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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 oxide round head Pozi stepped screw, carbon steel 10.9
Materials:Carbon steel (grade 10.9)
Surface treatment:Black oxide
Head Type:Pan head
Drive type:Pozi (Pozidriv)
Thread:Machine thread
Forming:Multi-station cold heading
Number:1318
We manufacture black round head Pozi screws in carbon steel grade 10.9, with a pan head, a Pozidriv recess and a stepped body that is larger than the thread, from M2 to M12 and up to 2,000 mm, cold headed on a multi-station header and finished in black oxide. Body diameter, step position, thread start and recess size are made to 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.
A black round head Pozi screw is a machine screw with a pan-shaped head, a Pozidriv recess and a black oxide finish. The version on this page is also a stepped screw: the thread at the tip is smaller than the plain body that runs through the assembly, so the body acts as a shoulder and the thread only engages at the far end.
Pan head and Pozi recess. The round pan head gives a bearing face with a low profile, and the Pozidriv recess adds four half-depth slots between the main cross so the driver can carry more torque without camming out. The recess is cut with a Pozi punch, and the matching PZ driver is what the customer needs on the line.
Stepped body. On a black round head Pozi screw of this type the plain body is turned or formed to a larger diameter than the thread. The body locates in a bore, the thread pulls into a smaller tapped hole, and the step shoulders against the mating part. That is what separates a stepped screw from a plain machine screw of the same length.
Black oxide on grade 10.9. The black oxide conversion coating adds almost no thickness, so the Pozi recess and the thread keep the dimensions they were made to. It also means the coating does not hide a burr or a thread defect, which is why the finish check comes after the gauges, not instead of them.
Together these decide how the part behaves on site: the body locates, the step shoulders, the thread pulls the joint closed, and the black finish stays dimensionally neutral.
The step is the feature that defines a black round head Pozi screw of this type. The body diameter is larger than the thread, and the transition between them is a shoulder that seats against the mating part. If the shoulder is not square to the body, the screw pulls the joint off line as it tightens, and the body will not sit in its bore.
The body itself has to be straight enough to enter the bore without binding. On a long black round head Pozi screw the body runs through several plates, so the diameter and the straightness are checked together, and the thread at the tip is kept short enough that it engages only after the body has located.
The pan head sits on top of the body. Head diameter, head height and recess depth are formed together, so the Pozi punch and the head die are a matched pair. The black oxide is applied after forming and thread rolling, and the recess is checked with the PZ driver after the coating.
Black round head Pozi screws are quoted from M2 to M12 and up to 2,000 mm, with length usually held to +0/-2 mm on the drawing. On this stepped version the body diameter and the thread size are two separate dimensions, and both are quoted from the drawing.
| Item | How it is defined | What we control |
|---|---|---|
| Total length | From the top of the pan head to the tip | Datum stated on the drawing; length measured on the shop plate |
| Body diameter | The plain step that locates in the bore | Body diameter and roundness checked on the first article |
| Step position | Where the shoulder sits along the length | Shoulder position measured from the head datum |
| Thread size and length | The smaller thread at the tip | Thread size, length and start checked per batch |
| Recess size | The Pozi recess that takes the PZ driver | Recess checked with the matching PZ bit after coating |
Each combination of body diameter, thread size and length is checked against the drawing before a quotation is issued. The thread call-out is read together with the body diameter, because the step has to leave a shoulder wide enough to seat on the mating part without cutting into the thread relief. A black round head Pozi screw with a long body and a short thread has less room for the step, so the check confirms that the shoulder and the thread start both fit in the length.
Length is measured from the top of the head, and the step position is read from the same datum. Body diameter, shoulder position and thread start are gauged on the first article before a batch is released.
For a black round head Pozi screw the drawing fixes six things: thread size and pitch, thread length, body diameter, step position, total length and its datum, and the Pozi size. A seventh line matters on a stepped part: which diameter is the locating body and which is the thread. The drawing is read from the tip up, so the thread, the step and the head are all tied to one datum before the part is quoted.
| Parameter | Why it matters on a stepped screw | What we control |
|---|---|---|
| Thread start position | It sets how much body runs before the thread bites | Start dimension checked on the first article |
| Body diameter | It locates the screw in the bore; too large will not enter | Body diameter held to the bore on the drawing |
| Step position | It sets where the shoulder seats | Position measured from the head datum |
| Recess size | A PZ bit in a Phillips-sized recess strips the flanks | Recess checked with the matching PZ bit |
Black oxide is a conversion coating: it changes the surface chemistry of the steel rather than adding a layer. On a black round head Pozi screw that is the point, because the Pozi recess and the thread keep their dimensions and the driver still fits after finishing. The coating gives a uniform black appearance but limited corrosion protection on its own, so it is usually specified with a light oil.
| Finish | How it protects | Effect on recess and thread | Typical use |
|---|---|---|---|
| Black oxide | Conversion coating, minimal thickness | No measurable build-up; recess as formed | Indoor assemblies where black is the finish |
| Black oxide plus oil | Conversion coating with a light oil film | No dimensional change; oil cleaned before use | Parts stored before assembly |
| Zinc electroplated (carbon steel) | Sacrificial zinc layer | Build-up on thread and recess | Carbon steel parts in dry indoor service |
| Zinc-nickel | Zinc alloy with higher corrosion resistance | Thicker film; recess masked where needed | Damp service on high-strength parts |
| Dacromet flake | Zinc-aluminium flake layer | Thin film; recess checked over the coating | Wet or outdoor assemblies |
Salt-spray exposure is agreed per project and written on the drawing. On a black oxide screw the test is run on the finished part in the condition it ships in, and the recess is checked with the PZ driver afterwards, because a coating that fills the recess has failed even if the appearance is even.
Packing protects the head and the body. Long stepped screws are packed in layers with the heads supported so the body cannot take a set, and the black finish is kept away from the carton wall so it does not rub.
Three assembly conditions where a black round head Pozi screw has to locate a body and pull a thread, and what it has to do instead:
Electric motors and gearmotor frames
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Motors – stepped screws locating an end shield |
Self-service equipment and vending machines
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Vending equipment – stepped screws in a serviced frame |
Industrial machinery covers and panels
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Machinery – stepped screws on covers and guards |
Four reasons that matter specifically on a black round head Pozi screw, each tied to what the drawing has to prove:
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Engineering review before tooling
Body diameter, step position, thread start and recess size are settled before a die is cut, so the first sample is measured against the drawing instead of against a guess. Basis: Drawing or sample reviewed before tooling is released. |
Body and thread formed in one piece
The pan head, Pozi recess, stepped body and thread are produced on one heading route, so the body and the thread stay on one axis and the shoulder stays square. Basis: One-piece heading route, body and thread in one part. |
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Body, step and recess gauged together
The body diameter and step position are checked against the drawing, and the recess with the matching PZ driver, so the part that locates on the bench locates on the line. Basis: Body, step and recess checked on the first article. |
First article to repeat production
The first article fixes the drawing revision, material heat, die set and recess tooling; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
These black round head Pozi screws are formed on a multi-station header. The pan head and the Pozi recess are formed in the die, the stepped body is produced with the thread at the tip, and the part is then thread-rolled, black-oxided and gauged. The operator checks the first parts of each run against the drawing before the batch continues.
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Between runs the die insert is changed to the drawing head form, body diameter and recess size; the first parts go to the gauges before the run continues, and the setting is recorded. Parts that pass the bench checks are packed in layers so the black finish and the body are not damaged.
What decides whether the screw passes is not its appearance: it is the body locating in the bore, the step seating square, the Pozi recess taking the PZ driver and the thread matching the tapped part. The inspection agreement covers those, and the criteria are the ones written on the drawing.
Thread gauging against GO/NO-GO gauges |
Body diameter and step profile on the optical projector |
Hardness testing of the 10.9 material |
Salt-spray testing of the black oxide finish |
Each batch is recorded against the drawing revision: body diameter and step position from the first article, the Pozi recess checked with the PZ driver, thread gauging per batch and hardness on the 10.9 material. If a gauge or the recess check fails, the parts back to the last good setting are held and re-checked.
If the material needs an outside report, the drawing calls for it, the paperwork travels with the shipment and the batch number on the label matches the inspection record.
Every black round head Pozi 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. 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. Buyers visit during the process to review samples and to see the forming, threading and finishing steps their parts will go through.
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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, the thread rolling and the black oxide 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 machine screw with a pan-shaped round head, a Pozidriv recess and a black oxide finish. On this stepped version the plain body is larger than the thread, so the body locates in a bore and the thread engages at the far end.
The step is a shoulder between the body and the smaller thread. It seats against the mating part, locates the screw in its bore, and stops the thread running through a thin panel.
A Pozidriv driver of the matching size (PZ1, PZ2 and so on). A Phillips driver will enter the recess but does not carry the additional torque the Pozi flanks are designed for, and it wears the recess.
Black round head Pozi screws are quoted from M2 to M12 and up to 2,000 mm, with length usually held to +0/-2 mm. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
The conversion coating gives a uniform black finish and almost no dimensional change, but limited protection on its own. It is usually specified with a light oil, and the salt-spray requirement is agreed per project.
Thread size and pitch, thread length, body diameter, step position, total length and datum, Pozi size, material grade and hardness, finish, and quantity.
How a black round head Pozi screw project runs from drawing to repeat delivery:
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1
Send the drawing or sample
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2
DFM review and quotation
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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 black round head Pozi screw quotation, send the drawing with thread size and pitch, thread length, body diameter, step position, total length and datum, Pozi size, material grade and finish. Body, step and recess are confirmed with you before production.
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Thread size and pitch
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Thread length
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Body diameter
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Step position
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Total length and datum
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Pozi size, material and finish
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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
