Dec 13, 2021 - 09:48 AM
Almost all embroidery designs are digitized for 40 wt. thread which is almost always rayon or polyester.
So the 50 wt. would be too light, and you would have areas sparsely covered. The 30 wt would be too heavy and you'd be trying to force a thread that is 1/3 heavier than 40 wt. into the same space the digitizer provided for a 40 wt. thread. The 12 wt. would not work well unless the design is specifically digitized for heavier thread.
Outline designs, like quilting, or redwork, will likely work with a heavier 30 wt. thread. You would need to upsize your needle to a 90/14. We have some designs digitized for the heavy 12 wt. Cotton on our site, and these could be stitched using a 16/100 needle. There are a few designs digitized for 50 wt. (lighter thread, too).
But basically, the answer is no, you should generally use a 40 wt. thread for most all embroidery. If you have specific issues you want to discuss about this you can email me at email@example.com.