MB Series Lock Washers Dimensions

An MB series lock washer (to DIN 5406) is used together with a matching KM series lock nut to secure a bearing or other rotating component onto a shaft. The washer has an internal tab that engages a keyway or flat on the shaft, preventing the washer itself from rotating, and one or more external tabs that bend up into a slot on the KM nut once it's tightened to the correct position — locking the nut against loosening from vibration or shaft rotation without needing a separate locking compound.

The chart below gives dimensional information for standard MB series lock washers. Dimensions shown are in mm; if you wish to convert to inches, please use our universal converter.

Lock (Tab) washers are simple, dependable and efficient elements for fastening locknuts in the KM series.

They can also be re-used.

They feature an inner tab with evenly spaced outer tabs. One of the tabs is folded into the slot in the slot of the lock nut for secure positioning.

MB SERIES LOCK WASHER DIMENSIONS

Designation	d (mm)	d1 (mm)	d2 (mm)	B (mm)	f (mm)	M (mm)
MB 0	10	13.5	21	1	3	8.5
MB 1	12	17	25	1	3	10.5
MB 2	15	21	28	1	4	13.5
MB 3	17	24	32	1	4	15.5
MB 4	20	26	36	1	4	18.5
MB 5	25	32	42	1.25	5	23
MB 6	30	38	49	1.25	5	27.5
MB 7	35	44	57	1.25	5	32.5
MB 8	40	50	62	1.25	6	37.5
MB 9	45	56	69	1.25	6	42.5
MB 10	50	61	74	1.25	6	47.5
MB 11	55	67	81	1.5	7	52.5
MB 12	60	73	86	1.5	7	57.5
MB 13	65	79	92	1.5	7	62.5
MB 14	70	85	98	1.5	8	66.5
MB 15	75	90	104	1.5	8	71.5
MB 16	80	95	112	1.75	8	76.5
MB 17	85	102	119	1.75	8	81.5
MB 18	90	108	126	1.75	10	86.5
MB 19	95	113	133	1.75	10	91.5
MB 20	100	120	142	1.75	10	96.5

RELATED PAGES

• KM Series Lock Nut Dimensions
• Bearing Dimensions
• Bearing Fit Tolerances

FREQUENTLY ASKED QUESTIONS

Can an MB lock washer be reused?

Generally yes, provided the tabs haven't been bent and straightened so many times that they're at risk of fatigue failure. Inspect the tabs carefully before reuse, and replace the washer if there's any visible cracking or thinning at the bend points.

What happens if I don't fit the internal tab into the shaft keyway correctly?

The washer itself could rotate with the nut instead of staying fixed to the shaft, defeating its locking function entirely — always confirm the internal tab is properly engaged in the shaft's keyway or flat before tightening the nut.