01
Pins break every 1,000–2,000 shots
A pin that is too long for its diameter bends under injection pressure, then cracks at the root. The die stops, and the run waits on a replacement pin.
Die Casting Tooling
Mold Tooling Core Pin Design
Inside every die casting die sit the pins that form its internal features. They are also the parts that break first. We design, machine and replace them to hold size over long runs.
±0.005 mmRa 0.2–0.8 μmOne-piece or two-pieceØ400 mm rotary tableNo MOQ
2011Tooling and machining since
127High-precision CNC machines
±0.005 mmAchievable tolerance
99.99%Qualification rate
Failure Modes
Where Core Pins Actually Fail
Most core pin problems show up as downtime before they show up as scrap.
02
Flash grows around the internal bore
A worn or undersized pin leaves a gap at the shutoff. Thin flash inside a bore is slow to deburr and often fails at incoming inspection.
03
Hot spots stretch the cycle
A long unsupported pin has no cooling inside it. That section of the casting stays hot, so the operator adds dwell time and output drops.
04
Replacement lead times stall the press
The pin is a single-source item with no drawing. The tool room measures the broken piece, guesses the alloy, and the machine sits idle for days.
Design Approach
Designing a Core That Survives the Run
Length, diameter, support and cooling decide how long a pin lasts.
Rule of Thumb
Watch the length-to-diameter ratio
A slender pin behaves like a column. Once the unsupported length climbs past roughly 3 to 4 times its diameter, injection pressure starts to bend it, and the bending concentrates at the root radius. That is where the crack opens.
We check the ratio before we cut steel. If the feature needs a long reach, we look at stepping the diameter, adding a support shoulder in the die, or splitting the pin into two pieces so the slender section stays short.
- 1Short and stubbyRatios under 3:1 usually run as one piece with no extra support.
- 2Mid range3:1 to 6:1 needs a stepped shank or a guide shoulder to share the load.
- 3Long reachPast 6:1 the pin is a candidate for a two-piece design with a hardened tip.
Two-Piece Construction
When a one-piece pin cannot hold up
A one-piece pin has to be made from one bar, and that bar has to be hard enough to resist wear and tough enough not to snap. On a long pin, those two requirements pull in opposite directions.
A two-piece design separates them. The tip is a short, hardened insert in a wear-resistant tool steel. The body is a softer, tougher shank that absorbs bending. The joint is machined to a light press or a precision shoulder so it cannot flash or shift under pressure.
We machine both halves on the same setup so the tip runs concentric to the shank within ±0.005 mm. That concentricity is what keeps the shutoff tight over the life of the die.
- 1Hardened tip insertTakes the wear at the shutoff and can be replaced alone.
- 2Tough shankAbsorbs bending load instead of transferring it to a brittle tip.
- 3Precision jointPress or shoulder fit prevents movement and flash at the seam.
Selection Guide
Matching the Pin to the Feature
Start with the feature geometry, then pick the construction.
| Feature condition | Recommended construction | Main risk if ignored |
|---|---|---|
| L/D below 3:1, low volume | One-piece, through-hardened | Little risk, lowest cost |
| L/D 3:1 to 6:1, high volume | Stepped shank, one piece | Root cracking under pressure |
| L/D above 6:1 | Two-piece with hardened tip | Bending and early breakage |
| Tight shutoff, cosmetic bore | Two-piece, ground concentric | Flash and visible parting line |
| Deep blind hole | Stepped pin with ejector support | Pin pull-out and drag marks |
What We Make
Tooling and Machining Services
Core pins rarely come alone. Most projects need the whole set around them.
01
Mold Tooling Core Pins
Round, stepped, D-shaped and blade cores machined to your die drawing, in hardened tool steel or beryllium copper for hot spots.
02
5 Axis CNC Machining
16 simultaneous 5-axis centers cut angled cores, slides and inserts that a 3-axis setup cannot reach in one fixturing.
03
CNC Milling & Turning
Mill-turn centers produce round cores with shoulders, threads and reliefs in a single operation, so concentricity stays tight.
04
Metal Die Casting
Production die casting in ADC12 and other alloys, with the thermal and flow behavior of the core built into the tool design.
05
Rapid Prototyping
Functional samples before the die is cut, so the internal feature is proven before steel is committed.
06
Part Surface Finishing
Polishing, hardcoat anodizing and bead blasting to control release and wear on cores and cavity surfaces.
Capability
Tooling Capacity at a Glance
Numbers you can check against your drawing.
| Item | Range | Notes |
|---|---|---|
| Maximum part size | 4,000 mm | Largest travel on the gantry machines |
| Core pin diameter | From Ø1 mm | Below this, grinding support is limited |
| Round tolerance | ±0.005 mm | Held on concentric features |
| Surface finish | Ra 0.2–0.8 μm | On ground and polished cores |
| Materials | Tool steel, 17-4PH, beryllium copper | Per drawing and thermal need |
| Inspection | 100% before shipment | Reports on request |
Why GreatLight
What We Bring to a Core Pin Job
2011
Tooling since 2011
Fifteen years of die and core work across three wholly-owned plants in Dongguan and Singapore.
127
CNC machines on site
16 simultaneous 5-axis centers, 12 four-axis mills, 16 mill-turn centers and 27 three-axis machines.
±0.005
Tolerance we hold
Concentric shank-to-tip fits that keep the shutoff closed over the die life.
12 h
Quote turnaround
Quotation and a free DFM analysis within 12 hours of receiving your files.
24 h
Production start
Manufacturing can begin within 24 hours once the design is agreed.
1 pc
No minimum order
One replacement pin or a 10,000-part run. The setup is the same.
7,600 m²Manufacturing space
150Technicians and engineers
3Wholly-owned plants
4,000 mmMaximum processing size
Industry Requirements
What Each Industry Demands from Tooling
Automotive & EV housings
Deep cores in long runs where a stop costs the full shift. We hold concentricity so the bore stays on size shot after shot.
- IATF 16949
- ±0.005 mm
Heat sink and thermal parts
Pin count climbs fast, and every pin sits in a hot zone. Beryllium copper cores and stepped shanks spread the heat.
- ADC12
- Ra 0.8–1.6 μm
Medical device enclosures
Small internal features with tight cosmetic rules. A two-piece pin keeps the shutoff clean enough to skip hand work.
- ISO 13485
- 100% inspection
Industrial machinery castings
Low to mid volume with frequent design changes. Replacement cores are made to the drawing, not reverse-engineered from a broken part.
- No MOQ
- 3–5 day shipping
FAQs
Questions Engineers Ask
How do I know my core pin needs a two-piece design?
Start with the unsupported length divided by the pin diameter. Below 3:1 a one-piece pin is normally fine. Above 6:1 the pin bends under injection pressure and the root is where it cracks.
Between those numbers the answer depends on volume and on how close the core sits to a gate. High shot counts and a hot location push the decision toward two pieces.
What is the real cost of a broken core pin?
The pin itself is cheap. The downtime is not. A press that stops for a replacement loses the shots it would have made during the wait, plus the scrap from the last cycle and the restart.
That is why we ask about shot count and cycle time before we quote. A design that costs slightly more to machine but runs twice as long usually wins.
Can you match a core pin without a drawing?
We can measure the worn or broken pin and rebuild it, but we prefer the die drawing or the 3D model of the casting.
Without the drawing, we cannot check whether the original diameter was correct in the first place. Rebuilding a pin that was already undersized just repeats the failure.
Which material should the core pin be?
Hardened tool steel covers most wear situations. Where the pin sits in a hot zone and cooling is limited, beryllium copper moves heat out of the core faster.
For corrosive alloys we look at 17-4PH stainless. The choice follows the alloy being cast and the thermal load, not a default.
How does cooling inside the core work?
A long core can be drilled and fitted with a bubbler or a baffle so coolant reaches the tip. That shortens the local solidification time.
Not every pin has room for it. Below roughly Ø3 mm the wall gets too thin to drill reliably, so we look at the surrounding insert instead.
What tolerance do you hold on a replacement core?
We hold ±0.005 mm on concentric features and on the shutoff diameter. That is what keeps flash from appearing at the bore.
Every core is inspected before shipment, and dimensional reports are available on request.
Do you work from our die drawings or reverse-engineer?
Either. Most customers send a 3D model and a 2D drawing with the fit and material called out.
When only a sample exists, we measure it, model it, and send the model back for approval before cutting steel. Your files stay confidential, and an NDA is available.
What is the lead time on a small core pin order?
Quotation and a free DFM analysis come back within 12 hours. Production can start within 24 hours after approval.
Most parts ship in 3–5 days. There is no minimum order quantity, so a single replacement pin goes through the same process as a full set.
Send Us the Core That Keeps Breaking
Upload the die drawing or the worn pin. You get a quotation and a free DFM analysis within 12 hours.
12-hour quote100% inspectionNo minimum order
