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:Star Screw, Star Head Screw, Torx Head Screws
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Flat Head (CSK)
Drive:Six-lobe star recess (Torx)
Thread:Machine thread
Point:Plain, chamfered
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
Number:885
We make star screws in plain A2 stainless with a countersunk head and a six-lobe recess, quoting them from M1 to M10. Cone angle, recess size and depth, thread and length come from your drawing, and the first article is driven with the bit you use.
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.
Star screws are screws driven by a star-shaped recess: six rounded lobes cut into the head, matched by a bit of the same profile. The part recorded here is a stainless steel machine screw with a countersunk head, quoted from M1 to M10 with Number 885.
Star drive. Six lobes with rounded tips, engaged by a bit that pushes on the lobe walls rather than the corners.
Countersunk head. A cone that seats flush in the countersink and carries the clamp on its face.
Machine thread. A uniform thread for a tapped hole or a nut.
A2 stainless, passivated. No coating on the lobes, which is what keeps the bit sitting at the correct depth.
Star screws are used wherever a small head has to take repeated driving without rounding: instruments, electronics, optical hardware, model engineering and small machinery. The drive is the reason the joints stay serviceable.
The star recess takes a matching bit, and the lobes carry the torque without cam-out.
Ask for star screws and you may be quoted three different things. Star is the common name; Torx is a brand name that became generic; six-lobe and hexalobular are the descriptive and the standard terms. All of them describe the same recess, and a supplier who understands that will quote the same part whichever word arrives on the enquiry.
On star screws the naming matters because the size systems do not line up. A Torx size is written as T followed by a number, and the number is not the screw diameter; the same screw might take T6 at M2.5 and T8 at M3. A pentalobe recess is written as P, and it is a different five-lobe shape that a Torx bit will not drive. Where a drawing says star without a size, the supplier has to choose, and the choice is a guess.
On star screws the recess itself is more forgiving than a cross. Each lobe presents an inclined wall to the bit, so torque is transmitted with the bit pushed inward rather than outward; a star screw therefore holds its drive at a much smaller head size than a cross would allow. On a countersunk head that is decisive, because the flat top is small and a cross recess cut there would be shallow enough to round on the first firm turn.
What star screws do not fix is depth. The recess still has to be cut deep enough for the bit to engage and shallow enough to leave material above the cone, and on a countersunk head the two limits are close. A star recess a few hundredths too deep gives a head that measures correctly and deforms under a driver.
On star screws the countersunk seat then decides the joint. The cone carries the clamp on its face, so it needs a matching countersink; a head of one angle in a countersink of another rocks on a ring and leaves a gap at the rim. On a flush joint that gap is the first thing anyone sees, and it is why the cone angle belongs on the same drawing as the recess.
The recorded range is M1 to M10, with lengths made to the drawing. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For star screws the quotation carries head diameter, cone angle and thickness, the size and depth of the star recess, thread pitch and overall length.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Countersunk, 90-degree cone | Diameter, angle, thickness and rim |
| Recess | Six-lobe star | Size, depth, lobe form and floor thickness |
| Thread | Machine thread | Pitch, length and start position |
| Length | Overall, head included | Length tolerance and thread start |
| Material | A2 stainless | Grade and heat number on the certificate |
| Finish | Passivated, plain | Surface condition and recess edges |
The recess size should be written as a number on the drawing rather than as a word. A star screw quoted without a size will be made to the supplier’s default for that diameter, and the default may not match the bit on the assembly bench.
Cone angle and head thickness are quoted with the recess, because all three come out of the same small head. A drawing that lists them separately leaves the floor thickness between the recess and the cone undefined.
Four features define star screws, and each one is a trade:
| Feature | What it gives | What it costs |
|---|---|---|
| Star recess | Torque without cam-out | Only the right bit fits; a worn one reams the lobes |
| Countersunk seat | Flush finish | Removes material where the thread holds |
| Machine thread | Joint can be reopened | Needs a tapped hole or a nut |
| Thin head | Sits below the surface | Little material above the cone |
| Plain stainless | Lobes as formed | Softer than the bit; galls in aluminium |
The value of star screws is serviceability. A star screw with a good bit can be opened and closed many times without the recess rounding, which is why the drive appears in products that are repaired rather than replaced.
The cost on star screws is that the tool matters. A star bit that is one size small will seat partway and then ream the lobes at the first hard turn, and on a countersunk head there is no edge to grip once the recess is gone.
The recorded finish is passivation on A2 stainless with no coating. On star screws that matters at the rim of the recess, which is the thinnest feature on the part: a coating would round it, and a rounded rim lets the bit sit slightly high and load the lobes at the wrong angle.
| Option | How it protects | Effect on cone and recess | Typical use |
|---|---|---|---|
| A2 stainless, passivated | Passive chromium oxide film | Cone and recess as formed | Instruments and covers |
| A4 stainless, passivated | Passive film with molybdenum | Cone and recess as formed | Marine and medical |
| Stainless, electropolished | Thicker passive film, bright | Edges rounded; recess checked | Visible hardware |
| Steel, black oxide | Conversion film, oiled | No measurable build | Tooling and optics |
| Steel, zinc plated | Sacrificial zinc | Build in recess; re-checked | General indoor panels |
Where the joint is seen, electropolishing brightens the cone and removes the burr at the recess edge that a bit would catch. It also rounds the edge slightly, which is why the recess is checked after the process.
Where a coated steel screw is used, the recess is gauged after plating. A star recess at small size has narrow lobes and little clearance, so a coating that is harmless on a cross can make it refuse the bit.
Three assemblies where the star drive keeps a small joint serviceable:
| Where it sits | The screw closes a housing or fixes a plate where the joint is adjusted and reopened, in a head that must be small. |
| When it goes wrong | The recess rounds after a few adjustments and the setting cannot be held. |
| Why it happens | The head is small, the drive is a bit, and the joint is serviced. |
| What we control | Recess size and depth checked; first article driven with the production bit. |
| Where it sits | The screw holds a mount or a cover where the head sits flush and the thread goes into a small standoff. |
| When it goes wrong | The bit climbs out and marks the housing around the recess. |
| Why it happens | The space is tight, the head is countersunk, and the drive is internal. |
| What we control | Recess centred and gauged; first article assembled in the housing. |
| Where it sits | The screw sets a linkage where the head must be flush and the joint is opened for maintenance. |
| When it goes wrong | A worn bit reams the lobes and the linkage cannot be dismantled. |
| Why it happens | The parts are small, the drive is a star bit, and the joint is reopened. |
| What we control | Recess and thread checked; first article assembled and released. |
Four reasons that matter on a flush star-drive screw, each tied to something the drawing has to prove:
|
Recess size written as a number
The star size, depth and cone angle are agreed as a set, because on a countersunk head the three share one thickness. Basis: Recess size and cone agreed. |
Formed, recessed and passivated in one route
The cone and star recess are formed in one stroke, the thread rolled, and the parts passivated as a batch. Basis: One route from wire to passivated screw. |
|
Recess proved with the bit
The recess is checked with the production bit, because a star recess that measures correctly can still refuse a worn one. Basis: Recess proved with the production bit. |
First article seated in your countersink
The first article is seated in the customer countersink, because flushness is a property of the head and the hole together. Basis: First article seated in the countersink. |
These screws are headed on single-die machines that form the countersunk cone and cut the six-lobe recess in one stroke, rolled with the machine thread and passivated as a batch. The first part of every run is measured on head diameter, cone angle, head thickness, recess depth and thread.
|
|
Cutting six lobes into the flat top of a cone is the step that limits the part. The punch reaches depth across a face only a few millimetres wide and has to leave material between the recess floor and the cone; on a countersunk head that gap is the thinnest section of the fastener, and a punch set a little deep gives a head that gauges correctly and splits at the rim.
The cone is formed before the recess and its angle is set by the die. Wear changes the angle slowly, and a cone that is off angle no longer sits fully in the countersink, so the screw reads as proud while every dimension is inside tolerance. The angle is checked against a master at the start of each run for that reason.
What decides whether star screws pass is the cone, the recess, the head thickness and the thread. The inspection agreement covers those, and the criteria come from the drawing.
Cone and recess on the projector |
Thread and start checked |
Core hardness checked |
Salt-spray testing of the grade |
Cone angle is measured against a master and proved on a countersink block, and head thickness is measured in the same pass, because recess depth only means anything against it. The recess is checked with the production bit as well as on the projector.
A sample from every batch is seated in the customer countersink block, driven to the joint torque and removed. That cycle shows a shallow recess or a soft rim, and neither appears in a dimensional record.
Every batch is traceable to the wire it was made from and to the passivation batch that finished it. The grade and heat number appear 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 shipment we supply the material certificate, the inspection record for the dimensions on the drawing and, where the grade is listed, the third-party report that covers it. The documents carry the drawing revision and the batch number, so a repeat order keeps the same recess and the same cone.
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 star screws the first article is driven with the bit the assembly uses, because a star recess is only proven against a real driver. Buyers visit during the process to review samples.
|
8,678+
customers served
|
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 headers 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 |
Yes in practice. Torx is a brand name that became generic, hexalobular is the standard term, and star is the common word for the same six-lobe recess.
No. Pentalobe has five lobes and its sizes are written P, not T. A Torx bit will not drive it properly.
Write the size as a number on the drawing or the enquiry. The size does not follow the screw diameter automatically.
Usually a worn or undersized bit. On a countersunk head there is no edge to grip once the lobes are gone.
A2 covers rain, A4 covers chlorides. With no coating, the recess stays as formed.
Head diameter, cone angle and thickness, recess size and depth, thread pitch and length.
How a star screw project runs from drawing to repeat delivery:
|
1
Send the drawing and the bit
|
→ |
2
Recess size and cone agreed
|
→ |
3
First article driven with your bit
|
→ |
4
Batch production and repeat orders
|
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, cone angle and thickness, the star recess size and depth, thread pitch and overall length.
|
Head diameter
|
Cone angle
|
Recess size
|
|
Recess depth
|
Thread pitch
|
Length
|
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
