Can someone help?
 

I have alot of 12 1/2" BOM blocks that I would like to use up to make quilts on point. Can someone tell me the sizes of squares I need to cut for the triangles & the size squares for the corners for putting it all together? I know there are lots of quilters used to doing these...I'm doing the mysterytrain#6 right now so I know what to cut for 8 1/2" squares. I have lots of 8 1/2" BOM blocks, so will use that for those. But I am at a loss for 10 1/2" & 12 1/2" blocks. Thanks in advance.

This might help:

http://quiltville.com/onpointmath.shtml

Or this:

http://www.ctpubblog.com/2010/08/03/...ing-triangles/

Wow, dakotamaid!! You were really a "johnny-on-the-spot" with this information! I have always wondered about it. Never have had the courage to place anything on point. Thanks for this go-to information.

Your existing blocks will become 2 sides of a right angle triangle. To make half square triangles that will finish at 12", so add 7/8"with 12" finished sides, or about 13". The outside edges will be on the bias, so starch a lot, or make them quarter square triangles. To do quarter square triangles, you need the size of the third side of the triangle is 12 x sqrt(2), or 12 x 1.41 = 17.0" finished square to make quarter = square triangle. Then add the seam allowance (1.25" for a quarter square triangle), so 18.25".

I hope you have a file on your computer where you can look up the sites in the future ... or where you can put what you have cut-and-pasted the info. I have quilting -sewing-serging files. It surely made my life easier.

Why can't you just cut squares the same size as the pieced blocks for center, then figure out quarter triangles for edges and HST for corners....

Thank you all so much for the quick answers...I printed them (site info) & will put them in my file. I knew I could count on this board for the quick answers. Should have thought of Quiltsville...she has a wealth of info. Thanks again!