A deep-hole borehole is a bore whose depth is significantly greater than its diameter – typically with a depth-to-diameter ratio of around 5:1 or more. Such bores are often machined axially into spindles, shafts or nuts, for example to allow lubricant supply, to reduce weight or for technical performance reasons.
Meaning
- Weight and mass inertia of components: longer shafts are lighter
- Bending and buckling stiffness: oversized bores can reduce stability
- Lubrication: central bores allow for targeted lubrication along the spindle
- Integration of media or conduits: oil, coolant, compressed air, or sensor lines
Technical aspects
- Deep-hole drilling is usually carried out using specialised tools such as deep-hole drilling bars, BTA or ejector drilling methods.
- The quality of the borehole is critical: roundness, surface roughness and straightness affect performance and wear.
- The diameter and position must be selected in such a way that the strength and stiffness of the spindle are not unduly reduced.
Practical relevance
- This is particularly important for long spindles in CNC machines or ball screws, where weight reduction and lubrication are crucial.
- Also used in medical technology, hydraulic systems and toolmaking for precise axial channels.
- Basis for dimensional calculations, buckling force and service life of the spindle.