DIN 988 Shim Washers: Dimensions, Thickness & Applications Guide
DIN 988 shim washers are used for precise axial spacing, end float adjustment, and component alignment in mechanical assemblies. This guide explains what DIN 988 washers are, how their dimensions work, where they are used, and when a slotted shim may be the better alternative.
What are DIN 988 shim washers?
DIN 988 shim washers are precision washers used to create accurate spacing between mechanical components. They are commonly installed to reduce axial play, control end float, and improve alignment in rotating or assembled parts. Unlike standard flat washers, DIN 988 washers are intended for spacing and adjustment rather than general fastening.
Because they are produced in controlled thicknesses, DIN 988 washers allow engineers and maintenance teams to make fine adjustments without relying on improvised packing pieces. They are widely used in bearing assemblies, shafts, pumps, gearboxes, electric motors, and other applications where even small dimensional changes can affect fit, movement, or wear.
In practical terms, a DIN 988 washer helps compensate for tolerance build-up within an assembly. By selecting the correct thickness, it is possible to position components more accurately, reduce looseness, and improve mechanical stability over time.
DIN 988 dimensions explained
DIN 988 shim washers are generally defined by three main dimensions: the inside diameter, the outside diameter, and the thickness. These measurements determine how the washer fits into the assembly and how much spacing it provides.
| Dimension | Description | Purpose |
|---|---|---|
| d1 | Inside Diameter (ID) | Fits over the shaft or fastener location |
| d2 | Outside Diameter (OD) | Provides support area and defines outer size |
| h | Thickness | Determines the amount of spacing or adjustment |
Thickness is often the most critical of the three because it directly affects the mechanical result. A change of only a few tenths of a millimetre may influence bearing preload, shaft position, running clearance, or the amount of axial movement within an assembly.
For that reason, DIN 988 washers are commonly selected as part of a calculated spacing or alignment requirement rather than as an afterthought during assembly.
Common sizes and thicknesses
DIN 988 shim washers are produced in a wide range of inside and outside diameters to suit different shaft sizes and engineering requirements. Thickness options are equally important, allowing washers to be used individually or stacked where a precise build-up is needed.
Typical thicknesses
- 0.10 mm
- 0.20 mm
- 0.30 mm
- 0.50 mm
- 1.00 mm
Typical purposes
- Reducing end float
- Fine axial adjustment
- Bearing spacing
- Shaft alignment
- Compensating for tolerance variation
| Example ID | Example OD | Typical application type |
|---|---|---|
| 3 mm | 6 mm | Small precision assemblies |
| 5 mm | 10 mm | General mechanical spacing |
| 8 mm | 16 mm | Shaft and bearing alignment |
| 10 mm | 20 mm | Larger support and spacing assemblies |
Where a single washer does not provide the exact spacing required, multiple washers may be combined. However, as with shim stock generally, excessive stacking is not always ideal and should be considered carefully in relation to stability and fit.
Materials used for DIN 988 washers
DIN 988 style washers can be produced from a number of shim materials depending on the environment, application, and performance requirement. Material selection affects corrosion resistance, workability, conductivity, and long-term durability.
Stainless Steel
Stainless steel is one of the most common materials for precision shim washers due to its strength, dimensional stability, and corrosion resistance. It is especially well suited to general industrial use, machinery, and assemblies exposed to moisture or variable operating conditions.
Brass
Brass offers good corrosion resistance along with a softer, more workable structure than stainless steel. It can be a suitable choice where a non-magnetic or more easily formed material is required for spacing applications.
Copper
Copper is typically selected where conductivity, thermal performance, or the properties of a softer non-ferrous material are useful. In certain specialist applications, copper washers provide both spacing and functional material benefits.
To understand more about the base metals used across shim products, visit our guide to shim stock materials, thicknesses and applications.
Typical applications
DIN 988 shim washers are used across a broad range of industries wherever precision spacing and axial adjustment are required. Their purpose may seem simple, but in the correct application they can have a significant effect on fit, stability, wear, and service life.
- Bearing assemblies
- Gearboxes and transmission systems
- Electric motors
- Pumps and rotating equipment
- General industrial machinery
- Maintenance and repair operations
- Automotive and transport equipment
In many of these applications, the aim is to reduce unwanted movement while maintaining reliable operation. A properly selected shim washer helps ensure that the assembly sits where it should, rather than allowing gradual drift, looseness, or accelerated wear.
DIN 988 washers vs slotted shims
One important practical distinction is that standard DIN 988 washers are closed rings. In many applications, this means the shaft or assembly must be partially dismantled before the washer can be fitted or removed.
Slotted shims are often used where quicker installation or adjustment is needed. Because they have an open slot, they can usually be inserted without full disassembly, making them especially useful for maintenance, alignment work, and field servicing.
| Feature | DIN 988 Washer | Slotted Shim |
|---|---|---|
| Format | Closed ring | Open slot design |
| Installation | May require disassembly | Often quicker to fit |
| Best suited to | Traditional closed washer applications | Fast adjustment and maintenance work |
If your application requires fast installation or minimal downtime, it may also be worth viewing our precut alignment slotted shim information.
Why precision thickness matters
In precision mechanical work, thickness is not just a nominal figure on a drawing. It has a direct effect on the final assembly. A small variation in shim thickness may alter preload, clearances, shaft position, or overall component alignment.
That is why high-quality shim washers should be cut from reliable precision material with controlled thickness and clean edges. Where dimensional accuracy matters, the consistency of the base material is just as important as the shape of the finished washer.
