Craftsman 351.243951 Owner's Manual page 7

OPERATING INSTRUCTIONS (Continued)
LOWER BLADE GUIDES
Refer'to Figure 6.
The lower blade guide employs two guide blocks for side
to side support.
The lower guide bracket is spaced close to table surface
to minimize unsupported length of blade
Loosen nut (Key No, 27) to position the lower guide
bracket on the alignment block (Key No. 33).
Adjust the lower' guide bracket so the block does not
interfere with the blade set.
Loosen set screws for' guide blocks and adjust blocks to
about 0,002" from each side of blade_
Adjust bearing (Key No. 19) at rear' of blade by loosening
the knob (Key NOo32)_
ALIGN TABLE
To perform any straight cut accurately, table must be
aligned to the blade.
Once blade is tensioned and tracked correctly, the tabte
can be adjusted to it
Lock table in horizontal position_ Attach rip fence to the
table and push it against the blade,
Make sure rip fence and blade are parallel,
If table is not aligned, loosen four hex nuts which attach
table to upper trunnion and reposition the table_
Secure table position with four' hex bolts when it is
aligned. (Review "Assembly," Number 6,)
BLADE SELECTION
Blades vary depending on type of material to be cut, size
of the workpiece and type of cut that is being performed.
Characteristics which make blades different are width,
thickness, type of tooth and blade pitch
The width of blade describes the distance from tip of a
tooth to back of blade
Width of blade will affect rigidity of blade. A wider' blade
will wander' less and produce a straighter cut
Width of blade also limits the smallest radius which can
be cut,. A 1/4" wide blade can cut about a 1" diameter_
Blade thickness describes distance between sides of
blade, A thicker blade has more rigidity and stronger
teetb_
The narrow thick blade would be used to cut curves in
metal, while a wide thin blade would be used to re-saw
lumber
Blade manufacturers should be able to supply informa-
tion about biades for specific applications
TYPE OF TOOTH
The shape of teeth are varied to achieve specific cutting
results_
A blade cuts the work by removing material
The blade must scrape a chip of the workpiece away
from the cut,
The shape of gullet between teeth determines how much
material can be taken out with each blade tooth
Rake angle is the angle which the cutting face of the
tooth makes with a line perpendicular to the back of
blade°
A 0° rake angle is used to scrape harder materiats away
from the cut.
A positive rake angle causes the blade to dig aggressive-
ly into the workpiece,
Softer materials require more aggressive chip removal,
Larger gullets provide for faster removaf but have to be
limited in size because they make the blade teeth
weaker.
Blade teeth will also vary in the way which the teeth have
been set from one side to the other.
A wider set is used for contour work because the wider
kerf allows the operator to cut tighter curves,
BLADE PITCH
Pitch describes number of teeth per inch or tooth size.
Blades with more teeth per inch will produce smoother
cuts_
The type of material being cut determines number of
teeth which should be in contact with wor k, There should
always be at least three teeth in contact with the cut to
avoid shocking the blade.
Blade shocking occurs when the pitch is too large and
the blade tooth encounters too much material. This can
strip teeth from the blade.
When the pitch is too small the gullets of the teeth will fill
up, leading to the creation of excess heat for the blade.
In soft materials the proper blade has between 6 and 12
teeth per inch.
In cutting hard materials, where shocking is more
detrimental, there should be between 12 and 24 teeth
per'inch.
BLADE SPEED
The amount of force that the blade cuts with is deter_
mined by blade speed.
High cutting speeds are used on soft materials where
less force is needed and a high rate of material removal
is desired_
Low cutting speeds are used on hard materials where
more force is required,
To change the blade speed, position the V-belts in the
proper configuration as indicated (see Figure 1).
Reposition the V-belts and tension them as described in
the next section
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