About This Part
A precision bushing is a simple-looking part that is unforgiving of small errors. It is a hollow sleeve — a bore, an OD, and a length — yet every feature matters: the ID carries a shaft, the OD pilots into a housing, the faces clamp against adjacent components, and if any of those are out of round, off-center, or the wrong size by even a few microns, the assembly binds, wears prematurely, or fails to load evenly. In stainless steel bushing cnc work, this is a part where the shop either has its turning process dialed in or it does not — there is no middle ground, and there is no way to hand-work a bad bore into a good one. This precision sleeve is machined from **Stainless Steel 304**, chosen for its corrosion resistance, good mechanical strength and availability for industrial, food-grade and medical applications. The bushing is produced by **CNC turning + milling** (milling for any cross-holes, oil grooves, clamp slots or keyways when specified). The ID, OD, face perpendicularity and any roundness-critical features are held to **±0.005 mm on critical dimensions**. Spacer bushing turning in small to medium batches requires process control across setup changes, not just a single good first article; a 0.005 mm bore tolerance held across a run requires the same tool pressure, the same thermal state and the same workholding grip on every part.
**Part:** Precision Bushing
**Process:** CNC turning + milling
**Material:** Stainless Steel 304
**Tolerance:** ±0.005 mm on critical dimensions
**Inspection:** 100% CMM verification, full report with shipment
Challenges of This Part & How We Machined It
ID-to-OD concentricity and roundness
The defining requirement of a bushing is that the inner and outer diameters share the same axis. If the ID is offset from the OD by 0.01 mm, the wall thickness varies around the circumference and the shaft sits eccentric in its housing — which causes vibration, uneven wear and seal runout that gets worse as the bushing beds in. Roundness is equally critical: a lobed or three-point bore will grip a shaft in some positions and be loose in others, producing inconsistent preload. We achieve concentricity by finishing the ID and OD in the same setup wherever possible, using a bore-and-turn sequence on a lathe with a collet or dedicated mandrel so that nothing shifts between operations. Out-of-roundness is controlled by taking light, consistent finish passes and avoiding tool pressure that would spring the thin-walled sleeve.
Thin-wall deflection during boring
Many bushings are thin-walled by design, and Stainless 304 does not give the machinist any favors when cutting pressure is applied. A boring bar pushing against a thin wall flexes the part away from the cut, producing a tapered or lobed bore that measures wrong the moment the chuck is released — a problem that is invisible during machining because the part is held rigidly by the chuck jaws. We use dampened boring bars with appropriate overhang, reduce depth of cut on the finishing pass, and support the OD with a soft jaw or steady rest when the wall is thin enough to flex under boring loads. Bores come out round and straight, not just dimensionally correct at the mouth.
Built-up edge and surface finish in 304 stainless
Stainless 304 forms a built-up edge on cutting tools when speeds and feeds are not tuned correctly. The welded workpiece material on the insert edge tears the surface instead of shearing it, leaving a cloudy, torn finish that looks bad and can accelerate wear on mating shafts. In a bushing bore, this torn finish also retains lubricant poorly, leading to premature galling when a shaft rotates under load. We use sharp inserts with appropriate chip-breaker geometry, run at surface speeds chosen to stay above the built-up-edge zone, and direct coolant to the cutting edge to keep temperature stable. The result is a consistent turned finish on both ID and OD with no tearing or chatter.
Machining Sequence
1. **CAM programming and workholding design** — soft jaws or mandrels are planned so that ID and OD finishing can be done without unnecessary re-chucking; tooling is selected to minimize boring bar overhang for thin-wall parts.
2. **CNC turning — roughing** — OD, ID and faces are roughed to leave a uniform finishing allowance, with chip load consistent enough to avoid work hardening the 304.
3. **CNC turning — finishing** — ID and OD finish passes are taken in the same setup or on a mandrel, with light cuts and tuned speeds to control built-up edge and deflection.
4. **Milling of secondary features** — any cross-holes, oil grooves, keyways or slots are milled with the bushing located off the finished OD/ID to preserve concentricity.
5. **CMM and air-gauge inspection** — ID/OD diameters, roundness, concentricity and face squareness are verified; bore surface finish is checked by profilometer or visual comparison.
What You Get With Every Order
- **Free DFM review before quoting** — we flag manufacturability risk early, not after parts are made - **First Article Inspection report** with the first batch - **CMM dimensional report** on critical features - **Material certificates** for aerospace and medical grades - **Direct communication with the shop** — no trading company in between, we make the parts ourselves
Have a Drawing?
Send us your drawing or STEP file and we will come back with pricing within 48 hours. Prototype quantities and production runs both welcome — no minimum order quantity.
**TruPart Precision** trupartprecision.com | sales@trupartprecision.com WhatsApp: +86 137 1278 3205 No.114 Xinhua Road, Xinhe Dev Zone, Wanjiang, Dongguan, China