JaneTea .... to make it real simple for you ........
The overall basic concept is that you match the needle with the thread!
So ..... the finer the thread, the smaller the needle.
That being considerations to the thickness of the needle, the hole size and the scarf.
An often misunderstood fact is that all 50 weight thread is NOT equal.
So .... you might have a match on needle size with a 50 wt, but a different brand of thread may require a different needle.
Different kinds of fabric ... different kinds of needles.
Different sewing techniques (eg. straight line stitching when piecing vs. FMQ vs. straight line quilting) ..... different kinds of needles and different sizes.
Different quilt sandwich and thread combos .... you got it ...... different needles and sizes.
That's the Easy-Peasy version ..... Now do yourself a favour and sit down with your favourite bevvy for a good read!! It is time more than well spent for what you will learn and how it will improve your enjoyment of sitching and quilting!
IOW there is no straight forward one-and-only answer
Suggestion ... keep notes for each project as to what needle worked best with which combo (along with machine settings, fabrics, battings etc.). I'm pretty consistent as to which needle I use for piecing, but when it comes to actual quilting, I refer back to the closest match on the combo of the quilt sandwich, thread and stitching method for where to start with my needle. Sometimes I hit a winner right off and sometimes I have to switch it out a time or two, til I find the magic needle! It really is quite surprising the difference the wrong/right needle can make to the enjoyment and ultimately the success of your projects.
And yes ...... always good to keep a supply of different needles on hand!
Last edited by QuiltE; 03-16-2021 at 12:17 PM.