Custom Bearing Lock Nuts & Spindle Nuts

Replacing a bearing and the locknut is seized, lost or a size nobody stocks? Rebuilding a machine spindle whose adjusting nut is long obsolete? Send the old nut or the shaft thread for a quote in 12 hours — we single-point the thread to match.

When the Standard Locknut Doesn't Exist

Bearing lock nuts and spindle nuts live by the catalogue — until the catalogue runs out. The KM and AN series cover the common bearing bores, but step outside them and the part vanishes: a shaft thread finer or coarser than the series pitch, a diameter above the largest KM, a machine-tool spindle nut the OEM stopped making decades ago, a left-hand adjusting nut, or a nut that needs extra height for more thread engagement. Standard shelves don't carry it, and no tap or die exists for the odd pitch.

EKINSUN machines it. We make custom bearing lock nuts and spindle nuts — round slotted (hook-spanner) nuts, precision set-screw and wedge locknuts, adjusting and retaining nuts — single-pointed to your exact thread and pitch, in the diameter, height and slot pattern you need. Reproduced from your old nut or the shaft it threads onto, no CAD file or part number required, one piece or a batch, quoted within 12 hours.

Nuts We Machine

Series & Standards We Match

You don't need to identify the series — send the nut or shaft and we measure it. If you know the standard, here is what we reproduce:

Series / Standard	What it is	What we match
KM (DIN 981)	Metric round slotted bearing locknut, KM0–KM40 and beyond	Metric fine thread, OD, height, slot count & width
AN (inch)	Imperial bearing locknut series (N-00 up)	Inch thread, slot pattern, tab-washer keyway
DIN 1804	Slotted round nut / hook-spanner nut	Thread, face or side slots, spanner fit
MB / AN tab washer	Tongued lock washer that pairs with the nut	Bore tongue, OD tabs — supplied with the nut
Non-standard / OEM	Obsolete spindle nuts with no published spec	Reverse engineered from your old nut or shaft

KM Series Thread Reference (typical)

Size	Thread	Size	Thread
KM0	M10 × 0.75	KM5	M25 × 1.5
KM1	M12 × 1	KM6	M30 × 1.5
KM2	M15 × 1	KM7	M35 × 1.5
KM3	M17 × 1	KM8	M40 × 1.5
KM4	M20 × 1	KM9+	M45 × 1.5 and up

Need a thread between series sizes, a left-hand version, or a size above KM40? That's exactly what we machine — the reference above is only where the standard shelf stops.

KM lock nut dimensions above M90 (DIN 981)

The catalogue thins out exactly where the shafts get big. DIN 981 carries the KM series to M165, always in the one pitch the standard allows — 2 mm up to M150, 3 mm above — and skips two numbers on the way (there is no KM29 and no KM33). If your size and pitch are in the table, buy it from stock — no one-off can match that price, and we will say so. The rows are the standard values; the column that matters when you cannot buy one is the pitch, because a shaft cut M100×3 or M120×4 has no KM nut in any catalogue.

KM	Thread d	Outside ø d2	Slot-bottom ø d3	Height h	Slot width b	Slot depth t	Tab washer
KM18	M90×2	120	108	16	10	4	MB18
KM19	M95×2	125	113	17	10	4	MB19
KM20	M100×2	130	120	18	10	4	MB20
KM21	M105×2	140	126	18	12	5	MB21
KM22	M110×2	145	133	19	12	5	MB22
KM23	M115×2	150	137	19	12	5	MB23
KM24	M120×2	155	138	20	12	5	MB24
KM25	M125×2	160	148	21	12	5	MB25
KM26	M130×2	165	149	21	12	5	MB26
KM27	M135×2	175	160	22	14	6	MB27
KM28	M140×2	180	160	22	14	6	MB28
KM30	M150×2	195	171	24	14	6	MB30
KM31	M155×3	200	182	25	16	7	MB31
KM32	M160×3	210	182	25	16	7	MB32
KM34	M165×3	210	193	26	16	7	MB33

Values per DIN 981, cross-checked between two published tables (Schrauben-Lexikon and Wegertseder, 2026). ISO 2982-2 continues the series to KM40 (M200×3) with the same construction. When the shaft thread is not the DIN pitch, when the housing needs a lower height than h, or when you need more or fewer than four slots for the tab washer you already have, that is the nut we machine — send the shaft thread and the washer, and we turn the nut to match.

What you need	In the catalogue?	What we machine
A KM nut in a DIN 981 size, M10×0.75 to M165×3	Yes — bearing distributors stock the series	Buy it from stock; we will tell you so in the quote.
A shaft cut to a pitch DIN 981 does not carry — M100×3, M120×4, or left-hand	No — the standard fixes one pitch per size	Nut single-pointed to the shaft’s actual thread, four slots to your MB washer.
Lower height than h, or a different slot count for a washer you already have	No	Turned to the height the housing allows, slots milled to the count and width you state.
A metric shaft with an imperial AN-series washer, or the reverse	No — the two series do not cross	Nut cut to the shaft, slots cut to the washer, one piece up.

Measure before you order. Ten pitches of a DIN 981 shaft thread measure 20 mm up to M150 and 30 mm above. Lay a rule across ten crests of your shaft: if it reads 20 on an M100, buy the KM 20 from stock; if it reads 30 or 40, the shaft was cut outside the KM series and no catalogue lock nut will run on it — send the diameter, the pitch and the washer you have, and we turn the nut to match. How to read the pitch off a large thread →

Materials

Material	Best for	Notes
Medium-carbon / alloy steel	Standard bearing & spindle nuts	Strength and thread-wear resistance; can be plated or blackened
304 stainless	Washdown, food, humid or outdoor service	General corrosion resistance
316 stainless	Marine and chemical service	Chloride resistance for seawater and coastal plant
Brass	Where a softer nut must protect the shaft thread	Non-galling, good for adjustment nuts
6061 / 7075 aluminium	Lightweight spindles — motorsport, aerospace	7075 where preload load is high and weight still matters

How It Works

Who Orders Custom Lock Nuts

What Buyers Search For

Will it fit? KM lock nut checks before you order

KM nuts come in one thread each: KM4 is M20×1, KM5 is M25×1.5, KM7 is M35×1.5. A spindle cut M20×1.5 takes no KM nut at all — the M20×1 nut starts, binds and stops. Above M150 the DIN 981 series changes to a 3 mm pitch, and two numbers do not exist (there is no KM29 and no KM33). If the shaft thread is between series sizes, left-hand, or at a pitch the table does not show, the nut is machined, and it is cut to the shaft you measure, not to a catalogue.

What do I need to lock a bearing on a shaft with a non-standard thread?

A lock nut cut to the shaft's thread, and an MB-style tab washer at the same bore, so the tab still locates in the shaft keyway. Send the thread readings — outside diameter, pitch over ten turns, hand — or the old nut, and both parts are drawn as a pair.

Same lock nut, but left-hand, taller, or in 316

A left-hand version for a shaft that runs the other way, an extra-tall body for more thread engagement, a slot count to suit your hook spanner, or stainless for a washdown machine — each is a variant of the same drawing, one piece and up, quoted in 12 hours.

A shaft thread that no nut series covers at all, such as M27×1.75, gets the same treatment: see the M27×1.75 nut page for hex, thin, coupling and slotted forms at that pitch.

Frequently Asked Questions

Related Custom Fasteners

Bearing and spindle nuts often ship with their neighbours. We also machine castle & slotted nuts to DIN 935, coupling nuts including reducing and LH/RH, and any non-standard thread bolts to match. For the shaft side of a bearing rebuild see pump replacement parts, and if the bearing itself is obsolete we can reverse engineer a bearing from a worn part. For anything one-off, special fasteners made to drawing.