Usually, I decrease the pressure for thicker items. In terms of testing, it’s more a matter of whether or not the materials are feeding correctly. For example, if the layers are being shifted away from each other in a quilt sanwich, then decreasing the pressure should help. If the item is not feeding, then it may be that the pressure needs to be increased. Thinner items may need increased pressure to keep them feeding properly. All but one of my machines has an adjustment for pressure and I can tell if it needs to be increased because the fabric doesn’t feel like it is being adequately “grabbed” by the feed dogs- if the feed dogs are up and functioning correctly, then the reason it feels that way is because the presser foot isn’t holding the fabric down firmly enough.
Sometimes it takes a little experimentation to get it right, but on most modern machines and some vintage machines it is a dial with numbered settings, so pretty straight forward.
Rob
Last edited by rryder; 12-13-2017 at 03:08 AM.