I made a block for a QOV type project which requested a specific block and a specific size, of course, but they asked that the block be sent un-trimmed. Assuming that must have made it easier for them to trim up the blocks to a usable size. I must say, it was really hard to send them that un-trimmed block. I wanted it to look perfect. I know this isn't exactly what you asked, but thought it kind of fit in here, within an 8th of an inch???:)

This thread is kinda refreshing. Sometimes the attitude toward the quilt police appears to make some people proud to be sloppy. I'm not perfect, but I sure try to do my best. I don't allow myself any specific tolerance, but sometimes I have to live with it anyway. If someone else was depending on me to produce a block in a certain size, I would be too embarrassed to send anything less that what was expected.

All that being said,,And I agree mostly..Where's the fun.I want perfect. I'm also new. I like swaps and appreciate every block I get. And have fun. If its a hassle it's no fun. learning and sharing gets harder if you can't appreciate the things you have. ie,, years of skill and practice.I learn from the great blocks and, ideas I receive from here and strive to do better .Thanks everybody

For myself, I tend to go with 1/8". If it's for a swap and I was told a specific size, there is NO tolerance. If mine was 1/4" too small and somebody else's was 1/4" too big, we're off 1/2" before we even start. I think 12.5" means just that-12.5".

If its for a group project, I think anything over 1/8" is too much. I've gotten squares in a block swap and trying to put them together, (made my quilters who I would have expected would know 12 1/2" is 12 1/2", not 13")was a PAIN to put together! For myself, I know what I can and can't work in, but not if I have to give it to someone else.

I haven't done a block swap in a long time. I used to do them; for the most part, the blocks were really nice. Did I measure them? No, they are all sitting in a project box like a bunch of orphans. They were never put into a quilt, and will probably wind up being tote bags one day, like all my other orphans do. So, if I were to do a block swap today, I would make sure my blocks were the right size, just in case the recipient actually wants to use them as they were intended <smile>.
For my own stuff, 1/16" is ok to be off; 1/8 is do-able, but makes me nervous. It also depends on the pattern. A rail fence can be trimmed down, no worries. But a block with points on the outside, well, not so easily. If I were a quarter inch off, I'd find out where the problem is and fix it. Were the strips cut narrow? Were the seams too wide? Did I change feet or machines?
One time I was sewing at a friend's house, using her machine. First day went fine. Next day went fine, until I tried to put the two days' blocks together. Turns out, her machine resets the needle when turned off, and I had not been using the default position the first day. Yup, that's still in the orphan box, too.

ps: If I had stopped to MEASURE between all that chain piecing, I would have caught the problem sooner.</smile>

Put this way, it does make 1/4 inch leeway on each side of the 'target' seem like too much!

If it's for an exchange, NO tolerance for something LESS than the expected measurement. It's just not fair to the others who work hard to get the exact measurement. and it's NOT impossible to attain.

However, when it's for my own quilt, and I want/have to fudge a bit, I do it. We've all done that. If I don't square my blocks as I sew them, which is often the case when I assembly-line sew, I sometimes wind up with surprises. Then I have to decide if I can live with the differences in sizes. If I have extra fabric, I MAY make more blocks, so I don't have to fudge done to 1/8 seams. Not always possible though.