A well-prepared RFQ for a granite base for CMM structures or semiconductor equipment gets a firm, comparable quotation within days. A vague one - a rendering, a size and the word "granite" - gets a budget number that will move, a lead time that will slip, and a specification negotiation that starts after the order instead of before it. The difference between the two outcomes is a checklist. This article is that checklist: the drawings to attach, the geometric tolerances to state, the inserts and vacuum grooves to define, the envelope and quantity details that size the process, and the packing and transport facts that complete the picture.
1. Drawings and Models: What to Attach
The quotation quality is set by the drawing package. Three items, in order of importance:
A 2D drawing with the functional definition: datums named, critical dimensions toleranced, inserts and grooves marked, and the revision number stated. A 3D model (STEP or IGES) so the machining and inspection planning can work from real geometry. And a short statement of the duty - what the base carries, what moves on it, where it will be used - which lets the supplier sanity-check the design rather than only price it.
Outline drawings without tolerances are welcome for early budgeting, but they support only a budgetary estimate, and every later revision restarts the quotation cycle. The single most useful sentence you can write in an RFQ is which drawing revision is frozen: quotes against a frozen revision are firm and comparable; quotes against a moving one carry contingency margins, for good reason.
2. Geometric Tolerances: the Three That Drive the Quote
Three geometric tolerances decide most of the machining content and therefore most of the price:
Flatness of each working surface - stated per face, referenced to its datum, with the measurement method (autocollimator, electronic level, laser) agreed or left to the supplier to propose and record on the certificate. Parallelism between machined faces - typically rail-to-rail on a CMM bridge base or between mounting rails on a semiconductor stage. Perpendicularity of end and side faces to the working surfaces - the tolerance most often forgotten in first drawings, and often the hardest to recover at assembly when it is missing.
The discipline that makes these quotable: each tolerance is a number, a datum reference and a measurement method. A tolerance with no datum cannot be measured reproducibly; a tolerance with no agreed method will be argued about at receiving. State all three, and the quotation you receive will describe the same part you intend to buy.
3. Inserts, Threads and Vacuum Grooves
Granite bases rarely end at a plain block. The features to define explicitly:
Threaded inserts and holes: type (drilled-and-bonded or steel insert), thread size and depth, position toleranced from the datum system, and any torque or pull-out requirement the assembly imposes. Vacuum grooves and channels: the route, the cross-section, which surface seals against them, and the entry and exit positions - these are machined features with real cost sensitivity, and a sketch beats a sentence. Cable and coolant channels, cover recesses and lifting features belong in the same pass over the drawing: every interface that touches another component should appear once, defined, in the RFQ.
A useful review before sending: walk the drawing feature by feature and mark each one machined, inserted or as-cast. Features left undefined default to the supplier's assumption - and assumptions are where budget numbers grow.
4. Envelope, Quantity and Lead Time
Two numbers size the whole process. The maximum envelope - length, width, height and, for large bases, the weight - determines which machine can produce the part and how it moves through the shop. The quantities - prototype now, annual volume later - determine the process plan: a one-piece base and a forty-per-year programme justify different machining strategies, different inspection cadences and different prices.
Lead time questions are fair to ask directly: raw block availability for the size you need, machining and lapping sequence, and the lead time implied by your tolerance scheme rather than someone else's. If your schedule is fixed, say so - a supplier who knows the deadline can propose a realistic plan instead of a hopeful one, and can flag the long-lead items before they become critical.
5. Packing and Transport: the Details That Protect the Part
Granite is stiff but brittle, and most transit damage happens at handling points, not at sea. The RFQ should state: destination (port or door), any site constraints at receiving such as crane access, door widths and floor load limits, and whether shock and tilt indicators are required on the packing. A responsible supplier packs large bases in custom steel frames or fumigated crates on shock-absorbing supports, with lifting points matched to the design - but the supplier can only match the design to the site if the site is described.
6. How Your RFQ Is Evaluated Behind the Quote
Knowing what happens on the supplier's side explains why the checklist pays. A granite base quotation is built in a fixed sequence: the raw block is checked against the envelope and grade availability; the features are classified by process (sawn, milled, drilled and bonded, lapped); the tolerance scheme is converted into a machining and inspection plan; and only then is the number assembled. Each undefined item in the RFQ forces an assumption into that sequence - and every assumption is priced defensively. That is why a vague enquiry and a complete enquiry for the same part can land at visibly different prices, and why the complete one is usually the lower of the two once the specification is finally agreed.
The reverse is also true, and worth stating honestly: a checklist that is over-specified - tight tolerances copied onto non-functional faces, vacuum grooves defined to dimensions the pump never sees - will be quoted exactly as drawn, and the buyer pays for precision that the machine never consumes. The checklist is not a request for more precision; it is a request for the right precision, in the right places, stated clearly enough to be quoted and verified.
7. The Downloadable RFQ Checklist
We have condensed the six sections above into a one-page RFQ checklist. Email us through the inquiry page, put "RFQ checklist" in the subject line, and we will send the checklist as a PDF that your purchasing team can fill in alongside the drawing package - and reuse for every granite base enquiry after this one.
Used properly, the checklist does two things. It makes your quotation comparable with every other quotation you request, because every supplier is pricing the same defined part. And it moves the specification conversation to where it is cheapest: before the order, while the drawing is still open to change.
As a custom granite components manufacturer serving CMM builders and semiconductor equipment makers, we quote from exactly this structure - and we respond with manufacturability comments on anything in the drawing that looks expensive to make for no functional gain. Send your drawing and duty description; the review costs you minutes and regularly saves weeks.
Ready to request a firm quotation?
Attach your drawing, close the checklist above, and send it through our inquiry page - ask for the PDF checklist in the subject line if you would like a copy for your team. Request a quotation →