M- Twist Drills and Square Drills Flashcards
Cutting tools that create holes by turning waste into chips
DRILLS
Most common type of drills
TWIST DRILL
Generally used POINT ANGLE or a good General Purpose value
118 degrees
Plain cylindrical portion of a drill used for gripping
SHANK
Includes the features in a drill that enable it to function
BODY
Small reduced section between the SHANK and BODY
NECK
Independent grooves that allow ingress of cutting fluid and egress of chips, while also forming a critical part of the cutting geometry where they emerge from the tip
FLUTES
What remains after the FLUTES are cut into the cylindrical BODY are the
LANDS
Thin bridge of material that connects the two LANDS is called the
WEB
At the tip, the WEB and POINT ANGLE interact to create the
CHISEL EDGE
The two straight blades formed at the tip where the FLUTES, LANDS, and POINT ANGLE combine are called
LIPS
Narrow raised areas along the edge of the LANDS where they border the FLUTES so the BODY doesn’t rub the bore as cutting progresses.
MARGINS
Are MARGINS blades?
NO, so TWIST BLADES are not intended for cutting on their flanks (sides)
TWIST DRILLS often have a ________ _____ of simple, plain, parallel-sided cylindrical design.
STRAIGHT SHANK
What can be used to hold a twist drill with a STRAIGHT SHANK?
a Jacobs drill chuck or a Collet chuck
Jacobs Drill Chuck
allows for quick swaps with drills of different sizes, but is prone to eccentric running and slippage
Collet Chuck
runs concentrically and holds securely, but is slower to use and will break the drill under excessive torque
Drills where the diameter of the straight dill shank is not the same as the nominal drill (hole) diameter.
STEPPED (REDUCED) SHANK DRILLS
What can be used to hold STEPPED (REDUCED) SHANK DRILLS?
a single size of COLLET
How do DRILLS and COLLET CHUCKS attach to the SPINDLE of a DRILL PRESS?
by using a special TAPERED SHANK
What is the advantage of using a TAPER SHANK instead of a straight one?
larger drills can be attached directly to the spindle, thereby eliminating the need for a CHUCK
What is the most common SELF-LOCKING TAPER?
MORSE TAPER
Who invented the MORSE TAPER? What year was it invented?
Stephen A. Morse in 1864
What is the size range for the MORSE TAPER?
MT#0 up to MT#7
What angle is the taper typically?
about 1.5 degrees from the parallel sides of a STRAIGHT SHANK
What would be used to fit a MT#3 TAPERED SHANK into a MT#5 SPINDLE BORE?
SLEEVES/SLEEVE ADAPTERS
It is possible to step up any MORSE TAPER SHANK to a larger size by using a ______ SLEEVE or by _______ SLEEVES.
single; nesting
Is it possible to step down the size of a MORSE TAPER SHANK to a smaller one?
NO
The flattened portion at the small end of a MORSE TAPER SHANK; performs an important role in the separation of SELF-LOCKING TAPERS.
the TANG
TAPERS that will tenaciously grip once a SHANK is inserted into a matching tapered bore.
SELF-LOCKING TAPER
What is used to separate SELF-LOCKING TAPERS?
a DRIFT/DRIFT KEY and a hammer
A thin wedge-shaped piece of metal that is inserted through a transverse slot which is always provided in a SPINDLE, QUILL, or SLEEVE when a MORSE TAPER bore is present
DRIFT/DRIFT KEY
Why are SELF-LOCKING TAPERS not used on CNC machine tools?
- because of the reluctance of such devices to release upon demand
- a DRIFT/HAMMER approach is not a viable option for automated systems
Most twist drills are purchased in sets containing a range of sizes including:
- fractional sizes increasing by 1/32”
- letter sizes A to Z
- number sizes #1 through #80
- metric (SI)
drills sets containing drills of increasing length as the diameter goes up (smaller diameter drills are shorter and larger diameter drills are longer)
JOBBER DRILLS
drill set of long twist drills of the same length and different diameters
LONG BOY DRILL
The disadvantage of LONG BOY DRILLS
they tend to whirl/whip when rotated in a drilling machine
What is the solution to the downside of LONG BOY DRILLS?
use a short JOBBER DRILL at first to predrill a shallow hole. with the machine off, the tip of the LONG BOY DRILL can be inserted into the predrilled hole.
Big diameter drills that are shorter than normal, and all of the same length
FAT BOY DRILLS
Type of shank that allows a set of drills to be held in a moderately sized chuck.
STEPPED SHANKS
Drills with only one FLUTE, such that the WEB is thicker and stronger.
STRAIGHT FLUTE DRILL
What are STRAIGHT FLUTES usually made of, making them ideal for cutting hard workpieces?
TUNGSTEN CARBIDE
What is the problem with TWIST DRILLS as a result of their twisted geometry?
removing material to create the 2 FLUTES leaves a narrow WEB, which results in a weak drill design.
Since the single FLUTE on a STRAIGHT FLUTE DRILL is straight, there is no ________ ______ to assist in the removal of chips.
elevator effect
What kind of chips come from a STRAIGHT FLUTE DRILL?
dust-like discontinuous chips
What soft metal is STRAIGHT FLUTE DRILLS sometimes used on?
BRASS
Because the single FLUTE is not twisted it won’t act like a _____ ______ and grab the workpiece.
screw thread
What kind of drills are renowned for lifting workpieces out of their clamp/vice restraint?
TWIST DRILLS
Why are brass hinges drilled with a STRAIGHT FLUTE DRILL instead of a TWIST DRILL?
to avoid the grabbing tendency of twist drills, especially given that clamping forces on brass must be kept low to avoid marring.
Is a ROUTER DRILL the same as a ROUTER BIT?
NO; a router bit is a woodworking cutter
A drill with no FLUTES at all, the body is covered with a sharp KNURLED type of pattern.
ROUTER DRILL
Using a ROUTER DRILL is ideal for drilling composite materials such as:
- carbon-reinforced plastic (CRP)
- glass-reinforced plastic (GRP)
Drills best for HEAVY DUTY drilling of a large diameter hole.
SPADE DRILL (metal-working variety)
What machine tools are SPADE DRILLS intended to be used on?
TAILSTOCK QUILLS
DRILL PRESS SPINDLE
What are the parts of a SPADE DRILL?
- body
- separate CUTTING TOOL INSERT
What material is the CUTTING TOOL INSERT usually made from?
TUNGSTEN CARBIDE, may be coated
A smaller version of the SPADE DRILL, usually one solid pice of material with no removable/replaceable blade.
DAGGER DRILL
Type of DRILL used on multi-layer composites where TWIST DRILLS would grab and separate the laminations.
DAGGER DRILLS
What challenges does creating the barrels for FIREARMS present?
the bore of a rifle is usually of small diameter but must be long, parallel, and straight.
Before drilling technology was available, how were gun barrels made?
by building up metal around a MANDREL, which was subsequently withdrawn.
How were the MANDRELS used in the making of early gun barrels made?
crude casting
Having created the MANDREL a __________ could easily wrap strips of red-hot iron around it.
Blacksmith
The technique only good for making shotguns and muskets because of a lack of rifling grooves and could only withstand BLACK POWDER (gunpowder) and not those generated by modern SMOKELESS POWDER.
DAMASCUS METAL
Describe the characteristics of shotguns with DAMASCUS METAL BARRELS.
decorative swirling pattern
DAMASCUS METAL is no longer applied to gun barrels, but it is applied to ___________ _____ ______.
collectible knife blades
On collectible knife blades, what can be added for more characteristics?
- acid, brings out grain boundaries
- heat-treated Titanium, adds color
What are two ways modern gun barrels can be created?
- COLD HAMMER FORGED (SWAGED)
- DRILLED (not with a twist drill)
How does the HANDEDNESS of a twist drill affect the hole?
it will cause a long flexible drill to follow a curved path, which is not desirable for a gun barrel
Why is a STRAIGHT FLUTE used for drilling a modern gun barrel?
it has no handedness and therefore no tendency to wander
A very small diameter drill designed specifically for drilling firearm barrels.
GUN DRILL
A removable bearing surface to keep the body of the GUN DRILL from rubbing on the bore of the hole
WEAR PADS
What are WEAR PADS generally made of? Why?
bronze because it is a good bearing material (no galling), but also softer than typical barrel materials.
The small, replaceable piece that does the cutting on the GUN DRILL.
CUTTING TOOL INSERT coated in TUNGSTEN CARBIDE with CHIP BREAKERS built-in
Since the GUN DRILL has no TWIST, the chips will not be lifted out of the hole. Why is this a problem?
for deep holes, the chips can become clogged, wearing the hole bore unevenly or snapping the drill
What are 3 types of small, straight passageways that run the entire length of the GUN DRILL from SHANK to TIP?
- SINGLE CIRCULAR
- KIDNEY-SHAPED
- DUAL
What is continuously pumped through the passageways of the GUN DRILL to blast the chips out?
CUTTING FLUID/COOLANT
Supplies lubrication directly to the cutting face deep within the hole
CUTTING FLUID/COOLANT
How are the passageways of a GUN DRILL usually created?
PM PROCESSING with a thin wire(s) acting as a MANDREL
How are SQUARE holes drilled?
SQUARE DRILL
What allows the SQUARE DRILL to freely move relative to the axis of rotation?
a FLOATING CHUCK
When drilling noncircular holes, the holes can be _______ or _____ with virtually no corner radii.
THROUGH, BLIND
What is the minimum size for a SQUARE HOLE?
1 inch
For cutting smaller blind polygon holes, it might be better to use _______, but this is slower and will result in significant corner radii.
MILLING