Microhole taper describes a change in diameter along a very small opening. Depending on the application, that change may be a deliberate design feature or a variation that needs a defined limit. Either way, specifying only one diameter can leave important questions unanswered.
Clear drawing helps coordinate the right manufacturing review. This guide explains how to describe the bore you need. Visit our microholes spotlight for related design considerations.
What Is Microhole Taper?
A tapered hole widens or narrows along its axis. A straight cylindrical hole is intended to maintain its diameter along the specified length, within the applicable drawing requirements. A component can also combine a tapered entrance with a short straight section.
Entrance and exit labels need an agreed reference. For a fluid component, define the intended flow direction. For a manufacturing discussion, clarify whether those labels refer to the processing direction or the part’s operating orientation. The two may not be the same.
Dimension the Shape You Actually Need
For a deliberately conical opening, identify the two end diameters and the distance between them. If an angle controls the design, specify whether it is the included angle or the angle between the wall and the axis. Use a section view to remove ambiguity.
As an illustrative calculation, suppose a conical hole changes from 60 microns to 40 microns over a length of 100 microns. The radius changes by 10 microns. The wall angle to the axis is arctan(10/100), approximately 5.7 degrees; the included angle is approximately 11.4 degrees. This example explains the geometry and is not a capability claim.
Matching End Diameters Does Not Prove a Straight Bore
Two acceptable end measurements do not describe every point between them. The internal passage could still narrow or widen locally. If the minimum clear opening or the complete profile is critical, include that requirement in the drawing and agree how it will be checked.
This becomes particularly relevant for high aspect ratio microholes. A longer passage can require a different approach to both manufacturing and verification.
How Does the Process Affect Taper?
The material and process influence the resulting bore geometry. Laser parameters and beam delivery, for example, affect the shape produced during laser hole formation. A different setup or finishing step may be needed when taper limits are tight.
Our Laser micromachining post explains the broader process. For a quote, provide the required geometry first so the manufacturing route can be reviewed against your part rather than a generic process description.
Specify How Microhole Taper Will Be Verified
State where each diameter is measured, how the length is defined, and which internal profile requirements apply. Also separate edge breaks from the bore itself. A chamfer should not be mistaken for an unintended change in hole diameter.
Our microhole inspection guide covers the difference between measuring an opening and checking an internal passage.
Discuss Your Microhole Geometry with IMC Intertech
Send a drawing with the material, entrance and exit dimensions, depth, and quantity. Include a section view and explain which features control performance.
- Upload your CAD file or drawing
- Review custom dimensions and material options
- Receive engineering support for your application