Johnson-level-tool-mfg RAS-1 Manual do Utilizador descarregar pdf (Página 14)

atailrunof1'9".Inthesame“Common”tableasused

above,foran8”rise,wend:

1' Run = 1' 2-1/2"

9" Run = 10-7/8"

1' 9" Tail = 2' 1-3/8"

COMMON RAFTER LUMBER LENGTH: To obtain the total

length of the rafter, an allowance for the bottom plumb cut

mustnowbemade(seeFigure4).Thisallowancecanbe

obtainedbyusingthetables.Inourexample,letususea2x

6pieceoflumberwhichwillgiveusadepthof51/2inches.

Fromthebottomallowancetable(using8"riseagain),the

commonandjackallowanceequals3-11/16inches.Thetotal

common rafter lumber length then becomes:

RAFTER LENGTH = 15' 7-1/2"

TAIL = 2' 1-3/8"

BOTTOM ALLOWANCE = 3-11/16"

TOTAL LUMBER LENGTH = 18' 0 9/16"

COMMON RAFTER LAYOUT

STEP 1. TOP PLUMB CUT: In choosing the side of your

raftertouse,putthecrown(highside)upiftherafter

is not straight. Now starting at the top of the rafter, lay

oursquareonthefaceoftheraftersothatthe“T”bar

isdrapedoverthetopedgeoftherafter(seeFigure6).

While holding the pivot point ﬁrmly against the edge of

therafter,pivotthesquaresothatthenumber8onthe

common scale lines up with the edge of the rafter. Starting

from the pivot point, mark the top plumb cut line along

the top edge of the square.

STEP 2. SEAT NOTCH OR BIRD’S MOUTH: With your rafter

length(inourexample15'7-1/2"),measuredownalongthe

top edge of the rafter and mark another plumb line as you

did in Step 1. This line represents the outside wall of your

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Johnson-level-tool-mfg RAS-1 Manual do Utilizador Página 14