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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:Hex Head Shoulder Screw
Materials:Steel
Surface treatment:Zinc Plated
Head Type:Hexagon head with shoulder
Drive:External hex (wrench or socket)
Thread:Machine thread, partial, with nylon patch (Nylok)
Point:Plain, chamfered
Forming:CNC turning and grinding; thread cut; nylon patch applied
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make hex head shoulder screws in steel with a zinc plate and a nylon patch on the thread, quoting them from M1 to M10 to the drawing. The patch position and the assembly torque are agreed so the shoulder fit stays intact, and the first article is assembled and measured.
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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 hex head shoulder screw has an external hexagon, a ground shoulder that locates the part and a smaller thread, with a nylon patch applied to the thread to keep it from loosening. The part recorded here is steel with a zinc plate, quoted from M1 to M10 with the shoulder dimensions made to the drawing.
Hexagon head. An external hexagon driven with a socket or a wrench, with a flat bearing face.
Ground shoulder. A precision diameter that passes through the bore and locates or carries the moving part.
Smaller thread. The thread behind the shoulder is smaller, so the assembly stops at the step.
Nylon patch. A spot of nylon fused onto the thread that interferes with the mating thread and resists loosening.
They are used on pivots and linkages that see vibration, on hinges that must stay adjusted, and on equipment where a shoulder pin must not work its way out between service intervals.
A shoulder screw separates into three zones: the head that clamps, the shoulder that locates, and the thread that holds the assembly together. Each has a different job, and the nylon patch belongs to only one of them. It is a locking feature on the thread, and its whole function depends on sitting there and nowhere else.
Put the patch on the thread and it does what it is designed to do. The nylon is slightly oversize relative to the thread flanks, so when the screw is driven into a nut or a tapped hole the nylon is compressed and presses back on the flanks. That interference adds friction that does not disappear at zero load, which is what resists vibration loosening.
Put it on the shoulder or across the step and the consequences are different. A patch on the shoulder changes the diameter the bore runs on, which turns a locating fit into an interference fit and can make the pivot tight or impossible to assemble. A patch across the step alters where the assembly stops, so the head may no longer seat on its face. On a shoulder part both are functional failures, not cosmetic ones.
The patch also changes the driving torque. A Nylok thread needs more torque to assemble than the same thread without it, and it needs that extra torque over the whole engaged length rather than at the start. On a small screw that matters because the recess or the key has to transmit the extra force, which is why the assembly torque is stated rather than left to the fitter.
What the joint gets in return is a fixing that does not need a washer, an adhesive or a second operation to stay put. For a pivot that must remain a pivot, that is the difference between a part that stays adjusted and one that develops play between services.
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, subject to DFM review after drawing submission. The quotation for hex head shoulder screws carries the shoulder diameter and tolerance, the shoulder length, the head across flats and height, the thread size and length, and the patch position and length.
| Item | How it is defined | What we control |
|---|---|---|
| Shoulder diameter | Ground diameter through the bore | Diameter, roundness and finish |
| Shoulder length | From the head underside | Length and squareness |
| Head | Hexagon head | Across flats, height and bearing face |
| Thread | Machine thread behind the shoulder | Size, length and start |
| Patch | Nylon, position and length | On the thread only, never on the step |
| Torque | Assembly torque with the patch | Stated on the drawing |
The patch position is a drawing dimension on this part. It has to start far enough from the step that it never touches the shoulder, and it has to be long enough to cover the thread that actually engages the nut or the tapped hole.
The shoulder fit is agreed against the bore, because on a locating part the pair of tolerances is the specification. A patch that creeps onto the shoulder destroys that fit, which is why the boundary is checked on the first article as well as the diameter.
The assembly torque is quoted with the patch, because the nylon adds resistance. A joint tightened to a torque set for a plain thread will be under-tightened, and on a pivot that shows as play rather than as a loose screw.
Four properties decide hex head shoulder screws with a Nylok patch, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| Ground shoulder | A defined locating diameter | Patch must stay off the shoulder |
| Nylon patch | Resists vibration loosening | Higher assembly torque |
| Hexagon head | Drive from outside the head | Needs clearance for a socket |
| Zinc plated steel | Lower cost than stainless | A film on the shoulder and thread |
The value is a pivot that stays a pivot. A shoulder screw without locking can back out under vibration until the shoulder no longer spans the bore, and the part it locates starts to move; the patch stops that without adding a part.
The cost is assembly discipline. The torque is higher, the patch can only be used a limited number of times, and reusing a screw that has already been driven loses most of the locking effect.
The recorded finish is zinc plated. On a part with a nylon patch that is worth thinking about in order: the plate is applied first, and the patch is fitted afterwards, so the nylon sits on a coated thread rather than on bare steel.
| Option | How it protects | Effect on shoulder and patch | Typical use |
|---|---|---|---|
| Zinc plated | Sacrificial zinc | Film on shoulder; patch applied after | Dry locating joints |
| Zinc nickel | Higher corrosion resistance | Build; shoulder and thread re-checked | Damp and industrial |
| Black oxide | Conversion film, oiled | Almost no build | Dark dry mechanisms |
| Stainless, passivated | Passive film, no coating | No build on the shoulder | Wet and visible pivots |
| Zinc flake | Lamellar coating | Low build; covers edges | Where a thicker plate is too much |
Where the shoulder is a bearing surface, a coating on it is a film rather than a fit, and a post-plate grind restores the diameter. That is an extra operation, and it is why a joint that needs both a bearing shoulder and corrosion protection often ends up in stainless.
The patch is the part that can be compromised by finishing. A heavy plate inside the thread reduces the interference the nylon provides, so the locking torque is checked on the plated part rather than assumed from the white one.
Three settings where a positioned pivot must not loosen:
| Where it sits | The screw is the pivot of a lever on equipment that runs continuously, where the joint is under vibration for hours. |
| When it goes wrong | The screw backs out and the lever develops play or drops out of position. |
| Why it happens | The movement is continuous, the joint is small, and it is not serviced often. |
| What we control | Patch position and assembly torque checked; first article cycled under load. |
| Where it sits | The screw holds a hinge knuckle where the assembly has to stay adjusted through repeated use. |
| When it goes wrong | The pin works loose and the frame droops or rattles. |
| Why it happens | The joint moves, the fixing is visible, and adjustment is not expected. |
| What we control | Shoulder fit and locking torque verified; first article opened and closed. |
| Where it sits | The screw is the axle of a roller or a cam follower where the position sets the timing. |
| When it goes wrong | The axle migrates and the timing changes without any part failing. |
| Why it happens | The part rotates at speed, the position matters, and the joint is enclosed. |
| What we control | Patch coverage and torque stated; first article checked for position. |
Four reasons that matter on a part where the locking feature must not touch the fit, each tied to something the drawing or the first article has to prove:
|
Patch position dimensioned
The patch position and length are stated on the drawing, because nylon that reaches the shoulder or the step changes the fit and the seating rather than the locking. Basis: Patch position dimensioned. |
Turned, ground, plated and patched
The shoulder is turned and ground, the parts plated, and the nylon patch applied afterwards on the thread only. Basis: Patch applied after plating. |
|
Fit proved with the patch on
The shoulder is fitted into the customer bore with the patch already applied, because that is the part the customer assembles. Basis: Fit proved with the patch. |
Same locking torque
The patch material and the assembly torque are recorded with the drawing revision, so a repeat order resists loosening the same way. Basis: Same locking across orders. |
These screws are turned from steel bar, with the shoulder and the hexagon head machined in one setup, the shoulder ground to its diameter, the thread cut behind it, and the parts zinc plated; the nylon patch is applied to the thread afterwards. The first piece of every run is measured on shoulder diameter and roundness, shoulder length, head across flats, thread and patch position.
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Applying the patch is the operation that decides whether the part behaves. The nylon is fused onto a defined span of the thread, and the spacing from the step is set so that the patch never touches the shoulder: a small drift towards the head turns a locating fit into an interference fit, and the pivot is tight before the customer ever sees it.
The patch is also checked for how much of the engaged thread it covers. A patch that is too short leaves part of the thread plain, and the locking effect depends on the thread that actually engages the nut or the tapped hole rather than on the whole screw.
The shoulder is ground before plating and the diameter checked after, because a zinc film on a bearing surface changes the fit. Where the joint needs the ground diameter to hold, the shoulder is measured in the plated state on a sample from every lot.
What decides whether hex head shoulder screws pass is the shoulder, the head, the thread and the patch. The inspection agreement covers those, and the criteria come from the drawing.
Patch position on the projector |
Thread and start checked |
Core hardness checked |
Salt-spray testing of the zinc layer |
The shoulder is measured for diameter and roundness and its length is taken from the head underside. The patch is measured for position and length along the thread, and the gap between the patch and the step is checked first, because that is the dimension that protects the fit.
The locking is proved functionally. A sample from every batch is assembled at the stated torque, and then the removal torque is measured: too low means the patch is insufficient, too high means it may not assemble in the customer’s process. Both numbers are recorded with the batch.
A sample is also fitted into the customer bore to confirm the shoulder still locates with the patch applied, which is the check that catches nylon that has crept onto the shoulder.
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 patch material and the torque results are 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 patch position, the torque results for the batch, and the plating report. The documents carry the drawing revision and the batch number, so a repeat order of hex head shoulder screws locks 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 locking part the first article is assembled at the stated torque and the removal torque measured. Buyers visit during the process to review samples.
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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 turning cell and the patch 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 |
It puts a nylon patch on the thread that interferes with the mating thread and adds friction, so the screw resists loosening under vibration.
No. Nylon on the shoulder changes the diameter the bore runs on, and the locating fit is lost.
Yes, it adds resistance. The assembly torque is stated for the patched part rather than for a plain thread.
A few times at most. The nylon is deformed on first assembly, so the locking effect drops with each cycle.
Cost. Where the joint is dry and the shoulder locates rather than bears, a plated steel part is enough.
Shoulder diameter and tolerance, shoulder length, head across flats, thread size and length, patch position and the assembly torque.
How a locking shoulder screw project runs from drawing to repeat delivery:
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1
Send the drawing and the bore
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→ |
2
Shoulder fit and torque agreed
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→ |
3
First article assembled and torque measured
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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 shoulder diameter and tolerance, shoulder length, head across flats and height, thread size and length, patch position and the assembly torque.
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Shoulder diameter
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Shoulder length
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Across flats
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Thread size
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Patch position
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Torque
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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
