machining and machining operations part A Flashcards
When should I use cutting fluid?
You should always use cutting fluid when performing a mechanical cut by machine or by hand, except when using abrasive tools.
What are common applications of cutting fluids?
Common applications include hand-held cutting operations, power drilling, hand cutting threads, using a reciprocating saw, and various powered machine cutting operations like horizontal band saws, drill presses, power tapping, lathes, milling machines, and CNC machines.
What forms do cutting fluids take?
Cutting fluids can appear in liquid, paste, gel, mist, or gas forms. Oils and emulsions (oil and water) are the most common.
What are the primary purposes of cutting fluids?
The primary purposes are to reduce heat and provide lubrication to reduce friction.
What are the benefits of using cutting fluid?
Benefits include reducing heat, lubricating the cutting tool, reducing cutting tool costs, increasing production speed, reducing power costs, controlling chip flow, and improving surface finish.
What are the characteristics of good cutting fluids?
Good cutting fluids must cool the workpiece and cutting tool, lubricate, resist corrosion, remain stable, resist rancidity, be non-toxic, be transparent, have a relatively low viscosity, and be non-flammable.
What is the best type of cutting fluid for cooling?
Water-based cutting fluids are best for cooling.
What is the best type of cutting fluid for lubrication?
Oil-based cutting fluids are best for lubrication.
What are the main categories of cutting fluids?
The main categories of cutting fluids are cutting oils, emulsifiable oils, and chemical cutting fluids.
What are cutting oils made out of?
Cutting oil is generally a mixture of mineral oil with additives like animal oils, sulphur, chlorine, and phosphorus.
When are cutting oils typically used?
Cutting oils are used on low cutting speed applications like tapping, reaming, or broaching.
What are extreme pressure (EP) additives?
Sulphur, chlorine, and phosphorous are considered extreme pressure (EP) additives that improve the surface of the cutting tool under heavy cutting conditions.
What are emulsifiable oils?
Emulsifiable oils are manufactured by blending oil with an emulsifying agent like soap, allowing them to be mixed with water to form an emulsion.
What is the composition of soluble oil coolants?
Soluble oil coolants consist of 90 to 98 percent water.
What applications are soluble oils used for?
Soluble oils are used for high-speed applications such as lathe operations and milling machine work.
what are types of extreme pressure lubricant additives?
phosphorus, sulphur, and chlorine for improved chemical lubrication
what is often used on grinding machines?
chemical cutting fluids
chemical coolants often contain EP lubricants which enable what?
enables severe machining operations to be carried out successfully on nickel alloys and stainless steels
what are chemical (synthetic) cutting fluids?
they are mixtures of inorganic chemicals and water. they have the cooling capacity of emulsifiable oil, but without its potential rancidity
how to make a good soluble oil emulsion (mixing ratio)
place required volume of water in clean tank or drum, calculate correct volume of soluble oil concentrate needed, always add soluble oil concentrate to water not vice versa
what happens if soluble oil emulsion solution is mixed incorrectly?
instability in the solution occurs, an unstable solution can cause separation of oil and water and result in tool failure, rust on machine
What are cutting fluids?
Cutting fluids are chemicals used in machine shops to aid in the cutting process.
What are the potential health hazards of cutting fluids?
Potential health hazards include dermatitis, throat irritation from mist inhalation, and irritation from bacteria in the coolant.
What contributes to contamination problems in cutting fluids?
Foreign matter such as fine metallic chips, grinding wheel particles, or other substances can contaminate the cutting fluid.
What is the first step in minimizing health risks from cutting fluids?
The first step is to avoid direct contact with the cutting fluids.
How can you avoid direct contact with cutting fluids?
Use splash guards, control coolant flow, wear protective clothing, safety glasses, and barrier creams, and ensure good ventilation.
manual machine types and when to use
sensitive drill press has 1/2” dia for smaller holes
upright drill press makes holes larger than 1/2” dia
radial drill press is used to drill XL work pieces
magnetic base drills or hand drills are used when doing work in the field
sensitive drill press parts top to bottom
drilling head, depth stop, hand feed lever, spindle, chuck, table and table clamp, column, base
what is sensitive drill press?
is meant for small precise work (holes up to 1/2” dia) has no power feed, can sense cutting pressure on drill (work drill press)
features of a sensitive drill press
spindle is driven by a V belt, permitting high speeds which can be set by moving belt from one pair of sheaves to another, equipped with only a drill chuck, table can be raised and lowered by hand and clamped in place, slots are machined in table to hold work with bolt, stand on floor or mount to table, don’t have coolant pumps
upright drilling machine has power feed and a coolant pump and is larger than sensitive press, features?
meant for drilling holes 1/2” to 4”, has geared head for slow spindle speeds and high torque, 4 or 5 feed rates to choose, spindle accepts drills with tapered shanks, table can be raised or lowered by cranking handle, table accepts t bolts to clamp work, t slots and channels in table return coolant to pump on base
parts of upright drill press (top to bottom)
motor, spindle speed levers, drilling head, hand feed lever, spindle, table, column, base with coolant pump/ reservoir
When would you use an Electric Hand Drill?
Electric hand drills are used for drilling small holes (up to ½ inch in diameter) by hand, where precision or set-up time of drill presses is not required.
What are the main components of an Electric Hand Drill?
An electric hand drill consists of a drill body containing the motor, a handle, a three-jaw chuck (ranging from ¼ inch to ½ inch), and a power cord. Some models are reversible and have variable speeds.
What are the limitations of Electric Hand Drills?
Electric hand drills are limited by the amount of feed pressure that can be applied for large-diameter drills and do not rotate fast enough for small drill bits. For example, a ⅛-inch drill bit requires 3200 revolutions per minute (rpm).
Why is drilling freehand dangerous on large-diameter holes?
Drilling freehand on large-diameter holes (over ½ inch) is dangerous because if the drill catches or binds, it can take the drill out of your hands. The drill must be very secure.
When should you use a Magnetic Base Drill?
Use a magnetic-base drill for large diameter holes and when drilling out threads to ensure stability and safety.
What is a Magnetic Base Drill?
A magnetic-base drill is a heavy portable drill that is secured to the workpiece by an electro-magnet, allowing drilling operations in place on heavy equipment without disassembly.
What advantage does a Magnetic Base Drill provide?
A magnetic-base drill allows for drilling operations on large workpieces that may not fit into a radial arm drill press, eliminating the need for transport to the shop.
What is an advantage of a magnetic-base drill?
It can drill, tap, and ream large diameter holes with more control over feed pressure, torque, and drilling angle than a large hand drill.
How does the drill head attach to the column in a magnetic-base drill?
The drill head attaches either by a dovetail slide with gibs for adjustment or by clamping screws.
What is used to set the height and down feed pressure of the drill head?
A gear rack on the column and a hand crank on the drill head are used.
What type of chuck do magnetic-base drills typically have?
A three-jaw chuck, usually ½ inch or ¾ inch.
What is the range of hole diameters a magnetic-base drill can handle?
It can drill holes from ⅛ inch to 1½ inches in diameter.
What feature helps locate the machine before drilling?
The centre finder, which is flipped down to locate the machine before switching on the magnetic base.
What should you ensure when operating a magnetic-base drill for horizontal drilling?
Ensure that your power source is secure and that the machine has a safety chain.
What should be done if the drill head is loose on the column?
Tighten the gibs on the dovetail to prevent the drill bit from wandering off centre.
What is a limitation of magnetic-base drills?
They often lack speed control, with only one or two speeds available for all sizes of drills, countersinks, and reamers.
What should you do when the drill is about to break through the far side of the hole?
Ease up on the feed pressure.
What are radial drilling machines used for?
Radial drilling machines are used to drill holes in very large workpieces that are difficult to position manually under the spindle of a standard drill press.
How is the spindle positioned on a radial drilling machine?
The spindle can be positioned anywhere within a certain radius of the column, depending on the size of the machine.
How does the drilling head adjust on a radial drilling machine?
The drilling head slides along the radial arm, allowing adjustment to the required distance from the column.
What mechanism is used to raise or lower the arm on the column?
Power is used to raise or lower the arm on the column by means of a lead screw.
How does the radial arm position the drill horizontally?
The radial arm pivots around the column to position the drill horizontally.
How can the spindle be operated?
The spindle can be operated by power feed or manually.
What are the two methods of manual feed on radial-arm drill presses?
One method uses a hand feed lever on the drilling head, while the other uses a hand wheel located on the underside of the drilling head.
How can a large workpiece be secured for drilling?
A large workpiece can be fastened to the table or base or set on the shop floor beside the machine.
What features do radial drilling machines typically have?
Radial drilling machines typically have geared heads, power feed, and coolant pumps.
radial drilling machine parts
column, elevating screw, drilling head, radial arm, arm elevating lever, spindle, table, base
what are two ways to size a drill press
some are sized by distance from column to tool, and some are sized by largest diameter of workpiece that can be centred under tool
what is radial arm drilling machine size designated by
the column diameter and by the greatest distance from the spindle axis to the edge of the column when the drilling head is extended to max distance along radial arm. typical machines range in size from 3-14ft, with column dia of 30” +
three drilling machine tools
twist drills, specialty drills, reamers
twist drill is divided into three main parts
the body, point, shank
body of twist drill characteristics
has two helical flutes (grooves) cut into it, grooves carry chips up and out of the hole, provide passage for cutting fluid and coolant, allow correct cutting geometry at the point (most have right hand helix)
what is margin on a drill bit?
margin is a narrow raised section that runs along flutes, dia of drill is measured across margins. body of drill is cut behind margins to provide clearance reducing running effect while drilling
What defines the geometry of the drill point?
The geometry is defined by the cutting lips, chisel edge, and lip clearance
These components determine how effectively the drill can cut into the material.
What is the cutting edge of the drill called?
Lip or Cutting Edge
It extends from the chisel edge to the margin and is responsible for cutting.
What is the included angle for grinding the lip or cutting edge?
118 degrees
This angle is critical for optimal cutting performance.
What is the role of the chisel edge in a drill?
The chisel edge is the portion remaining between the flutes and does not cut
It should be as small as possible to minimize resistance.
What should the lip clearance be ground to?
8-12 degrees
Lip clearance allows the drill to advance into the workpiece.
What are the two types of shanks for drills?
- Straight Shanks
- Taper Shanks
Each type has different applications and manufacturing costs.
What is a characteristic of straight shanks?
Used on drills up to ½ inch in diameter and less expensive to manufacture
However, they cannot be held as securely as taper shanks.
What are taper shanks?
Taper shanks are found on drills larger than ½ inch in diameter and feature a Morse taper.
The Morse taper is a standard taper of about ⅝-inch taper per foot.
What does the tang on a taper shank do?
The tang fits into a slot in the drill spindle, securing the drill.
This combination allows for quick changes of the drill.
What is the purpose of high helix drills?
High helix drills (35° to 40°) are used for deep holes in softer metals like aluminum, copper, and zinc.
These metals tend to jam in the flutes of a normal drill.
What is a core drill used for?
Core drills are used to enlarge existing holes and have three or four flutes.
They cannot cut at their center.
How do oil hole drills function?
Oil hole drills have one or two small holes that deliver cutting oil, coolant, or compressed air to the cutting edges.
This helps keep the cutting edges cool and flush chips from the hole.
What materials are straight fluted drills used on?
Straight fluted drills are used on soft materials such as brass, bronze, and plastic.
Normal drills tend to dig into these materials.
How can a twist drill be modified for soft materials?
A twist drill can be modified by grinding a small flat on the cutting edge parallel to the axis of the drill.
True or False: Core drills can cut at their center.
False
Core drills cannot cut at their center.
What feature allows taper shanks to drive the drill securely?
The self-locking taper drives the drill.
This feature ensures a secure fit in the spindle.
what are step drills used for
used to drill and countersink (or counterbore) hole in one operation. shoulder might be square or angular. use depth stop
what is saw type hole cutter
who gives a fuck
consists of cylindrical cutter with standard twist drill in center. think roil construction cutting holes in wood literally a circle with drill in the middle. make cleaner hole on thin material
what is masonry drill used for
cutting holes in shit drilling concrete + stone to install anchors
centre drill used for
drills center holes for lathe work with angle of 60
reamers used for
create accurate hole size and accurate surface finish on pre drilled holes fuck
fractional sized drills
dia from 1/16” to 4” increase in size of 1/64” to dia of 1 3/4” then increase by 1/32”
size drills
range from #97 (0.0059”) to #1 (0.228”)
letter size drills
range from .234” to .413” and from A (smallest) to Z (largest)
metric size drills
range from 0.04mm to 80mm dia
drill gauge
put the drill in hole if it fits that’s the size. fast and accurate way to check size
portable drill tooling commonly used for
through holes, dowel pin or threaded holes, anchors, pilot holes, removing broken fasteners, cutting larger dia holes with hole saw or annular cutter
main benefit to using heavy duty machines
we can use larger tooling with them
drill chucks
have 3 jaws, sized according to largest dia. 1/2” chuck holds 1/2” drill
advantages and disadvantages of drill chucks
a: can hold any cutting tool within range, less expensive than tapered shank cutters
d: lose accuracy when jaws wear, don’t hold cutters as securely, takes time to change tool
key type and keyless drill chuck differences
key type are tightened with a key (wow) keyless tighten by turning collar and don’t hold tools as tight, quicker and more convenient tho
drill sleeve and drill socket
drill sleeve used to make drill bit taper bigger and drill socket used to make drill bit shank smaller
when is quick change tool holder used
when sequence of operations has be performed repeatedly, each tool mounted in own socket and installed/ removed quickly by lifting collar on holder
what is a drift used for
separating morse tapers
features of power tapping attachment
adjustable clutch slips if tap binds, tap held in floating head so can align itself with hole, when pressure released attachment reverses rotation to turn back out of hole
how does floating reamer reduce effect of misalignment
axis of reamer must be aligned with axis of hole or it’ll deflect and lose hole accuracy. reduces effect of misalignment bc it’s self centering
vises
hold diff size and shaped work. most versatile and convenient. standard drill press, angle vises, contour vises
clamping sets
large and irregularly shaped work pieces not suitable for holding vice must be clamped directly to table. Clamping set includes strap, clamps, parallel step blocks, and spacer blocks.
jigs
special workholding devices used to guide the drill when drilling a large number of identical work pieces
other work holding devices
other types of workholding devices that support, hold, and clamp the work in the correct position include jacks, C clamps, V blocks and angle plates
different vises and clamps
Standard drill press vice is on drill press at shop, angle vice is hinged to a base can be swivelled and set at angle, clamps are convenient quick to use used to because workpiece can pivot around clamping point, the blocks hold square work at 45° round work at 90°, drill jig used to locate hole accurately on workpiece
what happens if drilling/ machining speed is too slow too fast
if speed is too slow, job takes too long, if speed is too fast cutting tools wear and must be replaced
what is cutting speed and why should it be calculated?
cutting speed is the rate at which the cutting tool moves through metal and is measured in metres per minute or surface feet per minute. If you move to too fast generates too much heat and loses hardness if you move too slowly takes very long time to make cut.
what does linear cutting speed show?
Show how fast the tool moves through the metal in a straight line linear value must be converted into spindle speed drill press can be set at proper RPM to obtain correct cutting speed for each drill size
what is peripheral speed?
The fastest moving part of a rotating object is outside edge. This is because it has to travel the greatest distance in each revolution. This is called peripheral speed. if cutting speed is only correct for middle outside edge will turn too fast and burn out.
what is feed rate what happens if it’s too high or too slow
Feed rate is rate at which the drill is fed into the work and is measured in inches per revolution. If feed rate is too high, cutting edges of drill will chip and drill could break if feed is too slow cutting edges rub instead of cut and production is slowed down.
Feed rate for carbide drills
Feed rate for carbide drills is less than that for high speed Steel drills because carbide is not as tough as high-speed steel. the larger the drill, the higher the feed rate.
what is drilling and what are the difficulties?
drilling is the process of making a new hole in metal. Friction creates heat chips flying makes lubrication and cooling difficult.
What is peck drilling?
caution should be taken when drilling thick work pieces because drilling chips can become long and get wrapped around the drill stopping and restarting feed will break long chips. This is commonly known as peck drilling slow the feed as drill breaks bottom of workpiece. This will prevent drill from grabbing material and possibly damaging itself
When is it acceptable to clamp a stop to a table?
for small holes under 3/8 inch diameter to prevent vice from rotating has advantage of allowing the vice to float into a position under point of drill but drill that grab can still pull workpiece up and over the stop
What do twist drills tend to do?
twist drills tend to grab when drilling soft materials to prevent grabbing, straight Fluted drill is recommended. conventional drill can be modified by grinding a 1/16th inch flat on both lips of drill which provides zero rake angle.
Why should a pilot hole be drilled?
when you’re using a large drill make a pilot hole first. if pilot hole is too large drill tends to chatter. pilot holes help larger drill bit cut easily and accurately. always clamp work to table when drilling pilot hole or drill can grab hole and rotate workpiece
What is the best method for drilling holes in mating parts?
clamp the two pieces together and drill them as one, the holes can’t be misaligned that way. think limbers in shop
If one mating part has already been drilled then holes must transfer from one piece to another. What are three methods used for hole location transfer
twist drill method is transfer hole with large drill then unclamp work pieces and finish with small drill. Transfer punch method is clamp two pieces together and use transfer punch to mark location of hole then unclamp work pieces and drill hole. transfer screw method Use transfer screws to Mark location of hole on bottom workpiece then tap top piece with hammer flip over top piece and drill.
how can you drill round work accurately
Centre punch mark must be deep, work must be clamped so centre punch mark is centred above axis of shaft, hold round work in a vice if jaws are taller than radius of workpiece
what is reaming and what problem does a reamer correct?
reaming is a process that is used to create an accurately sized hole with a good finish. An issue with twist drills is that the final hole is not totally round and with very rough surface. This problem is corrected by the Reamer, which won’t deflect and gives good surface finish.
What are guidelines for using a reamer?
Feed rate is 2 to 3 times of drilling and cutting speed is half cutting speed of drilling, use cutting fluid for hand reaming or coolant for machine Reaming. only run the ream in forward direction, which is clockwise.
what is countersinking and included angle of most screws?
countersinking is the process of cutting a bevel at the top of the hole so the hole can accept the head of a flathead screw. screws have an included point angle of 82°
What is counter boring?
counter boring is the process of enlarging the top of an existing hole to accept the head of bolt or screw. A pilot that’s between 0.002 and 0.005” smaller than hole dia guides the counterbore into hole, a counter bore dia usually 1/32” larger than bolt head diameter. counter hole has a flat bottom and is made deep enough so the head of the bolt or screw sits below the surface of work.
What is tapping?
Tapping is the process of cutting threads in a drilled hole. It can be done by hand but when done in drill press, the tap is held square to the work.
what does and doesn’t clear chips from a tapped hole
One of the difficulties encountered in machine tapping is breaking and clearing the chips. straight fluted tap does not clear the chips and can jam and break, a spiral point tap pushes chips down out of hole, spiral fluted tap pulls chips up out of hole
how to maintain sensitive drill press
Lubricate pulley shafts, restart drill after oiling to give bearings chance to absorb oil, grease points, any machine surfaces that can rust must be clean and oiled
radial arm drill press maintenance
Oil levels be kept up in sight glasses, screw shaft that raises column be greased, clean and oil the table, T slots must be free of chips and T nuts, change coolant if it becomes rancid.
What are two magnetic base drills maintenance items?
keep magnetic base clean to maintain strength of magnet, Gibs on the dovetail slide be tight to keep drill head study under pressure
how to sharpen a drillbit by hand
Use offhand grinder, cutting lips must be same length or drill will cut oversized holes, point angle must be even or the smaller angle does all the cutting, must be correct amount of clearance behind cutting edge or the drill can’t be fed into work efficiently, clearance for general purpose work is 8° to 12°
When would you have to modify a drills standard point geometry
When the chisel edge of drill becomes too thick from repeated sharpening, or the angle of the point must be changed to drill very soft or very tough materials
what are different drill point angles and what are they for?
60 to 90° for soft materials, 118° for general purpose, 150° for hard materials
why should a chisel edge on a drillbit be thinned?
The thickness of the chisel edge is determined by the width of the web. the web gets thicker as it gets closer to the shank of the drill, as the drill is made shorter through repeated sharpening the chisel edge becomes wide and must be ground away.
drill bit problem: discolouration
cause: cutting speed too high, not enough coolant
solution: reduce cutting speed, use more coolant
drill bit problem: broken or split web
cause: too much feed, not enough clearance
solution: decrease feed, grind more clearance
drill bit problem: poor tool life
cause: cutting speed too high (reduce speed) feed too high (reduce feed) chipped cutting edges (don’t overheat when grinding) point angle uneven (use drill gauge when grinding) too much clearance (grind less clearance)
drill bit problem: bell mouth hole
cause: cutting lips or point angle uneven (grind drill using drill gauge)
drill bit problem: out of round hole
cause: interrupted cut (plug existing hole)
drill bit problem: excessive drilling pressure
cause: not enough clearance (grind more clearance) chisel edge too wide (make chisel edge thinner)
problem: drill chatter
cause: set up not rigid enough (use larger machine and heavier work holding device) pilot hole too large (use smaller pilot hole)
problem: squeals and jams
cause: worn margins (grind drill) excessive heat (use coolant) inadequate chip removal (withdraw drill to clear chips more often)
problems: burr
blue chips
oversize hole
cause: rounded corners on drill (grind drill)
excessive heat (use coolant)
cutting lips not equal length (grind drill using drill gauge)
choosing cutting fluids
material: machine steel
tapping- sulphur based cutting oil
drilling, turning, milling- soluble oil
choosing cutting fluids:
material- alloy steel
tapping- mineral oil
drilling, turning, milling- soluble oil
choosing cutting fluids:
material- aluminum
tapping- mineral oil
drilling, turning- soluble oil
milling- soluble or mineral oil
choosing cutting fluids:
material- brass or bronze
tapping- mineral oil
drilling- soluble oil or dry
turning, milling- soluble oil
choosing cutting fluid:
material- cast iron
tapping, drilling, turning, milling- all dry because cast iron is loaded with carbon that under pressure becomes graphite which is a lube in itself
