okay, there are two situations here... one is an HST which is sewn on the bias but then cut apart to make squares with a diagonal seam on the bias and straight of grain on the outside.
the other is when you have a block on point and you need the filler triangles...NOW you want the long leg of the triangle to be on straight of grain....so.... measure the side of the block that the filler triangle will be sewn to.... now multiply by 1.414....that will give you the outside leg of the triangle needed to fill that spot.... so we will take a 10" block on point for an example.... 10" x 1.414 = 11.4"... so to simplify your cutting...you will cut one large square that is 11.5" (just a smidge extra and easier to measure on your ruler)....NOW cut that large square into 4 triangles by drawing an 'X' from corner to corner both ways. you now have 4 filler triangles and all 4 have the straight of grain on the long side (which is the outside for the filler area)... repeat with as many large squares as you need to go around the quilt....
when you get to the corners....they are different...straight of grain needs to be on the 2 shorts sides...so go back to the size of the original square...10"...now you multiply by .717 .... 10" x .717 = 7.17".... cut 2 squares this size (I would round up to 7.25 but mark at the 7.17 to sew correctly) from your filler fabric, cut each square one time from corner to corner....now you have 4 halves but their straight of grain is on the two short sides which become the corners of your filler row... the square is smaller because the bias edge is being sewn to the square and it is longer than the 90 degree sides
...sounds confusing but trust me, follow step by step and it will be fine...here is a pic to show what i'm talking about. all the filler triangles are on the straight on the outside edge so that it is easy to sew on your borders and binding without stretching and ruffling...sorry, the corner triangle is just a tiny pc, but i already had the pic and it wasn't taken to illustrate this technique...
it is not the only time you need these steps, but it is a common one... 1.414 and .717, these are the only two numbers you need to write down somewhere ... one of them will be right for whichever situation when you need a triangle on straight of grain...
just posted and found 'bearisgray's' diagrams and they are nice and clear even tho she was demonstrating a bit differently but you can see the edges i was talking about in her diagrams... thanks bearisgray....
Last edited by deemail; 11-10-2011 at 12:33 AM.