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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:Star head self-tapping screw, cap head, six-lobe drive, thread-forming (Non-Standard)
Materials:Stainless Steel
Surface treatment:Plain, cleaned (no applied coating)
Head Type:Cap Head: cylindrical side wall, flat top, flat full bearing face
Drive:Six-lobe star recess (Torx style), plain centre, no pin, no slot
Thread:Coarse single-lead thread-forming thread, trilobular form, full length to the point
Point:Blunt flat end; no gimlet point, no drill point, no cutting slot
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Forming:Single-die cold heading, thread rolling, cleaning and sorting
Number:648
We manufacture star head self tapping screws with a cap head and six-lobe drive, a trilobular thread-forming thread full length and a blunt flat end, in stainless steel with no coating. Recess size, thread, length, pilot hole and grade 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.
Star head self tapping screws are screws driven with a six-lobe star recess instead of a cross, and threaded so that they form their own mating thread in a prepared hole. The recorded item on this page has a cap head, a plain six-lobe recess with no centre pin, a trilobular thread-forming thread and a blunt flat end, in stainless steel with no coating, quoted from M1 to M14 with Number 648.
Six-lobe star recess. Six curved lobes that a matching star bit engages on six faces. The bit seats deeper than a cross, does not cam out the same way, and transfers more torque into the head — which is why star head self tapping screws are used where the joint has to be tightened hard or driven many times a shift.
Cap head. A short cylinder with a flat top and a full flat bearing face. It gives a clean circular footprint and a bearing area across the whole head, and the flat top is where the star recess is formed.
Trilobular thread. The thread is not round in cross-section; it has three shallow lobes. As the screw turns, the lobes press material aside into the thread form instead of cutting it away, which is what makes the thread-forming action work and leaves no chips in the joint.
Blunt flat end. There is no gimlet point and no drill point. The screw goes into a drilled or punched pilot hole and forms its thread there; it cannot start a hole of its own.
Stainless, uncoated. The alloy provides the protection and the parts are cleaned; nothing is plated on afterwards, so the recess and the thread that are gauged are the ones that ship.
The cap head and the six-lobe recess are formed in one heading blow. On a cap head the recess sits in a flat top with a cylindrical wall around it, and that wall is what gives the recess its depth — which is why the head height and the recess depth are decided together.
The thread is rolled with a trilobular profile. The three lobes run the full length of the thread and are what make the forming action possible: the lobes are slightly larger than the pitch diameter so they compress the hole wall, and the relief between them gives the displaced material somewhere to go.
The end is blunt and flat. A thread-forming screw with a point would try to start its own hole and would displace material ahead of the thread, which in a thin sheet is exactly how a hole gets distorted. The blunt end makes the pilot hole the only thing that decides where the screw goes.
Stainless changes the forming operation more than it changes the cutting one. The material work-hardens as the lobes press it, so the pilot hole size is less forgiving than on mild steel: too small and the screw binds halfway, too large and it strips. Both are checked on the first article in the customer’s material.
Cleaning is the last step, and the recorded part has no coating and no passivation specified beyond cleaning. A coated thread-forming screw can lose its forming ability, because the coating changes the effective diameter of the lobes.
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, and custom sizes on request. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission; star head self tapping screws are normally short, because the thread forms into sheet or a thin wall rather than clamping a deep stack.
| Item | How it is defined | What we control |
|---|---|---|
| Recess | Six-lobe star, no centre pin | Size checked with the star bit |
| Head | Cap head, flat top, flat bearing face | Diameter and height on the projector |
| Thread | Coarse trilobular thread-forming, full length | Gauged per batch; lobes checked on section |
| Point | Blunt and flat | Checked on the projector |
| Pilot hole | Set by the thread and the sheet | Confirmed in a sample of the customer’s material |
| Length | From under the head to the flat end | Measured on the shop plate |
The pilot hole is the customer’s dimension and the one that decides whether a forming screw works. A forming screw needs a hole close to the pitch diameter of the thread, which is a different size from the hole a cutting screw of the same thread needs. Where a drawing converts a cutting screw to a forming one without changing the hole, the joint either strips or never closes.
The recess size is the shop’s side. It is matched to the standard six-lobe series for the thread, and it is checked with the bit rather than with a gauge, because the bit is what will be used on the line. A recess that is a size small will take the bit only part way and cam out at a fraction of the intended torque.
The combination of a six-lobe drive and a thread-forming thread is deliberate: one gives torque without cam-out, the other gives a thread without chips. Together they suit a production line that drives a lot of screws into sheet and does not want swarf in the assembly.
| Feature | What it gives | What it costs |
|---|---|---|
| Six-lobe recess | High torque, low cam-out, long bit life | Needs the matching bit; not a standard cross |
| Trilobular forming thread | No chips; denser thread in the sheet | Pilot hole size is critical; less forgiving than cutting |
| Cap head | Full flat bearing face, clean footprint | Taller than a countersunk head |
| Blunt end | Cannot start its own hole or distort the sheet | Needs a drilled or punched pilot |
| Stainless body | No coating to fail; survives wash-down | Work-hardens; galls against stainless |
The star drive is the reason these screws are specified where a cross recess would fail. On a small screw driven into stainless sheet, a Phillips bit will cam out long before the joint is tight, and every cam-out damages the recess and the sheet. A six-lobe bit engages on six faces and stays seated, so the torque goes into the thread instead of into the bit tip.
The forming thread is the reason it holds. Displaced material is denser than cut material and has no chip channel to weaken it, so a formed thread in sheet resists pull-out better than a cut one of the same size. The trade is that the hole has to be right: a forming screw has no tolerance for a hole that is a size off.
Neither feature makes the screw reusable. A formed thread in thin sheet can be run in and out a limited number of times before it wears, and a stainless thread-forming screw in the same hole work-hardens it further each time. Where a joint is opened regularly, a machine screw in a tapped insert is the honest specification, not a forming screw.
The recorded finish is plain, cleaned stainless with no coating. For a thread-forming screw that is important: a coating changes the effective diameter of the lobes, and a thread-forming screw whose lobes are thicker than intended will bind before the head seats.
| Option | What it does | Effect on recess and thread | Typical use |
|---|---|---|---|
| Plain, cleaned | Alloy protection, no film | Lobes as formed | General and wet service |
| Passivated | Removes free iron | No dimensional change | Wash-down and coastal work |
| Satin bead blast | Even matte face | Softens edges slightly | Visible panels |
| Dry film | Reduces galling in stainless joints | Film checked in the recess | Joints opened often |
| Coated (steel variant) | Colour or extra protection | Lobes thicker; forming ability reduced | Dry indoor work |
Where a coated version is used instead of stainless, the coating is kept thin and the pilot hole is adjusted. That is a joint decision rather than a screw decision, and on star head self tapping screws it is worth stating explicitly, because a coating that is fine on a machine screw will make a forming screw too large for its hole.
Grade selection follows the exposure: 304 for general indoor and outdoor work, 316 where chlorides are present. The material certificate is what confirms it, and on stainless the grade also changes how the thread forms, so the grade belongs on the drawing before tooling rather than after the first article.
Three assemblies where a star drive and a chip-free thread are both wanted:
| Where it sits | The screw forms its own thread in a punched hole in a stainless or coated panel, clamping a bracket, a module or a cover. |
| When it goes wrong | A cross recess cams out on stainless sheet and damages both the recess and the face, and a cutting screw leaves swarf inside the housing. |
| Why it happens | The panel is thin, the drive is on a production line, and no loose metal is allowed inside. |
| What we control | Pilot hole confirmed in the customer’s sheet, recess checked with the star bit, thread gauged per batch. |
| Where it sits | The screw fixes a plate or a component into a formed thread in a panel, where the assembly must stay free of chips that could bridge a circuit. |
| When it goes wrong | Cutting screws produce swarf, and a loose bit in a cross recess strips the head on the line. |
| Why it happens | The enclosure is sealed, chips are a risk, and the fixing is driven by machine. |
| What we control | Lobes and recess checked on the first article, and the driving torque agreed with the customer. |
| Where it sits | The screw holds a panel or a fitting on stainless equipment that is cleaned daily, where a plated screw would shed its coating. |
| When it goes wrong | A plated screw corrodes at the recess, and a screw that binds in the hole work-hardens the sheet around it. |
| Why it happens | The equipment is stainless, it is washed, and the fixing is visible. |
| What we control | Grade and surface agreed, pilot hole verified, and the first article driven once and recorded. |
Four reasons that matter on a forming screw with a star drive, each tied to what the drawing has to prove:
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Pilot hole and recess reviewed together
The pilot hole, the trilobular thread and the recess size are reviewed as one set against the sheet, so a screw that will bind or strip is raised before tooling. Basis: Pilot hole and recess reviewed as one set. |
Head, recess and thread in one route
The cap head and the six-lobe recess are formed in one blow, and the trilobular thread is rolled full length to a blunt flat end. Basis: One route from wire to cleaned screw. |
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Recess and lobes checked on the part
The recess is checked with the production star bit, the lobes on a section, and the first article is driven in a sample of the sheet. Basis: First article driven in the sheet sample. |
First article to repeat production
At the first article the drawing revision, wire heat, die set and thread roll are recorded, and that record governs repeat orders. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these star head self tapping screws on a single-die header that upsets the cap head and the six-lobe recess in one blow, then rolls the trilobular forming thread over the full length to a blunt flat end. The parts are cleaned and sorted. The first part of every run is measured on the head and the recess, checked with the star bit and driven into a sample of the customer’s sheet, before the batch continues.
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The trilobular roll is the tool that defines the part. The three lobes have to be equally spaced and equally deep, because an uneven lobe spacing drives unevenly and strips the hole on one side. The roll is made for the thread and the grade, and it is checked on a section of the first article rather than by eye on the finished screw.
What decides whether star head self tapping screws pass is the recess, the head, the thread lobes, the end and the surface. The inspection agreement covers those, and the criteria come from the drawing.
Recess and head on the projector |
Thread gauged per batch |
Hardness testing of the wire |
Salt-spray testing where the service requires it |
The recess is checked with the star bit that will be used in production, not with a gauge. A six-lobe recess that measures correctly can still refuse the bit if the lobes are shallow, and the bit is what decides whether the head survives the line. The same check confirms the bit seats to the full depth.
The drive test in the sheet is done once on the first article and recorded with the pilot hole. A forming screw tests the material as much as the screw: running it twice in the same hole is a different test, because the first run work-hardened the wall. The record is what a repeat order is checked against.
Every shipment of star head self tapping screws is traceable to the wire it was made from. 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 material or the surface condition. 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 forming screw the first article is driven into the customer’s sheet and the pilot hole is recorded with the result, because the two only work as a pair. 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
|
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 finishing 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 six-lobe recess driven with a matching star bit. It engages on six faces, does not cam out like a cross, and transfers more torque into the head.
No. The recess is a standard six-lobe with a plain centre. A security version has a pin in the centre that blocks an ordinary bit.
A thread with three shallow lobes that rolls the material aside as it turns, forming a thread without cutting a chip. It needs a pilot hole close to the pitch diameter.
So the screw cannot start its own hole and cannot distort the sheet ahead of the thread. It goes into a drilled or punched pilot.
Only a limited number of times. A formed thread in thin sheet wears, and a stainless screw work-hardens the hole each time it is run in.
Thread size and pitch, head diameter and height, recess size, length and datum, pilot hole, stainless grade, and the sheet material.
How a star head self tapping 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
Pilot hole and recess 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 diameter and height, recess size, length and datum, the pilot hole, the stainless grade and the sheet being joined.
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Thread and pitch
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Head diameter and height
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Recess size
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Length and datum
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Pilot hole
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Grade and sheet
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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
