5. BLADE SET
7.4 Synthetic cutting fluids are recommended for
blade speeds above 200 surface feet per minute
Blade set is normally one of two types:
because of the more intense heat generated. Syn-
thetic cutting fluids are equally good below 200
5.1 Raker (or regular type). One tooth left, one
surface feet per minute and make a good all-pur-
tooth right, one tooth straight and then the pattern
pose coolant. We recommend using this type of
is repeated. This is the most common set and is
coolant for all general work.
almost universal in use and application. We recom-
mend using this type of set.
7.5 In general, all metals can be cut faster with
coolant; however, some alloys and cast iron are
5.2 Wavy set. All teeth slowly oscillate from center
best cut dry. Refer to the cutting speed chart for
to left across to right then back to center, repeating
this oscillating pattern. This set is common on
blade pitches that are too fine for regular setting,
8. CUTTING FORCE
usually 18 and finer. We recommend using this set
only when fine teeth are used, and regular set is not
8.1 Cutting force is the force required for a saw
blade tooth's cutting edge to penetrate the work
piece and form or shear a chip from the material.
5.3 A raker tooth form is best for all normal appli-
8.2 When the cutting force is too light, small dusty
chips will be formed. The blade will slide over the
6. TOOTH FORM OR STYLE
work, doing little cutting, and abrasive wear will
quickly dull the blade.
6.1 Regular or normal tooth style works well on
most applications, as the cutting angle does not
8.3 When the cutting force is correct, most chips
encourage the blade to dig into the work piece but
will be curled or rolled up with a few small chips
still generates a good chip. The tooth will normally
mixed in. At this point the blade is cutting full con-
have enough chip storage.
tact length of the work, giving the longest blade
life and most accurate cutting.
6.2 Skip tooth blades are used for cutting wide sur-
faces where maximum tooth gullet storage is re-
8.4 Increasing the cutting force beyond this point
quired, and for non-ferrous materials making larger
will produce coarse curled chips. This will put the
cutting edge at its maximum point of stress. Al-
though the blade will be cutting at the maximum
6.3 High positive cutting angles or hook tooth
possible speed, the high force will be undesirable.
forms are fast cutting in non-ferrous materials and
High shearing force, high heat generation, and the
are made with large gullet capacity. They are equal-
high chip storage load at these forces will cause the
ly good in cutting larger steel bars.
blade to fail or cut inaccurately.
8.5 The ideal cutting force is outlined in section
7.1 Coolant and cutting oil perform nearly the
8.3. Any additional cutting
force will shorten blade
same task. They lubricate the blade against wear
life, but increase production per hour, also blade
and absorb most of the cutting heat.
cost per cut.
7.2 At slow cutting speeds one can use a plain light
8.6 Any less cutting force than outlined in section
oil with very good results; however, most oils are
8.3 will increase blade cost per cut and decrease
combustible and use of them increases insurance
8.7 The proper cutting force can easily be reached
7.3 Soluble oil and water work together and do a
by operator's experience. Various blades will differ
good job with most of the advantages of other
slightly and the amount of blade wear causes vari-
ations. Different materials will vary also. There is
fluids. The oil is in an emulsion, but still gives good
no substitute for an observant, experienced oper-
lubricating properties. Water carries away cutting
heat better than pure oil. It can be used for all cut-
ting speeds below 200 surface feet per minute. Over
200 surface feet per minute the heat will break
8.8 Cutting force recommendations are given in
down the oil. At these higher blade speeds other
Chart 8.2. They are very general due to the varying
fluids will carry the heat away faster than a soluble
conditions in the field; however, they will serve
as a starting place and will usually provide good
oil and water solution.