1. Unit 13
Ag Mechanics
Fastening metal

2. Metals can be fastened together by many means:
Bolting
Screws
Rivets
Melting together
Soldering
Brazing
Welding

3. Drilling:
Holes are needed in metal so certain fasteners can pass
Through both pieces of metal.
Drill press:
An electric device that allows you to put more force
And maintain a constant speed when drilling.
Sometimes called a portable drill, makes drilling
Easier. It can be corded or battery operated.
Hand drill:
Drill bits:
Made out of High Speed Steel.(HSS). They can be
Round shank or tapered (special bits)
Drilling holes:
Center Punch:
Used to mark location of holes and to hold the
Bit so it does not move.
Set drill speed:
Larger bits need to be run at lower speed, while
Smaller diameter bits can be run at higher speeds.

4. Notice how the size of the
bit tells you how fast
The speed of the drill.
Harder metals will also
Cause you to use slower
Speeds.

5. Threading metal:
Must know the size and thread pattern needed.
Taps form threads on the inside of a hole
Die form threads on the outside of material
Taps are held with a tap wrench.
Dies are held with a die stock
Both use oil to reduce friction
A set of taps and dies can be called a set or a
Screw plate.
They can be either metric or English

6. Taps:
Three types of taps
A chart will tell you what
Size of hole to drill for what
Size of taped hole needed.
The hole must be smaller than
The bolt being used or no threads
Will be formed.
Always use a tapered tap to start threading.
Turn the tap ½ to ¾ of a turn in and then back up ¼ of a turn to break
Off the metal chips cut during the formation of threads

7. Starting a tap is essential or breakage of the
Tap will occur.
A set of taps and dies can be called a
Tap and die set, or a screw plate.

8. When starting a die the end of the stock should be rounded
So it is easier to start.
Dies:
Follow the same instructions for turning the die as used for
Turning the tap. Use plenty of oil.
Make sure to start the die
Straight.
Make sure to start the die
From the correct side.
Make sure that the material is
Not too big around to cut threads
On.

9. Threading pipe:
Pipe threads are tapered not straight like bolt
Threads.
Only thread pipe until the back side of the die
Is flush with the end of the pip NO FURTHER.
Use Teflon tape or pipe joint compound on threads
To seal and so they can be unthreaded easier.
The the outside diameter of the bolt through both
pieces of material to be joined.
Bolting material:
Joining with screws:
Drill outside diameter through one piece and
the shank diameter through the other so the
Threads can form threads in one side.

10. Metal objects used to join metal together with out threads.
Rivets:
Holes for rivets are slightly larger than the outside diameter
So the rivet can swell.
Types of rivets:
Forming rivets:
Make sure the rivet is not sticking through too far
Then start the forming process with the flat part of the
Ball peen hammer, finish with the ball.

11. Pop rivets:
Dill a hole the outside diameter of the pop rivet
Insert the stem of the rivet into the gun and place the
Other end in the hole.
Squeeze the handles on the gun until the rivet “pops” and
Breaks.

12. Soldering:
Joining two pieces of metal together with a dissimilar
Metal. Usually tin and lead alloy
Water systems must use tin and silver solder.
Tinning a copper:
Done to a clean copper
Heat the copper
Rub the copper on a block of sal ammoniac
Place a small amount of solder on the block and
Rub the copper on it until the copper end is
Covered with solder.

13. Soldering sheet metal:
Clean sheet metal off, remove coating with emery cloth or sand
Paper.
Apply flux to the metal (usually acid)
Heat with the soldering copper
When the metal is hot apply solder and follow the seam
Hole:
Clean and flux the hole
Gather solder on the end of the copper
Place the tip of the copper in the hole wait till it heats up, twist
And remove.

14. Soldering a patch:
Clean and flux the hole and one side of the patch
Heat and apply solder to the hole and one side of
The patch.
Reapply flux to the patch side and place it over the
Hole.
Apply heat to the patch until the flux runs, and
Carefully lift the copper off
Soldering wires:
Twist wires together
Heat the wires and apply rosin core solder, DO
NOT USE ACID FLUX ON WIRE.

15. Sweat soldering:
Clean the pipe and the fitting with emery cloth.
Apply acid flux to the pipe and place the fitting over the pipe
And twist it to spread the flux.
Heat with the torch until the flux bubbles all around the fitting
Apply the solder to the seam and watch the solder being drawn
Up into the joint.
Do not overheat.