Need to know if you can use invisible thread in the upper needle and the bobbin together....or will it tangle. I have used it in the upper only so far. Pauline

you can use it together but have to be extra careful winding a bobbin, it stretches, goes on too tight and can bust plastic bobbins

I use YLI .003 monofilament thread in the bobbin as well as the top. You must wind the bobbin slowly; otherwise the monofilament will stretch. Also be sure to underfill the bobbin and, if at all possible, use a metal bobbin (less likely to distort under the pressure of the monofilament than a plastic bobbin).

Some sewing machines can't seem to handle it, but my machine does fine. I suggest trying it out extensively on a sample quilt sandwich to make sure your machine will do okay with it.

After years of being too "chicken" to try using invisable in the bobbin and the top , I did it ..... the other posts are right on point about slowly winding the bobbin.
I use a smaller needle and have been using invisable thread in top and bobbin now for a few years. Do buy the good stuff when it comes to the invisable thread, there are enough issues with invisable , than to have to deal with a thread that no matter what just will not work properly. I tossed all my cheap stuff I got at JoAnn's ... wish I had back all the time wasted trying to get it to work, and restore the gray hair(s) I got in the process as well.

Thank you so much for your reply. I wished I had asked earlier because I love using the invisible thread on the top but when I couldn't match the bottom color, I wondered what would happen if I used invisible but was to chicken to try. Pauline

Thank you so much. I wished I would have asked this a long time ago. Btw what is YLI.003 ??? I have so much to learn. Pauline

I used to use it all the time in my older machines, but with the new electronic machines , that "see" the thread... My new machine can not see it on top.... but worked fine in the bobbin.. but i have to wind it on as slow as my machine will wind or ,it tightens the bobbin so tight, i have to cut the bobbin off the winder.....

It's a good brand of invisible thread. It was one of two brands recommended by Harriet Hargrave way-back-when. The other brand she recommended was SewArt. This is nylon monofilament. Nowadays many people have switched to polyester invisible thread which, I think, is what places like JoAnn Fabrics carry. I have not tried polyester invisible thread.

The .003 refers to the millimeter size of the thread. .003 is very fine, the size of a strand of fine hair. I don't know if polyester invisible thread comes in this size or not; it always seems to me that the poly looks thicker than my YLI .003 nylon.

What brand of invisible thread are you using? You may need to start a new thread about that particular brand in order to get the best advice.