Housings and manifolds are the parts that punish a shop for a weak process. They have features on four, five, or six faces, bores that must stay concentric and square, intersecting cross-drilled passages, and sealing surfaces that cannot leak under pressure. The machine that eats this work is the horizontal machining center (HMC), and getting the fixturing and setup right is most of the battle. This guide covers how we machine CNC machined manifolds and housings, the tolerances that matter, and what the work costs.
Why housings and manifolds belong on a horizontal machining center
A manifold is a block with ports on multiple faces and internal passages that connect them. Machining it on a 3-axis vertical mill means one setup per face, and every setup adds a chance to lose true position on the internal passages. An HMC with a rotary B-axis pallet reaches four faces in one setup, so cross-holes meet where the print says they should. We run this family on our six CNC milling horizontal machining centers.
The other HMC advantage is chip evacuation. Horizontal spindles let chips fall away from the cut instead of packing into a deep bore, which matters when you are drilling long intersecting passages in a solid block of aluminum or steel.
Common housing and manifold features
- Bores and counterbores for cartridge valves, seals, and bearings
- Cross-drilled passages that intersect inside the block
- Threaded ports: SAE ORB, NPT, or metric, on several faces
- O-ring grooves and spotfaces for face seals
- Mounting patterns and dowel holes that locate to other assemblies
Multi-face setups: how the part is held
Fixturing decides accuracy on a manifold. Three approaches cover most jobs:
- Tombstone fixturing: The block mounts to a tombstone on the pallet, and the B-axis rotates it to present each face. One setup, four faces, true position held across all of them.
- Vise or custom soft jaws: For lower volumes, soft jaws bored to the part hold it repeatably while the B-axis indexes.
- Dedicated fixture plates: For production runs, a fixture that locates on a machined datum and clamps the same way every time keeps the whole lot identical.
The goal is to establish one datum reference frame and machine as many features as possible without re-fixturing. Every time a part comes out and goes back in, position error compounds.
Typical tolerances on housings and manifolds
- Bore diameter: +/-.0005 in, tighter on bearing and seal bores
- Bore-to-bore true position: .005 in, or .002 in on precision assemblies
- Face flatness on sealing surfaces: .001 in to .002 in
- Perpendicularity of bore to face: .001 in per inch or tighter
- Surface finish on seal bores: Ra 16 to 32 uin
- Port thread position: +/-.005 in so mating fittings clear
Cross-drilled passages and the deburr problem
Intersecting passages are where manifolds leak or clog. Two rules govern the work:
- Break-through burrs: Where one drilled passage breaks into another, a burr forms at the intersection. Left in place it breaks loose and jams a valve. We deburr intersections with mechanical tools, and on complex blocks with abrasive flow or thermal deburring on the customer's spec.
- Passage cleanliness: After deburr, passages get flushed and, when specified, verified clean to a particle standard. This matters most on hydraulic manifolds feeding servo valves.
We map the drill sequence so that break-through happens into an open, accessible passage wherever the design allows, which makes deburr reliable instead of a guess.
Materials for housings and manifolds
- 6061-T6 aluminum: The default for weight-sensitive manifolds. Machines fast, anodizes well.
- Ductile iron and steel: For high-pressure hydraulic blocks that need burst strength.
- 303 / 316 stainless: For corrosion resistance and washdown or marine environments.
- DFARS material with certs: For defense work, traced to the lot. See government and defense machining.
What a machined housing or manifold costs
Cost scales with the number of faces, the number of ports and bores, and the tightness of true position. The table shows typical illustrative estimates for a mid-size aluminum manifold, roughly a 4 in to 8 in block, not a binding quote.
| Cost driver | Prototype / low qty (1-25) | Production (100-1,000) |
|---|---|---|
| Programming and fixture design | $400 to $1,500 amortized | $5 to $30 per part amortized |
| Fixturing / tombstone setup | $300 to $1,200 per lot | $1 to $8 per part amortized |
| Material (6061 block) | $25 to $120 | $18 to $90 |
| HMC machine time | $60 to $300 | $25 to $140 |
| Deburr and passage cleaning | $15 to $80 | $4 to $25 |
| CMM inspection / FAI | $150 to $500 per lot | $1 to $6 per part amortized |
These are illustrative ranges. A simple two-face bracket-style housing sits at the low end. A six-face servo manifold with tight true position and passage-cleanliness verification sits at the high end.
Inspecting a multi-face part
You cannot verify bore-to-bore true position on a manifold with hand tools. We run CMM inspection on our Brown & Sharpe CMM to check bore positions, perpendicularity, and face flatness against the datum frame, and we issue a first article inspection report before a production run releases. Full detail is on the inspection and quality page.
How to spec a housing or manifold for machining
- Provide a solid model plus a fully dimensioned print with datums called out.
- Flag which bores are critical for true position and which are clearance.
- State port standards by name and note sealing surface finish.
- Specify passage cleanliness if the block feeds precision valves.
- Name the material grade and any certification requirement.
Send the model and quantity and we will design the fixturing and pick the right HMC. Start on our instant quote page.