Technology and our changing world high Technology

Review questions

1. 
   What is toe purpose of a flux?
   
2. 
   List three kinds of heating devices for soldering.
   
3. 
   What two metals are generally found in soft solders?
   
4. 
   What is meantby tinning a copper? How is to is done?
   
5. 
   What is toe difference between welding and brazing?
   
6. 
   What are some safety rules to remember when welding and brazing?
   

Fastening Sheet Metal
Seams
Seams join two pieces of metal. They can be made in various ways. Some common metal seams or joist are shown. The butt joint is made when toe seam should show as little as possible. Lap, folded, and grooved seams are made when extra strength is needed.
A seam can be strengthened by adding rivets or sheet metal screws.


EQUIPMETN
Much of lhe equipment used for balding sheet metal is also used for making metal seams. The only new tool is the hand grooved. It is used for locking agrooved seam. The size of ahand grooved seam. The size of ahand grooved is determined by the width of its slot.


MAKING A BUTT SEAM
The simplest seam is made by butting together two metal edges. The metal should be cut carefully so the edges will join tightly. File both edges as the same time by moving the pieces back and forth across the face of a file locked a in a vise. Most butt seams are fastened permanently by soldering or brazing. It is a good idea to file a slight V-joint or bevel on the workpiece to allow the solder to run freely along the seam. This is the weakest of the sheetmetal seams.


MAKING A FOLDED OR GROOVED SEAM
The folded or grooved seam has three thicknesses of metal above the surface of the joint. Allow for this by adding an amount equal to three times the width of the seam. Usually half the amount of extra stock is allowed on either side of the seam during layout. For example, if a !4” folded or grooved seam is made, %” of extra stock must be allowed, with ³/₈” added to each of the two pieces to be joined. When making a seam, bend the fold on either edge as if you were making a hem. Do not close the fold completely, however. A bar folder, if available, can beused to fold theedges.