Machined Bike Brackets, Mounts and Hardware
This is the widest category and the one where the part price is smallest and the process cost largest. A seat collar is twenty minutes of machining and a full anodizing batch charge. Understanding that ratio is most of what it takes to buy these parts well.
What this covers
- Disc brake adapters and caliper mounts
- Derailleur hangers, frame specific and UDH
- Seat collars and seatpost heads
- Thru axles and quick release hardware
- Bottle cages, accessory and cargo mounts
- Headset spacers, top caps and shims
Interfaces you do not get to choose
- Brake mount standardsPost mount, IS and flat mount
- Rotor sizes to adapt140, 160, 180, 203 mm
- Seatpost diameters27.2, 30.9, 31.6 mm
- Derailleur hanger threadM10 x 1.0 on most modern hangers
- Accessory mount pattern64 mm two-bolt bottle cage
Full tables in the standards reference.
Material choice
What each option actually buys you on this part, rather than in general.
| Material | Why it gets used here |
|---|---|
| Aluminum 6061-T6 | Almost everything here. Cheap, cuts fast, anodizes to a consistent color across a whole accessory range. |
| Aluminum 7075-T6 | Brake adapters and thru axle levers where the section is thin and the load is high. |
| Stainless 303 or 17-4 PH | Axles, pivot pins and anything threaded that will be assembled repeatedly. |
| Titanium Grade 5 | Thru axles and bolt kits, where strength sets the size and weight is the selling point. |
Where the tolerance belongs
These are typical working ranges, not promises. Tolerance these dimensions and leave the rest at a general tolerance, because every step tighter than you need buys machine time you will pay for.
| Feature | Typical | Why it matters |
|---|---|---|
| Brake mount hole positions | ±0.1 mm | Calipers have limited adjustment. Position error becomes rub. |
| Seat collar bore | ±0.05 mm | A clamp fit against a standard post diameter. |
| Hanger thread position | ±0.1 mm, axis square | An angled derailleur mount cannot be fixed with a B screw. |
| Mounting face parallelism | 0.05 mm | Non-parallel faces put bending into the bolt as soon as it is tightened. |
| Everything else | ±0.1 to ±0.2 mm | Cosmetic. Leave it open. |
Finish
Group parts into one anodizing batch. A stem, a seat collar and a set of spacers in one color is one rack and one charge. Running them separately triples the finishing cost on the same quantity.
Realistic quantities
Here more than anywhere the anodizing batch sets the floor. Machining 25 collars is easy. Anodizing 25 collars on their own rack is what makes the per part price hurt.
What goes wrong on this part
Failure modes specific to this component, collected so you can design them out rather than discover them.
- Derailleur hangers should bendUse 6061, not 7075. The hanger is deliberately the weakest part so the frame survives. A hanger that snaps clean lets the derailleur into the spokes.
- Thread engagement in aluminumAbout 1.5 to 2 times the bolt diameter. For a joint assembled and disassembled repeatedly, specify a threaded insert instead.
- Standard drill sizesA 6 mm hole is a stock drill. A 6.15 mm hole is an interpolated feature and costs several times more.
- UDH changed the hanger marketOne geometry across every frame that adopts it, instead of hundreds of frame specific shapes. The economics are completely different.
What to send
A drawing with these on it gets quoted in a day. One without them gets quoted with padding in it, or gets four rounds of questions first.
- STEP file plus a PDF drawing
- The standard the part interfaces with, named
- Which holes and faces are functional and which are cosmetic
- Whether several parts can share one anodizing batch
- Thread sizes, depths and any insert requirement
Printable version: the RFQ checklist.
Go deeper
- Process
Machining Derailleur Hangers and the SRAM UDH Standard
Hangers are meant to bend before the frame does. What that means for material choice, thickness and tolerance, and how the UDH standard changed the part.
- Cost
Low MOQ CNC Bike Parts: What Is Actually Realistic
What order sizes shops really take for machined bike parts, why anodizing sets the true floor and how to keep a run of 25 pieces from costing more than it should.
- Finishing
Bike Part Finishes Beyond Anodizing: A Buyer Guide
Bead blast, tumble, polish, powder coat, electroplate, laser mark and cerakote. What each does to a machined bike part, what it costs and where it fails.
Other parts
Stems and faceplates
Two clamp bores against fixed standards, a faceplate that has to close evenly and a rider on top of it.
Chainrings and spiders
A flat part with the tightest tolerance on the site. Tooth width decides whether a 1x chain stays on.
Cranks and pedal hardware
Fatigue critical, envelope fixed by the frame and the rider. The part where anodize choice changes test results.
Hub shells and freehubs
Turning plus milling in one part. Concentricity between the bearing seats decides whether it drags.
E-bike drive hardware
Machined like a bike part, loaded like a light vehicle part, regulated like an electrical product.