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+86 13143444311
Email：sst@szsst88.com
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Address：Building 9, First Industrial Zone, Tantou Industrial City, Songgang Street, Baoan District, Shenzhen 518105, Guangdong, China
Type:Stainless Steel Tapping Screws
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Cap Head
Drive:Torx + Slot
Thread:Half Thread Self Tapping
Point:Flat Point
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:431-1
We make stainless steel tapping screws with a cap head, a combined star and slot recess and a half thread to a flat point, quoting them from M1 to M14. Recess, head, thread and grade come from your drawing, and the first article is driven with a star bit and with a blade.
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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.
Stainless steel tapping screws are screws that form their own thread in a prepared hole without a coating, so the fixing survives weather and washing on the strength of the alloy alone. The recorded item on this page is stainless with a plain finish, a cap head, a combined slot and star recess and a half self tapping thread, quoted from M1 to M14 with Number 431-1.
Cap head. A short cylinder with a flat top and a full flat bearing face. It seats in a counterbore, spreads the clamp load and leaves a clean circular outline on a machined surface.
Combined slot and star recess. Six star lobes with a straight slot cut across them, so the screw can be driven with either a star bit or a flat blade. The slot is a second way in, not a second recess — the star remains the working drive.
Half self tapping thread. Thread from the point to a defined position, with a plain shank under the head, ending in a flat point. The plain length passes the top member of a stack without cutting it.
Stainless, plain. Passivated and uncoated. There is no film to chip at the recess or to wear off the crest, and the alloy supplies the corrosion resistance without a finish to maintain.
A combined recess is a compromise, and it works because the two drives are cut into the same space. The star lobes are formed first; the slot is then cut across the top of them, deep enough to take a blade but not deep enough to remove the flanks the star bit needs. The result is a recess where a star bit still seats on all six lobes and a blade can still find the slot.
On stainless steel tapping screws the slot costs something. It cuts two of the lobes down at the top, so the star engagement is shallower than on a plain star socket, and the sharp corners of the slot are stress risers in a head that is already thin at the recess. On a stainless steel tapping screw, which is driven to a rising torque as the thread forms, that loss of engagement is the number that matters.
The combined drive is chosen for service, not for production. An assembly line wants one drive and a controlled torque; a field technician wants to open the fixing with whatever is in the bag. A screw with both can be assembled with a star bit at a defined torque and opened later with a coin, which is exactly the compromise the recess is designed to make.
The cap head gives the recess depth to make that possible. A low head could not contain a star socket and a slot at the same time; the cylinder of a cap head has enough material for both, and the flat bearing face keeps the head from digging into the panel.
Plain stainless is passivated after forming. Passivation removes free iron left by the tools and rebuilds the oxide film; on a recess that has been cut twice, that film is the only protection there is, and it is invisible.
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 stainless steel tapping screws the recess size, the head height and the thread length are quoted together, because the recess has to fit inside the head and the thread has to clear the top member.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Cap head, flat bearing face | Diameter, height and face flatness |
| Recess | Star with a slot across it | Lobe width, slot width and depth |
| Thread | Self-tapping, half length | Thread length and position from the end |
| Point | Short taper, flat tip | Checked on the first article |
| Finish | Plain stainless, passivated | Surface condition and film |
| Length | From under the head to the point | Measured on the shop plate |
The recess is quoted by both of its parts. Slot width and depth decide what blade will turn it, and the lobe width decides what star bit will; a drawing that names only one of them produces a screw that can be driven one way and not the other, which is the opposite of why the combined drive exists.
Length is measured from under the head, because that face bears. On a half thread the thread length is quoted from the point as well, so the plain shank that clears the top member is a defined feature rather than a leftover.
Three features define this part: the combined recess, the cap head and the stainless body. The first is convenience, the second is depth for the recess, and the third is the reason the screw can go outdoors without a coating.
| Feature | What it gives | What it costs |
|---|---|---|
| Star plus slot | Driven by a bit or by a blade | Slot cuts the lobes and adds a stress riser |
| Cap head | Depth for a dual recess, full bearing face | Needs a counterbore, not just a hole |
| Half thread | Plain shank passes a clearance hole | Thread length must be specified |
| Self tapping | Holds without a nut or tapped hole | Needs the right pilot hole |
| Plain stainless | No coating to chip at the recess | Galls against stainless; pits in chloride |
The slot earns its place in the field and not on the line. A line that tries to drive a combined recess with a blade gets a lower torque and a slot that rounds; the same screw driven with the star bit behaves like a normal star drive. The two tools do not produce the same joint, and the drawing should say which one is the assembly method.
The cost is in the head. A dual recess takes more material out than a single one, so on a small cap head the remaining wall above the bearing face can be thin. That is why the form appears on a cap head rather than on a low head, and why the first article is checked on the section as well as from the top.
The recorded finish is plain, passivated stainless. Nothing is added, so the recess is as cut, the thread is as rolled, and there is no coating to hide a burr or to fill the slot.
| Option | How it protects | Effect on recess and thread | Typical use |
|---|---|---|---|
| Stainless A2, plain | Passive chromium oxide film | None; gauged as formed | Outdoor and general fitting |
| Stainless A4, plain | Passive film with molybdenum | None; gauged as formed | Coastal and washdown |
| Zinc plated steel | Sacrificial zinc | A few microns; recess re-checked | Indoor, cost-driven work |
| Dacromet on steel | Zinc-aluminium flake layer | Film builds; recess re-checked | Outdoor steel assemblies |
| Black zinc on steel | Sacrificial zinc, dark passivation | A few microns; recess re-checked | Dark visible panels |
Stainless into stainless is the case to watch. Tapping into a stainless part work-hardens both surfaces and the driving torque climbs further than it does in mild steel, and the combined recess — already compromised by the slot — is where that extra torque shows. Where the joint is stainless into stainless, the drive is chosen for the torque, not for convenience.
The other limit is chloride. A2 pits at the recess and at the thread in a salt-laden joint, and the pit is where the screw eventually gives. Where that service is expected, the grade is the answer, and the drawing should say which grade rather than leaving it to the sample.
Three assemblies where stainless steel tapping screws with a dual recess are the fixing:
| Where it sits | The screw closes a panel or fixes a bracket where the joint sees rain, the head sits in a counterbore, and the fixing may be opened in the field. |
| When it goes wrong | A plated screw rusts at the recess, and a recess that needs a special bit leaves the technician without a way in. |
| Why it happens | The joint is outdoors, the fixing is serviced on site, and the head is counterbored. |
| What we control | Recess tried with both a star bit and a blade, thread gauged, passivation checked. |
| Where it sits | The screw fixes a fitting where salt water is constant and the part has to be opened for maintenance with whatever tool is aboard. |
| When it goes wrong | A stainless screw that cannot be opened without a star bit becomes a cut-off job, and a plated one rusts into its hole. |
| Why it happens | The joint is wet, the access is improvised, and the fixing is permanent enough to seize. |
| What we control | A4 grade where chloride is present, recess and thread checked, lubricant recommended. |
| Where it sits | The screw holds a guard or a panel where the part is cleaned daily and the fixing is opened for inspection. |
| When it goes wrong | A coating chips into the product area, and a recess that fills with residue cannot be driven. |
| Why it happens | The joint is washed, the fixing is inspected, and the head is visible. |
| What we control | Passivation confirmed, slot and lobes checked for burrs, thread gauged. |
Four reasons that matter on a dual recess in a stainless head, each tied to what the drawing has to prove:
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Recess, head and thread reviewed together
The lobe width, the slot, the head height and the thread are reviewed as one set, so a recess with too little wall left or a shank that would not clear the top member is raised before the tool is set. Basis: Recess, head and thread reviewed as one set. |
Heading, recessing and rolling in one route
The cap head and the star lobes are formed in one stroke, the slot is cut and the half thread is rolled in the same route. Basis: One route from wire to passivated screw. |
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Both drives tried on the part
The recess is checked for lobe and slot dimensions and then turned with both a star bit and a blade, because a combined recess can fail one way and work the other. Basis: Both drives tried on the first article. |
First article fixes the setting
The first article fixes the wire heat, the recess punch, the slot cutter, the roll and the passivation; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these stainless steel tapping screws from stainless wire on single-die headers that form the cap head and the star lobes in one stroke, cuts the slot across the recess, rolls the half thread to a flat point and passivates the parts. The first part of every run is measured on the head and recess, turned with both a star bit and a blade, and driven into a sample of the customer’s material before the batch continues.
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Cutting the slot after the lobes is the operation that decides the part. Cut too deep and the star bit has nothing to seat on; too shallow and a coin will not turn the screw. Stainless makes it worse, because the cutter work-hardens the slot walls and a dull tool leaves a burr that closes the slot at the top and stops the blade from entering.
What decides whether stainless steel tapping screws pass is the recess, the head, the thread, the point and the alloy. The inspection agreement covers those, and the criteria come from the drawing.
Recess lobes and slot on the projector |
Thread gauged per batch |
Hardness checked on the formed head |
Salt-spray testing of the stainless grade |
The recess is checked on the projector for lobe width, slot width and slot depth, and then turned with a star bit and with a blade. The star bit is the production check; the blade is the service check, and a screw that has one and not the other has lost the reason it was specified.
The head of a stainless steel tapping screw is checked for diameter, height and face flatness, and the wall above the bearing face is checked on the section of the first article. A combined recess takes more material out than a single one, and the section is the only place that loss shows.
The thread is gauged per batch and driven into the customer’s material, and the point is checked for taper and tip flat. On a half thread the position of the thread start is checked as well, because a start that is a turn early removes the plain shank and turns a flat-sitting cover into a lifted one.
Every shipment of stainless steel tapping screws is traceable to the wire it was made from and to the passivation 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 grade or the passivation. 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 dual recess the first article is tried both ways, so the customer confirms the bit and the blade at the same time. Buyers visit during the process to review samples and to see how the heads and recesses 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 headers, the slotting operation 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 |
Six star lobes with a straight slot cut across them, so the screw can be driven with a star bit or a flat blade. The star is the working drive; the slot is the way in when a bit is not available.
The star bit. It transmits more torque and does not damage the lobes; the slot is for service, not for assembly.
It removes material from a head that is already thin at the recess, and its corners are stress risers. That is why the form is used on a cap head, which has the depth for it.
So the joint survives weather and washing without a coating. The alloy is the protection, and there is no film to chip at the recess.
In stainless, yes, especially into a stainless part. A lubricant or a different grade for the mating part prevents it; once seized, the screw usually tears the material.
Head diameter and height, slot width and depth, lobe size, thread size and length with the datum, point form, and the stainless grade.
How a stainless steel tapping screw project runs from drawing to repeat delivery:
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1
Send the drawing or the sheet sample
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→ |
2
Recess, head and thread review
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→ |
3
First article driven both ways
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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 slot width and depth, the lobe size, the thread size and length with the datum, the point form and the stainless grade.
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Head diameter
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Head height
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Slot size
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Lobe size
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Thread and datum
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Stainless grade
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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
