CNC Turned Stainless Steel Flanged Spindle
Flanged spindles turned and ground from 17-4PH stainless in the H900 condition, with bearing journals held to 0.005 mm and 0.003 mm roundness, a flange face square to the axis within 0.01 mm, a nose thread cut to 6g and residual unbalance within G6.3 at 4,000 rpm. Journals are concentric to the flange outside diameter within 0.01 mm.
- Journals Ground 0.005 mm
- Flange Face Square 0.01 mm
- Nose Thread Gauged
- Spindle Balanced G6.3
*Send the bearing and tool-holder drawings. The journal size, the flange register and the nose thread are all set by the parts on either end, and a spindle made to its own drawing will not assemble.
Flanged Spindle Overview
A flanged spindle carries a tool or a chuck on a flange and runs in bearings on ground journals. Its accuracy comes from two relationships: journals to each other, and flange face to the journals. Both have to be ground, not turned.
The spindle is turned with grinding allowance, heat treated, then ground between centres so the journals share one axis. The flange face is ground square to that axis, the nose thread is cut after grinding, and the assembly is balanced before shipping.
17-4PH Stainless, H900
17-4PH is used because it reaches high strength with a single low-temperature treatment, which keeps distortion small enough for a spindle. It also resists corrosion from coolant, which is what a spindle sees every day.
42CrMo4 or 440C
42CrMo4 is the choice for high-load machine tool spindles, through-hardened and ground, where corrosion is controlled by the coolant. 440C is used where both hardness and corrosion resistance are needed, at a higher material and grinding cost.
For a spindle running above 6,000 rpm the balance and the journal roundness matter more than the alloy; for a spindle in a wet environment the alloy decides the life.
Flanged Spindle Specifications
Turning and grinding data for flanged spindles, with the journal, flange and balance values that decide whether the tool runs true.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Flanged Spindle / Bearing Spindle Shaft | Machining Process | CNC Turning, Grinding, Thread Milling |
| Material | 17-4PH Stainless (H900) | Length | 120 – 600 mm |
| Journal Diameter | Ø 15 – 80 mm, Ground to 0.005 mm | Roundness | 0.003 mm on Journals |
| Flange Diameter | Ø 60 – 260 mm | Flange Face Squareness | 0.01 mm to the Axis |
| Nose Thread | M20 – M64 or UN, 6g, Gauged | Concentricity | Journal to Flange OD 0.01 mm |
| Surface Finish | Ra 0.4 µm Journals, Ra 1.6 µm Flange Face | Balance | G6.3 at 4,000 rpm |
| Customization | Drive Key, Draw Bar Thread, Tooling Taper | Lead Time | 9 – 12 Days Sample, 18 – 24 Days Batch |
| Inspection | Air Gauge Journals, CMM Flange Squareness, Thread Gauges, Balance Report | Packing | Journal Protection, VCI Wrap, Timber Case |
Key Features of Our Flanged Spindles
Ground between centres, flange faced square.
Journals Ground From One Centre
Both journals are ground from the same centres, so they share an axis and the spindle does not preload one bearing against the other.
Flange Face Ground Square
The face is ground square to the journal axis within 0.01 mm, which is what stops a chuck or a tool holder from running out at the rim.
Nose Thread Cut After Grinding
Grinding is finished before the thread is cut, so no wheel mark or grit is left in the thread and the gauge fit is clean.
Balanced as an Assembly
Each spindle is balanced after grinding and the correction is made in the flange web, not the journals, so the bearing surfaces stay untouched.
Spindle that has to run true at speed?
Surface Finishes for Flanged Spindles
Journals and threads are fits; the flange face is a locating surface; the rest is corrosion protection.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Passivation | Removes free iron after grinding | Hard Chrome | Wear resistance on a seal journal |
| Masked Threads | Keeps the nose thread at gauge size | Electropolishing | Lowers Ra on visible stainless faces |
| Oil Coating | Corrosion protection in transit | Laser Marking | Serial and balance position |
*Hard chrome adds 10 to 25 µm and is applied before the finish grind. Threads and the flange face are masked so the fits and the squareness are not changed.
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Turning and Grinding Process
The journals and the flange face are ground from the same centres, so the tool that mounts on the flange runs true to the bearings that carry it.
01. Bearing and Tool Review
Check the bearing bores, the flange register and the nose thread, and confirm the heat treatment condition before rough turning.
02. Rough Turn and Treat
Rough turn with 0.4 mm of grinding allowance, leave the flange oversize and treat to H900 before any finish operation.
03. Grind the Journals
Grind both journals between centres, checking roundness and taper at both ends, and keep the part on the same centres for the flange face.
04. Grind Flange and Cut Thread
Grind the flange face square to the axis, then cut the nose thread and check it with a Go/No-Go gauge before balancing.
05. Balance, Mark, Pack
Balance the spindle, correct in the flange web, mark the balance position, then protect the journals and pack in a timber case.
Send the bearing and tool-holder drawings, and we will quote a spindle with the journals ground and the flange face square to 0.01 mm.
Flanged Spindle FAQs
A turned journal cannot hold 0.005 mm reliably and leaves a feed mark that a bearing race follows. Grinding gives the size, the roundness and the finish that a precision bearing needs.
0.01 mm to the journal axis, ground on the same centres. That is what keeps a chuck from running out at the rim, where the error is multiplied by the diameter.
Yes, from a drawing or a measured sample. The journals, the flange register and the thread are all measured, and the replacement is machined to the same fits.
17-4PH at H900 moves 0.1 to 0.3 mm depending on section, which is why the part is roughed oversize and finished after treatment. Larger spindles get a stress relief before roughing.
G6.3 at 4,000 rpm, measured on the finished spindle. Higher speeds need the spindle balanced with the chuck or tool holder fitted.
Yes, a draw bar thread is cut concentric to the nose thread, and the through bore is drilled before grinding so the grinding wheel does not break into it.
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