It drives me crazy when salespeople and technicians tell us NOT to adjust something. It's the same thing as the bobbin tension. If we're NOT supposed to adjust it, then why does the manufacturer make a knob or button that does exactly that?!?!?

I have been working on a bag with multiple layers of foam stabilizer and have had to adjust the presser foot pressure for the first time ever.
It is an easy setting adjustment on my machine so I can't see any reason why I wouldn't.

I adjust it a lot on all of my machines. Whether quilting or sewing garments or home dec items I test the needle, thread and pressure before I start a project. I try for the least amount of pressure I need. I was not good about doing this when I was younger but now I take the time to sample before plunging ahead.

Yes, I adjust it based on the materials I’m working with.

Rob

I adjust the machines that are adjustable. My Elna is supposedly self adjusting which is why she can't quilt. Too much pressure shifts pieces just as they reach the presser foot. She did a imperfect job of stitch in the ditch for the same reason, which is why I purchased vintage machines that can be adjusted.

I'm just learning how to adjust the pressure on my machines but my DD's machine is supposed to be self adjusting. Well, as someone stated above it puts way to much pressure on the quilt so she can't use it for quilting at all. Also the needle bar does not go up very high and she has a hard time getting the quilt under the foot in the first place.

And, can anyone tell me the best way to test for correct pressure?

I agree, if it is on the machine it has a purpose

It seems that the instruction books give little info on how to adjust the presser foot pressure.

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