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:Very Long Machine Screws Carriage Bolt
Materials:Stainless steel
Surface treatment:Plain
Head Type:Truss Head
Drive:None; square neck locks it
Thread:Machine thread
Point:Blunt
Forming:Two-die heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:163
We make carriage bolts in passivated A2 stainless with a smooth truss head, a square neck and a machine thread, in long lengths quoted from M1 to M14. Head, neck size and depth, length and thread come from your drawing, and the first article is drawn into your timber.
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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.
Carriage bolts are fasteners with a smooth domed head, a square neck under the head and a threaded shank, used where a bolt has to be drawn into timber from one side and tightened from the other. This one is stainless steel with a plain finish and a truss head, quoted from M1 to M14 with Number 163, and it is made in long lengths.
Truss head. A wide, low dome with no recess, so the head pulls down into the timber and leaves a smooth surface.
Square neck. A short square section under the head that bites into the wood as the bolt is pulled in and stops the bolt turning.
Machine thread. A rolled thread along the shank that takes a nut on the far side.
Plain stainless. A2 grade, uncoated, so the head, the neck and the thread stay as made and the alloy is the protection.
A carriage bolt has no drive. There is no slot, cross or socket in the head, and that is deliberate: the bolt is not turned, it is pulled. The nut on the far side does the work, and the square neck under the head is what stops the bolt spinning while the nut is tightened.
The mechanism is a press fit into the material. When the bolt is drawn in, the square neck is forced into the hole and its corners cut or compress into the timber, which locks the bolt against rotation. That only works if the hole is sized for the neck rather than for the thread: a hole large enough for the shank to slide will not hold the square, and the bolt will spin as soon as the nut starts to bite.
The truss head completes the assembly. It is wide and domed so that it can be drawn down into the timber without splitting it, and so that it sits almost flush when the neck is seated. A head with a recess would be weaker in the draw and would collect water; a smooth dome sheds it and leaves nothing to catch.
Length is measured under the head and includes the neck, which is a detail worth confirming on a long part. A carriage bolt that is a centimetre short does not reach the nut; one that is long leaves the neck standing proud of the timber and the head does not seat, which is visible on a finished deck.
Stainless is the material that suits the job. Carriage bolts are used outdoors in timber structures, where a plated bolt rusts from the thread and stains the wood; a stainless body removes the question and leaves the head able to weather without leaving a rust line down the panel.
The recorded range is M1 to M14, with long lengths made to the drawing. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For carriage bolts the quotation carries head diameter and height, neck size and depth, overall length, thread length and the grade.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Truss, no recess | Head diameter, height and dome form |
| Neck | Square, under the head | Square size and neck length |
| Thread | Machine thread | Pitch, length and gauging |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Material | A2 stainless | Grade and heat number on the certificate |
| Finish | Passivated | Surface condition and film |
| Process | Two-die heading | Head form and neck sharpness |
Neck size is the number that decides whether the bolt holds. It is bigger than the thread and it is what the hole has to grip; a carriage bolt with a neck that is too small turns in the timber, and no amount of torque on the nut will draw it.
Neck depth is the other half. The neck has to sit below the surface of the timber when the bolt is drawn in, so the head seats; if the neck is too long or the hole too shallow, the head stands proud and the assembly looks unfinished.
Three features define the part: the smooth head, the square neck and the stainless body. The first lets the bolt disappear into the timber, the second locks it against rotation, and the third lets it stay there.
| Feature | What it gives | What it costs |
|---|---|---|
| Smooth truss head | Sits flush, sheds water | No drive; needs access to the far side |
| Square neck | Locks the bolt in the timber | Hole must be sized for the neck |
| Long shank | Spans thick timber | Bends in handling; packing matters |
| Stainless body | No rust staining outdoors | Galls dry; lubricant at assembly |
| Passivated finish | Head and neck as formed | Not a lubricant |
The locking neck is the whole idea of the part. Without it a carriage bolt is a smooth-headed bolt that turns as soon as the nut is tightened, and the assembly cannot be made up at all; with it, one person can tighten a nut on the far side without a second pair of hands on the head.
The lack of a drive is a limitation worth stating. A carriage bolt cannot be tightened from the head, so the joint needs access to the nut and it needs the timber to hold the neck. Where neither is true, a different fastener is the right answer.
The recorded finish is passivation with no coating on A2 stainless. For a carriage bolt that is the finish that matters most, because the bolt lives in timber and timber holds water: a plated bolt rusts at the thread and in the joint, and the stain runs out along the grain where it cannot be removed.
| Option | How it protects | Effect on head and neck | Typical use |
|---|---|---|---|
| A2 stainless, passivated | Passive chromium oxide film | Head and neck as formed | Outdoor timber and decking |
| A4 stainless, passivated | Passive film with molybdenum | Head and neck as formed | Coastal and marine timber |
| Steel, hot dip galvanized | Thick sacrificial zinc | Build on head and thread; allowances | Structural timber |
| Steel, zinc plated | Sacrificial zinc | Thin; stains timber when it fails | Sheltered indoor work |
| Copper and bronze | Alloy; patinates | Softer neck; cuts into timber easily | Boatbuilding and decorative |
Where the timber is structural and the bolts are large, hot dip galvanizing is the conventional answer and the coating has to be allowed for in the thread and the hole. Where the work is visible or coastal, stainless is the specification that keeps the timber clean.
Where the bolt goes into a marine timber, A4 is the grade and the assembly needs a lubricant: stainless on stainless galls, and a nut that seizes on a coach bolt in a deck is a nut that has to be cut off.
Three assemblies where carriage bolts are the fixing:
| Where it sits | The bolt passes through a joist and a board, with the smooth head on the walking surface and the nut underneath. |
| When it goes wrong | A hole sized for the thread lets the bolt spin, and the nut cannot be tightened. |
| Why it happens | The joint is timber, it is outdoors, and the head is visible. |
| What we control | Neck size and hole size agreed; first article assembled in sample timber. |
| Where it sits | The bolt joins rails to posts where the head sits on the outside face and the nut is reached from behind. |
| When it goes wrong | The neck does not bite, and the rail works loose as the timber moves. |
| Why it happens | The joint is exposed, it moves with the seasons, and the head is seen. |
| What we control | Neck depth and head diameter checked; first article fitted. |
| Where it sits | The bolt holds planks to a frame where the heads must be flush so cargo slides over them. |
| When it goes wrong | A proud head catches cargo, and a short bolt leaves the nut short of thread. |
| Why it happens | The deck is loaded, the heads are flush, and the joint is long. |
| What we control | Length and neck checked; first article assembled through the deck. |
Four reasons that matter on a carriage bolt, each tied to what the drawing has to prove:
|
Neck and length agreed
Neck size and depth, head diameter, overall length and thread are agreed as one set, because on carriage bolts the neck is what holds the bolt still. Basis: Neck and length agreed. |
Two-die heading for a sharp neck
The truss head and square neck are formed in one route on two-die headers, which keeps the neck corners sharp and the dome even. Basis: Two-die heading for the neck. |
|
Neck measured square
The neck is measured across the square and for depth, because a neck that is rounded at the corners will not bite and will not hold. Basis: Neck measured across the square. |
First article in timber
The first article is drawn into a sample of the customer timber, because the neck only proves itself in the material it grips. Basis: First article drawn into timber. |
Shi Shi Tong makes carriage bolts on two-die headers that form the truss head and the square neck in one sequence, then draw the long shank, roll the machine thread to a blunt chamfer and passivate the parts. The first part of every run is measured on head diameter and height, neck size and depth, overall length and thread before the batch continues.
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The square neck is where the part is decided. It is formed between dies that have to leave four sharp corners and a shoulder that meets the head cleanly; a neck with rounded corners looks right and turns in the timber, and a neck that is too long holds the head off the surface.
What decides whether carriage bolts pass is the neck, the head, the thread and the length. The inspection agreement covers those, and the criteria come from the drawing.
Head and neck on the projector |
Thread gauged per batch |
Hardness checked on the wire |
Salt-spray testing of the grade |
The neck is measured across the square and for depth, and checked for sharp corners; the head is measured for diameter, height and dome form. The thread is gauged per batch, and the length is measured from under the head, including the neck.
The first article is drawn into a sample of the customer timber with a washer and a nut. That is the check that shows whether the neck bites and whether the head seats, and neither can be measured on the bolt alone.
Every shipment of carriage bolts 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. The documents carry the drawing revision and the batch number, so a repeat order keeps the same neck and head geometry.
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 carriage bolt the first article is drawn into the customer timber, because the neck is only proved in the material it grips. 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 two-die 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 |
A carriage bolt is pulled, not turned. The nut on the far side does the work and the square neck stops the bolt spinning.
One sized for the square neck, not for the thread. A hole that lets the shank slide will not hold the neck and the bolt turns.
Under the head, including the neck. A short bolt misses the nut; a long one leaves the head proud.
Carriage bolts live in timber that holds water. A plated bolt rusts and stains the wood, and the stain runs along the grain.
Yes, by taking the nut off. The head is smooth, so it is pushed out from the far side.
Head diameter and height, neck size and depth, overall length, thread length and the grade.
How a carriage bolt project runs from drawing to repeat delivery:
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1
Send the drawing and the timber it goes into
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→ |
2
Neck, head and length agreed
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→ |
3
First article drawn into your timber
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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, neck size and depth, overall length, thread length, the grade and the finish.
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Head diameter
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Head height
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Neck size
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Neck depth
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Overall length
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Thread
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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
