. Dimensions per JIS B 5112 Table 2.
JIS B 5112 CType D — Flat, Pre-hardened
Flat seat on a pre-hardened steel body, hardness 40±3 HRC. For flat-tip nozzles in medium workloads. Dimensions per JIS B 5112 Table 2.
JIS B 5112 DType E — Spherical, SKD61
Spherical (SR) seat in SKD61 or equivalent hot-work steel, hardness 50±2 HRC. Chosen for long-run, high-wear tooling. Dimensions per JIS B 5112 Table 3.
JIS B 5112 EType F — Flat, SKD61
Flat seat in SKD61 or equivalent hot-work steel, hardness 50±2 HRC. For flat-tip nozzles in long-run, high-wear tooling. Dimensions per JIS B 5112 Table 3.
JIS B 5112 FHot / Heated sprue bushings (custom, per drawing)
Hot sprue bushings incorporate a built-in heating element that keeps the melt at processing temperature, eliminating the cold sprue and its regrind. They are used in hot-runner systems and to retrofit standard molds that currently produce a cold sprue. Unlike cold sprue bushings, heated types are not covered by an ISO or JIS standard — each manufacturer builds to its own design. GUNRI accepts custom hot sprue bushing orders on request. When you inquire, please specify overall length, head style, flow channel diameter, tip form and heater voltage (120 or 240 V).
GUNRI also manufactures related precision mold components including ejector pins, ejector sleeves, guide pillars, guide bushings and other parts commonly used together in injection mold assemblies.
Sprue bushing applications
Sprue bushings serve any injection mold that must introduce molten resin cleanly and repeatably.
Connector Mold
Electronic and automotive connector tooling with tight concentricity demands.
Cap & Closure Mold
High-cavity closures and bottle caps needing fast, balanced melt delivery.
Automotive Mold
Dashboards, bumpers and interior parts molded in glass-filled resins.
Electronics Mold
Thin-wall housings and micro components requiring stable, thin-wall flow.
Medical Mold
Syringes, diagnostics and surgical devices, with S136 stainless options.
Thin-Wall Molding
Packaging and containers molded at high cycle speeds with leak-free sealing.
Sprue bushing specifications & capabilities
Typical manufacturing capabilities for OEM and standard sprue bushings.
| Item | Capability |
|---|---|
| Standards | ISO 10072, JIS B 5112 (Types A–F), DIN design dimensions, or customer drawings |
| Materials | SKD61 / H13, SKD11, S45C, pre-hardened steels, alternative steels by agreement |
| Hardness | Through-hardened or nitrided surfaces up to HRC 65–70 (e.g. nitriding), depending on material & application |
| Precision | Concentricity and cylindricity up to 0.002 mm; bore and body tolerance controlled per standard or drawing |
| Surface finish | Ground, polished or SPI A-1 mirror finish options |
| Packaging / marking | Private label packaging and part marking available |
| Lead times | Quotation response within one business day; prototype orders accepted |
What you can expect when working with GUNRI
Practical outcomes that matter to purchasing, quality and sales teams.
Brand flexibility
Support for private label production so you can offer sprue bushings under your own name.
Specification control
Once samples are approved, production follows the agreed drawings and process parameters.
Documented quality
Material information and inspection records can be provided to support your internal quality requirements.
Realistic scheduling
We aim to give achievable timelines and communicate early if any adjustment is needed.
Export experience
Products are regularly shipped to customers in Europe, the USA and Southeast Asia.
Direct factory contact
Communication is handled directly with the manufacturing team rather than through multiple intermediaries.
Reducing risk when choosing a new sprue bushing supplier
We understand that adding or changing a manufacturing partner requires care.
Sample verification first
Production quantities begin only after you have approved samples against your requirements.
Transparent process
Key process steps and material information can be shared so you understand how the parts are made.
Scalable volumes
Start with smaller quantities and increase once quality and communication have been confirmed.
Established factory
GUNRI has manufactured precision mold components since 2006 and regularly supplies international customers.
How sprue bushing collaboration typically works
A straightforward sequence designed to protect both sides.
Share requirements
Drawings, standards reference, estimated volumes or sample photos.
Review & quotation
Feasibility feedback and clear pricing with a realistic lead time.
Sample approval
You evaluate samples before any larger production begins.
Ongoing supply
Repeat orders follow the approved specification and agreed communication.
Sprue bushing FAQ
Quick answers for buyers and engineers evaluating sprue bushing supply.
What is a sprue bushing?
A sprue bushing is a mold component that guides molten plastic from the injection molding machine nozzle into the mold. It is flush-mounted in the sprue (clamp) plate, keeps the sprue aligned with the nozzle, and its polished bore and spherical radius help material flow smoothly.
What standards are used for sprue bushings?
Sprue bushings are commonly manufactured to ISO 10072 (international), JIS B 5112 (Japanese, Types A–F) and DIN design dimensions. GUNRI produces to these dimensional standards, to your drawings, or to a reference/sample part you provide.
What materials are used for sprue bushings?
Common materials include SKD61 / H13 hot-work steel, SKD11, S45C and pre-hardened steels. Hardness can be through-hardened or produced by nitriding to work-hardened surface levels around HRC 65–70, depending on the application and material.
Can GUNRI make sprue bushings under our own brand?
Yes. GUNRI offers OEM / private label production: parts are manufactured to your requirements with your packaging and marking, so you keep the brand relationship with your customers.
How precise are your sprue bushings?
Concentricity and cylindricity can be controlled up to 0.002 mm, with tolerance verification against the drawing or standard. Samples are supplied for approval before production quantities begin.
Which sprue bushing material should I choose?
For most tooling, SKD61 / H13 or pre-hardened steel is a reliable default. Pre-hardened grades are cost-effective for high volumes, while SKD61 / H13 suits higher wear and temperature demands. A/B types allow material by agreement; C/D and E/F follow the JIS B 5112 material designations.
What is the difference between Type A and Type B sprue bushings?
Under JIS B 5112 the type letter mainly defines the nozzle seat: Type A has a spherical radius that matches a radius-tipped machine nozzle, while Type B has a flat nozzle seat for flat-tip nozzles. The same pairing repeats for types C/D and E/F.
Do you provide inspection reports and what is the MOQ?
Yes. Dimensional inspection reports are supplied with each batch on request. We keep order volumes flexible — from prototype and sample quantities up to repeat production runs for distributors and OEM customers.
What is the difference between cold and hot sprue bushings?
Cold sprue bushings are the unheated standard type covered by ISO 10072 and JIS B 5112: the sprue solidifies with each cycle and is separated from the part and reground. Hot (heated) sprue bushings build a heating element into the bushing to keep the melt molten, which eliminates the cold sprue; they are used in hot-runner systems or to retrofit existing molds. Heated types have no ISO or JIS standard and are made to the customer’s drawing. GUNRI supplies standard cold sprue bushings and accepts custom heated-type orders on request.
Related mold component manufacturing
Combined with sprue bushings, these precision components complete your mold supply program.
Tell us about your sprue bushing project
The more details you provide, the faster and more accurate our response will be.
Please email us with your standards reference or drawing (DWG / DXF / PDF / STEP / IGS), approximate volumes and any private label requirements.
GUNRI · Dongguan Gunri Precision Hardware Co., Ltd. · Dongguan City Hengli Town Liujia Industrial Zone, China · milla@gunri.com.cn
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