Guides / Design
UAV component machining: what to put on the drawing
September 21, 2026
A machined UAV part fails in one of three ways. It is heavier than it needed to be, it does not interchange with the last one, or it fits the model but not the tube, the motor or the seal it has to meet in real life. All three are decided on the drawing, before a quote is ever sent.
This is what to put on that drawing, in the order it matters.
Start with the two features that actually locate
Most UAV parts have one or two features doing the real work. A boom clamp has a bore. A motor mount has a bolt circle and a face. A gimbal bracket has two bearing seats that have to stay square to each other. Everything else on the part is just material holding those features in space.
Tolerance those features and leave the rest alone. A drawing that calls ±0.01 mm on every dimension does not get you a better part, it gets you a slower and more expensive one, because the shop has to inspect features that were never going to matter.
| Feature type | Sensible call out | What happens if you tighten it further |
|---|---|---|
| Locating bore | ±0.01 mm or an H7 fit | Honing or grinding gets added, price goes up |
| Mating face | Flatness 0.02 mm over 100 mm | Extra finishing pass, small cost |
| Bolt circle | True position 0.04 mm | Needs one setup on a 5 axis, usually free if the part is already machined that way |
| Outside profile | General tolerance | Nothing, and that is the point |
Pick the material per part, not per aircraft
The common mistake is choosing one alloy for the whole airframe. The parts do different jobs.
- 6061-T6 for plates, housings, heat sinks and anything that needs welding or good corrosion resistance. It machines cleanly and takes anodise evenly.
- 7075-T6 for clamps, landing gear, hinges and lugs. Around twice the yield strength of 6061. It is not weldable and it corrodes faster, so hard anodise it.
- Titanium Grade 5 where strength to weight has to beat 7075, where the part runs hot, or where it bolts against carbon fibre and you want to avoid a galvanic couple.
- POM or PA66 for bushings, skids and non conductive standoffs. Cheap, quiet and forgiving.
- PEEK or PTFE for insulators and thermal breaks next to motors, ESCs and payloads that run hot.
Weight is the reason most of these choices exist, and the material notes on the capabilities page list what we keep and what has to be bought in. For the full choice across alloys and polymers, see our guide to drone parts materials.
Say what the part has to survive
A finish is not decoration on an aircraft. Write down the environment and the finish choice follows:
- Clear or black anodise, type II for general airframe parts. Thin, light, cosmetic and mildly protective.
- Hard anodise, type III for clamps, wear faces and anything in an agricultural aircraft that meets spray. Thicker, harder, and it grows the part by roughly half the coating thickness, which is why a bore has to be masked or machined undersize.
- Passivation for stainless parts.
- As machined and deburred for internal parts nobody sees. It costs less and weighs the same.
Two details that catch people out. Anodise is an insulator, so a part that needs a ground path has to be masked. Anodise also adds thickness, so a 25 H7 bore that is hard anodised after machining will not accept the tube it was cut for.
Think about where weight really goes
Pocketing a plate is the obvious move. The less obvious one is that a part with most of its mass removed will move when the stress in the billet rebalances. A 2.5 mm web that was flat on the machine can lift half a millimetre off the surface plate a day later.
That is a process problem, not a design problem, and the fix is roughing both sides, letting the part rest and finishing light. Ask the shop how they plan to hold a thin part. If the answer is vague, the flatness on your drawing is a wish.
There is more on this in designing machined drone parts for weight.
What a quote should contain
A quote that is only a number is not a quote. It should tell you:
- Unit price at the quantity you asked for, and at least one other quantity so you can see the break.
- Tooling or fixture cost, listed separately or stated as none.
- Lead time for the first article and, separately, for the lot.
- Which finish and which documents are included in the price.
- The Incoterm and the currency. Ours are EXW and USD.
- Any question about the drawing that would change the price if it were guessed.
That last one is the tell. A shop that quotes a drawing with an ambiguous fit without asking about it has either not read it or intends to interpret it in their favour later.
Before you send the RFQ
- One drawing revision, clearly marked, matching the STEP file you attach.
- Quantity for the first order and the likely annual quantity, if there is one.
- Finish and any masking requirement.
- The two or three features that matter, called out as such.
- What the aircraft does. Every shop should ask, and if you are talking to us we will screen it before we quote.
Send those and a useful number comes back within 24 business hours rather than a week of email.
Frequently asked questions
How many features on a UAV part actually need a tolerance?
Usually two or three. Bores that locate something, faces that mate with something and bolt circles that have to interchange. Everything else can run to the drawing general tolerance, which on a milled aluminium part is typically ±0.05 mm and costs nothing extra.
Is 7075 always better than 6061 for drone parts?
No. 7075 has roughly twice the yield strength, which matters on clamps, landing gear and hinge parts. It is not weldable, it costs more and it corrodes faster, so plates, housings and heat sinks are usually better in 6061. Pick per part, not per airframe.
What lead time should I expect on machined UAV parts?
For a small aluminium part in a normal alloy, expect a first article inside two weeks and a lot of a few hundred pieces two to three weeks after approval. Anodising adds several days. Exotic material that has to be bought in adds whatever the mill takes.
Need this part quoted?
Send the model and the quantity. Price and lead time come back within 24 business hours.