Metal Exam Part 1 Flashcards
What units is cutting speed usually given in?
surface feet per minute (sfpm) or meters per minute (mpm)
What is the formula for spindle RPM?
RPM = CSx4/D
What is the speed of a rotating machine measured in?
Revolutions per minute (RPM)
Where is the fastest moving surface on a rotating part?
The outer circumference
What diameter is used in RPM calculations when TRUNING on a lathe?
stock diameter
What diameter is used in RPM calculations when DRILLING on a lathe?
drill diameter
What should your lathe speed be for rough cuts?
0.015”/rev (0.38mm/rev)
What should your lathe speed be for finishing cuts?
0.007”/rev (0.13mm/rev)
In gas welding how can the weld pool be cooled?
adding more filler
material or moving the torch away
In arc welding how can the weld pool be cooled?
change the angle of the rod or
turn down the power
What is the tank startup procedure for gas welding?
- A before O
- Regulators backed out
- No leaks
- Acetylene ¼ turn
-Oxygen all the way open - Always use a striker
-Take great care with the torch
Away from people
Away from the tanks and hoses
What should your pressures be for gas welding?
- Acetylene never exceeds 7 or 8 psi (max is 15 psi, Unstable at 28 psi)
- Oxygen can go up to 40 psi for cutting
Pewter is made up of what alloys?
Tin, Copper, Antimony
What are the dangerous of old pewter?
Can contain lead
(Lead free is available)
Can cuttle bone molds be reused?
Yes
What are the methods of using cuttlebone for casting pewter?
ONE PIECE MOLD
-Cut the shell in half (for one flat side)
TWO PIECE MOLD
-Use both halves for more “3D”
What are some safety for cuttlebone casting?
-Ensure sheet metal is tightly sealed around the mold
-Put mold in/above coffee can for any molten drips
What are the two main functions of a cutting fluid in a machining operation?
To provide cooling and lubrication. The reduced friction improves surface finish and
machining speeds, and extends tool life
Give four examples of benefits of using cutting fluids.
Reduced heat to increase tool
life; less power is required for machining; surface finish is improved; faster
machining is possible
Explain why plain water is rarely used as a cutting fluid.
It offers poor lubricating
qualities and promotes rusting of the work and equipment.
The “milky” fluid used extensively in the shop is a water soluble oil. Describe the
proper procedure for mixing this fluid.
Emulsified or soluble oils must be added to
water and agitated to mix. They provide lubrication and rust resistance qualities to
water, which has good cooling characteristics. Ratios range from 1:100 to 1:20,
depending on the type of oil and the machining operation. They are among the least
expensive cutting fluids and are widely used.
Some cutting oils contain sulfur. What is the advantage of using these oils?
They
provide excellent antiweld properties as well as lubrication for extreme conditions. In
use, high pressure causes a chemical reaction to take place resulting in sulfide film
which reduces friction at the cutting edge of the tool.
Often cutting fluids contain germicides. Why would this be an important feature?
To prevent the fluid from harboring bacteria and other micro-organisms which cause
bad odors and health problems for the operator.
Explain the importance of personal cleanliness when working in the machine shop.
Oils and other fluids can cause dermatitis and other health problems. Skin should be
kept clean by frequent washing with soap and warm water. Clothing should be kept
clean as well
What are the angles of a tool bit?
Cutting Edge
The Point
Relief Angle
Rake Angle
What is different from a brass tool bit?
Brass needs a negative rake angle
Sheet stock must be less than what dimensions makes it “Sheet Metal”
3mm or 1/8” thick
Anything thicker is plate
Max gauge of material thickness for snips
22 Gauge and thinner only
Methods for transferring patterns to sheet metal:
1) measurements taken directly from drawing
2) tape a full size drawing onto the sheet stock
3) make a full size template & scribe around it
4) photocopy a drawing & glue it onto the metal
What does the “Slip Roll Former” do?
-used to roll curves, cylinders & cones
-feed rollers available in different widths
-can do wired edges
What does the “Bar Folder” do?
-Bends edges on light gauge sheet metal (not thicker that 22 gauge)
What is the maximum gauge in the box and pan brake?
16 gauge mild steel
What are some safety considerations for STICK welding?
- # 11 to # 13 shield
- Protect yourself and those around you from arc flash at all times
- No lighters
- Protect all skin
- Ear plugs
- Protect eyes with goggles when chipping, grinding, etc.
- Ensure proper grounding
- Avoid moisture
- Hot material, handle with pliers
How can you get the necessary amperage from the rod thickness in STICK welding?
Convert fractional dimension to thousands of an inch & multiply by
1000
What signs may there be that your amperage is too high in STICK welding?
excessive splatter, undercutting, blowing holes, or if
you have to weld too fast
What signs may there be that your amperage is too low in STICK welding?
arc won’t start, keeps going out, there is not enough
penetration or the arc bead sits up on top of the parent material
When do you have to “pull” when welding?
If it has slag, you must drag
What should shielding gas be set to when MIG welding?
Turn on shielding gas 20 to 30 Cubic Feet per Hour (CFH)
