friquant

Yes the machine was running before teardown. The user manual on page 14 says to "take out set screw 20 (Fig. 4) and pull the hook up out of the machine." Set screw 20 appears to be the screw at the center of the bowl that is removed in the photo. My guess is that the hook is rusted to its supports.

After carefully filing and polishing the end of the moving part of the hook, here is the new tip alignment (photo) The original symptom is much improved. It will even stitch with TEX 30 now, so long as I'm careful while hooking the bobbin thread.

Is there a secret way to knock the hook loose? I've removed the center screw, but the hook still seems to be stuck. I've even tied parachute cord around one side of the hook and pried up with a long screwdriver. The hook flexes somewhat, but does not budge.

Your photos are super helpful! I like those alignments a lot better, as there is no way for the thread to get stuck. The part numbers stamped on mine are pfaff 18348 (Cap), and pfaff 18346 (Base) As for checking the exploded view of parts, I found this document: https://www.diamondneedle.com/documents/Pfaff Parts Manual/145_545.pdf but the part numbers in there all start with "91-010".

How should the fingers of the bobbin case Cap align with those of the bobbin case Base? Attaching a photo of the alignment I've got. The alignment looks off to me on two accounts: 1. the hole one the Cap is offset form the hold on the Base 2. The longest protrusion of the Base sticks out farther than the longest protrusion of the Cap. The symptom is that when the thread comes around the bobbin, sometimes it gets caught on the outermost protrusion of the bobbin case Base, so instead of making a stitch in the fabric it has made a loop around the undercarriage. With TEX 90 or TEX 70 thread the machine is usable, as then the above-named conundrum only happens if you pull excessively on the needle thread while hooking the bobbin thread. But with TEX 30 it happens even during normal stitching...It might get five or six good stitches in before it locks up. (Not that I expect to be doing much stitching with TEX30, but we didn't yet have the color we wanted in a heavier thread.) I'd be interested to see photos of alignments on other 545s, and especially to hear if anyone has adjusted/modified their alignment to make it work more reliably.