TM 9-3405-215-14&P
CHAPTER 2
OPERATING FEATURES
GENERAL DESCRIPTION
The Model DBW#15 is a '"resistance -type" butt welder, The two clamping jaws of the welder hold the butted band ends
together. When the welding switch lever is pressed, an electric current is induced through the butted band ends, creating
enough heat to soften and join them.
Pressing the welding lever also releases a spring which causes the jaws to force the band ends together. The electrical
current is shut off before the movable jaw completes its movement. Final upset or "forging" occurs when the band is still
hot, but is no longer being heated by its electrical energy source.
JAW GAP AND UPSET FORCE CONTROLS
The initial gap between the welder jaws and the spring upset force must both be adjusted in proportion to the cross-
sectional area of the band being welded. A greater jaw gap will allow a wider or thicker band to reach its proper welding
temperature. A greater upset force produces the same unit pressure in welding a wider or thicker band.
A jaw upset force selector is used to provide a variable control of upsetting force. Initial jaw gap is set by adjusting the
position of the weld lever before making the weld.
ANNEALING
When the band is heated in the butt welding process, the steel at the point of weld "air-hardens" and becomes brittle. The
annealing push button is used to "anneal" the weld by reheating it. This returns the band to an approximation of its
original condition. A selector switch is provided for choosing the correct annealing heat, depending upon the width of the
saw blade.
WELD GRINDER
The grinding wheel is used to prepare the blade for welding and to remove flash from the weld. Flash on both sides of the
weld must be ground off to blade's thickness. The gage at the top of the wheel guard is used to check for complete
removal of the flash. After grinding, the weld should pass freely through this gage.
Since it may be difficult to see if the grinding wheel is rotating, a pilot light is provided as a safety feature. This light is "on"
when the grinding motor is running.
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