METC 1312 Machine Tool Operation - Midterm Exam KNOW THESE ABBREVIATIONS A - Indicates external thread B - Indicates internal thread U - Indicates unified thread SAE - Society of Automotive Engineers ISO - International Standards Organization NPS - American standard straight pipe thread NPT - American standard taper pipe thread NPTF - American standard dryseal thread OMFS - Optimum Metric Fastener System UNEF - Unified national extra fine UNF - Unified national fine thread UNC - unified national coarse thread KNOW THE CORRECT DRILL SIZE FOR EACH TAP 5mm - M 6.3 x 1 6.75mm - M 8 x 1.25 5/16" - 3/8" x 16 UNF 15/16" - 3/4" NPT 27/64" - 1/2" x 13 UNC 29/64" - 1/2" x 20 UNF KNOW THESE FACTS In 1975 the ISO Metric Standards were revised to accept a single series of diameter-pitch combinations. Howmany combinations did they agree upon? 25 A set of serial taps has how many taps in the set? 3 The unified thread has what included angle? 60 The metric thread has what included angle? 60 What is larger, the major diameter or the pitch diameter? major The lead screw on a lathe is what style thread? The American standard pipe thread has what taper per foot? 3/4" The compound on the lathe is set at what angle when cutting threads? 29 A drill bit is sharpend so that point has this included angle? 118 The taper tap will have how many threads tapered? 8-10 The plug tap will have how many threads tapered? 3-5 The bottom tap will have how many threads tapered? 1-1 1/2" BE ABLE TO WORK THESE PROBLEMS Determine the correct drill speed required to drill a 3/4" hole in a 1" thick mild steel plate. 509 rpm A 2" steel bar is mounted in the lathe and you need to drill a 3/4" hole in the center of the bar. What is the correct lathe spindle speed for drilling the hole? 509 rpm The lathe spindle is running at 500 rpm and you are drilling a hole in the end of a 1" bar with a 1/2" drill bit. What is the cutting speed of the 1/2" drill? 65.5 fpm You are fiven a drill bit by the lab instructor and asked to drill a hole in a 3/4" thick steel plate. The drill speed is to be set on 1018 rpm and you are told that the cutting speed will be 100 fpm. What is the size of the drill bit? .38 or 3/8" You are to drill a 1 27/64 hole in a 4" steel plate. You have a 1/4" drill bit for the pilot hole. What would be the correct cutting speed for the pilot hole? 100 fpm What would be the correct drill speed when drilling the pilot hole? 1528 rpm KNOW THESE TERMS Bottom Tap Die Gun Tap Plug Tap Screw Extractor Screw Pitch Gage Serial Taps Taps Taper Tap Tap Extractor Tapping Threading Thread Forming Tap Tap Wrenches Wire KNOW THESE PARTS TO THE DRILL PRESS Column Table lift crank Guard base Power feed Switch Table lock Motor Variable speed control Head Spindle Table Quill lock handle KNOW THESE HOLE MACHINING OPERATIONS Drilling Reaming Boring Countersinking Counterboring Tapping KNOW THESE PARTS OF A DRILL BIT Lip Flute Tang Web Shank Land Margin Lip clearance KNOW THESE TERMS Major diameter Minor diameter Pitch diameter Pitch Lead Crest Root KNOW THESE PARTS OF A SCREW Helix angle Root Crest Thread angle Major diameter Minor diameter Pitch Pitch diameter Thread depth KNOW THESE THREAD SPECIFICATIONS for 3/4 - 10 UNC 2A - LH 3/4 - Major Diameter 10 - Number of threads per inch UN - Unified National thread form C - Coarse series 2 - Class of fit A - External fit LH - Left-handed thread