How MA Locks From the Front Face
MA locks with set 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. Every size carries two screws and four wrench slots, so the screws grow with the nut rather than multiplying, from M4 on MA17 up to M12 from MA135.
The full explanation is on the Axial Locking Series page.
Ground Contact Surface and Thread
Maximum axial run-out 0.002 mm
Locked From the Front Face
Screws parallel to the shaft axis
Shortest Body in the Series
19 mm against 25 mm at M50 x 1.5
Two Set Screws Per Nut
M4 to M12. 2.2 to 56 Nm max
Where MA Locknuts Are Used
Machine tool spindle bearings at the front and rear ends, where the cartridge or the housing covers the outside diameter of the nut
Ball screw support bearings at the fixed and motor ends, both usually built into confined supports
Any drawing calling for 0.002 mm axial run-out on a nut that has to be locked from the front
Assemblies short of axial length as well as tolerance, since MA runs several millimeters lower than the other axial types on the same thread
Shafts too highly stressed to carry a keyway
Find Your Size(M17 to M200)
Filter MA 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 MA Locknut
The MA is the accuracy type in NIKKI's Axial Locking Series, in metric threads from M17 x 1 to M200 x 3 with 0.002 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 MA locknut is 0.002 mm. NIKKI grinds both the thread area and the contact surface by a high-precision process, which is what holds the run-out at this level. MKR, MKK and MKW in the same series have the contact surface ground and hold 0.005 mm.
Two, on every size from M17 x 1 to M200 x 3, along with four wrench slots. Rather than adding screws as the nut grows, MA takes progressively heavier ones, reaching M12 at 56 Nm from MA135. Those are the heaviest screws in the axial series.
Each MA size lists a catalog maximum per screw in the dimension table, from 2.2 Nm on the M4 screws of MA17 up to 56 Nm on the M12 screws fitted from MA135. Tighten the two screws gradually and alternately rather than driving one fully home first.
Add L to the order code for a left-hand thread (MA30x1.5P-L) or U for an inch thread (MA30-U18). Standard right-hand metric versions are ordered by the plain name, for example MA30x1.5P.
Choose the MKR locknut where 0.005 mm meets the drawing and the thread sits outside MA's range, below M17 or between the usual steps, as MKR carries 58 sizes against MA's 33. Choose the MKK locknut where the clamping load is better spread over four to eight screws than concentrated in two. MA is the type to specify whenever the drawing calls for 0.002 mm, and it gives the shortest body in the series as well.
No. MA locks through set 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.