Johnson-level-tool-mfg RAS-1 Manual de usuario descargar pdf (Pagina 28)

The common scale on the square is used for all jack rafters.

Whenever a jack rafter rests against a hip or valley rafter, mark

aplumbcut,andthencutata45°alongthemark.Thiswill

give both the side cut and the plumb cut. Angles should be

checked for direction before cuts are made. See Figures 11 and

14 for the center common rafter at the end of the ridge.

DORMER RAFTERS

Sometimes when adding a room or remodeling, it is easier to

build a valley on top of the main roof. This saves cutting into the

main roof that could cause weakening.

STEP 1. Referring to Figure 1, mark location of valley on roof at

45°tocommonrafters.Thensetlongpointofbottomendof

rafterevenwiththemarkjustmadeatline“A”.

STEP 2. PLUMB CUTS ON THE DORMER RAFTER: Using what-

ever inch rise has been determined, make them the same as the

common rafter.

STEP 3. RAFTER LENGTH: Once the shortest rafter is mea-

sured, the rafter length may be determined using the same

method as with jack rafters.

STEP 4. BOTTOM CUT: The heel or bottom cut is the same as

thehorizontalcutoftheseatnotch(seeFigure7).Butcutall

thewayacrosstherafter(andwithoutmakingaseatplumb

cut). The saw should be tilted at the same angle as the rise of

the roof. Thus allowing your horizontal cut to lay ﬂat against the

roof.Forexample,usingthecommonscalewithan8"rise,you

willnoticethatthenumber8linesupat331/2°onthedegree

scale.Sotiltyoursawat331/2°beforemakingthebottomcut.

DOOR OVERHANG

InFigure1ispicturedaroofextensionthatmaybefoundover

adoorway.Tondtheendcutatpoint“B,”holdthesquareso

thatthe“T”barisatagainsttherafter.Thenusingthecom-

monrafterscale,makeamarknexttotheinchrisethatwas

used for the main roof. Now draw a line from the mark just

made to the pivot point. This is then the cut required for a ﬂat

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Johnson-level-tool-mfg RAS-1 Manual de usuario Pagina 28