CNC Machined Stainless Steel Split Clamp Ring
Split clamp rings machined from 304 stainless, with a H7 bore round to 0.01 mm, a 1 mm sawn split, clamp lugs matched within 0.02 mm and a closure of 0.2 mm at the rated screw torque. Every ring is closed on a mandrel before packing.
- Bore H7, Roundness 0.01 mm
- Split Sawn to 1 mm
- Lugs Match Within 0.02 mm
- Closes Evenly on the Shaft
*Send the shaft diameter measured, not nominal. A clamp ring bored to nominal for a shaft that is 0.03 mm under will not grip, and a ring bored 0.02 mm tight will not close at the split.
Split Clamp Ring Overview
A split ring grips by elastic closure, so the bore has to be round, the split has to be clean and the two lugs have to be the same height, or the ring closes on one side and marks the shaft.
The ring is turned and bored as a solid collar, the lugs are milled, the screw holes drilled and tapped, then the split is cut by wire EDM so the bore does not distort from a saw cut.
304 Stainless Steel
304 is used for clamp rings because it springs back predictably when the screw is released, so the ring can be moved and re-clamped many times without losing grip.
316L or 303 Stainless
316L is chosen for washdown and marine shafts, and 303 where the ring is small and the free-machining grade keeps the bore finish without a separate reaming pass.
For a plastic or coated shaft the ring is supplied with a bonded liner, because a stainless bore at H7 will mark a painted or anodized shaft on the first clamp.
Split Clamp Ring Specifications
Turning and EDM data for split collars, with the bore, split and lug values that decide whether the ring grips without marking.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Split Clamp Ring / Split Shaft Collar | Machining Process | CNC Turning, Boring, Milling, Wire EDM Split |
| Material | 304 Stainless Steel Bar or Tube | Envelope | Bore Ø 10 – 120 mm |
| Inner Diameter | H7, Roundness 0.01 mm | Outside Diameter | Bore + 12 to 30 mm |
| Ring Width | 8 – 40 mm | Split Gap | 0.8 – 1.5 mm as Supplied |
| Clamp Lugs | Matched Within 0.02 mm | Clamp Screw | M3 – M10, Class 6H |
| Concentricity | OD to Bore 0.02 mm | Face Parallelism | 0.02 mm |
| Surface Finish | Ra 1.6 µm Bore, Ra 3.2 µm Outside | Clamp Force | Closes 0.2 mm at Rated Torque |
| Customization | Two-Piece Version, Keyway, Threaded Bore, Plastic Liner | Lead Time | 5 – 7 Days Sample, 12 – 16 Days Batch |
| Inspection | Bore Air Gauge, Lug Match on Pins, Closure Test on a Mandrel | Packing | Screw Fitted Loose, Oil Paper, Boxed |
Key Features of Our Clamp Rings
Split after boring, lugs matched, every ring closed on a mandrel.
Bored Before the Split
The ring is bored as a solid collar and split afterwards, so the bore stays round to 0.01 mm instead of closing in at the saw cut.
Split Cut by Wire EDM
The split is wire cut to 1 mm, which leaves a clean gap with no saw marks and no burr inside the bore to score the shaft.
Lugs Matched to 0.02 mm
Both lugs are milled to the same height, so the screw closes the ring evenly and the gap at the split stays parallel instead of tapering.
Closed on a Mandrel Before Packing
Every ring is fitted to a mandrel at the rated torque and checked for closure and marking, so a ring that will not grip is found here and not at the machine.
Collar that has to grip without marking?
Surface Finishes for Clamp Rings
The bore is the grip surface, the outside is visible and the split edges must stay clean.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Passivation | Restores the oxide layer after machining | Glass Bead Blasting | Even matte on the outside |
| Masked Bore | Bore stays at H7 | Electropolishing | Bright finish on visible collars |
| Light Oil | Prevents fretting marks in storage | PTFE Coating | Low friction on a rotating shaft |
| Bore Protection | Plugged for Shipping | Laser Marking | Bore size on the outside |
| Split Edge Deburr | Hand Finished After Wire EDM | Ultrasonic Clean | Before Passivation |
| Screw Treatment | Anti-Seize on Request | Closure Check | Every Ring on a Mandrel |
*The bore is always left bare and passivated. A coating on the bore reduces friction and the ring slips at half the rated torque, which is the most common field failure on a coated collar.
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Machining Process for Clamp Rings
The ring is split after boring, so the bore stays round and the two halves close on the shaft without a step at the split line.
01. Shaft and Torque Review
Check the measured shaft diameter and the clamp torque, then set the bore tolerance and the screw size.
02. Turn and Bore the Collar
Turn the outside, face both sides and bore to H7 as a solid collar, checking roundness with an air gauge.
03. Mill the Lugs
Mill both lugs to the same height within 0.02 mm and drill and tap the clamp screw hole through both.
04. Wire Cut the Split
Wire EDM the split to 1 mm, then deburr both cut edges by hand so nothing stands proud inside the bore.
05. Close, Inspect, Passivate
Close the ring on a mandrel at rated torque, check closure and marking, then passivate, oil and pack with the screw loose.
Send the measured shaft diameter and the clamp torque, and we will quote a split ring bored to your shaft and closed on a mandrel before packing.
Split Clamp Ring FAQs
A saw cut leaves a burr inside the bore and a rough gap that closes unevenly. Wire EDM gives a 1 mm gap with clean edges, so the ring closes parallel and does not score the shaft.
H7 with 0.01 mm roundness, bored before the split. A ring bored after splitting closes oval and grips on two points instead of around the circumference.
0.2 mm at the rated screw torque, which is enough to grip a shaft with a 0.02 mm clearance. More closure than that and the ring yields and stops springing back.
Yes, split on both sides with two screws, which suits a shaft that cannot be reached from the end. The two halves are matched as a pair and packed together.
Not at the rated torque on a ground or turned shaft. On a painted or anodized shaft a bonded plastic liner is fitted, because stainless on coating marks on the first clamp.
Every ring is closed on a mandrel at the rated torque and checked for closure and marking. Rings that will not grip are rejected before passivation.
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