ESSENTIAL GUIDE lon-point settings
FABRIC GR AIN
Theotherimportantthingto understandwhenusingon-pointsettings
is theneedto considerfabricgrainwhencuttingthesettingandcorner
triangles.A primeaimin patchworkis to keepthepatchesas stableas
possible,andthisis achievedbyusingthefabricgrain.Fabricis less
stableandhasmorestretchalongits45-degree(bias)direction– see
Fig 5. Therefore,whencuttingtriangles,theaimis to avoidhaving
thesestretchybiasedgesontheoutsideedgesof a blockorproject.
Fig 5 showsthemainfabricdirections.It alsoshowssquarescutinto
fourtrianglesandtwotriangles,withtheredlinesshowingthebias
(stretchy)edges.Thisis whyinstructionsforcuttingtrianglessaycut
a squareintofourtrianglesforsettingtrianglesbutcutintotwo
trianglesforcornertriangles.Fig 6 showshowthesetrianglesare
placed in a design. The stable edges are shown as blue lines.
MATHS FOR
SETTING
TRIANGLES
So,weknowhowdiagonalmeasurementsare
calculated,whyfabricgrainis importantandwhy
trianglesarecutdi erentways.Wecannowlookat
themathsforworkingoutwhatsize of squares need
to be cut for setting triangles.
1
Finishedblocksizex 1.414(round to nearest
in)=finished diagonal.
2
Add 1 in (1.25in)(forseams)to thisfinished
diagonal measurement=size of square to cut.
3
Cutthesquarediagonallytwiceto givefour
settingtriangles.Repeatto cut the number of
setting triangles needed.
Example
If wehavea finishedblocksizeof 3in(3 in
unfinished),thenthesizeof squareto cutforsetting
triangleswouldbe 5 in,calculatedas follows:
Fig 5 Fabric grain
Fig 6 Trianglesin placeshowingstable edges
Selvedge Selvedge
Crosswise grain (weft threads)
Straight grain (warp threads)
Bias directions
Setting
triangles
Corner
triangles
1
Finishedblocksize3in x 1.414 = 4.24in (4 in) =
finished diagonal.
2
Add 1 in (1.25in) to 4 in = 5 in = size of
square to cut.
3
Cutthesquarediagonallytwiceintofoursetting
triangles.Repeatas needed.Fig7Ashowsthe
relativesizesof theblockandthetrianglesandFig7B
showstheextra size needed on the triangle, to allow
for seams.
Fig (^7) Corner triangles
5 in
squarecut
intofour
setting
triangles
Trianglewill
belarger
thanblock
toallowfor
seam
allowance
Block
Setting
triangle
B
3 in
un nished
Block block size
Stable edge A