Precision Lock Nuts
Lock nuts with the clamping face ground square to the thread axis to a close tolerance, and locking arranged so tightening does not pull the nut off square. They are used where inner ring squareness directly affects running accuracy. SES holds the range as an authorised SKF distributor, covering thread range About M15 to M200 in common precision series; face squareness Ground to a few microns relative to the thread axis; locking Axial clamping screws acting through a pressure ring; tightening Torque controlled, to a stated value. Executions include nuts with axial clamping screws, nuts with a separate pressure ring, hydraulically assisted precision nuts on large sizes, balanced executions for high speed spindles, among others. It is specified most often into grinding and turning spindle bearing stacks and machine tool live centres and index heads. Every part is genuine SKF through official channels, with designation, specification and options confirmed against your duty before it ships — supplied from Kolkata and our branch network, with breakdown cover that does not sit in an inbox.
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Face
Ground square to the thread axis
Locking
Axial screws or a pressure ring
Purpose
Controls inner ring tilt and runout
Use
Spindles and precision bearing stacks
Where it runs.
You will find Precision Lock Nuts in the parts of a plant where this particular duty actually occurs. In practice that means grinding and turning spindle bearing stacks, machine tool live centres and index heads, high speed test rigs and balancing machines, and equally precision gearbox and actuator assemblies, roll grinder head and tailstock spindles, instrument and metrology rotary tables. What links them is the duty rather than the machine name — face: Ground square to the thread axis. If your installation is not on that list it matters less than you would think: the operating condition decides the specification. Send us the load, the speed, the running temperature and the environment it runs in, and we will match it to the right execution in the SKF range and confirm what is in stock.
Specify it against the duty.
Specification here follows the operating condition, not the catalogue. Spindle runout at the nose must be held within a few microns — A precision nut with a ground face and a stated squareness tolerance. A standard nut tilts the inner ring, and the tilt turns up directly in the workpiece surface. The bearing stack is preloaded and the preload must be repeatable after service — A nut tightened to a specified torque with a torque wrench, using the axial screws. Hook spanner tightening gives a different preload every time the spindle is rebuilt. The spindle runs fast enough for nut imbalance to matter — A nut with a balanced design and matched screws, and balance the assembly after fitting. An unbalanced nut on a high speed spindle raises vibration at running speed only. Where two of those apply at once, specify for the harsher of the two — under-specifying is what puts the part back on the bench a month later. Send us the duty and we will confirm the execution.
Ordering this from SES.
Tighten the clamping screws in a diagonal sequence and in two or three passes, exactly as you would a flange. Running around the circle in one pass cocks the pressure ring, and you lose the squareness that you paid for in the first place.