Card Set Information
Rule of Thumb for runout
Runout must be minimum <0.025mm
Cutting Speed of carbide? Compared to steel.
3 x cutting speed of HSS
Why are carbide drills self-centering?
No chisel edge. Starts cutting right at the tip.
Angles of Carbide Drills?
135, 138, 140.
Angles of HSS drills.
Rule of Thumb for drill (2 flute twist drills)
0.001"(1 thou) FpR for every 1mm diameter of drill.
Rule of Thumb for exiting into an uneven surface
Reduce feedrate to 30%.
3 times diameter depth for each peck.
HSS Twist Drills
Low Cost/Lower cutting speeds/tough but not hard/use in lower rpm machines/around 90 sfm for steel
Carbide tip drills
cheaper than solid carbide/tips can break off/can run at higher speeds than HSS due to hardness
Solid Carbide Drills
Expensive/Hard but not tough/For smaller diameters and holes with tighter tolerances.
Stubby length/ Provides an accurately positioned pilot hole for gundrills or other deephole drills.
Replaceable Tip Drills
Expensive/Higher chiploads than indexable style drills/ coolant thru/ two effective flutes
Higher speed/ Lower Feed/ One Flute effective/ faster toolchanges
Drilling Theory for Indexable Drills- Cutting Speed
Cutting speeds for indexable drills declines from 100% at the outside to 0% in the center.
Less tools required/Reduces cycle time/Adds chamfers or counterbores/can produce multiple diameters with one tool
Sefas and BF Bodies
Can do chamfers or spot faces/eliminates need for separate chamfer tool/eliminates need for stepdrill/replaceable inserts are expensive/possible runout problem if setup in endmill holder
reduced downtime due to tool changes/ for deeper holes/ for cored holes/ body holds various sizes of insert/ lower cutting speeds than indexable style
drill and chamfer
For Aluminum or Cast iron/ 4 Guiding margins/ works well for deep drilling/ requires coolant thru
3 flute drill
better stability/ good on cored holes/ higher feedrates due to more flutes/ good for breaking out into uneven surfaces/ good for only free chipping materials (iron)
Opening previously cored holes/ Not centre cutting/ 2 effective flutes/ Can have good feedrates/ Generally Specially made
For drilling centres for tailstocks/ Bell type centredrill has a seperate 120 degree angle to protect the 60 degree angle
short and rigid/ creates accurate starting spot for drills to maintain true position/must have smaller tip angle than drills/usually 90 or 120 degrees/ chamfering existing holes
Flat bottom drill
not an endmill/creates flat bottom holes/ pilot holes/ speed and feed alot faster than endmill/ creates a starting flat for drills on an angled surface
greatly reduces exit burrs/self centering/good on cored holes
universal standards for hose fittings/ predrilled first/ complex geometries with spotfaces
spot facing tools
used for spotfacing an existing hole/ not centre cutting
Deep Hole Drilling
with guide pads/ requites good coolant volume and pressure
for straight deep holes/high RPM, low chipload/used with high pressure coolant or oil/hollow body/must be used with pilot hole or bushing/regrindable
Parabolic flute drill
deep hole drilling/ helps chip evacuation/ commonly used in aluminum/slow helix
High helix drill
good surface finish/fast helix/creates less radial force
Double margin drill
for good reamer like surface finish/ burnishing effect/ more stability when drill in bushing/ for interrupted cuts or uneven breakouts
custom shapes/eliminates many tools/complex profiles/expensive
What is the largest factor determining tool life?
What size should a predrilled hole be/
smaller, only 25% of the drill diameter to avoid drill deflection