Dosnt EQ5 tell you? Even cheapy Quilt Wizard gives you a pattern to go by.

I think this is what you are looking for . If your block is finished size 12 unches . Setting triangles should be cut 18.25 inches and cut diagonally into 4 triangles and your corner cut 9.375inches and cut diagonally in half I hope this helps try with some paper first to mke sure this is right Good Luck and Happy Quilting Andie

Here's another chart to bookmark - it has the most common sizes worked out.

http://www.karencombs.com/setting_triang.htm

Love her charts!! But she doesnt have the size you need for your corners, so here is the formula to use;

for side setting triangles ( 1/4 sq)- finished size of block times 1.4142 +1.25
corner setting triangles (1/2 sq)- finished block size divided by 1.4142 + 7/8

Thank you all sooo much! I got it done, and as soon as I square itup, I'll post a pic.

OK, here is the calculation....

For the setting triangles, take the finished size of the block x 1.414, round to the nearest 1/8 and add 1.25. Cut your square that size and cut on the diagonal both directions giving you four quarter square triangles

Your example:
12 x 1.414 = 16.968, round to 17 + 1.25. cut your square 18.25 and cut on the diagonal both directions.

For the corner triangle:
take the finishes size x 1.414 /2 + 7/8 cut in half on the diagonald

Your example:

Since your corners span two blocks, the finished size is 24 inches.

24 x 1.414 = 33.936 round to 34, divide by 2 = 17 & 7/8 = 17 7/8. Cut in half on the diagonal giving two half sqaure triangles.



I went to my cutting mat and measured.

You can follow this too and see that it is what you want.

Lets start with the corners.

The corner triangle spans TWO 12 inch blocks and you are going to want to make it from a half square triangle because you want the bias edge to be against your blocks and the straight of grain on the outside two sides.
So, the finished length of this seam across two 12 inch blocks is 24 inches.
Take your 24 inch ruler and go to your cutting mat and lay it diagonally across the corner at the 17 inch mark you see the size of the finished triangle is 17 x 17 x 24. So this is the size your triangle will be after sewing into your quilt. Now, you need a 1/4 seam allowance on the 17 inch side and 3/8 inch on the diagonal or 24 inch seam and another 1/4 inch for the other triangle. So, thats 7/8 inches added to the 17 inch measurement (17 7/8 inches) to get the size of the square. Cut this in half on the diagonal and that will give you your corner triangles.


What do you think?

Judy

Just saw your post that you got it done.
Cant wait to see it..

Thanks jstitch, I really appreciate your help! :D

If you're like me - I love setting blocks on point and equally love changing patterns around - check out the Fons and Porter Easy Diagonal Sets ruler. I'm not normally one to have a ton of specialty rulers, but this one I consider a must-have - the price has been well worth the saved aggravation for me! It does corner and side setting triangles; just follow your finished block size (ie: 12") and it tells you to cut 9" strips for your triangels - the ruler has the angles, you just lay it on your strip and cut, flip the ruler and cut again. IIRC, I got mine at Joann's with either a coupon or when they had their Fons and Porter stuff on sale.

Here, here, I agree

These rulers are the best... Marti Mitchel has one too. I think her's was the first one on the market

Either one is good and they are great as they allow you to cut your setting triangles from a strip intead of a square.


Judy