Technical specification packs: the document set a supplier quotes from

What a complete pack contains

A dimensioned drawing at a stated revision, a material specification with acceptable equivalents identified, surface finish and treatment requirements, any applicable performance or test requirement, the characteristics designated as critical with how they are to be verified, annual and batch quantities with the intended release pattern, packaging and labelling requirements, the approval evidence required before series supply, and the rules governing change. Anything omitted becomes a supplier assumption. The pack does not need to be long; it needs to leave no question whose answer materially moves the price or the process.

Requirements against solutions

There is a real difference between telling a factory what the part must achieve and telling it how to achieve that. Over-prescription — naming a process, a machine type, a sequence — closes off suppliers with better routes and transfers responsibility for the outcome onto you, since a part made exactly as instructed that fails in service is arguably your problem. Under-specification invites a cheap route you would never have accepted. The usable line is to specify function, interface and verifiable characteristics tightly, and to constrain process only where the process genuinely determines a property you depend on.

The pack is a controlled document, not an email attachment

Packs travel by attachment, get forwarded, and end up cached on a supplier's server in a version nobody can identify. Months later a part is made to a superseded print and both sides have evidence they were right. Issue by a controlled route with a revision the supplier must acknowledge, require quotes and shipments to reference the revision they were made against, and confirm at part approval which revision the approval covers. This is unglamorous administration that prevents the most expensive and most avoidable category of supplier dispute.

Writing for a reader who is not in the room

The pack will be read by someone who cannot ask you a question, possibly in a second language, possibly a process engineer rather than a designer. Notes referring to internal standards the supplier does not hold, drawings whose critical intent lives only in a colleague's memory, and terminology particular to your company all fail silently. Include the standards you invoke or say precisely where to obtain them, define plant-specific terms, and where a characteristic matters for a reason that is not obvious, say why. Understanding what a feature is for prevents more defects than tightening the tolerance on it.

Restricted substances and market requirements belong in the pack

Chemical restrictions, recycled content obligations, marking and conformity requirements for the destination market, and customer-specific prohibited materials all constrain what the supplier may use. Raising them after award means the supplier has already priced a route that may be non-compliant, and the correction lands as a change request. Put the applicable restrictions and the declarations you will require in the enquiry, so every quote is priced against the same constraints and no supplier wins on a basis it cannot lawfully deliver. Name the destination markets as well, since the same product can face different marking and conformity obligations in each, and the supplier cannot infer them from the drawing. Ask for the declarations at quotation stage so compliance is priced rather than discovered.

Frequently asked questions

How much detail belongs in an enquiry pack for a simple part?

Enough that a competent stranger could quote and make it without contacting you. Even for a simple bracket that means the drawing revision, the material and its acceptable equivalents, finish, quantities and release pattern, packaging, and the approval evidence expected. Simplicity reduces the number of open questions but does not remove them, and simple parts are exactly where teams skip the pack, receive incomparable prices, and then argue about packaging and finish after the order is placed.

Who should own the specification pack inside the buying company?

Engineering owns the technical content and any change to it. Purchasing owns the commercial content, the release pattern and the issue process. Quality owns the verification requirements and the approval evidence. In practice one person should assemble and issue the pack so a single version exists, with the three functions signing what is theirs. Packs assembled ad hoc by whoever is running the enquiry are the reason suppliers receive contradictory instructions from the same customer.

What happens when a supplier proposes a change to the specification?

Treat it as a proposal to be evaluated, not a nuisance. Suppliers often see cost drivers your design team cannot, and a suggestion to relax a tolerance, change a radius or switch to a stock size can remove real cost without touching function. Route it through the same change control as an internal request, record who approved it and against which revision, and update the pack. What must not happen is a verbal agreement between a buyer and a sales contact that never reaches the drawing.