Category: Clay Sand Casting
Electrical power fittings connect, support and protect conductors and insulators in overhead power transmission and distribution systems. At Zhaoyuqi Machinery, we manufacture these fittings as customized iron castings produced directly from customer drawings, with more than 20 years of foundry experience behind every piece. Whether you need connector bodies, line hardware, bracket plates or special accessories for a rural grid upgrade or an industrial power project, we deliver castings that match your design, your material spec and your delivery schedule.
Ductile iron combines high tensile strength with good elongation, which makes it a practical choice for fittings that carry mechanical loads and see vibration over decades of outdoor service. Gray iron, with its excellent damping properties, suits brackets and housings where stiffness matters more than impact resistance. We produce both, in the grades your drawing calls for, and we verify nodularity of ductile iron at a spheroidization rate above 90% before any batch ships.
Five families cover most overhead line work. Connector and clamp bodies hold conductors and earth wires at joints and tap points, and they are the parts most often rejected for shrinkage porosity, so they run on the automatic line under tighter sand control. Insulator fittings and attachment hardware, meaning caps, pins and yoke plates, transfer the mechanical load into the insulator string and are cast in ductile iron for that reason. Brackets, clevises and coupling parts fix the assembly to the pole or tower, and their hole patterns are almost always the customer's own. Terminal and lug housings for distribution boxes are smaller and get machined on two or three faces. The fifth family is the one no catalogue covers: special accessories drawn by the utility or its contractor, tooled from a STEP file and sampled before the batch run.
Parts are produced on our fully automatic clay sand casting line, with raw material purchased directly from steel mills. For lighter fittings weighing 0.5-50 kg we use sand casting; larger housings and brackets up to 200 kg can be produced by lost foam casting where the design suits it. After casting, every fitting passes through shot blasting to clean the surface, followed by finishing operations your part needs: polishing, tapping, screwing, drilling or CNC machining. Outdoor fittings can be painted or hot-dip galvanized against rust.
Depending on voltage class and line configuration, power fittings take many shapes we can cast to your design: single-bolt and double-bolt line clamps, tension and suspension bodies, insulator pin and cap fittings, pole-top brackets, cross-arm end fittings, downlead clamps, earthing connectors, and special transition pieces between two hardware types. Most of these are medium-weight sand castings in the 0.5–50 kg band; we also welcome heavier designs up to 200 kg through our lost foam line.
Our automatic clay sand line routinely handles fittings from 0.5 to 50 kg per piece. Larger housings, base plates and structural brackets up to 200 kg are made by lost foam casting when the geometry fits. Typical cast wall thickness starts around 5 mm for ductile iron; mounting faces and bolt holes are brought to your print by machining afterwards. If your drawing calls for a non-standard weight or section, send it over and we will confirm feasibility before tooling.
Use ductile iron where the fitting sees tension, bending or impact — connector bodies, clamps and clevises rely on its elongation and yield strength. Choose gray iron for housings, covers and static support plates where vibration damping and good machinability matter more. We also produce parts in carbon and stainless steels for special corrosion or temperature requirements. When you are unsure, attach your load case and service environment and we will recommend the grade.
Drawing review — engineering checks castability, draft, risering and machining allowance before quoting.
Sample casting — a first piece is poured and measured so you can approve geometry and material.
Sample confirmation — you sign off the sample and inspection report, locking the spec for bulk.
Bulk production — cast on the automatic line, shot blasted, fettled and machined to order.
Inspection and export packing — 100% checked, then crated for sea freight on the agreed schedule.
To get an accurate quote quickly, include a PDF or STEP drawing with dimensions and tolerance, the required material grade or a request for us to recommend one, annual and trial order quantities, and any surface coating preference such as painting or hot-dip galvanizing. Technical questions go to the engineers who pour and machine your parts, and we reply within one working day.
Buyers often specify ductile iron everywhere because it sounds strongest. That is safe, but not always the best value. Grey iron does one job better than ductile: it damps vibration and holds dimension at lower cost. The table below is how we talk through grade choice on real projects:
| Fitting duty | Grade we recommend | Why |
|---|---|---|
| Dead-end and tension hardware, guy attachments | EN-GJS-450-10 / ASTM A536 65-45-12 | Tensile load with some shock; ductile iron bends before it breaks |
| Insulator brackets subject to vibration | EN-GJS-400-15 | Highest elongation in the family; tolerates handling and thermal swing |
| Fixed support brackets, base plates | EN-GJL-250 grey iron | Static load, cost-sensitive, dimensionally stable as-cast |
| Clamps tightened repeatedly by crews | EN-GJS-500-7 | Higher yield resists thread and seat deformation |
If your drawing already names a grade, we cast to it. If it does not, tell us the duty and we will name one — and say why in writing, so your engineering team can check our reasoning against the line design.
Fittings are usually small, heavily cored parts, and the cores are where cost and quality collide. A cored hole saves a drilling operation but needs a core that survives pouring; below a certain diameter, the core is too fragile to be economic and drilling wins. Our rule of thumb on hardware-sized fittings: holes above roughly 12 mm core cleanly, smaller holes get drilled. Wall sections thinner than about 5 mm next to a thick hub create a hot spot where shrinkage porosity forms, which is why we thicken or radius those transitions at the drawing review rather than after the first article.
This is also where a buyer's drawing habits show up in price. Parts drawn as if they were machined from solid — sharp inside corners, uniform thickness everywhere, holes right against an edge — always cost more to cast than the same function drawn for casting. Fifteen minutes with your designer at the drawing stage is worth more than any negotiation on unit price.
Overhead fittings live outdoors for decades, so the coating system is part of the design, not a finishing choice. Hot-dip galvanizing to ASTM A153 or ISO 1461 is the default for utility work and gives the longest service life in most atmospheres. Zinc-rich paint systems suit cases where galvanizing heat would distort thin sections or where a specific color is required. In coastal or industrial atmospheres with chloride exposure, a duplex system — galvanizing plus a compatible topcoat — is what actually holds.
The detail that gets missed is the interface between casting and fastener. A galvanized fitting bolted with uncoated hardware creates a galvanic couple at the joint, and the fastener corrodes first. Specify the bolt coating with the fitting coating, and ask your supplier to quote the hardware set rather than the casting alone. We do that by default on utility orders because the failure we see most often in the field is not the casting at all.
Ferritic grades such as EN-GJS-400-15 keep useful impact toughness below freezing. If your line runs through hard-winter areas, say so at inquiry — we select grade and heat treatment around the lowest service temperature you expect.
Yes, and that is the right order: machine first, galvanize second, so the coating covers machined faces too. Threads are cut after dipping or masked, and coating thickness is checked against the spec you name.
Each production heat keeps its furnace record and coupon results, and castings are marked with the heat number before finishing. We map batch numbers to heat certificates on the packing documents.
You get a written DFM note before tooling starts, with options: thicken the section, move the hole, or add a core. Deciding at the drawing stage costs nothing; deciding after first articles costs a tooling change.
Yes. Sample quantities for mechanical and coating tests are produced on the production pattern so the tested item matches what will ship. Tell us the test standard at inquiry so the sample carries the right documentation.
Fittings are usually ordered by project or annual contract volume. Batches in the low hundreds keep the automatic line efficient; below that, expect a setup share in the unit price.
Every electrical power fitting we ship is 100% inspected before packing, with dimensions and surface checked against the approved sample. Send us your drawing and we run drawing-based OEM production on our automatic sand line, supported by a 10,000 t/y capacity and a regular 30-day lead time. For a quick reply, use the quote form at the foot of this page.
Send your drawing and quantity for a quotation — we reply quickly with pricing, tooling cost if any, and a production schedule.
Professional technical research and development team to provide customers with the best solution.
Jimo District, Qingdao City, Shandong Province, China
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