Laydown Threading Catalogue Numbering System Laydown Threading Insert Identification System 3ERAISO 3 E R A ISO Insert Insert Type Hand Thread Thread Number of Teeth Size of Insert Pitch Profile E— R— Single tooth profile — External thread Right-hand No symbol thread I— L— Multi-tooth profile — Internal thread Left-hand Number of teeth thread (cutting edge and symbol) Multi-tooth profile with two teeth — 2M 55 Partial Profile 55° 60 Partial Profile 60° ISO ISO Metric 60° TR ISO Metric 60° UN ISO Inch/American UN 60° Partial profile inserts W Whitworth 55° symbol mm NPT American National Pipe Thread 60° A 0,5–1,5 AG 0,5–3,0 RD Round G 1,7–3,0 N 3,5–5,0 PG Steel Conduit Q 5,5–6,0 APIRD API Round d Full profile inserts L1 symbol d L1 symbol mm 2 0.250 11 ActualTPI 0,5–0,4 3 0.375 16 4 0.500 22 5 0.625 27 F44 widia.com