How These Guides Are Written and Checked

Where the figures come from

Material properties, coating thicknesses and tolerance bands are taken from published standards and from mill and supplier data, not from memory and not from other machining blogs. The standards the guides lean on most:

• ASTM B209 / B221Aluminum sheet, plate, bar and extrusion specifications. Background
• MIL-A-8625Anodic coatings for aluminum, the Type I/II/III definitions. Background
• MIL-DTL-5541Chemical conversion coatings on aluminum. Background
• ISO 2768General tolerances for linear and angular dimensions. Background
• ISO 286The H7/h6 limits and fits system. Background
• ISO 4287 / ISO 21920Surface texture parameters including Ra and Rz. Background

Published values are ranges, not promises

A yield strength or a typical tolerance is a property of a test coupon, not a guarantee about your part. Section thickness, temper, heat treatment and geometry all move the real number.

So the guides say "typical" where a figure is typical, give a range where the sources give a range, and state plainly that the shop quoting your part is the one who confirms what it can hold. Any guide here that reads like a guarantee is a guide we have written badly, and we would like to know.

What we will not publish

• Prices. Machining prices move with alloy, quantity, geometry, region and the week. A published number would be wrong for almost every reader, so the cost guide explains what drives a quote instead of inventing figures.
• Certifications we do not hold. None are claimed anywhere on this site.
• Shop names or capabilities we have not verified. Partner shops are never named publicly.
• Sponsored or paid placements. No shop can buy a mention in a guide. Shops pay for matched requests and that is the only thing money changes here.
• Invented credentials. Bylines, experience claims and numbers about ourselves are either true or absent.

Conflict of interest, stated plainly

This site earns when a machine shop pays for a matched request. That gives us an interest in you sending a request.

It does not give us an interest in you sending a bad one. Guides that talk you out of a tight tolerance, out of an expensive alloy or out of machining a part that should be cast are guides that make our matching work better, because shops judge us on the quality of what arrives, not the quantity.

Where a guide recommends against something we could otherwise sell, that is the reason.

Corrections

If a figure is wrong, tell us at and point at the source. Substantive corrections are made in the article and the page shows an updated date. We do not quietly rewrite a published figure and pretend it always said that.

Who is responsible

The Alu CNC Parts editorial desk is responsible for what appears in these guides. More about the business behind them is on the about page.