Start with the shops that price themselves. FOCAL and Wai Innovation both turn a DXF into a price online with no conversation, and FOCAL states no minimum order. For anything you can draw flat, that is a free answer in minutes rather than a week of phone tag.
Send a STEP file, not just a PDF. Every machining shop here works from 3D CAD. A STEP or Parasolid export plus a dimensioned drawing for the features that matter gets a quote back fastest.
Say “one-off prototype” in the first sentence. It changes who picks up the job. Small shops price a single part happily; production shops may quote it high or decline, and you want to find that out in the first minute.
Dimension only what matters. On a rotary chamber that is bore roundness, slot width and parallelism, and shaft-to-bore concentricity. Tolerancing everything to the same spec is the fastest way to make a prototype expensive.
Ask what they would change. Fourteen shops here offer design or CAD help, and several will convert a sketch. A five-minute manufacturability conversation routinely halves the price of a first article.
Ask who does the hardening. Most general CNC shops sub out heat treatment. Whether it leaves the site usually matters more to your lead time than the machining does.
Worked with one of these shops?
Three shops have a review available: Barton Machine Works, Wai Innovation and Machining Solutions. We have put real work through each of them, so we can tell you how it went. A review here is a first-hand account rather than a recommendation, and not all of them are glowing. Ask and we will give you the straight version.
The other 37 have no first-hand account attached, which is the weakest part of this directory. If you have used any of them, send a few lines about how it went to natalia@galinengine.com and it will be added. What the part was, what it cost, how long it took and whether you would go back is more useful than a score.
