Buying machined parts is mostly a communication problem. The part is rarely hard to make - the quote goes wrong when the drawing does not say what the buyer actually needs. After twelve years of quoting other people's drawings, here is the short version of what we check first.

Start With the Function, Not the Number


A tolerance is only expensive when it is tighter than the function requires. A base plate that carries a gearbox needs two things: bores that locate the shafts, and a face that does not rock. The outer silhouette can be loose - nobody assembles a machine against an outside edge.

So the practical habit: mark tight tolerance only on locating features. For a typical custom machined base plate, we quote bores at +/-0.02 mm, tapped holes at standard pitch tolerance, and everything else to ISO 2768-m. That single distinction often cuts 20-30% off the price.

What "ISO 2768-m" Means on a Quote


General tolerance standards exist so drawings do not need a number on every dimension. When a drawing says ISO 2768-m, a 100 mm dimension carries +/-0.3 mm automatically. If you need better on a specific face, call it out - do not tighten the whole drawing for one bore.

At ForteForge every batch ships with a dimensional inspection report against this default, so "general tolerances" are measured, not assumed.

Three Things That Make Shops Quote High


1. Tight tolerance on long threads. A 6g thread is already standardized; asking for ±0.05 mm on thread length adds setup cost and no function.

2. Surface finish without a datum. If you specify Ra 0.8, say which face. Otherwise we quote the whole part polished.

3. Mixed materials on one drawing. Aluminum and steel on the same part number means two setups and two part marks. Split the drawing instead.

The 24-Hour Loop


Send a PDF, DWG or STEP file with the function of each critical feature noted - one line each. We come back within 24 hours with a price, a material suggestion if you want one, and a first-article option of 1-3 pieces with a full dimensional report before the batch. Prototypes start at one piece; the 1-2-3 setup blocks on our own benches are held to 0.005 mm per face, which is the standard we measure your parts against.

Tolerances are a purchasing tool, not a technical ornament. Spend them where the machine pays you back.