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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:Self Tapping Shoulder Screw
Materials:Carbon Steel
Surface treatment:Color Zinc Plated
Head Type:Truss head with shoulder
Drive:Phillips cross recess
Thread:Self-tapping
Point:Sharp, tapered
Forming:Single Die Heading; shoulder ground
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make self tapping shoulder screws in carbon steel with a colour zinc finish and a truss head, quoting them from M1 to M10 to the drawing. The shoulder fit and the pilot are agreed against your materials, and the first article is driven and removed twice before the batch runs.
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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 self tapping shoulder screw combines a precision shoulder that locates a part with a thread that cuts its own path in the material behind. The part recorded here is carbon steel with a colour zinc finish and a truss head, quoted from M1 to M10 with lengths made to the drawing.
Ground shoulder. A plain diameter that passes through a bore and locates or carries the moving part.
Self-tapping thread. A spaced thread with a sharp point that cuts or forms its path in plastic, wood or sheet.
Truss head. A wide, low head that spreads the clamp on a soft or thin surface.
Colour zinc. A trivalent zinc with a coloured passivate, thicker than clear and visible where the head is seen.
They are used where a component has to be located on one side and held on the other without a nut: plastic housings, wooden panels, laminated boards and sheet fabrications with a soft substrate behind.
A shoulder screw does two things: the shoulder locates and the thread fastens. On a machine screw the split is simple, because the thread engages a tapped hole that was prepared for it. On a self tapping shoulder screw the thread has to make its own hole, and that raises the question of where the cutting stops.
The answer is at the step between shoulder and thread. Everything above it passes through a prepared bore and must not cut: the shoulder is a locating surface and a bearing surface, and a shoulder that cuts its way into the top member will enlarge the bore and take the fit out of the joint. Everything below the step cuts. On self tapping shoulder screws the transition is a sharp change of diameter with a short lead-in, and the boundary is a drawing dimension rather than a manufacturing detail.
The bore in the top member then has to be sized for the shoulder, and the material behind has to be sized for the thread. Those are two different holes in two different materials, and the joint only works when both are right. A bore that is too tight for the shoulder will not let the screw pass; a pilot in the substrate that is too large will not give the thread enough material to bite.
The head closes the joint. A truss head is wide and low, so it spreads the clamp on a plastic or laminated face without standing up where it would catch. On a soft substrate the head is doing most of the work of holding the assembly together, because the thread in plastic has limited pull-out strength and reaches it quickly.
That sets the endurance limit. In plastic and wood a self tapping thread loses grip a little each time it is removed, and a joint that is opened repeatedly ends up with a screw that turns without holding. The design assumption is therefore a limited number of cycles, and the head and shoulder are what carry the joint between them.
The recorded part is quoted to the drawing, with the shoulder diameter and length stated separately from the thread. Custom lengths up to 2,000 mm are subject to the drawing submission and DFM review. The quotation for self tapping shoulder screws carries the shoulder diameter and tolerance, the shoulder length, the thread type and pitch, the point form, the head dimensions and the overall length.
| Item | How it is defined | What we control |
|---|---|---|
| Shoulder diameter | Ground diameter through the bore | Diameter, tolerance and finish |
| Shoulder length | From the head underside | Length and squareness |
| Thread | Self-tapping, spaced | Pitch, spacing and length |
| Point | Sharp tapered or blunt | Point angle and length |
| Head | Truss, wide and low | Diameter, height and bearing face |
| Bore and pilot | Mating dimensions | Agreed with the first article |
The shoulder diameter is agreed against the bore in the top member, and the fit is a decision rather than a default: a clearance fit lets the part rotate, a close fit locates it, and an interference fit turns the screw into a fixed pin.
The thread and the pilot are one pair. The pilot in the substrate decides how much material the thread has to displace, and on self tapping shoulder screws that is what sets the driving torque and the risk of splitting the substrate. It is agreed on the first article rather than assumed from a table.
The point form follows the substrate. A sharp point starts a hole in sheet or soft plastic; a blunt point is used where the hole is pre-formed and the thread must form without piercing the material behind.
Four properties decide self tapping shoulder screws, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| Ground shoulder | A defined locating diameter | Bore must be sized for it |
| Self-tapping thread | No nut or tap needed | Loses grip with each removal |
| Truss head | Wide face on a soft surface | Stands slightly above |
| Colour zinc | Visible finish at low cost | Wears at the recess and the head |
The value is a joint that needs one part and one operation: locate, cut, clamp. On a plastic housing or a laminated board there is no nut, no insert and no access behind, and this is the fixing that works from one side.
The cost is that the joint is not designed to be opened many times. The thread in the substrate degrades with each removal, and the head takes more of the load as it does.
The recorded finish is colour zinc. On self tapping shoulder screws it is a visible, low-cost finish, and it has one specific consequence on this part: the coating sits on the self tapping thread, where it changes the cutting action slightly, and in the shoulder bore, where it changes the fit.
| Option | How it protects | Effect on shoulder and thread | Typical use |
|---|---|---|---|
| Colour zinc | Trivalent zinc, coloured | Film on thread and shoulder | Visible indoor joints |
| Clear zinc | Trivalent zinc, bright | Thinner; less effect on the cut | General indoor work |
| Zinc flake | Lamellar coating | Low build; covers edges | Where the substrate is damp |
| Black oxide | Conversion film, oiled | Almost no build | Dark assemblies |
| Stainless, passivated | Passive film, no coating | No build at all | Wet and food equipment |
Where the shoulder has to run in a bore, a coating on it is a film on a bearing surface, and the plain or post-ground option is the better answer. Where the part simply locates a plate in a dry assembly, colour zinc is adequate and cheaper.
On the thread, a coating that is too heavy reduces the bite in plastic: the zinc takes the place of steel at the cutting edge. The plating thickness is therefore kept to what the cutting test shows it can afford, and the first article is driven and removed before the batch runs.
Three settings where a part is located on one side and held without a nut:
| Where it sits | The screw passes through a front panel and cuts into a moulded boss, while the shoulder centres the panel. |
| When it goes wrong | The boss splits at the thread start, or the shoulder does not locate and the panel shifts. |
| Why it happens | The material is plastic, the boss is moulded, and the joint is opened once. |
| What we control | Pitch and pilot proved on a sample moulding; first article driven and removed. |
| Where it sits | The screw locates a fitting on a board and cuts into the timber behind the laminate. |
| When it goes wrong | A hole that is too small splits the board along the grain. |
| Why it happens | The board is finished, the joint is visible, and the fixing is repeated. |
| What we control | Bore and pilot agreed; first article driven in the customer board. |
| Where it sits | The screw passes through a metal skin and forms its own thread in the material behind it. |
| When it goes wrong | The thread strips before the head seats, and the assembly cannot be tightened. |
| Why it happens | The skin is thin, the substrate is soft, and there is no access behind. |
| What we control | Point and pitch checked; first article assembled and torque recorded. |
Four reasons that matter on a part that both locates and cuts, each tied to something the drawing or the first article has to prove:
|
Shoulder and thread boundary stated
The shoulder diameter, its length and the point where the thread begins are agreed at review, because everything above the step must not cut and everything below it must. Basis: Boundary dimensioned on the drawing. |
Turned or headed, ground, threaded
The head and shoulder are formed, the shoulder ground to its diameter, and the self tapping thread rolled on the smaller section. Basis: One route, two zones. |
|
Fit and bite proved in your material
The shoulder is fitted in the customer bore and the thread driven into the customer substrate, because the joint is a pair of fits in two different materials. Basis: Proved in your bore and your substrate. |
Same fit, same bite
The grinding setting and the thread rolls are recorded with the drawing revision, so a repeat order locates and cuts the same way. Basis: Same result across orders. |
These screws are formed with the truss head and the shoulder in one operation, the shoulder ground to its diameter, and the self tapping thread rolled on the smaller section below the step. The first piece of every run is measured on shoulder diameter and roundness, shoulder length, thread pitch and spacing, point, head and overall length.
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The step between shoulder and thread is the feature that defines the part. It has to be a clean change of diameter with a short lead-in, so the thread starts immediately below the shoulder without cutting its way up: a lead-in that is too long leaves an unthreaded zone that reduces engagement, and one that is too short drives the first thread into the shoulder and enlarges the bore.
Rolling the self tapping thread on the smaller section needs clean rolls. A smeared crest in a self tapping screw tears plastic rather than forming it, and a torn boss is a joint that has lost most of its strength before the head even seats.
Plating follows and is kept to a thickness the cutting test can afford. The first article is driven into the customer substrate and removed, and if the bite is affected by the coating the thickness is reduced rather than the thread being changed.
What decides whether self tapping shoulder screws pass is the shoulder, the thread, the point and the step between them. The inspection agreement covers those, and the criteria come from the drawing.
Step and thread on the projector |
Thread and point checked |
Core hardness checked |
Salt-spray testing of the zinc layer |
The shoulder is measured for diameter and roundness, and its length from the head underside. The step and the start of the thread are measured on the same setup, because the boundary is what keeps the shoulder from cutting.
The functional check is a drive into the customer substrate and a removal, followed by a second drive. That pair shows the bite on the first assembly and how much grip is left afterwards, which is the honest measure of a self tapping joint.
A sample from every batch is also fitted into the customer bore to confirm the shoulder locates without play, since that is the other half of the part’s job.
Every batch is traceable to the wire it was made from and to the plating lot that finished it. The grade and heat number appear on the material certificate supplied with the parts, and the plating thickness is recorded for the batch.
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 including the step and the thread, and the plating and RoHS reports. The documents carry the drawing revision and the batch number, so a repeat order of self tapping shoulder screws locates and cuts the same way.
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 substrate twice, because the second assembly is where the grip shows. 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 thread rolling station 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 |
At the step between shoulder and thread. Everything above it passes through a prepared bore; everything below it cuts its own path.
It is the locating and bearing surface. If it cuts, it enlarges the bore and the fit is lost.
It is agreed with the first article against the substrate. A pilot for a self tapping screw is not right for a metre of thread, and every material has its own value.
Only a limited number of times. A self tapping thread in plastic or wood loses grip with each removal, so the design assumes few cycles.
It spreads the clamp on a soft or laminated face without standing tall, which matters where the substrate has limited pull-out strength.
Shoulder diameter and tolerance, shoulder length, thread type and pitch, point form and overall length, plus the bore and pilot.
How a self tapping shoulder screw project runs from drawing to repeat delivery:
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1
Send the drawing and the substrate
|
→ |
2
Shoulder fit and pilot agreed
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→ |
3
First article driven and removed twice
|
→ |
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 shoulder diameter and tolerance, shoulder length, thread type and pitch, point form and overall length, plus the bore and pilot.
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Shoulder diameter
|
Shoulder length
|
Thread pitch
|
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Point form
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Bore
|
Pilot
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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
