Design Guidelines

Doweling for Permanent Positioning
If components are located or positioned by methods other than the doweling itself, and the issue is to allow for disassembly and then re-assembly with the components in exactly the same location - then it is recommended that the components be drilled together and the dowel installed in the assembled condition. During disassembly, the dowel may be removed and reinstalled during re-assembly. This method eliminates the need for hole toleranclng and hole centerline concerns. It provides for very accurate permanent locating.

Doweling to Fix Relative Location Of Components
The more common application is to use the dowels to fix the relative location of two or more components. In this situation, the dowels are partially installed in one component, the initial installation, and then holes in the mating component are pushed over the exposed end of the partially installed dowel The following factors need to be considered for precision location:

• Hole dimension tolerance
• Relative depth of initial installation
• Total length of the bushing
• True position of hole centerlines

These factors are interrelated and need to be considered together. The following general guidelines are helpful in determining the best design in a specific situation.

• Precise holes with reduced hole tolerances increase the cost but also increase location accuracy and simplify the design considerations.
• Wider hole tolerances require longer dowels to assure a tight, non clearance fit in both components.
• Hole tolerance should be minus in the initial installation hole and plus in the mating component hole.
• The maximum hole tolerance should not exceed one half (1/2) of the recommended tolerance range to allow for hole toterancing of both holes within the tolerance range.
• Fixing the dowel location in a through hole can be achieved through length of engagement and hole tolerancing, or both. Generally, an engagement of 60% of the total length in the smaller hole is recommended for the fixed location.
• If more than one dowel is used, holes in the upper recommended tolerance range allow for a wider tolerance in centerline location.