CNC Turned Stainless Steel Shaft Clamp Collar
Stainless split clamp collars turned and bored to H7 or H8, with the split sawn after boring, a clamp screw square to the bore within 0.05 mm and an outside diameter concentric to the bore within 0.02 mm. The collar grips by friction rather than by a set screw, so the shaft is not marked and the position can be adjusted without leaving a dimple.
- Bore Fit H7 to H8
- Split Sawn After Boring
- Clamp Screw Square to Bore
- No Shaft Marking
*Send the shaft tolerance and the axial load. A collar that only locates axially can run a looser bore than one that also has to transmit torque, and the screw size follows from the load.
Split Shaft Clamp Collar Overview
A clamp collar holds by friction around the whole shaft, which is why it does not mark the surface the way a set screw does. That only works if the bore is round, the split is straight and the screw pulls the two halves together evenly.
The collar is turned and bored as a solid ring, then sawn through on one side with a thin slitting saw and tapped for the clamp screw across the split. Sawing after boring is what keeps the bore round; sawing a tube first and boring afterwards leaves a collar that closes oval.
303 Stainless Bar
303 is the default because a collar is a small part made in quantity: the sulphur addition makes it free-machining, so the bore and the thread come out clean without the work-hardening that 304 gives on a small lathe.
316L for Washdown Service
316L is chosen for food, pharmaceutical and marine equipment where the collar is cleaned daily. It machines more slowly than 303, so the price per piece is higher, but the bore still holds H7.
303 for general machine building, 316L where the collar is washed or sees chlorides, and aluminium only where weight matters more than grip.
Split Clamp Collar Specifications
Turning, boring and sawing data for clamp collars, with the bore, split and screw values that decide whether the collar grips without slipping.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Split Shaft Clamp Collar | Machining Process | CNC Turning, Boring, Sawing, Tapping |
| Material | 303 or 316L Stainless Bar | Bore Diameter | 6 – 120 mm, H7 / H8 |
| Outer Diameter | Bore + 12 – 40 mm | Width | 8 – 50 mm, ±0.05 mm |
| Bore Concentricity | 0.02 mm to the OD | Split Gap | 1 – 3 mm, Sawn After Boring |
| Clamp Screw | M4 – M16, Socket Head | Screw Squareness | 0.05 mm to the Bore Axis |
| Surface Finish | Ra 1.6 µm Bore, Ra 3.2 µm OD | Passivation | ASTM A967 |
| Customization | Two-Piece Design, Handle Lever, Threaded OD, Keyway | Lead Time | 4 – 6 Days Sample, 10 – 14 Days Batch |
| Inspection | Bore Plug Gauge, Concentricity on Mandrel, Screw Torque Test | Packing | Assembled with Screw, Bagged, Carton |
Key Features of Our Clamp Collars
Bored first, split second, screw square to the bore.
Split Sawn After Boring
The slit is cut into a finished bore, so the collar closes evenly around the shaft and the two halves meet without a step at the split line.
Screw Square to the Bore
The clamp screw hole is drilled square to the bore axis within 0.05 mm, so tightening pulls the halves straight together instead of twisting the collar on the shaft.
Bore Concentric to the OD
Bore and outside diameter are cut in one set-up, holding concentricity to 0.02 mm, so a collar used as a bearing spacer also runs true.
Grip Without Marking
The full circumference carries the clamp load, so the shaft is held by friction and can be repositioned without the dimple a set screw leaves.
Collar that has to hold without marking the shaft?
Surface Finishes for Clamp Collars
The bore is a fit and the outside is handled constantly, so the coating choice is about the bore first.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Passivation | Corrosion protection on a part handled daily | Electropolishing | Bright bore for food and pharma shafts |
| Bead Blasting | Matte OD that hides clamp marks | Masked Bore | Bore kept at fit size after any coating |
| Laser Marking | Bore size and torque on the OD | Black Oxide (Steel Variant) | Colour coding on carbon steel collars |
*Any coating on the bore changes the grip and the fit. Collars are passivated or electrophished rather than anodized, and where a coating is required the bore is masked.
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Turning and Sawing Process
The bore is finished before the split is sawn, so the collar closes on the shaft evenly instead of pinching at one edge.
01. Shaft and Load Review
Confirm the shaft tolerance, the axial load and whether the collar also transmits torque, then size the clamp screw to the load rather than to the wall.
02. Turn and Bore the Ring
Turn the OD, both faces and the bore in one set-up, finishing the bore to H7 or H8 and checking it with a plug gauge before the part leaves the lathe.
03. Saw the Split
Slit one side with a thin saw to a gap of 1 to 3 mm, keeping the cut parallel to the axis so the two halves close evenly rather than at an angle.
04. Drill and Tap the Clamp Screw
Drill across the split square to the bore and tap the thread, then check that the screw pulls the halves together without closing the bore oval.
05. Passivate and Assemble
Passivate, fit the screw, test the grip on a gauge shaft at the specified torque and bag the collar assembled so the screw is not lost in transit.
Send the shaft diameter and the load the collar has to hold, and we will quote it with the bore and screw sized for that duty.
Split Clamp Collar FAQs
A 303 stainless collar at 30 mm bore with an M6 screw holds roughly 1.5 kN before slipping on a clean shaft, which is about three times a set screw of the same size.
No, the load is spread around the circumference, so there is no dimple. On a polished shaft a light polish mark can appear after many adjustments, but nothing that changes the fit.
Yes, a two-piece collar is split on both sides and assembled with two screws, which lets it be fitted without sliding it over a shaft end.
H7 for a locating collar and H8 where the collar only clamps. Both are checked with a plug gauge after sawing, because sawing can relax the ring slightly.
By up to 0.01 mm on a thin collar, which is why the bore is gauged after sawing and the batch is accepted on the post-split measurement.
Yes, an adjustable lever replaces the socket screw on the same thread, and the collar is drilled to the thread of the lever rather than to the screw size.
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