KM Series Lock Nuts
A KM series lock nut (to DIN 981) is used to secure a bearing, pulley, or other rotating component onto a shaft — commonly known as a bearing nut, shaft nut, or withdrawal nut. It's particularly associated with mounting bearings onto a tapered shaft seat or sleeve, where tightening the nut draws the bearing's tapered bore up the taper to expand it onto the shaft, setting the correct internal clearance as it goes. Four evenly spaced slots machined around the nut's outer diameter accept a tab from a matching MB series lock washer, which is bent into one of the slots once the nut is correctly torqued, locking it against loosening in service.
The chart below gives dimensional information for standard KM series lock nuts. Dimensions shown are in mm; if you wish to convert to inches, please use our universal converter.
Lock (Tab) Nuts are simple, dependable and efficient elements for fastening bearings etc on shafts when used with locknuts in the KM series.
They can also be re-used. They feature a fine rate thread and grooves around the periphery.
One of the tabs on the washer is folded into the slot in the slot of the lock nut for secure positioning, with the tab on the washer located in a groove in the shaft diameter.
KM SERIES LOCK NUT DIMENSIONS
| Designation | Thread (M) | d3 (mm) | B (mm) | b (mm) | h (mm) | d (mm) | d1 (mm) | Weight (kg) |
|---|---|---|---|---|---|---|---|---|
| KM 0 | M10x0.75 | 18 | 4 | 3 | 2 | 13.5 | 10.5 | 0.004 |
| KM 1 | M12x1 | 22 | 4 | 3 | 2 | 17 | 12.5 | 0.006 |
| KM 2 | M15x1 | 25 | 5 | 4 | 2 | 21 | 15.5 | 0.009 |
| KM 3 | M17x1 | 28 | 5 | 4 | 2 | 24 | 17.5 | 0.012 |
| KM 4 | M20x1 | 32 | 6 | 4 | 2 | 26 | 20.5 | 0.018 |
| KM 5 | M25x1.5 | 38 | 7 | 5 | 2 | 32 | 25.5 | 0.028 |
| KM 6 | M30x1.5 | 45 | 7 | 5 | 2 | 38 | 30.5 | 0.039 |
| KM 7 | M35x1.5 | 52 | 8 | 5 | 2 | 44 | 35.5 | 0.059 |
| KM 8 | M40x1.5 | 58 | 9 | 6 | 2.5 | 50 | 40.5 | 0.078 |
| KM 9 | M45x1.5 | 65 | 10 | 6 | 2.5 | 56 | 45.5 | 0.11 |
| KM 10 | M50x1.5 | 70 | 10 | 6 | 2.5 | 61 | 50.5 | 0.13 |
| KM 11 | M55x2 | 75 | 11 | 7 | 3 | 67 | 55.5 | 0.15 |
| KM 12 | M60x2 | 80 | 11 | 7 | 3 | 73 | 60.5 | 0.16 |
| KM 13 | M65x2 | 85 | 12 | 7 | 3 | 79 | 65.5 | 0.19 |
| KM 14 | M70x2 | 92 | 12 | 8 | 3.5 | 85 | 70.5 | 0.23 |
| KM 15 | M75x2 | 98 | 13 | 8 | 3.5 | 90 | 75.5 | 0.27 |
| KM 16 | M80x2 | 105 | 15 | 8 | 3.5 | 95 | 80.5 | 0.36 |
| KM 17 | M85x2 | 110 | 16 | 8 | 3.5 | 102 | 85.5 | 0.41 |
| KM 18 | M90x2 | 120 | 16 | 10 | 4 | 108 | 90.5 | 0.51 |
| KM 19 | M95x2 | 125 | 17 | 10 | 4 | 113 | 95.5 | 0.56 |
| KM 20 | M100x2 | 130 | 18 | 10 | 4 | 120 | 100.5 | 0.64 |
RELATED PAGES
FREQUENTLY ASKED QUESTIONS
Do I always need a lock washer with a KM lock nut?
In most applications, yes — the lock washer's tab is what actually prevents the nut from working loose under vibration or shaft rotation. Some specialised variants (self-locking or adhesive-secured nuts) exist that don't require a separate washer, but a standard KM nut should always be paired with its matching MB washer.
How do I know which MB washer matches a given KM nut size?
The washer and nut share the same size number (e.g. KM8 pairs with MB8) — see our MB Series Lock Washers chart for matching dimensions.
Can a KM lock nut be reused after removal?
It can generally be reused provided the threads and tab slots aren't damaged, but always inspect it carefully first — a bent-back tab that's been straightened and re-bent multiple times can fatigue and snap off, losing its locking function.
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