Stack drilling
What is stack drilling?
Stack drilling is a method used for drilling a large number of holes through thin plates. Typical applications include the drilling of baffle plates for heat exchangers and components for bridges.
General recommendations
Minimizing the gap between the stacked plates is crucial for successful stack drilling. This can be done by clamping or welding the plates together. A good common practice is to insert industrial paper (thickness of approx. 0.5-1 mm (0.020-0.039 inch)) between the plates to level out any irregularities and dampen vibrations. As the axial force will be several thousand newtons during the drilling process, the clamping supports are an important consideration.
If the gap is not minimized:
- Exit disks can move along the plates, be re-cut and thereby damage the drill
- The plates tend to deflect more and can spring back when the drill exits cut and damage both the hole and the tool
Indexable drills
- Asymmetrical drill point tools should not be used for stack drilling.
Exchangeable-tip drills
- Ensure a stable set-up and fixturing
- If possible, use industrial paper between the plates to smooth out irregularities, minimize gap and reduce vibrations
- Use normal cutting parameters if set-up is good, otherwise consider reducing feed
- For improved process and tool life, use a TM tip with sharp ER and corner radius (5%)
- Use medium feed rate to avoid exit chips between the plates
Solid carbide drills
Feed reduction is not usually needed.
CNC drilling
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Hand held drilling
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