Key principles.
To 4× D
Standard drilling up to 4× diameter. Beyond needs specialty.
To 6× D
Drill, retract, drill cycle removes chips. Up to 6× D.
To 100× D
Single-flute drill with internal coolant. Up to 100× diameter.
Large diameter
Boring Trepanning Association. > 12 mm diameter. Up to 200× D.
Medium-large
Two-tube system. 12-200 mm diameter. Up to 100× D.
±0.05 mm typical
Specialty processes hold tighter than standard drilling.
FAQ
Above 4× diameter, drill deflects. Chip evacuation fails. Heat builds up. Specialty tooling required.
Single flute drill with high-pressure coolant. Holds straight-through bores 100× diameter. Aerospace, oil-and-gas.
BTA: larger diameter (>12 mm), faster, lower precision. Gun: smaller, slower, tighter tolerance.
Standard drilling $1-5/hole. Gun drilling $10-50/hole. BTA $15-80/hole.
Hydraulic cylinder bores, gun barrels, oil-and-gas tubular components, heat exchangers.
Most specialty drilling for steel. Stainless OK. Aluminum easier with standard methods.
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