machining

machining

1. chip formation

   • discontinuous
     • formed when cutting soft ductile materials such as aluminium or copper.
   • continuous
     • formed when cutting hard brittle material.
   • built up edge
     • forms when particles of the workpiece material welds to the rake face of the tool during cutting

2. tool wear

   • crater wear
     • occurs on the rake face of a tool just behind the cutting edge + caused by the rubbing of the chip across the surface.
   • flank wear
     • occurs on the clearance angle of the tool causing rubbing and degradation of the surface finish

3. turning operation

   • performed on a lathe, produces solids of revolution
     • tapered turning, longitudinal turning
       • facing, parting off, grooving

4. other operations

   • drilling/boring:tailstock is used, end of the workpiece must be faced off then centre drilled prior to drilling taking place
   • knurling: very slow, the serrated pattern brought to the surface, used for hand grip
   • threading:external tool set in an angle, run along piece

5. grinding tool

   • the process to improve finish and slightly alter surface tolerance by removing small amounts of material
     • loading:when it is loaded with grains of debris between the abrasive grains, causes over heating
       • glazing: shiny appearance, has become dull and not cutting properly
         • dressing: this is the cleaning of the grinding wheel. to fix other said problems

6. milling

   • cutting away material by feeding workpiece
     • horizontal milling machine,verticle milling machine
       • slab milling and face milling
         • end milling and gang milling
     • up cut (conventional) milling; cutter rotation-opposite piece
       • down cut (climb) milling: direction of cutter is the same as the feed motion