Question about on point quilt
 

I am adapting a square in a square type pattern to set on point. There will be 6 half blocks, and the 4 quarter blocks in the corners. Do I need to make 10 whole blocks and cut them to have a seam allowance- so they finish as "perfect" halves & quarters? Or can I make just make 4 blocks and chop 3 in half & 1into quarters? Or do I need to make these blocks bigger, to allow a seam allowance when cut? And if making bigger- how would I figure size?

I know you definitely can't make the blocks and cut them and half and quarters because you will definitely lose your seam allowance. In fact I like to make my setting triangles a bit oversized so my full blocks float and I don't chop the points.

If I were doing pieced blocks as the setting triangles I think I would redraft them out. I'm not sure if there is a set formula for pieced blocks. I only know the formula for cutting setting triangles that are not pieced.

I use the Robert Kaufman calculator ap, it's the best

Ah, thank you Feline Fanatic. Sounds like I should not take the easy route! Maybe I should find some on point pattern & see what they did. I really appreciate your advice! (To me, patterns are 'suggestions'. I like the challenge of design. Too bad for me that I don't really have the 'know-how' LOL! Thanks, happy quilting

ooooh, an app. Thanks, Nana, I will Google.

If you provide a link to your block pattern we could give you a much more precise answer.
With pieced blocks you can calculate the size for on point placement along the edge, but it is a lot easier to make full blocks and cut them down, however, you can't get away with just 4. If you do this, you will loose the points along the edges of your quilt. The blocks need to be cut on the diagonal with an additional quarter inch past the edge to edge line. Also, these blocks will probably have bias edges, so it's best to stay stitch first.
Also, depending on your block pattern, you may be able to make partial blocks. Make one, stay stitch and cut. see if any of the individual patches lay entirely in the discarded portion. You can also make full blocks and sew the discarded portions together for another project.
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I have done this before. If you have a Thangle, that is what you need to do. You have to make the blocks an inch longer so there will be no waste otherwise you only other choice is to do as PaperPrincess showed in her drawing. Sometimes, it is just easier to use a fabric for the setting triangles.

Are you talking about the triangles along the edge and the corners? Try doing a search for setting triangles and see if that doesn't give you a graph for measurements. You should be able to cut these with no waste. I have a basic quilting book that has that and I use it over and over.

Bonnie Hunter has a great schedule of sizes to be cut for the setting triangles and the corner triangles. I recently used the information for an on point quilt I made. She does all the math for you. Go to Quiltville.com

Thanks for the info.....I've installed the app on my tablet...