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:Special countersunk flat head screw tail with hexagon socket
Materials:Carbon steel
Surface treatment:Color zinc plated
Head Type:Countersunk head
Drive type:Hex socket (Allen)
Tail feature:Hexagon socket in the tail (driven from the tail); per drawing
Thread:Machine thread
Forming:Multi-station cold heading with tail socket
Number:1009
We manufacture socket head flat screws in carbon steel with a countersunk head and a hexagon socket cut into the tail, colour zinc plated and made to drawing. Head angle, tail socket size and depth, thread class, plating and the key access through the pocket are settled before the batch runs.
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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 socket head flat screw is a countersunk screw that is driven from a hexagon socket cut into its tail rather than from its head. The one on this page is carbon steel, colour zinc plated, with a smooth countersunk head that sits flush in the panel and a tail socket that takes an Allen key from the back of the joint.
Countersunk head, no drive. The head is a cone with no slot and no socket, so the face that shows is smooth and sits level with the surface. All the driving happens at the tail, which is why the head can stay unbroken on a visible panel.
Tail socket. The hexagon is cut into the tail end of the shank and driven with an Allen key from that side. Its size and depth are limited by the thread: cut too deep and the socket breaks into the thread flanks; cut too shallow and the key does not engage enough to take the torque.
Colour zinc. The part is colour zinc plated after the socket is cut, so the plating covers the socket walls as well as the head. That layer changes the socket fit by a few microns, and the key is checked after plating in the condition the customer assembles.
Together these decide whether the part works: the head sits flush and unbroken, the key reaches the tail socket through the joint, and the thread and plating hold to the drawing.
This socket head flat screw is made from carbon steel wire, cold headed on a multi-station machine, thread rolled, and then plated in colour zinc. The wire heat number is recorded on the material certificate so the batch stays traceable to the coil.
The countersunk head is formed in the heading die, so the cone angle and the head diameter come off the same tool. The tail socket is cut in a separate operation after heading and before plating, because a socket cut after plating would leave bare steel inside the hexagon.
The thread is a machine thread, rolled before the socket is cut. The socket sits behind the threaded section, and the wall between the socket flats and the thread flanks is what carries the driving torque; that wall is set on the drawing and checked on the first article.
Colour zinc is the finish: a zinc layer with an iridescent passivation. It adds a few microns to the thread, the cone and the socket, so all three are checked after plating rather than before it.
Socket head flat screws of this type are quoted in metric sizes from M3 to M10 and in lengths up to 120 mm, with the head angle, the tail socket and the thread measured on the projector and with gauges. 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 angle | The cone that matches the panel countersink | Checked on the projector on the first article |
| Head height | The depth the head sinks into the countersink | Measured from the bearing cone |
| Tail socket size | The Allen key that drives the screw | Checked with the key and on the projector |
| Tail socket depth | Engagement and thread wall | Checked on the projector after plating |
| Thread size and length | Machine thread to the drawing | Gauged per batch after plating |
| Total length | From the top of the head to the tail face | Datum stated on the drawing; measured on the shop plate |
Each size is quoted against the joint it closes. The countersink angle, the panel thickness and the head height are reviewed together, and the tail socket is reviewed against the pocket that gives the key access.
Head height is measured from the bearing cone and the total length from the top of the head to the tail face. The batch is checked on the features the process can drift on: head angle, socket depth and thread class, all read after plating.
The tail socket is what makes this socket head flat screw different from a standard countersunk socket screw. The head has no recess, so the only way to turn the part is from the tail, and that changes both the tooling and the assembly: the key has to reach the tail through the joint, and the socket has to survive the torque on a shank that is already threaded.
Access is decided by the pocket. In a fixture plate the screw is dropped into a blind pocket head-first and turned from the tail side through a bore; in a mould clamp the head face sits against the mould and the key comes in from behind. The pocket depth, the bore diameter and the key length are reviewed with the drawing before production.
Torque is carried by the wall between the socket and the thread. A socket that is too large for the shank cuts into the thread flanks; one that is too small cannot take the key without rounding. The drawing fixes across-flats and depth, and the first article is checked with the key that will be used at assembly.
| Tail feature | Why it matters | What we control |
|---|---|---|
| Across flats | It is the key size | Checked with the key and on the projector |
| Socket depth | Engagement and thread wall | Checked on the projector after plating |
| Socket-to-thread wall | Material that carries the torque | Reviewed on the drawing and checked on the part |
| Key access | The key must reach the tail through the joint | Pocket and bore reviewed with the drawing |
This socket head flat screw is colour zinc plated. The zinc protects the carbon steel sacrificially, so a scratch at the cone or on the head face does not start rust immediately, and the iridescent passivation gives the colour that the name refers to.
| Finish | How it protects | Effect on head and socket | Typical use |
|---|---|---|---|
| Colour zinc | Zinc layer with iridescent passivation | Build-up in the socket; key-checked after | Indoor fixtures and mould hardware |
| Clear zinc | Zinc layer, clear passivation | Same build-up; key-checked after | Parts where a bright finish is wanted |
| Black oxide | Conversion coating, minimal thickness | No measurable build-up | Indoor parts where black is required |
| Dacromet flake | Zinc-aluminium flake layer | Thin film; socket checked over coating | Outdoor and wet assemblies |
| Stainless (equivalent part) | Alloy resists corrosion without coating | No coating build-up | Wash-down and marine service |
Salt-spray exposure is agreed per project and written on the drawing, and the plated parts are tested in the condition they ship in. On this part the socket is the face that matters: a coating that fills the hexagon changes the key fit even when the head looks perfect.
Packing protects the cone and the head face. Parts are packed so the heads do not knock and the sockets stay clear of debris, and the label carries the batch, the wire heat and the plating lot.
Three assemblies where a socket head flat screw is chosen because the head side is closed or visible and the drive has to come from the tail, and what the screw has to do instead:
| Where it sits | The screw is dropped head-first into a blind pocket and turned from the tail through a bore in the plate. |
| When it goes wrong | A socket that is too shallow slips the key, and a head angle that does not match the pocket leaves the plate face proud. |
| Why it happens | The pocket is blind, the plate face is a datum, and the screws are adjusted during set-up. |
| What we control | Pocket and bore reviewed, head angle matched, and the tail socket key-checked after plating. |
| Where it sits | The screw clamps a plate where the head face sits against the mould and the only access is from the back. |
| When it goes wrong | A head that stands proud marks the mould face, and a socket that rounds under torque leaves the clamp loose. |
| Why it happens | The mould face is a sealing surface, the joint is torqued, and the screw is re-used between runs. |
| What we control | Head height and flatness checked, socket depth held to the shank, and the thread gauged after plating. |
| Where it sits | The screw closes an extrusion joint where the head is buried in the slot and the tail socket is reached through the frame. |
| When it goes wrong | A key that cannot reach the socket stalls the build, and a plated socket that is tight seizes on the key. |
| Why it happens | The frame is assembled on site, the access is through a slot, and the joint is adjusted after alignment. |
| What we control | Key access reviewed, socket size checked with the key, and the plating thickness agreed. |
Four reasons that matter on a socket head flat screw with a tail socket, each tied to what the drawing has to prove:
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Tail socket and thread wall reviewed first
The socket size and depth, the thread wall behind it and the key access through the pocket are reviewed before the die and the socket tool are set, so a part that cannot be driven or would cut its thread is raised first. Basis: Socket, thread wall and access reviewed before tooling. |
Headed, threaded and socketed in one route
The head and thread are formed on the multi-station header and the tail socket is cut in a fixtured step before plating, so the socket stays on the screw axis. Basis: One route for head, thread and tail socket. |
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Socket checked with the key after plating
The socket is checked with the Allen key and the head on the projector after plating, so the part that passes is the part the key engages on site. Basis: Socket and head measured in the plated condition. |
First article to repeat production
The first article fixes the drawing revision, wire heat, die set, socket tool 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 socket head flat screws on a multi-station header: the countersunk head is struck in the die, the thread is rolled, the tail socket is cut in a fixtured operation, and the parts go to colour zinc plating as a batch. The first part of every run is measured on the head, checked with the key 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 socket tool to the key size; the first parts go to the projector and the key check before the run continues, and the setting is recorded. Plated parts are checked again after the bath, so the record covers both the cut and the plated condition.
What decides whether a socket head flat screw passes is not the colour of the zinc: it is the head angle and height, the tail socket size and depth, the thread class and the plating thickness. The inspection agreement covers those, and the criteria come from the drawing.
Thread gauging after colour zinc plating |
Head angle and tail socket on the projector |
Hardness testing where the drawing requires it |
Salt-spray testing of the colour zinc finish |
Each batch is recorded against the drawing revision: head and socket from the first article, the key fit checked, and the thread gauged per batch after plating. If a gauge or the key 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 socket head flat 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. Parts with a tail socket are approved together with the key, so the socket and the tool are signed off as a pair. Buyers visit during the process to review samples and to see how the heads are formed and the sockets cut.
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8,678+
customers served
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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 socket cell 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 countersunk screw with a hexagon socket cut into its tail, so it is driven with an Allen key from the back while the head stays smooth and flush in the panel.
Because the head side is closed or visible. In a blind pocket or against a mould face there is no room for a tool on the head, and a socket in the head would break the flush face that the joint needs.
As much as the wall between the socket and the thread flanks allows. The across-flats and depth are set on the drawing so the socket does not cut into the thread, and the first article is checked with the key that will be used.
Socket head flat screws of this type are quoted from M3 to M10 and in lengths up to 120 mm. Where a long version is required, custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
Yes. Colour zinc builds a few microns on the socket walls and the thread, so the key is checked and the thread gauged after plating, in the condition the customer assembles.
Head diameter, height and countersink angle, tail socket size and depth, thread size and length, total length and datum, material, plating, and the pocket and bore that give the key access.
How a socket head flat screw project runs from drawing to repeat delivery:
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1
Send the drawing or sample
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2
Tail socket and access 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 socket head flat screw quotation, send the drawing with the head diameter, height and countersink angle, the tail socket size and depth, thread size and length, total length and datum, material, plating, and the pocket and bore that give the key access.
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Head diameter and angle
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Tail socket size and depth
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Thread size and length
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Total length and datum
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Material and plating
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Pocket and key access
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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
