Extra long hexagon socket m6 pan head machine screw

We manufacture extra-long M6 pan head machine screws in stainless steel, with a hex socket drive and a partial (half) machine thread, from M1.4 to M12 and up to 2,000 mm, formed one-piece by split-die cold heading and supplied plain or passivated. Head diameter, socket depth, thread start and material grade are made to your drawing.

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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.

What Defines an Extra-Long M6 Pan Head Socket Machine Screw

An M6 pan head machine screw combines three features that have to agree with each other: a 6 mm metric thread, a pan head with a rounded top and a flat bearing face, and a hex socket recess that takes an Allen key instead of a screwdriver. Make the screw extra long and a fourth condition appears: the shank has to carry the head through a long stack while the thread only bites at the far end.

Pan head bearing area. The pan head spreads load over a wider face than a cheese or fillister head of the same thread, and the rounded top keeps the head from catching on a moving part. On an M6 pan head machine screw the head diameter and the bearing face are dimensioned together, because the face is what clamps the plate, not the thread.

Hex socket and torque. The socket drives from inside the head, so the head can sit close to a wall or inside a bore where a Phillips driver cannot reach. A long screw driven from a socket needs the recess to be cut concentric with the shank; if the socket is off centre the key cocks over and the head walks sideways as it tightens.

Partial thread on a long shank. The plain shank passes through the plates or spacers and the thread engages only in the last section, which keeps the thread out of the shear plane and lets the stack slide into place before the screw is turned.

On a stainless M6 pan head machine screw the finish is the metal, so a burr left at the socket or under the head cannot be hidden by plating. Deburring and a clean passivated surface are part of the part, not an afterthought.

Split-Die Forming, One-Piece Shank

A long M6 pan head machine screw is formed in one piece on a split-die header. The die opens along the shank, so the head and the first part of the shank are headed from the same billet even when the finished length is far beyond a standard heading window. A welded or brazed shank is not the default for this part, and for stainless work it is not used at all.

The reason is not cost. A joint under the head or down the shank is a corrosion cell in stainless steel and a fatigue origin in any steel; it also sits under the same passivation as the rest of the screw, so nothing about it looks different until it fails. Forming the shank in one piece removes that risk from the drawing review stage.

The die set fixes head form, socket position and thread start together. The thread is rolled after forming, because rolling moves material rather than cutting it and leaves an uninterrupted grain flow at the thread root. When the length or the head changes, the die insert and the thread rolls change with it, and the first parts of each run go to the gauges before the run continues.

Size Range and Tolerances

M6 pan head machine screws are quoted as part of a family that runs from M1.4 to M12 and up to 2,000 mm. Length is normally held to +0/-2 mm on the drawing, and custom lengths up to 2,000 mm are subject to DFM review after drawing submission.

Diameter and length are quoted per part, and each M6 pan head machine screw combination is checked against the drawing before a quotation is issued. A long M6 and a short M6 in the same thread class take different routes through heading and rolling, so the check confirms that the route can hold both the length and the thread start.

Length is measured from the bearing face, not over the thread, and the thread length is read as a position from the same datum. Head diameter, socket depth and thread start are gauged on the first article before a batch is released, because those three dimensions decide whether the screw clamps the stack or bottoms out before it does.

Thread, Length and Direction: What to Specify

For an M6 pan head machine screw the drawing fixes five things: thread size and pitch (M6x1.0 unless the drawing says otherwise), thread length and position, plain shank length, total length and its datum, and right- or left-hand direction. A sixth line matters on stainless parts: the grade and the surface condition the parts are supplied in.

Surface Finish, Salt-Spray Testing and Packing

A stainless M6 pan head machine screw is supplied with the metal as the finish. There is no plated layer to build up the thread or fill the socket, so the thread fits at nominal size and the socket keeps the dimensions it was cut to. What the part does need is a clean, burr-free surface and passivation where the drawing calls for it, because free iron left on the surface is what starts corrosion, not the alloy itself.

Finish Selection for Long Machine Screws

Plain stainless parts are checked for finish and cleanliness rather than salt spray; salt-spray exposure is agreed only where the drawing specifies a coating. Parts are degreased and deburred before passivation, and the socket is cleaned after deburring so no cutting compound is left in the recess where a key will sit.

Packing protects the head and the thread in transit. Long screws are packed in layers with the heads supported, so the shank cannot take a set under its own weight, and the thread section is kept away from the carton wall. Batch and material information go on the label, so the part that arrives matches the record used for gauging.

Where M6 Pan Head Socket Screws Are Used

Three assembly conditions where a long M6 pan head machine screw has to hold a stack together, and what it has to do instead:

Automation and robot gantry frames Where it sits The screw runs through a machined block, a spacer and a frame plate on a gantry module, with the pan head sitting against the block face. When it goes wrong A head that stands proud interferes with the moving carriage, and a thread that starts early leaves the block loose on its faces. Why it happens The span is long, the blocks are not in one bore, and the module carries reversing loads. What we control Length from the bearing face, the plain shank through the stack, and the thread start at the far end.

Robot gantry – long screws through machined blocks

Battery module and pack racks Where it sits The screw clamps end plates and module frames in a pack, passing through insulating spacers before it reaches the threaded insert. When it goes wrong A thread cut into the spacer loses preload, and a length error leaves too few threads engaged in the insert. Why it happens The stack tolerance adds up across cells and spacers, and the joint sees vibration for the life of the pack. What we control Length and thread position, the plain shank through the stack, and the pan head bearing area on the end plate.

Battery module – screws clamping the pack frame

Chemical process skids and instrument racks Where it sits The screw fixes instrument brackets, cable-tray supports and panel frames on skid-mounted equipment, often in a washdown area. When it goes wrong Corrosion starts at a burr under the head or at the thread root, and a damaged socket stops the joint being re-torqued in service. Why it happens The atmosphere is damp and chemically active, and the hardware is stainless while the frame may not be. What we control Stainless grade per the drawing, plain or passivated finish, thread gauging and the socket checked with the matching key.

Chemical skid – stainless hardware on instrument frames

Why Shi Shi Tong for M6 Pan Head Machine Screws

Four reasons that matter specifically on a long M6 pan head machine screw, each tied to what the drawing has to prove:

How These Screws Are Manufactured

These M6 pan head machine screws are formed, not assembled. Stainless wire goes through the heading aisle; on a split-die header the die opens along the shank so the head and the first part of the shank come from the same billet, and the operator sets the die and checks the first parts against the drawing before the run is released. The thread is rolled after forming, the socket is formed with the head, and the parts are deburred and passivated before final gauge.

Between runs the die is changed to the drawing length and head form; the first parts go to the gauges before the run continues, and the setting is recorded. Parts that pass the bench checks are packed in layers so a long shank is supported over its length rather than hanging from the head.

Inspection: Pan Head, Socket Recess and Machine Thread

What decides whether an M6 pan head machine screw passes is not its appearance: it is the head and bearing face against the clamped part, the socket fit against the key in service, and the thread fit in the condition it ships in. The inspection agreement covers those, and the criteria are the ones written on the drawing rather than a generic standard.

Thread gauging against GO/NO-GO gauges	Head diameter and profile on the optical projector
Hardness testing of the base material	Salt-spray testing where a coating is specified

Each batch is recorded against the drawing revision: head diameter and height from the first article, the socket checked with the matching hex key, thread gauging per batch, and the material heat number on the certificate. If a gauge or the key fit fails, the parts back to the last good setting are held and re-checked before anything ships.

An outside report on the material, where the drawing asks for one, is filed with the batch so the paperwork and the parts share one batch number.

Certificates and Material Documentation

Every M6 pan head machine screw shipment is traceable to the material it was made from. The grade, heat number and standard 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 material. The documents carry the drawing revision and the batch number, so the paperwork can be matched to the parts.

Customers and Projects

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. Buyers visit during the process to review samples and to see the forming, threading and finishing steps their parts will go through.

Buyers and quality engineers visit for sample review, process discussion and supplier audits; the visit is arranged around production so the header, the thread rolling and the finishing 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

Related Products and Guides

Technical Guides

Long Thin Screws: Drawing and Manufacturing Requirements What to put on the drawing for long, thin parts: datum, shank, thread position and handling. Read the guide

How Long Does It Take to Customize Extra-Long Screws? Where the time goes in a custom long-screw order, from drawing review to first article. Read the guide

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M6 Pan Head Machine Screws FAQ

Order M6 Pan Head Machine Screws

How an M6 pan head machine screw project runs from drawing to repeat delivery:

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.