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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 self-tapping metal screw, pan washer head, single-lead coarse thread, sharp gimlet point (Non-Standard)
Materials:Carbon Steel
Surface treatment:Black Zinc Plated
Head Type:Pan washer head: low pan dome with a wide thin integral washer flange at its base, flange underside flat and forming the bearing face; no separate washer, no slot in the flange
Drive:Phillips cross recess, four tapered wings with a pointed centre; no slot, no hexagon socket
Thread:Coarse single-lead self-tapping thread, full length from the underside of the flange to the point, no plain shank
Point:Sharp tapered gimlet point; no drill point, no cutting slot, no notch
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Forming:Single-die cold heading, thread rolling, black zinc plating, sorting
Number:325-2
We manufacture black self tapping metal screws with a pan washer head, a wide thin integral flange and a Phillips recess, a coarse self-tapping thread and a sharp gimlet point, in carbon steel with black zinc plating. Flange diameter and thickness, recess, point and length are taken from your drawing.
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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.
Black self tapping metal screws are self-tapping screws finished in black zinc and used to fix into sheet metal, board and similar materials without a nut on the far side. The recorded item on this page has a pan washer head — a low dome with a wide thin integral flange that forms the bearing face — a Phillips recess, a coarse single-lead thread over the full length and a sharp gimlet point, with Number 325-2.
Pan washer head. The flange is part of the head, thin and wide, with a flat underside that is the surface bearing on the panel. There is no separate washer to fit, lose or leave off, and the flange carries the load out to its edge rather than concentrating it on a ring under the dome.
Self tapping thread. A coarse thread rolled the full length from the flange underside to the point, with no plain shank. It forms or cuts its own mating thread in a prepared hole, which is what makes it a metal screw rather than a machine screw.
Sharp gimlet point. A tapered point that starts in the hole and leads the thread in. It is the point used where the pilot is drilled or punched, and it will not drill its own hole.
Black zinc. A zinc plate with a black passivation. The zinc is sacrificial, so a scratch is protected by the metal around it, and the black passivation gives the dark tone that these screws are chosen for.
Together these decide the joint: the flange spreads the load, the thread holds in the sheet, the black finish keeps the fixing quiet on a dark panel, and the point starts where the hole has been prepared.
The head and the integral flange are upset in a single heading stroke, so the flange is formed from the same material as the head and cannot shift. That is the structural difference from a washer: a pressed-on ring can rotate or fall off, a formed flange cannot.
The flange is deliberately thin and wide. A thin flange follows the panel and spreads the load over a larger face, which is what black self tapping metal screws need on thin sheet; a thick flange would be stiffer but would also stand the head higher and weigh more. The trade is that a thin flange can dish under heavy torque, so the joint torque is set from the first article rather than from the thread size.
The Phillips recess is formed in the same stroke as the head, which keeps it concentric with the shank and with the flange. On a washer head that matters: a recess that is off centre makes the bit push the head sideways, and a flange that is thin will tilt before it gives.
The thread is rolled from the underside of the flange to the point, with no plain shank. The gimlet point is formed after rolling and is a sharp taper with a slight lead-in; on sheet metal that lead-in matters, because a point that is even slightly blunt will skate across the hole and mark the panel.
Black zinc is applied last, over the flange, the recess and the point. The deposit adds a few microns, so the thread is gauged after plating and the recess is checked with the production bit in the same condition.
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; black self tapping metal screws are normally short, because the thread is holding through a panel rather than clamping a stack.
| Item | How it is defined | What we control |
|---|---|---|
| Thread | Coarse single-lead self-tapping, full length | Gauged per batch after plating |
| Head dome | Low pan dome, set by the JIS form | Checked on the projector |
| Flange diameter | Wide and thin, integral with the head | Measured on the first article |
| Flange thickness | Thin enough to follow the panel | Checked on the section |
| Recess | Phillips cross | Driven with the production bit |
| Point | Sharp gimlet | Checked on the first article |
| Length | From under the flange to the point | Measured on the shop plate |
Length is measured from under the flange, which is the face that bears on the panel. That is not the same as measuring from the underside of the dome, and the difference is the flange thickness — a fraction of a millimetre, but on a thin panel it is the fraction that decides whether the joint closes.
The flange diameter is the dimension that decides both the bearing area and whether the fixing fits. A wider flange spreads the load further and covers an oversized hole, but it also needs clearance around the head and leaves a wider mark if the paint is disturbed. It is quoted with the head diameter, not left to the standard.
The three features on this part are each a compromise, and knowing where each one stops is what keeps a specification honest.
| Feature | What it gives | What it costs |
|---|---|---|
| Integral thin flange | Bearing area without a loose washer | Can dish under heavy torque |
| Self-tapping thread | Holds in sheet without a nut | Needs the right pilot hole |
| Gimlet point | Clean start in a prepared hole | Not for sheet that has not been drilled |
| Black zinc | Dark tone with sacrificial protection | A few microns; recess and thread re-checked |
| Full thread | Engagement over the whole shank | No plain shank to centre the screw |
The flange is the reason to choose this head over a plain pan head. On thin sheet the plain head bears on a narrow ring, and the sheet dishes around the fixing; the flange spreads the same load over a wider face and the sheet stays flat. On a soft or coated panel that difference is visible in the finished product, not only in the test report.
The thin flange has a limit, and it is torque. A flange that is only a few tenths of a millimetre thick will dish if the screw is driven past its yield, and a dished flange loses its bearing area at exactly the moment it is needed. That is why black self tapping metal screws of this type are driven to a stated torque and why the first article is checked for flange flatness after driving, not just before.
The black zinc is a cosmetic and a protective choice at once. It hides the fixing on a dark panel and it protects the steel sacrificially; it will not survive long in salt air, and a black Dacromet or stainless version of the same head is what that environment actually needs. The drawing should say which one it is for.
The recorded finish is black zinc plating on carbon steel. On a washer head the flange is the largest visible surface, so the colour is judged there first, and the flange is also where a thin deposit shows unevenness most clearly.
| Finish | How it protects | Effect on flange and thread | Typical use |
|---|---|---|---|
| Black zinc | Sacrificial zinc plus black passivation | A few microns; gauged after | Dark sheet assemblies, indoor and damp |
| Black oxide | Thin conversion film, oiled | Almost no change | Dry indoor assemblies |
| White zinc | Sacrificial zinc, blue-white passivation | A few microns; gauged after | General indoor work |
| Dacromet | Zinc-aluminium flake layer, cured | Thin film; flange and thread re-checked | Outdoor and wet assemblies |
| Stainless (equivalent part) | Alloy provides protection | No coating | Wash-down and coastal work |
Plating a thin flange has a visible consequence: the deposit builds more on the flange edge than on its face, so the colour at the rim can read slightly darker or brighter than the middle. That is normal and it is not a defect, but it is worth saying so before a customer sees a batch and wonders why the edges differ.
The recess is where plating causes a functional problem. Every micron of deposit narrows the cross, and on the small sizes a few microns is enough to make a bit tight; that is why the first article is driven with the production bit after plating and why the plating range is on the drawing rather than left to the line.
Three assemblies where a dark washer head fixing into sheet is the right choice:
| Where it sits | The screw fixes a panel, a bracket or a module to a black or dark painted sheet, with a flange spreading the load on the thin skin. |
| When it goes wrong | A plain head dishes the sheet and shows a ring, and a bright screw breaks the dark face. |
| Why it happens | The sheet is thin and dark, the fixing is on a visible face, and the assembly is made on a line. |
| What we control | Flange diameter and flatness checked, thread gauged after plating, and the first article driven in a coated sample. |
| Where it sits | The screw closes a cover or fixes a trim on a coated steel skin, where the flange protects the coating from the head and the black finish matches the panel. |
| When it goes wrong | A narrow head concentrates load and cracks the coating around the hole, and a bright head reads as unfinished. |
| Why it happens | The panel is coated, the head is seen, and the joint is opened occasionally. |
| What we control | Flange checked for burr and flatness, and the coating around the sample hole inspected after driving. |
| Where it sits | The screw assembles a black frame, a shelf bracket or a display fitting where the fixings are visible in a row. |
| When it goes wrong | A flange that is too wide overlaps a neighbouring part, and one that is too narrow lets the board dish. |
| Why it happens | The faces are dark, the fixings are in rows, and the appearance matters. |
| What we control | Flange diameter matched to the spacing, colour matched to a sample, recess driven with the production bit. |
Four reasons that matter on a thin-flange screw, each tied to what the drawing has to prove:
|
Flange and torque reviewed together
The flange diameter, flange thickness and joint torque are reviewed as one set, so a flange that would dish under the production torque is raised first. Basis: Flange and torque reviewed as one set. |
Head and flange in one stroke
The pan dome and the integral flange are upset in one heading stroke, so the flange is formed from the same material and cannot shift. Basis: Flange formed with the head. |
|
Flange and recess checked on the part
The flange is checked for flatness and burr, and the recess is driven with the production bit after plating. Basis: First article driven with the production bit. |
First article to repeat production
The first article fixes the drawing revision, wire heat, die set, thread roll and plating, and repeat orders are compared with that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these black self tapping metal screws on a single-die header that upsets the low pan dome and the wide thin flange in one stroke, rolls the coarse thread from the flange underside to a gimlet point and finishes the parts in black zinc. The first part of every run is measured on the flange, gauged on the thread after plating and driven into a sample of the customer’s sheet, before the batch continues.
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The flange is where the die wears. A worn die leaves a flange that is slightly thicker at one side, and a flange that is not uniform in thickness will dish unevenly when the screw is driven — the head then sits at a slight angle and the joint reads as loose without any visible cause. The flange is therefore checked on the section of the first article and sampled through the run.
What decides whether black self tapping metal screws pass is the flange, the head, the recess, the thread, the point and the plating. The inspection agreement covers those, and the criteria come from the drawing.
Head and flange on the projector |
Thread gauged after plating |
Hardness testing against the property class |
Salt-spray testing of the black zinc plate |
The flange is checked by driving the first article into a sample panel and looking at the contact ring and the flatness afterwards. A flange that is flat before driving and dished after has told you something the drawing did not: the joint torque is above what that flange thickness will take.
The recess is checked after plating with the production bit, and the plating is checked for colour evenness across the flange. Both are appearance checks as much as functional ones, and on a black washer head the two features a customer looks at first are exactly those.
Every shipment of black self tapping metal 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, the plating thickness is recorded per batch, 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 a washer head the first article is driven into a sample of the customer’s own sheet, because the flange only proves itself against the panel it will bear on. Buyers visit during the process to review samples and to see how the heads are formed.
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8,678+
customers served
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87%
of orders from repeat customers
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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 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 low pan dome with a wide thin integral flange at its base. The flange underside is the bearing face, and there is no separate washer to fit or lose.
A thin flange follows the panel and spreads the load, which is what thin sheet needs. It can also dish under heavy torque, so the joint torque is set from the first article.
Less readily than black oxide. The zinc is sacrificial, so a scratch is protected by the metal around it. For wet or salty air a black Dacromet or stainless part is still the better choice.
From under the flange to the point. That is not the same as from under the dome; the difference is the flange thickness.
Yes, with a drilled or punched pilot hole. The gimlet point starts in the hole and leads the thread; it does not drill its own hole.
Thread size and pitch, head and flange diameter, flange thickness, recess size, point form, length and datum, plating and the panel material.
How a black self tapping metal screw project runs from drawing to repeat delivery:
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1
Send the drawing and a sheet sample
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→ |
2
Flange and torque review
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→ |
3
First article driven in the sheet
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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 thread size and pitch, head and flange diameter, flange thickness, recess size, point form, length and datum, plating type and the sheet being joined.
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Thread and pitch
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Head and flange
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Flange thickness
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Recess size
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Point form
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Length 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
