Triton BRA100 Instrucciones De Funcionamiento página 8

6. Compound Mitres
Each piece making up a compound mitre frame
needs to be cut twice. The first cut is done on
the compact table against the protractor, and the
second is done on the bevel ripping guide.
Choose the shape you wish to build, (try the
triangle or square first - they're the easiest).
Then decide how steep a bevel angle you want,
shown as b° on the chart overleaf.
(Shallow angles and narrow boards result
in picture frames or trays, larger angles and
wideboards result in planter boxes).
Accurate compound mitre joints require carefully
estimated settings to fractions of a degree on
the protractor and the bevel ripping guide, so
take your time and practice all cuts on scrap
material.
Step 1: Crosscut your workpieces to exactly the
required lengths, preferably using a sub-fence
and stop-block on the protractor. Then cut the
opposing MITRE ANGLES (M°) at each end of
each workpiece against the protractor on the
Compact table, using the settings shown under
'PROTRACTOR SETTINGS'. Use the protractor in
the 'trailing mode' or 'leadingmode', whichever
gives you better support closer to the blade.
Note that the settings given are the complement
(to 90°) of the MITRE ANGLES. If your
workpieces are flat on both faces (ie. not
moulded or contoured), simply turn them over
for the second cuts rather than resetting the
protractor from +X° to -X°.
Step 2: Fit the bevel ripping guide and set it
to the BEVEL GUIDE ANGLE shown for your
selected shape and bevel angle. Re-cut all of
your mitres on the bevel ripping guide using the
protractor positions and settings shown in the
chart.
You cannot short-cut this procedure by turning
the wood over, because the cuts won't form an
inclusive angle. Cut one end of each workpiece
GB
at one protractor setting, and then reset and re-
position the protractor for cutting the other ends.
Other shapes: Mitre and bevel angles for
shapes not shown can be determined by
using the following equations and a scientific
calculator.
Operating
8
Equations
( )
M° = tan tan m°
-1
cos b°
( )
B° = cos sin m°
-1
sin M°
M° = True mitre angle to be cut
B° = True bevel angle (BEVEL GUIDE ANGLE)
m° = Corner half angle
b° = Side angle to be horizontal
Protractor Settings
Used for cutting MITRE ANGLES (M°) and for
recutting into compound mitres