Drilling Flashcards
What is a sensitive drill press used for?
-Small, precise work
- usually v belt driven
- Typically holes up to 1/2”
- drill chuck only
Sensitive drills do not have?
Power feed or coolant pumps
What type of chuck is typically found on sensitive drills?
Drill chuck
What is different about a upright drill press then a sensitive drill-press?
- Meant for drilling 1/2”-4”holes
- Geared head to permit slow spindle speeds and high torque
- power feed
- accepts tapered shank drill bits
- has coolant pump and reservoir
What is a hand drill best suited for?
Holes up to 1/2” and do not require precision.
What drill should be used when disassembling is not desirable?
Magnetic base
What can be done with a mag base drill?
Ability to drill, tap and ream large holes
What size and type of chucks can mag base drill take?
Three jaw chucks
1/2” and 3/4” chucks
Some Models have a #3 Morse taper in the spindle
When must you secure mag base drills?
When drill is mounted anywhere other then flat.
Don’t use to much pressure when drilling. It could cause the magnet to detach
What is a radial drilling machine used for?
Drill holes in very large workpieces that are hard to position manually under the spindle of a regular drill press.
What are the two ways drill presses are sized?
Distance from column to tool
Largest diameter of workpiece that can be centred under tool.
What is a drill sleeve?
A drill sleeve makes up the difference between the drill bit and drill press spindle.
When is a drill socket needed?
A drill socket is used when the tapered shank of the drill bit is larger then the tapered bore of the drill press.
What is a drift used for?
To separate the tapered tool from the spindle.
What are the features of a power tapping attachment?
When downward pressure is released the tapping attachment reverses.
Adjustable clutch slips of tap bonds
Tap is held in floating head so it can self align
What is used to reduce misalignment when reaming?
Floating reamer holder
What are three main holding devises?
Vises-standard, Angle
Clamping sets-c clamps, B-blocks
Jigs
What are the 3 parts of twist drills?
Point
Body
Shank
What are two types of drill bit shanks and advantages?
Straight-less expensive, up to 1/2”
Taper- over 1/2”, hold power is much stronger.
Morse taper about 5/8 per foot of taper
What is the purpose of the flutes in a drill bit?
Carry chips out of the hole and a passage for cutting fluid.
The diameter of a drill bit is measure across what?
Margins(narrow raised section that runs along the flute)
What does the point of a drill consist of?
Lip or cutting edge-extends from chisel edge to the margin.
Chisel edge-portion remaining between the flutes
Lip clearance-heel must be lower then cutting edge for the drill to advance into material.
What are some specialty drills and uses?
High helix drills-deep holes in softer material
Core drills-used to enlarge existing holes
Oil hole drills-deep holes where it would be difficult to deliver cutting fluid to tip
Straight fluted drill-soft materials
Step drill-drills and counter sinks(counter bore) at the same time
Mason drill-drills concrete and stone
Centre drill-drills centre point for lathe
What are the 4 drill sizes?
Fractional-1/16 to 4”
Number-#97(.0059) to #1(.228)
Letter-A(smallest) to Z (largest) picks up where number range left off. (.234 to .413)
Metric-.04 to 80mm
What is a drill gauge for?
Accurately checking drill size.
How big should a centre punch or pre drill be?
Just larger then the chisel edge.
What are four methods for transferring holes?
Clamping-secure plates together drill all holes at the same time.
Twist drill method-if second hole is smaller use this method. Drill just the tip into second piece and un clamp
Transfer punch
Transfer screw- use when piece is already threaded
Typical angle of screw head?
82 degrees
What is one difficulty when machine tapping?
Chips not clearing causing taps to break.
What two taps work best for clearing chips when machine tapping?
Spiral fluted tap-chips pull out top
Spiral point (gun) tap - chips fall out bottom
What is cutting speed? How is it measured?
Cutting speed is the rate the cutting tool moves through the piece.
Meters per minute (m/min) or surface feet per minute(sfpm)
What’s the difference between cutting speed and spindle speed?
Cutting speed is the rate the tool moves through the material in a straight line
Spindle speed is rotation value (rpm)
Rpm imperial =
Cutting speed x 4 / diameter of drill
Rpm metric =
Cutting speed x 320 / diameter of drill
Feed rate is measured in?
Inches per foot (IPF)
Millimetres per foot (MPF)
Over size hole?
Cutting tips not the same size
Drill dulls quickly or a bell mouthed hole?
Point angle is not even
Cutting speed to high
Feed to high
Chipped cutting edges
To much clearance
Drill does not feed into material?
Not enough clearance angle
(8 -12 degrees is ideal)
Chisel edge to wide
60-90 degree drill point?
Drilling soft materials
118 degree point angle?
General purpose
150 degree point angle
Hard materials
Discolouration
Cutting speed to high
Not enough coolant
Drill chatter
Set up not rigid enough
Pilot hole to large
Squeals and jams
Worn margins
Excessive heat
Inadequate chip removal
Bell mouth hole
Point angle uneven
Cutting lips e even length
When drill big holes with a hand drill it is important to only drill the pilot hole and your main size. Stepping up the hole will cause the large bit to______?
May bind or break if not held perfectly steady
How big should the pilot hole be when drilling?
Just a little bigger than the chisel edge. If the pilot hole is two big the drill begins to chatter.
Three methods of transferring holes when drilling are?
Twist drill method - clamp the two pieces together and use the first hole to guide the bit. Drill only as deep as the point then I clamp the pieces and finish the hole. If you are going to tap the second hole make sure you reduce the drill bit size to the tap drill size
Transfer punch method - clamp both pieces together and use a transfer punch to transfer the holes.
Transfer screw method - if the holes are blind you can insert transfer screws into the hole and hammer the plate to be drilled on top.
Counter sink bit chatters?
Feed pressure to light
Spindle speed for a counter bore bit in a drill press will be approximately ________ of the speed you had to drill the hole?
1/4 the speed
When does the chisel edge on the top of the drill bit need to be thinned?
When the chisel edge gets to wide from multiple sharpens. Chisel edge should be as thin as possible.
Helix angle chart for twist drills
