20. Troubleshooting Intro Undersize cutting of internal thread Bad surface, surface damaged SP Improve cutting performance Selection and design of tap Work material Improve cutting performance Prevent welding Check cutting condition ∙ Use workpiece which ∙ Check workmaterial. has regular structureand hardness.SL ∙ Pay attention to ∙ Pay attention to tapping position and tapping position and material thickness. material thickness. PO ∙ Adopt bigger bored hole.∙ Prevent work hardening ST of material. ∙ Prevent work ∙ Provide bigger bored ∙ Prevent slanting of hardening. holes. hole. ROLL ∙ Feed according to pitch. ∙ Use floating type CARBIDE holder. ∙ Prevent vibration of tap. ∙ Prevent centering-off with work piece. LONG ∙ Reduce cutting speed ∙ Provide proper timing for changing or filling-up ofcutting oil. HAND ∙ Prevent mixing of different type of oil. TAPS ∙ Use cutting oil which prevents cold welding. ∙ Use cutting oil. ∙ Adjust flow of cutting oil and method of lubrication. EG (STI) ∙ Remove unnecessary chips during tapping. SPECIAL THREADS, GAUGES ∙ Provide Nitride on taps. ∙ Use oversized taps. ∙ Use spiral pointed taps ∙ Provide oxide coating(for through hole).on taps.∙ Use oil hole taps. THREAD MILLS ∙ Provide larger cutting ∙ Provide larger cuttingangle.∙ Adjust relief angle oncutting chamfer.∙ Provide thread relief.angle.∙ Adjust relief angle oncutting chamfer.∙ Change of no. of flutes∙ Reconsider length ofon taps.cutting chamfer.∙ Provide smaller margin.DIES CENTER ∙ Increase re-sharpening ∙ Provide better surface DRILLS frequency. finishing on flutes. ∙ Increase re-sharpening frequency. ∙ Provide precise re-sharpening. Technical info 705