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:Long Black Screws, Hex Washer Flange Head
Materials:Steel
Surface treatment:Black Zinc Plated
Head Type:Hex Washer Head
Drive:External hex
Thread:Machine thread
Point:Blunt
Forming:Multi-station heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:137
We make long black screws in black zinc plated steel with a hex washer head and a machine thread, quoting them from M1 to M14. Across flats, flange diameter, head height, lengths and finish come from your drawing, and the first article is assembled in your joint.
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.
Long black screws are long fasteners with a dark zinc finish, used where a joint spans a gap and the fixing should not stand out against a dark assembly. This one has a hex washer head, a machine thread and a black zinc finish over steel, quoted from M1 to M14 with Number 137.
Hex washer head. Six flats with an integral flange underneath, so the clamp is spread without a separate washer.
Long shank. A body long enough to pass through a spacer or a frame and reach the tapped part behind it.
Machine thread. A rolled thread for a tapped hole or a nut, ending in a blunt chamfer.
Black zinc. A dark sacrificial zinc deposit, chosen so the fixing disappears into a dark assembly.
Long black screws are used where a joint spans a gap in a dark assembly and the fastener should not be noticed: black frames, coated panels, machine housings that are opened for service. The flange does the spreading, the length does the reaching, and the black zinc does the disappearing.
A long black screw is bought for two things at once: reach and invisibility. The length carries the fastener through the parts of the joint, and the dark finish keeps it from drawing the eye in a black chassis or a dark frame. The flange is the third part of the design, and it is what makes the head usable on a thin or coated surface.
The flange is formed with the hex in one strike, so it cannot be dropped or lost. On a long screw that matters more than on a short one, because the joint is often opened to get at something behind the fastener, and a loose washer in a deep assembly is a part that has to be fished out. A flanged head is the same bearing area with nothing to lose.
Black zinc is the reason the part is specified rather than a white zinc screw. It is a thin sacrificial deposit with a dark conversion layer, and it wears where the shank passes through holes: the contrast between the dark coating and the bright steel below makes that wear visible as a line. Indoors that is cosmetic; on a joint opened often it is the first thing the customer sees.
The length is where the assembly feels the screw. A long shank has a small polar section relative to its length, so it takes part of the wrench torque as twist before the thread turns; the drive has to be steady and the thread fit has to be reasonable, or the joint seats on a shank that is still sprung. On a black zinc screw the friction is not much lower than on plain steel, which is why the wrench feels the length.
What the combination gives is a fastener for a deep, dark joint: a flange that spreads the clamp without a washer, a length that reaches, and a finish that does not show. What it does not give is corrosion protection worth the name out of doors, because the coating is thin and the shank is the surface that wears it away.
The recorded range is M1 to M14, with lengths made to the drawing. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For long black screws the quotation carries across flats, flange diameter, head height, overall length, thread length and the finish.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Hex washer head | Across flats, height and flange diameter |
| Flange | Integral flat annulus | Flatness and edge condition |
| Shank | Long body to the thread | Diameter and length |
| Thread | Machine thread | Pitch, length and gauging after plating |
| Material | Carbon steel | Grade and heat number on the certificate |
| Finish | Black zinc plated | Thickness, colour and coverage |
| Process | Multi-station heading | Head form and shank condition |
Flange diameter is the number to specify against the panel. It is larger than the hex and it is what spreads the load, so a flange one size down no longer does the job the head was chosen for.
Thread length is quoted from the tip and plain length from the head. On a long black screw the plain section is most of the part, and it is what passes through the clearance holes of the joint.
Three features define the part: the black finish, the flange and the length. The first makes it disappear, the second spreads the clamp without a washer, and the third gives the reach.
| Feature | What it gives | What it costs |
|---|---|---|
| Black zinc | Dark finish for dark assemblies | Wear shows as a bright line |
| Flange | Clamp spread without a washer | Larger head footprint |
| Long shank | Reaches through a spacer or frame | Twists under driving torque |
| Hex head | Wrench drive, full bearing face | Head stands above the surface |
| Carbon steel body | Strength and cost | Needs the coating for corrosion |
The dark finish is what most customers come for. In a black assembly a bright zinc screw is the one detail that draws the eye, and black zinc removes it at a small cost in protection and a visible wear line if the joint is opened often.
The flange is what makes the head practical. A long screw in a thin panel with a narrow hex head will dish the panel; the flange spreads the same clamp over a ring wide enough that the panel stays flat.
The recorded finish is black zinc plating over carbon steel. It is a zinc deposit with a dark conversion layer on top: sacrificial like white zinc, but thinner-looking and much less forgiving of handling marks, because the contrast between the dark coating and the bright steel is high.
| Option | How it protects | Effect on flange and thread | Typical use |
|---|---|---|---|
| Black zinc plated | Sacrificial zinc, dark | Thin build; wear visible at the shank | Dark chassis and frames |
| Black oxide | Conversion film, oiled | No measurable build; wears gradually | Internal mechanisms |
| White zinc plated | Sacrificial zinc, bright | Thin build; wear less visible | General indoor work |
| Dacromet | Inorganic zinc-aluminium layer | Thick; thread allowances needed | Wet outdoor assemblies |
| Stainless alternative | Passive film, no build | Flange and thread as made | Wet and food service |
Where the joint is opened often, black oxide is the better dark finish on a long screw: it does not sit on the surface as a deposit, so it wears into the steel gradually instead of showing a bright ring at the first assembly.
Where the joint is damp, neither dark finish is enough. A long carbon steel screw has the least protection exactly where it passes through the parts, and the stainless version is the specification that removes the question.
Three assemblies where long black screws are the fixing:
| Where it sits | The screw joins a panel to a frame through a spacer, where the fixing should not stand out against a black finish. |
| When it goes wrong | The black zinc wears at the shank and shows a bright line after the panel has been off once. |
| Why it happens | The joint spans a gap, the finish is dark, and the panel is serviced. |
| What we control | Finish thickness and colour checked; first article assembled twice. |
| Where it sits | The screw clamps a painted or powder-coated panel where a flanged head spreads load without marking the coating. |
| When it goes wrong | A narrow head marks the coating, and a long shank twists before the joint seats. |
| Why it happens | The joint sets a distance, the panel is coated, and the head is visible. |
| What we control | Flange diameter and face flatness checked; first article fitted on the panel. |
| Where it sits | The screw holds frame members together where a wrench reaches the head and the length is structural. |
| When it goes wrong | A long shank twists under the wrench, and the joint never seats. |
| Why it happens | The joint is structural, the access is by wrench, and the head is visible. |
| What we control | Thread fit and shank checked; driving tested on the first article. |
Four reasons that matter on a long dark part, each tied to what the drawing has to prove:
|
Flange and length agreed
Across flats, flange diameter, head height and both lengths are agreed as a set, because on long black screws the head and the reach both decide the joint. Basis: Flange and lengths agreed. |
Headed, threaded, plated in one route
The hex and flange are formed, the thread rolled and the parts black zinc plated within one route, so the flange face stays square to the shank. Basis: One route from wire to plated screw. |
|
Flange and coating checked
The flange is checked for diameter and flatness and the coating for thickness and colour, because both are what the customer sees first. Basis: Flange and coating checked. |
Packing fixed by the first article
Packing is agreed with the first article, because on a long part the transit is part of the process. Basis: Packing agreed at first article. |
Shi Shi Tong makes long black screws on multi-station headers that form the hex and the flange in one strike, draw the long shank, roll the machine thread and black zinc plate the parts. The first part of every run is measured on across flats, flange diameter and flatness, overall length and thread before the batch continues.
|
|
Forming a flange under a hex is where the head is decided. The punch has to push metal outward into a flat annulus without leaving a step where the flange meets the flats, because a step becomes a stress line and the face deforms there first under a wrench.
What decides whether long black screws pass is the flange, the coating, the shank and the thread. The inspection agreement covers those, and the criteria come from the drawing.
Head and flange on the projector |
Thread gauged after plating |
Hardness checked on the wire |
Coating proved by salt spray |
The flange is measured for diameter and checked for flatness, the hex for across flats and height, and the shank for diameter along its length. The thread is gauged after plating, and the coating is compared with the approved sample for colour as well as thickness.
The first article is assembled into the customer joint and checked for how the flange bears. A flange that measures correctly and marks a coated panel has still failed the purpose it was specified for.
Every shipment of long black 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 coating. The documents carry the drawing revision and the batch number, so a repeat order keeps the same flange and the same colour.
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 long black screws the first article is fitted into the customer joint and assembled twice where the finish is visible, because wear is what the customer sees first. Buyers visit during the process to review samples.
|
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 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 |
The dark finish disappears into a dark assembly. It is chosen for appearance and it wears more visibly than white zinc.
It spreads the clamp over a ring wider than the hex, so a thin or coated panel is not marked, and it cannot be lost like a washer.
It wears where the shank passes through holes. The steel shows bright and the zinc beside it still protects.
The shank absorbs part of the torque before the thread turns. Steady driving and a clean thread matter more than force.
Overall length, with the thread length quoted from the tip and the plain length from the head.
Across flats and head height, flange diameter, overall length, thread length, the grade and the finish.
How a long black screw project runs from drawing to repeat delivery:
|
1
Send the drawing and the joint it spans
|
→ |
2
Flange, lengths and finish agreed
|
→ |
3
First article assembled in your joint
|
→ |
4
Batch production and repeat orders
|
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 across flats and head height, flange diameter, overall length, thread length, the grade and the finish.
|
Head A/F
|
Flange diameter
|
Overall length
|
|
Thread length
|
Grade
|
Finish
|
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
