CNC Turned Steel Stepped Drive Shafts
Stepped drive shafts turned from 1045 steel, with journals ground to h6 and round within 0.005 mm at Ra 0.4 µm, shoulders square to the axis within 0.02 mm, step-to-step concentricity of 0.01 mm and a runout of 0.015 mm checked between centres.
- Journals Ground to h6
- Shoulders Square to 0.02 mm
- Runout 0.015 mm Between Centres
- Keyway Cut After Grinding
*Send the bearing part numbers and the step layout. A journal ground to the bottom of h6 on a bearing that sits at the top of its bore gives 0.02 mm of play, which is enough to hear at 3000 rpm.
Stepped Drive Shaft Overview
A stepped shaft carries torque through a keyway and locates a bearing on each journal. The journals have to be concentric to each other, or the bearing outer ring runs out and the housing wears oval.
The shaft is turned between centres leaving 0.3 mm on each journal, heat treated, straightened, then ground on the same centres so every diameter shares one axis.
1045 Carbon Steel
1045 takes an induction-hardened case at the journal and still machines a straight shaft. It is the default for general drive shafts where the load is steady and the speed is under 4000 rpm.
4140 or 420 Stainless
4140 is used where the shaft takes shock load through a keyway, and 420 stainless where the shaft runs in washdown and a black oxide coating would break down in a season.
Straightening after heat treatment is not optional: a 500 mm shaft in 1045 typically bows 0.15 mm out of the furnace, and grinding a bowed shaft gives journals that are on size but not concentric.
Stepped Shaft Specifications
Turning, grinding and keyway data for drive shafts, with the runout and concentricity values that keep bearings quiet.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Stepped Drive Shaft | Machining Process | CNC Turning, Cylindrical Grinding, Keyway Milling |
| Material | 1045 Carbon Steel, 4140 on Request | Envelope | Ø 8 – 60 mm, 80 – 600 mm Long |
| Journals | h6, Roundness 0.005 mm | Journal Finish | Ra 0.4 µm Ground |
| Shoulders | Square to the Axis Within 0.02 mm | Runout | 0.015 mm Between Centres |
| Steps | Diameter ±0.02 mm, Length ±0.10 mm | Concentricity | 0.01 mm Step to Step |
| Keyway | Width +0.02 / 0 mm, Depth ±0.05 mm | Threads | M8 – M24, 6g, Rolled |
| Hardness | HRC 28 – 32 on Request | Straightness | 0.02 mm per 300 mm |
| Customization | Step Layout, Keyway, Snap Ring Groove, Thread, Chamfer | Lead Time | 6 – 8 Days Sample, 14 – 18 Days Batch |
| Inspection | Micrometer at Three Planes, Runout on Centres, Keyway Gauge | Packing | Journal Wrap, VCI Paper, Tube |
Key Features of Our Stepped Shafts
Ground between centres after heat treat, keyway after grinding, journals protected in transit.
Ground on One Axis
All journals are ground in one set-up between centres, so step-to-step concentricity stays at 0.01 mm instead of being built up from separate turning operations.
Shoulders Faced Square
Each shoulder is faced square to the axis within 0.02 mm, which is what stops a bearing inner ring from cocking when it is pressed up against the step.
Keyway Cut After Grinding
The keyway is milled after the journals are ground, so the broach does not raise a burr on a finished journal and the key does not sit proud on a hard surface.
Heat Treated Then Straightened
Shafts are induction hardened and straightened on a press before grinding, because grinding a bowed shaft produces a part that measures on size but runs out at the bearing.
Shaft that has to run quiet at speed?
Finishes for Stepped Shafts
Journals stay bare, the rest can be coated for corrosion.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Black Oxide | Rust protection with the journal masked | Electroless Nickel | Uniform 15 µm on all steps |
| Hard Chrome | Wear surface on a sliding journal | Phosphate | Keyway and thread break-in |
| Masked Journal | Grinding size kept after coating | Rust Preventive Oil | Film for transit |
| Induction Hardening | HRC 50 at the bearing journal | Stress Relief | Before finish grinding |
| Journal Wrap | Protects Ra 0.4 µm in packing | VCI Paper | Prevents condensation rust |
| Salt Spray | 96 h on Black Oxide | Journal Recheck | Size After Coating |
*Hard chrome adds 10 to 20 µm per side and must be ground back at the journal; on a h6 fit the journal is ground 0.02 mm under and chromed to size.
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Machining a Stepped Shaft
Every journal is ground after heat treatment, so the shaft stays straight and the bearing fit does not close up when the part cools.
01. Fit and Step Review
Confirm each bearing fit, the keyway size and the torque direction, then set the step diameters and the order of grinding.
02. Turn Between Centres
Face and centre both ends, rough and finish the steps between centres leaving 0.3 mm on each journal for grinding.
03. Heat Treat and Straighten
Induction harden the journals, temper, then straighten on a press to within 0.05 mm before the finish grind.
04. Grind and Cut Keyway
Grind every journal in one set-up between centres, check roundness in two planes, then mill the keyway and cut the snap ring grooves.
05. Check, Protect, Pack
Measure runout on centres, wrap each journal, apply rust preventive, and pack in a tube with VCI paper.
Send the bearing part numbers and the step drawing, and we will quote a shaft ground between centres with the runout recorded on the inspection sheet.
Stepped Drive Shaft FAQs
Turning holds about 0.02 mm on diameter and leaves a 0.8 µm finish; grinding holds 0.005 mm roundness at Ra 0.4 µm, which is what a bearing needs to sit without a rumble.
Yes, from a sample. We measure each journal and the keyway position, then cut to the measured values, which is what a replacement needs when the housing is already worn.
0.02 mm per 300 mm after straightening and grinding. Longer than 600 mm the shaft is supported on a steady and the straightness depends on the steady pressure.
Only the journals are induction hardened, to HRC 50 at the surface. Through hardening makes the keyway brittle and the shaft will snap at the key end under shock load.
Hard chrome at 20 µm ground back to h6, or induction hardening plus grinding. Black oxide is only for corrosion protection where nothing slides.
Each journal is wrapped in paper tape, the shaft goes into a tube with VCI paper, and the ends are capped so the centres are not damaged.
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