Figure 12-11.Butt welder-grinder unit.
hold the WELD button until the blade ends fuse
together. Let the weld cool for a few seconds and then
press the ANNEAL button until the welded area heats
to a dull cherry red. Hold the welded area at that
temperature momentarily by jogging the button, and
then allow the temperature to fall off slowly and
gradually by increasing the time between jogs. (Allow
about 10 seconds for this last phase.)
2. After the band has been annealed, take it out of
the welder jaws and grind the weld bead with the small
grinder. Grind the weld area to the same thickness as the
rest of the band. Check the back edge of the band for
burrs and misalignment; grind off irregularities. After
the grinding is completed, place the band in the butt
welder-grinder unit and reanneal the welded areas to
destroy any hardness that may have developed. See the
technical manual furnished with each machine.
Causes of Blade Breakage
A number of conditions may cause a band saw
blade to break. Breakage is unavoidable when it is the
result of the peculiar stresses to which such saws are
subjected. The most common causes of blade
breakage that may be avoided by good judgment on
the part of the operator are as follows: (1) faulty
alignment and adjustment of the guides, (2) forcing or
twisting a wide blade around a curve of short radius,
(3) feeding too fast, (4) dullness of the teeth or the
absence of sufficient set, (5) excessive tension on the
blade, (6) top guide set too high above the work being
cut, and (7) using a blade with a lumping or improper] y
finished braze or weld. When a saw blade breaks, shut
off the power immediately, and then wait until the
wheels stop turning before replacing the blade.
Replacing Saw Blades
To replace a bandsaw blade, open the wheel guard
on each wheel. Raise the guide to the top position.
Remove the throat plate from the table. Release the
tension on the blade by turning the top wheel adjusting
screw. Remove the blade and install the replacement.
HORIZONTAL BAND CUTOFF SAW
A relatively new metal-cutting band saw is shown
in figure 12-12. This HORIZONTAL BAND
CUTOFF SAW is being used in shops to replace the
reciprocating type of power hacksaw. The continuous
cutting action of the blade provides greater speed,
accuracy, and versatility for metal-cutting jobs.
Good results from the use of any metal-cutting
band saw depend upon careful choice of blade, speed,
rate of feed, and feed pressure. The primary
consideration in selecting the blade is the tooth pitch.
Tooth pitch should be considered in relation to the
hardness and toughness of the material being worked
and the thickness of the workpiece. At lease two teeth
should be in contact with the work. When cutting thick
material, do not select a tooth pitch that will allow too
Figure 12-12.HorizontaI band Cutoff saw.