For the Classroom - Machine Screws

Objectives:
Familiarize students with the various types of machine screws, along with some of the things to consider
when selecting screws for specific applications.

Discussion Topics:

Screws:

• Metric vs. Imperial (Inch)
• Fine threads vs. coarse threads
• Miniature Screws
• Drill and tap information
• Different bolt grades, materials (Steel, Stainless Steel, Aluminum, Brass, Plastic, etc.), and finishes (Black Oxide, Galvanized, Zinc Plated, Nickel, etc.)
• Purpose of lock nut, lock washer, Loctite
• Advantages and disadvantages of one type of screw over the other (Allen vs. Phillips vs. Slotted vs. Tamper Proof) or (Button Head vs. Socket Head vs. Flat Head)

 

Holes:

• Blind holes, clearance holes, and tapped holes
• Thru. vs. C’bore vs. C’sunk
• Drilled Hole Tolerances

Tools for installing and removing screws and the advantages and disadvantages to each:

Hand tools

• Wrench Clearances
• Wrenches (open and box) vs. Sockets
  (6 - 8 - 12 point, shallow & deep, universal, 1/4 - 3/8 - 1/2 - 3/4 drive)
• Allen keys
• Ratcheting screw drivers and wrenches
• Torque wrenches
• T-Handle

Power tools

• Electric drill, pneumatic ratchet, and impact

Advanced Topics:

• Tensile & Shear – Stress area and general equations
  
• Stripped screw heads — How to remove a screw with a stripped head
  
• Broken Taps—How to remove a broken tap from a hole
  

Classroom Practice (with other supporting materials):

• Drill and tap a hole in a piece of aluminum or steel
  
• Show examples and/or pictures of how different screws are used
  
• Hands on - Show examples of various screws made out of different materials, with different finishes and sizes
  
• Hands on – Use some of the various tools for tightening and loosening screws, paying attention to wrench clearances, lock washers and lock nuts, ergonomics issues