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+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:Black Security Screws Carbon Steel Triangle Machine Screws
Materials:Carbon Steel
Surface treatment:Black Zinc Plated
Head Type:Pan Head
Drive:Internal Triangle
Thread:Machine Thread
Point:Blunt
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:550
We make black security screws in black zinc plated carbon steel with a pan head, an internal triangle socket and a machine thread, quoted from M1 to M14. Socket size, head, thread and plating come from your drawing, and the first article is turned with the key your service team uses.
Watch the factory video·Email sst@szsst88.com
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.
Black security screws are screws finished in a dark protective coating and driven through a recess that an ordinary screwdriver will not turn, which here means an internal triangle socket. The recorded item on this page is black zinc plated carbon steel with a pan head, a triangular socket and a machine thread, quoted from M1 to M14 with Number 550.
Internal triangle socket. A three-sided recess with three flat faces and three corners, driven with a triangular key. It takes none of the common bits, and it seats with a positive fit on all three faces.
Pan head. A low dome on a flat bearing face. It covers the hole, spreads the load and stays inside its own diameter, so a row of fixings on a narrow pitch still closes.
Machine thread. A rolled thread with a blunt chamfered end, made for a tapped hole or a nut rather than for forming its own thread.
Black zinc. Electroplated zinc with a dark passivation. It is sacrificial, it is thin enough not to close the socket, and the dark tone is what keeps a fixing from standing out on a black panel.
On black security screws the internal triangle is a socket, not a slot. The recess is formed by a punch in the heading stroke, and it leaves three flat faces inside the head, each driven by a corresponding face of the key. Because the faces are flat and parallel to the key, the contact is a surface rather than a line, which is what gives the drive its grip.
Only three orientations are possible, which sounds like a disadvantage and is not. A cross recess can be entered at four orientations and a hexagon at six, but a triangle is easier to find blind or in a corner, and the key either seats fully or not at all — there is no half-engaged position to drive from.
On black security screws the recess depth is set by the head height, and on a pan head there is enough material for a full-depth socket. That is the reason the form appears on pan heads: a low or wafer head cannot contain a socket deep enough to carry torque, so a triangular drive on a shallow head would only be decorative.
The corners are where a worn key or a forced bit does its damage. The three corners of the socket are the smallest features, and a bit that rocks will round them first; once one corner is rounded the key no longer seats and the screw becomes unremovable without drilling.
Black zinc goes on after the thread is rolled. It builds a few microns inside the socket as well as on the head, so the socket is checked with the production key in the plated condition — the same reason a plated socket drive is always checked after plating.
The family is quoted from M1 to M14, with M1, M2, M3, M4, M5, M6, M7, M8, M9, M10 and M14 in the recorded range. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission; on black security screws the socket size and the head height are quoted with the thread, because the socket has to fit inside the head.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Pan head, flat bearing face | Diameter, height and face flatness |
| Socket | Internal triangle, three faces | Across corners, depth, key tried after plating |
| Thread | Machine thread | Pitch and length, gauged per batch |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Plating | Black zinc, dark passivation | Thickness range and socket clearance |
| Length | From under the head to the end | Measured on the shop plate |
Across corners is the dimension that matters, not across flats. A triangular socket is specified by the width across its three corners, and a key that is a few hundredths small will rock while one that is large will not enter — the window is narrow and it is quoted on the drawing.
Length is measured from under the head, because that face bears on the part. On a machine thread the end is blunt and chamfered so the screw can bottom gently in a tapped hole instead of cutting into the last thread.
Three features define black security screws of this form: the triangular socket, the pan head and the machine thread. The first is the access control, the second is the bearing area, and the third is the joint.
| Drive | Bit needed | Contact on the recess | Where it fits |
|---|---|---|---|
| Internal triangle | Triangular key | Three flat faces | Service access control, electrical |
| Cross recess | Phillips bit | Four tapered wings | General assembly |
| Hex socket | Hex key | Six flat faces | Machine and fixture work |
| Tri wing | Slanted Y bit | Three wings | Consumer products, tamper resistance |
The reason to choose a triangle over a cross is not torque, it is who can open it. A cross recess is in every toolbox; a triangular key is not, and in many markets the triangle is the recognised symbol for a fixing that should only be opened by someone authorised. That is why the drive appears on electrical and gas fittings, where the panel behind the screw carries something dangerous.
The reason to choose it over a tri-wing is the direction of the wings. A tri-wing is built for a shallow head and a small screw; an internal triangle is a deeper socket with flat faces, which suits a machine screw that has to be tightened and re-tightened. Both defeat the same casual attempt, and they suit different heads.
Black security screws carry a black zinc finish with a dark passivation, applied after the thread is rolled. It is a sacrificial coating: a scratch at the head still has zinc around it, and the dark tone keeps the fixing from reading as a bright dot on a black panel.
| Finish | How it protects | Effect on socket and thread | Typical use |
|---|---|---|---|
| Black zinc | Sacrificial zinc, dark passivation | A few microns; key tried after plating | Dark panels and equipment |
| White zinc | Sacrificial zinc | A few microns; socket re-checked | General indoor work |
| Black oxide | Thin conversion film, oiled | No measurable build | Unseen security fixings |
| Dacromet | Zinc-aluminium flake layer | Film builds; socket re-checked | Outdoor and wet assemblies |
| Nickel plate | Hard barrier deposit | Thicker; socket re-checked | Visible handled parts |
On black security screws the socket is the feature plating can spoil. Every micron narrows it, and because the socket is already small the window between a key that enters and one that does not is tiny. On a black zinc part the first article is driven with the production key after plating; a batch that was not checked that way can be unusable with no visible defect.
The tone is the secondary question. Black zinc on a black panel disappears, which is usually the point; but the coating wears at the socket edge and at the corners first, so a screw that has been opened a few times shows bright metal in the recess. That is normal for the finish and worth saying before a customer compares a serviced unit with a new one.
Three assemblies where black security screws with a triangular socket are the fixing:
| Where it sits | The screw closes a cover over terminals or a valve where access has to be restricted and the fixing is small and close to live or pressurised parts. |
| When it goes wrong | A cross recessed screw invites an unqualified owner into a panel that carries mains voltage or gas. |
| Why it happens | The cover protects something dangerous, and the fixing repeats on every unit. |
| What we control | Socket checked with the production key, thread gauged, plating thickness held. |
| Where it sits | The screw holds a panel or a bracket where the manufacturer wants the case opened only by service and the fixing has to sit flush and dark. |
| When it goes wrong | A standard screw is removed with whatever is in the drawer, and the case comes back damaged. |
| Why it happens | The product is serviced by a technician, and the panel is visible. |
| What we control | Recess depth and across corners checked, key supplied with the order. |
| Where it sits | The screw fixes a cover plate or a bracket on equipment that is unattended and contains something worth taking. |
| When it goes wrong | A commonly available drive makes the plate a target, and a stripped recess means the whole unit has to be replaced. |
| Why it happens | The site is unattended, the content is valuable, and the fixing is one of many. |
| What we control | Socket and key checked on the first article, plating held to the sample. |
Four reasons that matter on black security screws, each tied to what the drawing has to prove:
|
Socket and key reviewed together
The across-corners dimension, the socket depth and the key the customer will use are reviewed as one set, so a socket that would not take their key is raised before the die is cut. Basis: Socket and key reviewed as one set. |
Heading, rolling and plating in one route
The pan head and the triangular socket are formed in one stroke, the thread is rolled and the parts are black zinc plated and baked in the same route. Basis: One route from wire to plated screw. |
|
Key tried in the plated socket
The socket is checked for across corners and depth, then driven with the production key in the plated condition on the first article. Basis: First article turned with the production key. |
First article fixes the setting
The first article fixes the wire heat, the socket punch, the roll and the plating barrel; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these black security screws from carbon steel wire on single-die headers that upset the pan head and form the triangular socket in one stroke, rolls the machine thread to a blunt chamfered end and black zinc plates the parts. The first part of every run is measured on the head, turned with the production key and entered into a thread gauge before the batch continues.
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The socket punch is the tool that limits the die, and it wears at the three corners. A worn punch leaves a socket that is slightly wider at the mouth than at the floor, which lets the key sit high: the torque then goes into the corners instead of the faces, and those are the first features to round. The socket is checked with the key on the first article and sampled through the run.
What decides whether black security screws pass is the socket, the head, the thread and the plating. The inspection agreement covers those, and the criteria come from the drawing.
Socket across corners on the projector |
Thread gauged after plating |
Hardness testing against the property class |
Salt-spray testing of the black zinc plate |
The socket on black security screws is checked across corners and for depth on the projector, and then driven with the production key. The two checks are not interchangeable: the dimensions say whether the socket is in tolerance, and the key says whether the batch can be used — and on a socket this small the gap between the two is where most returns come from.
The head is checked for diameter, height and face flatness, and the thread is gauged per batch. On a black part the plating is also read on the head as a colour sample, because the tone is what the customer sees on a row of fixings.
Every shipment of black security screws is traceable to the wire it was made from and to the plating batch. The grade and heat number 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. On black security screws the first article is also the point at which the key is agreed, so the customer confirms the tool at the same time as the screw. Buyers visit during the process to review samples and to see how the heads and sockets are formed.
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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 headers 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 |
A three-sided socket with three flat faces, driven with a triangular key. It takes none of the common bits and seats positively on all three faces.
Across corners, not across flats, plus the socket depth. A key a few hundredths small will rock and a large one will not enter.
It will cam out and round the three corners, and once one corner is rounded the key no longer seats. The damage is not repairable.
It is a deterrent. Triangular keys are sold; what the drive does is stop the improvised attempt and signal that the fixing is not for the owner.
It is sacrificial, thin enough not to close the socket, and dark enough to disappear on a black panel. It wears at the socket corners first.
Head diameter and height, socket across corners and depth, thread size and length, the datum, material and plating thickness.
How a black security screw project runs from drawing to repeat delivery:
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1
Send the drawing and the key you drive with
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→ |
2
Socket, head and thread review
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→ |
3
First article turned with the key
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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 quotation, send the drawing with the head diameter and height, the socket across corners and depth, the thread size and length with the datum, the material and the plating.
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Head diameter
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Head height
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Across corners
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Socket depth
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Thread and length
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Material 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
