How MKR Locks From the Front Face
MKR locks with clamping screws driven straight down the axis rather than in through the outside diameter. The hex key approaches the nut head-on, so nothing has to reach the flank, and the nut can be secured after a bearing bore, a housing shoulder or an adjacent component has closed around it. Three screws carry the load up to MKR15, four to six through the middle of the range, and eight from MKR140 upward.
The full explanation is on the Axial Locking Series page.
Locked From the Front Face
Screws parallel to the shaft axis
58 Sizes From M10 x 0.75
Intermediate threads no other series lists
Ground Contact Surface
Maximum axial run-out 0.005 mm
3 to 8 Clamping Screws Per Nut
M3 to M8. 3 to 25.5 Nm max
Where MKR Locknuts Are Used
Bearing retention in recessed and counterbored housings, where only the front face of the nut stays exposed
Small shafts from M10 x 0.75, below the range of every other axial type
Threads that fall between the usual catalog steps, among them M14, M18, M22, M26, M38, M52 and M62
Preloaded bearing arrangements set by rotating the nut, where the listed helical angle gives the axial travel per turn
Gearboxes, spindle cartridges and pump ends that get opened at service intervals
Find Your Size(M10 to M200)
Filter MKR locknuts by shaft thread, pitch, or height.
Products in this Axial Locking Series
All four lock the same way, with screws driven through the front face parallel to the shaft, so the nut can be secured with its outside diameter buried. What differs is the finishing grade, whether the nut takes clamping screws or set screws, how many of them carry the load, and how much body height the type asks of the design.
MA
0.002 mm
Two set screws · four wrench slots
M17×1 to M200×3 · h 15–37 mm
MA is the accuracy type in the series, ground on the thread area as well as the contact surface. It also carries the heaviest screws in the axial range, M12 at 56 Nm from MA135, spread over two positions rather than four or six.
MKR
0.005 mm
Clamping screws · three to eight per nut
M10×0.75 to M200×3 · h 14–40 mm
MKR is the general-purpose axial locknut and by a wide margin the densest range NIKKI makes, at 58 sizes. It reaches M10 x 0.75, the smallest thread in the series, and it is the type to look at whenever the thread falls between the usual steps. MKR10 to MKR15 use a different body form from MKR16 upward.
MKK
0.005 mm
Clamping screws · four to eight per nut
M15×1 to M130×2 · h 18–32 mm
MKK carries the heaviest clamping screws in the series, M10 at 36 Nm from MKK75, in a body no taller than 32 mm. Three threads, M30, M35 and M40, are listed in a second outside diameter, larger on M30 and M40 for a bigger contact face, smaller on M35 to fit a tighter housing bore.
MKW
0.005 mm
Clamping screws · four or six per nut
M20×1.5 to M70×1.5 · h 28–46 mm
MKW is the tall type, 28 to 46 mm of body where the rest of the series runs 14 to 40 mm, which suits designs that would otherwise carry a separate spacer. The height sits in the code: MKW40-28 stands 28 mm high, MKW40-44 stands 44. Most threads to M50 are offered in two heights, and MKW runs a little softer than the others at HRC 25-28.
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Questions About the MKR Locknut
The MKR is the general-purpose axial locknut in NIKKI's Axial Locking Series, in 58 metric sizes 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 MKR locknut is 0.005 mm. NIKKI finishes the contact surface by a high-precision grinding process, which is what sets the run-out at this level. Where a drawing calls for 0.002 mm, the MA locknut in the same series has the thread area ground as well.
The helical angle runs from 2.48° at MKR12 x 1.5 down to 0.28° at MKR200 x 3, and corresponds to the lead angle of the thread. It lets you work out how far the nut advances along the shaft for a given amount of rotation, which is the relationship you are setting on a preloaded bearing arrangement. Having it on the datasheet saves calculating it from the pitch and the effective diameter.
Each MKR size lists a catalog maximum per screw in the dimension table, from 3 Nm on the M3 screws of MKR10 up to 25.5 Nm on the M8 screws fitted from MKR160. Tighten gradually and alternately rather than driving one screw fully home first.
Add L to the order code for a left-hand thread (MKR30x1.5P-L) or U for an inch thread (MKR30-U18). Standard right-hand metric versions are ordered by the plain name, for example MKR30x1.5P.
Choose the MA locknut where the drawing calls for 0.002 mm axial run-out, since MA has the thread area ground alongside the contact surface, or where two heavy set screws suit the design better than several light ones, as MA reaches M12 at 56 Nm. Choose the MKK locknut where the clamping force matters more than the size coverage, as MKK carries screws to M10 at 36 Nm. MKR remains the type to specify below M15, which neither of the others reaches, and wherever the thread falls between the usual steps.
No. MKR locks through clamping screws driven into the front face of the nut, so nothing else goes on the shaft. The shaft keeps its full section strength, no slot has to be cut, and the nut is reusable if handled properly.