How SFZ Locks on the 30° Thread Flank
SFZ locks through a brass pad rather than through the set screw itself. Each screw drives the pad onto the shaft's thread flank at a 30° radial angle, spreading the load along the flank instead of denting the thread crest. The shaft keeps its full section, and the nut can be taken off and refitted.
The full explanation is on the 30° Flank Locking Series page.
Two Wrench Flats to SFZ75
Ordinary open-end wrench, no hook wrench
No Thrust Washer or Keyway
Fewer parts, simpler assembly
Precision-Turned Contact Surface and Thread
Maximum axial run-out 0.005 mm
4 or 6 Set Screws Per Nut
M5 to M10. 4.8 to 36 Nm max
Where SFZ Locknuts Are Used
Small Shafts From M10 x 0.75, Below the Range of Every Other Type in the Series
Bearing and Pulley Retention on General Machinery
Assemblies Built and Serviced With Ordinary Hand Tools
Cost-Driven Builds Where a Drawing Tolerance of 0.005 mm Is Enough
SFZ Specifications
Please enter your specifications below to find the right product for your project.
L is listed only up to SFZ75 x 2.0P, the largest size carrying wrench flats.
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Products in this 30° Flank Locking Series
Grinding
MF
Grinding
Hook wrench · nut exposed
M12×1 to M260×4 · h 14–36 mm
MF is the original 30° flank locknut, ground to 0.002 mm. Use it where the nut sits clear of the housing and a hook wrench has room to work.
BF
Grinding
Hook wrench · nut recessed
M15×1 to M260×4 · h 14–40 mm
BF has a straight outer profile that stays reachable when the housing covers part of the nut, so a hook wrench still has a square surface to seat against. Same locking as MF.
TMF
Grinding
Pin wrench
M20×1 to M200×3 · h 18–32 mm
TMF is driven through holes in its face with a pin wrench (pin spanner in UK and EU practice). It is ground only, with no precision-turned equivalent.
Precision turning
MFZ
Turning
Hook wrench · nut exposed
M12×1 to M260×4 · h 14–36 mm
MFZ is the precision-turned version of MF, with the same envelope and hook-wrench profile at 0.005 mm run-out instead of 0.002 mm.
BFZ
Turning
Hook wrench · nut recessed
M15×1 to M260×4 · h 14–40 mm
BFZ is the precision-turned version of BF, with the same straight profile and hook-wrench access at 0.005 mm run-out.
SFZ
Turning
Open-end wrench · two flats, to M75
M10×0.75 to M200×3 · h 14–32 mm
SFZ has two parallel flats for an ordinary open-end wrench, up to M75 only. It is the only type down to M10 × 0.75, and the type used most in Japan.
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Questions About the SFZ Locknut
The SFZ is the wrench-flat locknut in NIKKI's 30° Flank Locking Series, in metric threads from M10 x 0.75 to M200 x 3 with 0.005 mm maximum axial run-out. The questions below are the ones buyers ask before a first order.
Contact UsThe maximum axial run-out of an SFZ locknut is 0.005 mm. We finish both the thread and the contact surface by precision turning, which is what sets the run-out at this level and keeps the cost below the ground grade.
SFZ carries two parallel flats for an ordinary open-end wrench, listed as dimension L in the table. The flats run up to SFZ75 x 2.0P, which is the largest size that has them. Above that size the table gives no L dimension.
Each SFZ size lists a catalog maximum per screw in the dimension table, from 4.8 Nm on the M5 screws of SFZ10 up to 36 Nm on the M10 screws fitted from SFZ85. Sizes to SFZ75 carry four set screws, and SFZ80 and above carry six. Tighten gradually and alternately rather than one screw fully first.
Add L to the order code for a left-hand thread (SFZ30x1.5P-L) or U for an inch thread (SFZ30-U18). Standard right-hand metric versions are ordered by the plain name, for example SFZ30x1.5P.
Choose the ground types where the drawing calls for 0.002 mm rather than 0.005 mm axial run-out, or where the thread runs above M200 x 3. The MF locknut and BF cover metric threads to M260 x 4 in the ground grade, both driven by hook wrench rather than open-end wrench.
No. SFZ locks between the set screws, the brass pads, and the thread flank, all inside the nut, so neither a thrust washer nor a shaft keyway is required. Nothing else goes on the shaft, and the nut is reusable if handled properly.