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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:Slotted Truss Head Screw
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Truss Head
Drive:Slotted
Thread:Self Tapping Thread
Point:Sharp
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:523
We make slotted truss head screws in passivated stainless, a wide shallow head with a single slot and a self-tapping point, quoting them from M1 to M14. Head diameter, slot depth, thread and point come from your drawing, and the first article is driven into your own sheet.
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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 slotted truss head screw combines the widest low head in the catalogue with the simplest drive: a shallow dome carrying a single slot, on a self-tapping shank that cuts its own thread. The head spreads load over a broad ring, the slot takes a flat blade, and the sharp point starts in the hole. This family is made in passivated stainless, quoted from M1 to M14 with Number 523.
Truss head. A very wide, shallow dome with a flat bearing face, spreading the clamp load close to what a washer would give.
Single slot. One straight slot across the top face, cut into a dome that has very little height to give it.
Self-tapping thread. A coarse thread with a sharp crest, sized to form its own thread in the panel.
Passivated stainless. No coating, so the slot is exactly as cut and the alloy is the whole of the protection.
Every truss head is a compromise between bearing area and height, and a slotted truss head screw puts a drive into the thinnest part of that compromise. The head has to be wide to spread load and shallow to stay out of the way, and the slot has to be deep enough to take a blade — three requirements competing for the same few millimetres.
The result is a slot that is shallower than the one on a cheese or pan head of the same thread. A shallow slot means less contact length for the blade, more chance of the blade rocking, and a head that marks as soon as the driver slips. That is not a defect in manufacture; it is what the geometry allows, and it sets the limit on how hard the joint can be driven.
It matters more here than on a machine screw because the thread is self-tapping. Forming a thread in a panel takes more torque than running into a tapped hole, and stainless takes more again. A slotted truss head screw in stainless is therefore a part where the driver, the blade and the pilot hole do most of the work, and the head is the thing that has least margin.
What the form is good at is the face. A wide flat bearing ring on a thin panel spreads the load so the sheet does not dome, and the shallow dome leaves the fixing close to the surface without a countersink. Where the panel is thin and the fixing is visible, that combination is worth more than a deeper slot would be on a stronger head.
The slot’s failure mode is sideways. Unlike a cross, which lifts the driver out, a slot lets the blade rotate and run across the head, so a slip marks the face and can cut the wall. Holding the driver down while turning, and using a blade that fills the slot, is what keeps a slotted truss head screw looking new.
The recorded range is M1 to M14, covering M1, M2, M3, M4, M5, M6, M7, M8, M9, M10 and M14. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For a slotted truss head screw the quotation carries head diameter, head height, slot width and depth, the thread and the point, because the slot depth is decided by the head height.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Truss head, wide and shallow | Head diameter and height |
| Slot | Single straight slot | Slot width, depth and burr |
| Thread | Self-tapping, coarse pitch | Pitch and major diameter, gauged |
| Point | Sharp, tapered | Point angle and thread start |
| Finish | Passivated stainless | Surface condition and film |
| Length | Under the head to the point | Measured on the shop plate |
Slot width should be fixed with the blade that will drive it. A slot that is narrow binds the blade and lifts a burr at the ends; one that is too wide lets the blade rock and rounds the slot floor. On a shallow slot the second failure is much more likely, and it is the one that ends the life of the head.
Head diameter is the feature that was chosen deliberately, so it deserves a tolerance. On a narrow margin the truss rim overhangs the edge of the panel, which looks wrong and protects nothing. Where the panel is small, a pan head of the same thread is often the more sensible choice.
Three features define this part: the wide head, the shallow slot and the self-tapping thread. The first spreads load, the second limits the drive, and the third makes the joint without a nut.
| Feature | What it gives | What it costs |
|---|---|---|
| Wide truss head | Washer-like bearing area | Thin rim, easily bent |
| Shallow dome | Stays low on the panel | Little depth for the slot |
| Single slot | Simple blade, easy to see | Blade can slide sideways |
| Self-tapping thread | No nut or tapped hole | Higher torque in stainless |
| Passivated stainless | No coating to chip | Galls against stainless |
The wide face is the reason to accept the shallow slot. On a thin panel the alternative is a smaller head plus a washer, and a washer is a part that can be forgotten at the bench. A truss head solves the load spread in one piece, provided the joint does not need to be driven hard.
The thread and the drive pull against each other in a way that is worth planning for. If the pilot hole is on the tight side of the window, the torque needed to form the thread may exceed what the shallow slot will take, and the head is damaged before the screw seats. Opening the hole slightly, or lubricating the thread, keeps the torque within the drive’s limit.
The recorded finish is passivated stainless with nothing added. On a shallow slot that matters: a coating narrows the slot and rounds its edges, and the deposit wears off exactly where the blade presses. A passivated part keeps the slot as cut, and the alloy does the protecting.
| Option | How it protects | Effect on slot and head | Typical use |
|---|---|---|---|
| A2 stainless, passivated | Passive chromium oxide film | Slot as cut | Outdoor and general panels |
| A4 stainless, passivated | Passive film with molybdenum | Slot as cut | Coastal and chemical |
| Steel, white zinc | Sacrificial zinc | A few microns; slot re-checked | Indoor sheet metal |
| Steel, black zinc | Sacrificial zinc, dark | A few microns; slot re-checked | Dark equipment |
| Aluminium, anodised | Thick oxide layer | Oxide dulls the slot edges | Lightweight panels |
Where the joint is indoors, zinc-plated steel is the cheaper answer and behaves the same in the joint. What changes is the head: a plated slot is a few microns narrower and a little slicker, which on a shallow slot is a measurable difference to how the blade sits.
Stainless is the version to choose wherever the panel is outside, washed or in a food area, and on a truss head the benefit is visible: no plate to chip at the rim, no rust streak running down the panel from under the head. The alloy choice follows the environment, A2 for general exposure and A4 where chlorides are present.
Three assemblies where slotted truss head screws are the fixing:
| Where it sits | The screw fixes a panel or a cover where the sheet is thin, the head is on show and the joint is driven once with a hand tool. |
| When it goes wrong | A narrow head dimples the sheet, and a shallow slot is damaged if the blade is worn or the hole too tight. |
| Why it happens | The panel is thin, the fixing is visible, and the driver is a flat blade. |
| What we control | Slot width and head diameter checked, first article driven into the sheet. |
| Where it sits | The screw closes a cover where the head must not catch and the blade is the tool the technician carries. |
| When it goes wrong | A bent truss rim looks like a damaged screw, and a slipped blade marks the face. |
| Why it happens | The head is exposed, it is low, and the joint is opened occasionally. |
| What we control | Head form and slot driven with the production blade. |
| Where it sits | The screw holds a plate or a frame where a wide head reads as a deliberate fixing and the panel is thin. |
| When it goes wrong | Over-driving bends the rim, and a slot that is too wide will not hold the blade. |
| Why it happens | The fixing is visible, it is flat to the panel, and the blade is hand held. |
| What we control | Head diameter and face flatness checked, first article reviewed on the panel. |
Four reasons that matter on a shallow-drive part, each tied to what the drawing has to prove:
|
Slot depth and blade agreed
The slot depth is quoted with the head height and matched to the blade, because on a shallow dome the slot is the first thing to fail and it cannot be recovered. Basis: Slot depth and blade agreed in writing. |
Head, slot and thread in one route
The wide head and the slot are formed in the heading stroke, the self-tapping thread is rolled and the point is formed, with passivation last. Basis: One route with passivation last. |
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Driven into a test sheet with the blade
The first article is driven into a sheet of the customer thickness with the production blade, because the joint is judged by whether it seats without damage. Basis: First article driven into a test sheet. |
First article fixes the setting
The first article fixes the wire, the truss die and the slot cutter; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these slotted truss head screws from stainless wire on single-die headers that form the wide shallow head and cut the slot in one stroke, rolls the self-tapping thread, forms the sharp point and passivates the finished parts. The first part of every run is measured on the head and slot, driven into a sheet of the customer thickness and entered into a thread gauge before the batch continues.
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The truss die is the tool that decides this part. It has to spread the head wide without letting the dome flatten into the slot, and the slot cutter has to open the slot ends cleanly where they meet the thin rim. When the die wears, the first symptom is a slot that is shallower or that has a raised lip at the ends, and the part still passes a general height check.
What decides whether slotted truss head screws pass is the slot, the head, the thread and the alloy. The inspection agreement covers those, and the criteria come from the drawing.
Head and slot on the projector |
Thread gauged per batch |
Hardness checked on the wire |
Salt-spray testing of the grade |
The slot is checked for width, depth and for a clean edge at both ends, and then it is driven with the production blade. The head is checked for diameter, height and face flatness, and the rim is inspected for bends, because a truss rim is thin and a bent one cannot be straightened.
The thread is gauged per batch and the point is checked for angle and start. The first article is driven into a test sheet and judged for whether the head seated flush without the blade slipping — on this part that is the check that predicts the customer’s experience better than any single dimension.
Every shipment of slotted truss head 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 a repeat order is made from the same grade that was approved.
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 self-tapping part the first article is driven into the customer’s own sheet, because the joint is the function. Buyers visit during the process to review samples and to see how the heads and slots are formed.
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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 |
Because the truss head is shallow by design. The head is wide to spread load and low to stay out of the way, so there is less height available for the slot.
With care, and with a blade that fills the slot. A slotted drive slips sideways rather than camming out, so a fast driver marks the head quickly.
Sized to the sheet and the material. In stainless the torque needed to form the thread is high, and a hole that is too tight can damage a shallow slot.
Over-driving, or a seating face that is not flat. The rim of a wide shallow head is thin, and it cannot be straightened.
That is what it is for. The wide face spreads load so the panel does not dimple, provided the margin around the hole is wide enough.
Head diameter and height, slot width and depth, thread size and length, the point form, the grade and the blade that will drive it.
How a slotted truss head screw project runs from drawing to repeat delivery:
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1
Send the drawing and the blade you use
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→ |
2
Head, slot depth and thread agreed
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→ |
3
First article driven into your 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 head diameter and height, the slot width and depth, the thread size and length, the point form and the grade.
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Head diameter
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Head height
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Slot width
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Thread size
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Length
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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
