Oxyacetylene Cutting

After completing this chapter, you will be able to:
◦ Demonstrate the proper and safe method of setting up
cylinders, regulators, hoses, and the cutting torch
◦ Demonstrate how to maintain a cutting tip and torch
◦ Demonstrate how to light a torch, adjust it, and make a
cut
◦ Describe a good oxyacetylene cut
◦ Discuss safety procedures to be followed when oxyfuel
cutting
Chapter #21 – Oxyacetylene Cutting

Primary cutting process in oxyfuel gas cutting
(OFC)
◦ Uses heat from oxygen fuel gas flame
 Raises metal temperature to kindling temperature
 High-pressure stream of oxygen is directed onto the metal,
causing it to be cut (rapidly oxidized)
◦ Processes are identified by fuel type mixed with oxygen
to produce the preheat flame
Chapter #21 – Oxyacetylene Cutting
Table 21-1 Fuel Gases
Used for Flame Cutting
A
B
FIGURE 21-1 (A) Oxyacetylene
portable cutting rig mounted on a
handcart for use in a shop area.
(B) Oxyacetylene setup mounted on a
trailer for use outside of a shop.
Larry Jeffus
Chapter #21 – Oxyacetylene Cutting

Oxyfuel gas cutting
◦ Used to cut iron base alloys (ferrous metals)
◦ Low carbon steels (up to 0.3% carbon)
 Easy to cut
◦ High nickel steels, cast iron, and stainless steel
 Considered uncuttable with OFC-A
◦ Nonferrous metals (e.g., brass, copper, and
aluminum)
 Cannot be cut by oxyacetylene cutting
Chapter #21 – Oxyacetylene Cutting
Chapter #21 – Oxyacetylene Cutting
Chapter #21 – Oxyacetylene Cutting
Chapter #21 – Oxyacetylene Cutting



1) GOGGLES (shade 4-6)
2) GLOVES
3) PROTECTIVE CLOTHING
Chapter #21 – Oxyacetylene Cutting

1) Working area must be clear of unnecessary items

2) Protect yourself and others from flying sparks

3) Support and balance the metal being cut

4) Clear space underneath the cut

5) Use proper technique in starting a cut
Chapter #21 – Oxyacetylene Cutting

Oxyacetylene hand torch
◦ Most common oxyfuel gas cutting torch
 Most cutting tips are made of copper alloy, but some tips
are chrome
FIGURE 21-2 Oxyfuel cutting torch.
Thermadyne Industries, Inc
Chapter #21 – Oxyacetylene Cutting
FIGURE 21-4 A mixing
chamber located in the tip.
American Welding Society
FIGURE 21-5 Injector
mixing torch.
American Welding Society
Chapter #21 – Oxyacetylene Cutting
FIGURE 21-7 Different manufacturers have
differently designed cutting torch tip seats.
Larry Jeffus
Chapter #21 – Oxyacetylene Cutting
Other Gases

Acetylene
THE CUTTING
TIP
Preheat
Flame Holes
Cutting
Oxygen Hole
Chapter #21 – Oxyacetylene Cutting

Exactly like setting up oxyfuel welding
equipment
◦ Except for adjustment of gas pressures
 Refer to Chapter #21 of the text
 Greater detail and practice will take place in shop
Chapter #21 – Oxyacetylene Cutting

Proper alignment of preheat holes will speed
up and improve the cut
FIGURE 21-19 Tip alignment for
a square cut. American Welding Society
FIGURE 21-20 Tip alignment
for a bevel cut. American Welding Society
Chapter #21 – Oxyacetylene Cutting

Laying out a line
◦ Done with soapstone or a chalk line
◦ Scribe or a punch can be used
FIGURE 21-22 Holding the
punch slightly above the surface
allows the punch to be struck
rapidly and moved along a line
to mark it for cutting.
Larry Jeffus
Chapter #21 – Oxyacetylene Cutting

Tips size selection:
◦ Designated by manufacturer numbering system
◦ Refer to manufacturer’s recommendation chart
◦ Size needed is determine by “material thickness”
◦ Pressure are then selected from chart
Chapter #21 – Oxyacetylene Cutting
Table 21-6 Cutting Pressure and Tip Size
Chapter #21 – Oxyacetylene Cutting

Oxyfuel gas cutting torch
◦ Metal cut rapidly oxidizes or burns
 High-pressure stream of oxygen is directed on metal
preheated above kindling point
◦ Burning away of metal is a chemical reaction with iron
(Fe) and oxygen (O)
 Oxygen forms an iron oxide
 Heat is produced by metal as it burns
Chapter #21 – Oxyacetylene Cutting

THE WELDING TORCH OXYGEN VALVE MUST BE
WIDE OPEN
Chapter #21 – Oxyacetylene Cutting

THE HIGHER OXYGEN PRESSURE WILL CAUSE THE
OXYGEN TO BACK UP THE ACETYLENE HOSE,
CAUSING A HIGHLY EXPLOSIVE GAS TO COLLECT
IN THE ACETYLENE HOSE
Chapter #21 – Oxyacetylene Cutting

PRESS THE CUTTING OXYGEN VALVE
Chapter #21 – Oxyacetylene Cutting
Chapter #21 – Oxyacetylene Cutting

THE SPACE LEFT WHEN THE METAL IS CUT
Chapter #21 – Oxyacetylene Cutting

THE THICKNESS OR DISTANCE OF THE BEVEL
1.4 “
1”
1”
Chapter #21 – Oxyacetylene Cutting

MAKE A SMALL GOUGE WITH A COLD CHISEL,
HACK SAW OR ZIP CUT
Chapter #21 – Oxyacetylene Cutting

Oxyacetylene torch
◦ Indispensable tool
 Speedy
 Accurate
 Saves time
FIGURE 21-92 Nuts and bolts on this rusty
plow could not be taken off without a torch.
Larry Jeffus
Chapter #21 – Oxyacetylene Cutting

Next set of slides deal with flame cutting
technique

Review if time permits
Chapter #21 – Oxyacetylene Cutting

Allow better control and even cutting
FIGURE 21-38 Using angle irons to aid in making cuts.
© Cengage Learning 2012
Chapter #21 – Oxyacetylene Cutting

Easier if one side of the metal is scrap
◦ Cut is turned out a short distance into the scrap side

No side is scrap
◦ Forward movement should be stopped before
releasing cutting lever
FIGURE 21-40 Turning out into
the scrap to make stopping and
starting points smoother.
© Cengage Learning 2012
Chapter #21 – Oxyacetylene Cutting

Burning a hole in the plate
FIGURE 21-59 Sequence for piercing a plate.
© Cengage Learning 2012
Chapter #21 – Oxyacetylene Cutting
FIGURE 21-83 Small diameter pipe
can be cut without changing the angle
of the torch. After the top is cut, roll
the pipe to cut the bottom.
© Cengage Learning 2012
FIGURE 21-84 On large diameter
pipe, the torch is turned to keep it at
a right angle to the pipe. The pipe
should be cut as far as possible
before stopping and turning it.
© Cengage Learning 2012
Chapter #21 – Oxyacetylene Cutting

THE CUT WILL BE CLEAN AND FREE OF SLAG
Chapter #21 – Oxyacetylene Cutting

THE KERF WILL HAVE A ROUNDED TOP EDGE AND
SLAG WILL ADHERE TO THE BOTTOM OF THE CUT
Chapter #21 – Oxyacetylene Cutting
Chapter #21 – Oxyacetylene Cutting

NOT ENOUGH PREHEAT WAS USED
Chapter #21 – Oxyacetylene Cutting