Energy storage · battery modules

Extra-long screw — length is easy, straightness is not

Anyone can make a 300 mm screw. Making one that goes through four stacked components without forcing is a different problem: straightness and thread run-out over the full length.

Extra-long screw

The part

What it is

Battery modules clamp prismatic cells between end plates with long screws. If the screw bows, the stack does not seat, and the assembler compensates with torque — which is where modules fail in the field.

  • Up to 300 mm, headed then thread rolled
  • Straightness checked over full length, not at the ends
  • Thread run-out measured relative to the screw axis
  • Socket head formed, not welded or machined on

Specification

Typical range we run

These are the ranges we produce most often. If your drawing sits outside them, send it anyway — the answer will be honest, including when the answer is no.

MaterialCarbon steel · stainless steel
ThreadM4 – M8
Length100 – 300 mm
Straightness0.3 mm per 100 mm typical
FinishZinc-nickel or plain, per pack requirement
ProcessCold heading + thread rolling + straightening check

Values shown are typical for this part family, not a catalogue limit. Final specification is agreed against your drawing.

Why it is difficult

What goes wrong, and why it is not visible

A part that looks correct can still fail in the field. These are the failure modes the process is designed around.

BowA screw that is straight at both ends can still bow in the middle — measured over the full length.
Thread run-outIf the thread axis is offset, the nut cross-threads at the far end.
Thread length varianceToo long and it bottoms out; too short and it does not reach the torque spec.

Inspection

What we check, and with what

Straightness

Rolled on a surface plate, checked over the full length.

Thread run-out

Measured against the screw axis on the projector.

Thread length

Gauge check per lot.

Head integrity

Visual and torque test on the socket.

Where it goes

Applications

Battery modules

Clamping stacks of prismatic cells.

Rack structures

Long fasteners in energy storage cabinets.

Structural assemblies

Where a standard screw cannot reach.

Send the drawing. We will tell you if it can be made.

Feasibility, process route and an indicative price in 48 hours — including when the answer is that turning is the better route.

Send a drawing