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:socket head cap captive screws stainless steel
Materials:Stainless steel
Surface treatment:Plain
Head Type:cap head
Drive type:Hex socket (Allen)
Thread:Partial (half) machine thread, captive design
Forming:Single-die cold heading with captive step
Number:1689
We manufacture stainless steel socket head cap captive screws with a cap head, a hex socket and a partial machine thread shaped to stay with the panel when the joint is opened. Head, captive step, shank travel, thread class and finish are made to your drawing and the panel hole.
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.
A socket head cap captive screw is a cap head socket screw that stays attached to the panel when it is unscrewed, so it cannot be lost or dropped into the machine. The one on this page is stainless steel, plain finished, with a hex socket and a partial machine thread shaped for the captive function.
Cap head and hex socket. The head is a cylindrical cap with a hexagon socket, driven with an Allen key. It gives a clean, high head that a gloved hand or a key can find, and it takes the torque a panel joint needs without a slot to cam out of.
Captive shank. The thread runs over part of the length, and the plain shank behind it carries a step or undercut that catches behind the panel. The screw backs out of the thread, then stops against that step instead of coming free, which is what keeps it with the door or cover during service.
Stainless, plain. The body is stainless, supplied plain and passivated, so there is no coating to build on the thread, the socket or the captive step. The alloy supplies the corrosion resistance, which matters on panels that are opened often and handled with gloves.
Together these decide the fit: the head seats on the panel, the captive step passes the hole but not the thread, and the thread engages the tapped insert without galling in repeated service.
This socket head cap captive screw is formed from stainless wire on a single-die header, thread rolled, then finished plain and passivated. The grade comes from the drawing, with 303, 304 and 316 the common choices, and the wire heat number stays traceable to the material certificate.
The cap head and the hex socket are formed in the die. The captive step is produced in a separate operation behind the thread, because its diameter has to sit between the panel hole and the thread major diameter for the screw to pass in and still be caught.
The thread is a partial machine thread, rolled before passivation. The plain shank between the thread and the step is the travel the screw has when it backs out, so its length decides how far the screw retracts and whether it clears the panel.
Plain stainless keeps every dimension the process produced. Passivation restores the chromium film after forming without adding thickness, so the captive step and the socket keep the sizes that were measured on the first article.
Socket head cap captive screws of this type are quoted from M3 to M8 and in lengths to suit the drawing, with the head and the captive step measured on the projector and the thread gauged. 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 height | The cap head that seats on the panel | Checked on the projector on the first article |
| Hex socket | Key size and depth | Checked with the key and on the projector |
| Captive step | The diameter that passes the hole but not the thread | Checked against the panel hole on the first article |
| Plain shank | The travel the screw retracts | Measured from the step and the thread |
| Thread size and length | Partial machine thread to the drawing | Gauged per batch |
| Total length | From the top of the head to the tip | Datum stated on the drawing; measured on the shop plate |
Each size is quoted against the panel it stays with. The hole diameter, the step diameter and the thread length are reviewed together, because a step that is right for one panel lets the screw pull through another.
Head height is measured from the bearing face, and the total length from the top of the head. The batch is checked on the features the process can drift on: socket depth, step diameter and thread class.
The captive function is geometry, not a separate part. The panel hole is larger than the plain shank but smaller than the thread major diameter, and a step behind the thread stops the screw from being pulled out once it is unscrewed. The screw travels in the panel, clears the tapped insert, and stays in place while the cover is lifted away.
The step diameter is the critical dimension. Too small and the screw pulls through the panel and is lost; too large and it will not enter the hole at assembly. It is checked against the actual panel hole on the first article, not only against the drawing.
The plain shank length sets the travel. It has to be long enough for the thread to clear the insert, and short enough that the head still covers the hole at full extension. A captive screw that is one or two millimetres short of travel will not release the panel.
Stainless on stainless can gall in repeated service, so the thread and the insert are checked together and the first article is assembled and cycled. Where the joint is opened often, the drawing states the thread class and any lubrication that will be used.
This socket head cap captive screw is supplied plain and passivated. There is no coating to build on the thread, the socket or the step, so the captive travel and the key fit stay as they were measured, and the screw can be cycled in service without a coating rubbing off at the step.
| Finish | How it protects | Effect on thread and step | Typical use |
|---|---|---|---|
| Plain, passivated stainless | Alloy resists corrosion; passive film restored | No build-up; travel unchanged | Panels opened often, wash-down areas |
| Electropolished | Surface levelled, chromium enriched | Step edges smoothed; travel re-checked | Hygienic and visible panels |
| Black oxide (carbon steel) | Conversion coating, minimal thickness | No measurable build-up | Indoor carbon steel equivalents |
| Zinc plated (carbon steel) | Sacrificial zinc layer | Build-up on thread; gauged after | Carbon steel parts where cost matters |
| Dacromet flake (steel) | Zinc-aluminium flake layer | Thin film; thread checked over coating | Outdoor carbon steel parts |
Salt-spray exposure is agreed per project and written on the drawing; plain stainless is tested in the condition it ships in. On a captive screw the step is the face that matters: a coating that builds there changes the travel and can stop the screw backing out of the insert.
Packing protects the step and the socket. Screws are packed so the steps do not knock, and the label carries the batch, the material heat and the finish reference.
Three assemblies where socket head cap captive screws are chosen so the fastener stays with the panel, and what the screw has to do instead:
| Where it sits | The screw holds a panel that is opened for adjustment, and it has to stay in the panel while the cover is set aside. |
| When it goes wrong | A screw that comes free is dropped inside the machine, and a step that is too small lets it pull through the panel. |
| Why it happens | The panel is opened often, the screw travels in the hole, and the joint is re-tightened by hand and key. |
| What we control | Captive step matched to the panel hole, travel checked on the first article, and the thread gauged per batch. |
| Where it sits | The screw closes a door that is opened by a technician, where a loose screw would fall into a live cabinet. |
| When it goes wrong | A screw that drops into the cabinet is a hazard and a shutdown, and a short travel keeps the door from releasing. |
| Why it happens | The cabinet is opened for service, the screws are captive in the door, and the joint is key-tightened. |
| What we control | Step diameter and travel checked, and the thread matched to the insert so it releases cleanly. |
| Where it sits | The screw fixes a cover that comes off for calibration, where the screws have to stay with the cover. |
| When it goes wrong | A screw that is lost in a lab is a delay, and galling in repeated service seizes the thread. |
| Why it happens | The cover is opened for calibration, the screws are stainless, and the joint is cycled often. |
| What we control | Thread class and step checked, and the part assembled and cycled on the first article. |
Four reasons that matter on a socket head cap captive screw, each tied to what the drawing has to prove:
|
Panel hole and captive step reviewed together
The panel hole, the step diameter and the travel are reviewed before the die is cut, so a screw that would pull through the panel or fail to release is raised with you first. Basis: Hole, step and travel reviewed before tooling. |
Headed, threaded and stepped in one route
The head and socket are formed, the thread is rolled and the captive step is produced behind it in one route, so the step stays on the screw axis. Basis: One route for head, thread and captive step. |
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Step and socket checked on the part
The step is measured against the panel hole, the socket is key-checked and the thread is gauged, on the first article and per batch. Basis: Step, socket and thread checked on the first article. |
First article to repeat production
The first article fixes the drawing revision, wire heat, die set and finish batch; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these socket head cap captive screws on a single-die header: the cap head and the hex socket are struck in the die, the partial thread is rolled, the captive step is produced behind it, and the parts are passivated. The first part of every run is measured on the head and the step, 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 punch to the key size, and the step tool is set with the thread length; the first part goes to the projector and the gauges before the run continues. The setting is recorded, and the first article is assembled with the panel hole before the batch is released.
What decides whether a socket head cap captive screw passes is not only the thread: it is the head, the hex socket, the captive step diameter and the travel that step gives in the panel. The inspection agreement covers those, and the criteria come from the drawing and the panel hole.
Thread gauging against GO/NO-GO gauges |
Head, socket and step on the projector |
Hardness testing where the drawing requires it |
Salt-spray testing of the passivated part |
Each batch is recorded against the drawing revision: head, socket and step from the first article, the travel checked in the panel hole, and the thread gauged per batch. If a gauge or the step check fails, the parts back to the last good setting are held and re-checked.
If the material or finish needs an outside test, the request is set at the drawing stage, and the report ships with the parts under the batch number.
Every socket head cap captive 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 finish. 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. Captive screws are approved with the panel hole, so the step and the travel are signed off as a pair. Buyers visit during the process to review samples and to see how the heads and steps 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 header and the passivation 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 cap head socket screw that stays with the panel when it is unscrewed. A step behind the thread catches in the panel hole, so the screw retracts but cannot be pulled out or lost.
The panel hole is larger than the plain shank but smaller than the thread major diameter, and a step behind the thread stops the screw at full extension. The screw travels in the panel and stays with the cover.
Enough for the thread to clear the insert, and no more than the head can cover at full extension. The plain shank length sets that travel and is checked against the panel on the first article.
Socket head cap captive screws of this type are quoted from M3 to M8 and in lengths to suit the drawing. Where a long version is required, custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
Stainless on stainless can gall when a joint is cycled often. The thread class is agreed on the drawing, the first article is assembled and cycled, and any lubrication used at assembly is stated.
Head diameter and height, hex socket size and depth, the panel hole, the captive step diameter, the plain shank length or travel, thread size and length, total length and datum, material and finish.
How a socket head cap captive screw project runs from drawing to repeat delivery:
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1
Send the drawing or sample
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2
Panel hole and travel 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 cap captive screw quotation, send the drawing with the head diameter and height, hex socket size and depth, the panel hole, the captive step diameter, the plain shank length or travel, thread size and length, total length and datum, material and finish.
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Head diameter and height
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Socket size and depth
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Panel hole and step diameter
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Shank travel
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Thread size and length
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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
