Printed from Kezuriba (kezuriba.net/en/troubles/drill-surface/)

Rough hole inner surface (drilling)

Drilling Drilling

Check first

Poor chip evacuation or clogging
Feed is large
Insufficient or poorly selected cutting fluid

Try first

Reduce the feed (if keeping feed per tooth, raise the speed)
Reduce runout, shorten the overhang, and stabilize the workpiece
Increase the flow and use a highly lubricating fluid

?Likely causes

Poor chip evacuation or cloggingAgreed by 2+ makers^[1][2]
Feed is largeAgreed by 2+ makers^[1][2]
Insufficient or poorly selected cutting fluidAgreed by 2+ makers^[1][2][3]
Welding or wear on the marginAgreed by 2+ makers^[2][4]
Runout or lip height causes wobble (rifling marks)Agreed by 2+ makers^[2][4]
Long overhang or unstable workpieceOne maker^[1]

✓Fixes

Cutting conditions

Reduce the feed (if keeping feed per tooth, raise the speed)Agreed by 2+ makers^[1][2]

Tool

Regrind properly or use a coated drillOne maker^[2]

Setup

Reduce runout, shorten the overhang, and stabilize the workpieceAgreed by 2+ makers^[1][2]

Coolant

Increase the flow and use a highly lubricating fluidAgreed by 2+ makers^[1][2][3]

↔Related problems

Hole becomes oversized (drilling)Hole becomes undersized (drilling)Hole bends or leans (poor straightness)Hole position shifts or hole is not round (rice-ball shape)Drill breaks Burrs at the hole exit (breakthrough)Chips clog (drilling)Drill chipping (periphery, chisel edge)

📚Sources

Causes and fixes are summarized in our own words from cutting-tool makers’ troubleshooting guides and technical data. “Agreed by 2+ makers” means two or more makers say the same thing.

Sandvik Coromant — Drilling wear and troubleshooting sandvik.coromant.com
OSG — Series No.24 Drilling, Table 7.4 Damage observation and Table 8.1 Troubleshooting, pp. 48-51 osg.co.jp
Tungaloy tungaloy.com
Mitsubishi Materials — Advanced Drilling: Accuracy & quality mmc-carbide.com