Tel：
+86 13143444311
Email：sst@szsst88.com
Fax：+0086-755-27322278
Address：Building 9, First Industrial Zone, Tantou Industrial City, Songgang Street, Baoan District, Shenzhen 518105, Guangdong, China
Type:Polished chrome plated irregular truss head carriage head screw
Materials:Carbon steel
Surface treatment:Polished + chrome plated
Head Type:Irregular truss head
Drive type:None (no slot; per drawing)
Thread:Partial (half) machine thread
Forming:Multi-station cold heading with square neck
Number:1615
We manufacture polished chrome carriage head screws in carbon steel with an irregular truss head, a square neck and a partial machine thread, made to drawing. Head profile, square neck, thread class and plating are checked in the plated condition before the batch ships.
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ISO 9001:2015 · Manufacturing since 1998 · 8,678+ customers · 89 countries and regions
Made to order – there is no stock catalogue. Each part is produced to your drawing, and production starts after drawing review and first-article approval.
A carriage head screw is a bolt-like fastener with a smooth, wide head, a square neck under the head and a partial machine thread. It is not turned from the head: the square neck keys into a square hole in the panel, and a nut on the thread pulls the joint together while the neck stops the screw from rotating.
Smooth head, no drive. The head has no slot and no socket, so nothing shows on the face except the polished shape. That is why a carriage head screw is used where the head is visible: furniture, railings, trim and equipment where the fastener is part of the finish.
Square neck. The neck is a short square section between the head and the thread. It fits a square hole in the panel, so the screw is held against rotation while the nut is tightened from the other side. The across-flats of the neck and the hole are a pair.
Irregular truss head. The head on this page is a modified truss: wide and low, with the exact profile set on the drawing rather than taken from a standard table. The profile is polished before plating, so the shape has to be smooth enough to take a mirror finish without showing tool marks.
Together these decide the joint: the head seats on the panel, the square neck keys into the hole, and the partial thread takes the nut without the screw turning.
This carriage head screw is formed from carbon steel wire on a multi-station header, thread rolled, polished and chrome plated. The grade comes from the drawing, and the wire heat number stays traceable to the material certificate.
The irregular truss head is formed in the die, and the square neck is produced under it. The head profile is what the customer sees, so it is polished before plating; a die mark or a lap line on the head would show through the chrome like a scratch under glass.
The thread is a partial machine thread, rolled before polishing. Chrome plating builds on the thread, the neck and the head, so all three are checked after plating, in the condition the nut and the panel see.
The finish is polished carbon steel with a chrome layer on top. Chrome is decorative and hard, but it is also brittle: it covers a polished surface and it does not hide a scratch, a pit or a sharp edge underneath. That is why the polishing step is part of the process and not a preparation.
Carriage head screws of this type are quoted from M5 to M12 and in lengths to suit the drawing, with the head and the square neck measured on the projector and the thread gauged. Where a long version is required, custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
| Item | How it is defined | What we control |
|---|---|---|
| Head diameter and height | The irregular truss profile | Checked on the projector on the first article |
| Head finish | The polished face under the chrome | Checked for marks before plating |
| Square neck | The neck that keys into the square hole | Checked with the mating hole on the first article |
| Thread size and length | Partial machine thread to the drawing | Gauged after plating |
| Plated dimensions | Head, neck and thread read after plating | Measured again after chrome |
| Total length | From the top of the head to the tip | Datum stated on the drawing; measured on the shop plate |
Each size is quoted against the panel it passes through. The square hole, the neck across-flats and the head diameter are reviewed together, because a neck that is right for one panel rattles in another and a head that is too wide covers the wrong area.
Head height is measured from the bearing face and the total length from the top of the head. The batch is checked on the features the process can drift on: head profile, neck size and thread class, all read after plating.
The truss head is wide and low, with a bearing face that spreads the load over the panel. On a carriage head screw the head is also the visible face, so the profile is polished rather than left as headed. An irregular profile is made to the drawing: the radius, the edge and the height are set by the customer, not by a standard.
The square neck is the feature that replaces the drive. It sits in a square hole, and the hole takes the torque that a driver would otherwise take from a recess. The neck has to be square to the head and the thread, or the head sits at an angle when the nut is tightened.
The partial thread leaves a plain shank between the neck and the thread. That shank passes through the panel without cutting it, and the thread behind it takes the nut. A thread that runs too close to the neck grips the panel and stops the head seating.
Chrome changes all three by a few microns. The thread is gauged after plating, the neck is checked in its hole, and the head is inspected under light for pits or polishing marks that the chrome would amplify.
This carriage head screw is polished and chrome plated. The polishing step levels the head and the shank, and the chrome layer goes on top as a hard, reflective finish. The result is a part that is meant to be seen, so the inspection of the finish is as strict as the inspection of the thread.
| Finish | How it protects | Effect on head and thread | Typical use |
|---|---|---|---|
| Polished + chrome | Hard reflective layer over polished steel | Build-up on thread; gauged after | Visible furniture and trim |
| Nickel plated | Barrier layer with a warm tone | Build-up on thread; gauged after | Indoor decorative hardware |
| Zinc plated | Sacrificial zinc layer | Build-up on thread; gauged after | Indoor structural joints |
| Dacromet flake | Zinc-aluminium flake layer | Thin film; thread checked over coating | Outdoor and wet joints |
| Stainless (equivalent part) | Alloy resists corrosion without coating | No coating build-up | Marine and wash-down service |
Salt-spray exposure is agreed per project and written on the drawing. Chrome over carbon steel is decorative rather than a marine finish: a scratch through the layer exposes steel, and the corrosion spreads under the chrome. Where the joint sees salt, stainless or a flake coating is the specification.
Packing protects the polished head. Screws are packed in layers with the heads separated, and the label carries the batch, the wire heat and the plating lot.
Three assemblies where carriage head screws are chosen for the smooth visible head and the square neck, and what the screw has to do instead:
| Where it sits | The screw passes through a timber or metal frame into a nut, and the polished head is part of the visible finish. |
| When it goes wrong | A head that is not polished shows lap marks under the chrome, and a neck that is loose lets the frame rack during assembly. |
| Why it happens | The frame is visible, the joint is pulled up once, and the head sits on a finished face. |
| What we control | Head profile polished and checked, neck matched to the square hole, and the thread gauged after plating. |
| Where it sits | The screw holds a rail or a fitting where the head is visible and the joint sees weather. |
| When it goes wrong | Chrome over steel pits at a scratch, and a neck that is not square to the head leaves the fitting at an angle. |
| Why it happens | The parts are outside, the heads are seen, and the joint is exposed to salt or rain. |
| What we control | Finish agreed for the environment, neck squareness checked, and the head inspected before plating. |
| Where it sits | The screw fixes trim or a panel where the head has to sit low and smooth on a painted surface. |
| When it goes wrong | A head that is too tall fouls the trim, and a plating build on the thread stops the nut running down. |
| Why it happens | The trim is thin, the head is exposed, and the joint is assembled on a line. |
| What we control | Head height checked, thread gauged after plating, and the neck tried in the square hole. |
Four reasons that matter on a polished chrome carriage head screw, each tied to what the drawing has to prove:
|
Head profile and neck reviewed first
The irregular head profile, the square neck and the thread are reviewed before the die is cut, so a head that would not polish or a neck that would not key is raised first. Basis: Head profile and neck reviewed before tooling. |
Headed, polished and plated in one route
The head and neck are formed, the thread is rolled, the parts are polished and then chrome plated as a batch, so the finish and the thread are controlled together. Basis: Polishing and plating recorded per batch. |
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Thread and neck checked after plating
The thread is gauged after chrome and the neck tried in the square hole, so the part that passes is the part that assembles. Basis: Thread and neck checked in the plated condition. |
First article to repeat production
The first article fixes the drawing revision, wire heat, die set and plating lot; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these carriage head screws on a multi-station header: the irregular truss head is struck in the die, the square neck is produced under it, the partial thread is rolled, and the parts are polished and chrome plated. The first part of every run is measured on the head and the neck, checked with the square hole and gauged on the thread before the batch continues.
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Between runs the die insert is changed to the drawing head and the neck tool is set with the thread length; the first part goes to the projector and the gauges before the run continues. Polishing is checked before plating, because a mark that goes into the bath comes out under the chrome.
What decides whether a carriage head screw passes is not only the shine: it is the head profile, the square neck, the plating thickness and the thread class. The inspection agreement covers those, and the criteria come from the drawing and the mating square hole.
Head profile and neck on the projector |
Thread gauging after chrome plating |
Hardness testing where the drawing requires it |
Salt-spray testing of the plated finish |
Each batch is recorded against the drawing revision: head and neck from the first article, the neck tried in the square hole, the finish inspected under light, and the thread gauged after plating. If a gauge or the finish check fails, the parts back to the last good setting are held and re-checked.
Where a third-party report is required for the material or the plating, it is listed on the drawing so the paperwork ships with the parts, and the batch number on the label matches the record used for inspection.
Every carriage head screw shipment is traceable to the wire it was made from. The grade, heat number and standard are recorded on the material certificate supplied with the parts, and the inspection records follow the criteria agreed on the drawing.
ISO 9001:2015 |
RoHS test report |
Registered trademark |
Patent: security screw and driver |
With each batch we supply the material certificate, the inspection record for the criteria on the drawing and, where it is listed, the third-party report for the material or the plating. The documents carry the drawing revision and the batch number, so the paperwork can be matched to the parts.
More than 8,678 customers in 89 countries and regions have ordered from Shi Shi Tong; 87% of orders come from repeat customers and 56% through referrals. Most projects follow the same route: drawing review, first-article approval, then batches checked against that sample. Polished parts are approved by eye under agreed light as well as on the projector, because the chrome shows every mark the polishing left. Buyers visit during the process to review samples and to see how the heads are formed and polished.
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8,678+
customers served
|
87%
of orders from repeat customers
|
56%
of orders through referrals
|
89
countries and regions shipped to
|
Buyers and quality engineers visit for sample review, process discussion and supplier audits; the visit is arranged around production so the header, the polishing line and the plating line can be seen on the day the parts run.
Customer group visit – sample review |
Customer group visit – process discussion |
Customer group visit – factory tour |
Customer visit – project kick-off |
Danish customer – drawing review |
Industry exhibition – meeting customers |
It is a bolt-like fastener with a smooth wide head, a square neck under the head and a partial machine thread. A nut pulls the joint together while the square neck stops the screw from turning.
From the nut side. The head has no recess, so a driver cannot turn it; the square neck keys into a square hole in the panel and holds the screw while the nut is run down.
A wide, low head whose profile is made to the drawing rather than taken from a standard table. It is polished before chrome plating, so the shape has to be smooth enough to take a mirror finish.
Carriage head screws of this type are quoted from M5 to M12 and in lengths to suit the drawing. Where a long version is required, custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
Yes. Chrome builds on the thread, the neck and the head, so the thread is gauged after plating and the neck is checked in the square hole in the plated condition.
Head diameter, height and profile, square neck across flats, the panel hole, thread size and length, total length and datum, material, polishing and plating specification.
How a carriage head screw project runs from drawing to repeat delivery:
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1
Send the drawing or sample
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→ |
2
Head and neck review
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→ |
3
First article approval
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→ |
4
Batch production and repeat orders
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Each step is confirmed with you before the next one starts; the drawing revision from the first article is what repeat orders are checked against.
For a carriage head screw quotation, send the drawing with the head diameter, height and profile, the square neck across flats, the panel hole, thread size and length, total length and datum, material, and the polishing and plating specification.
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Head diameter and profile
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Square neck across flats
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Panel square hole
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Thread size and length
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Total length and datum
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Polishing and plating
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Sending a drawing? The form below does not take attachments. Email the PDF, DXF or STEP file to sst@szsst88.com with the part name and quantity in the subject line – the drawing is reviewed and a quotation follows.
+86 13143444311
sst@szsst88.com
