bought used machine - needle broke - diagnosis needed

micheal65536, 6 months ago

This sounds like a timing issue to me. The thread bunching up may be due to the hook not grabbing the thread or the take-up lever not taking up the slack at the correct time. If it’s missing stitches in zig-zag mode then that would also be due to either hook timing or possibly needle bar alignment.

Simple things to check:

• Make sure that the needle is installed correctly, especially that it is oriented the right way and inserted all the way in
• Make sure that the take-up lever is threaded correctly

Assuming these are both correct, you can try the following:

• If possible, insert a fresh needle (at least, you will need a needle that is undamaged and not bent from the shank up to the eye)
• Remove the plate, leave the machine unthreaded
• On the straight stitch setting, turn the hand wheel slowly and check that the eye of the needle is exactly level with the hook as they pass each other (this should happen close to the bottom of the needle’s stroke but may not be exactly at the bottom)
• On the widest zig-zag stitch setting, again turn the hand wheel slowly and check that the eye of the needle passes closely to the hook (it won’t be exact because the needle has moved, but it should be just slightly early on one side and just slightly late on the other, not noticeably early or late on one side) and also check that the needle is not colliding with any solid parts of the machine on either side

If the eye and the hook are not aligned as they pass each other, then you have either a timing or a needle height alignment issue. If they pass correctly on the straight stitch but the needle is noticeably early or late on one side of the zig-zag stitch (and fine on the other side) then you have an issue with the horizontal alignment of the zig-zag stitch.

activistPnk, 6 months ago (edited 6 months ago)

I appreciate your detailed explanation!

The shuttle hook is a bit higher than the needle eye when they cross. This seems necessary for this machine so the hook can grab the thread. If I understand the service manual correctly, the shuttle hook should be ~⅛ inch above the needle eye. I can only eye-ball it because it’s quite hard to measure.

I don’t see an early/late difference between left and right. Left right and center appear the same as far as I can tell.

The presser foot was loose so I hope that explains how I broke a needle.

When manually cranking a straight stitch, it seems to miss ~1 in 10 stitches. When manually cranking the widest zig-zag, the left misses most of the time. Probably ~7-9 out of 10 stitches miss on the left, while on the right probably 1 out of 10 miss. So without fabric and with the machine on its side, it appears to work correctly most of the time on the left and right. That is, it grabs the top thread, drags it in a circle and then it wraps the lower thread. Effectively each cycle adds a twist to the threads. It seems to be a hindenbug (the kind of bug that hides when you’re looking closely at it). I could really use a tiny camera to record what happens underneath when sewing fabric.

Before today I’ve been inserting the bobbin so it spins counter-clockwise (a Youtuber said that’s the correct way) but I just noticed the manual shows a clockwise insertion. So I switched to clockwise. I’ve noticed no difference in that regard at least when hand cranking.

micheal65536, 6 months ago

You are correct, page 10 does say that the hook point should meet 1/8 inch above the needle eye, at the bottom of the needle’s stroke.

Missing stitches only when the fabric is in place suggests that your thread tension may be too high. Check the top thread tension, make sure that you can pull the thread through with only a slight pull at the “0” position (check page 9 of the service manual).

mishellaneous, 6 months ago

I’m definitely no expert, but being an old machine I think the best thing to do is to get it serviced by a professional (sorry I don’t know how many big Mac’s that will cost), but it should be a good investment. From what I understand those old Singer sewing machines are great workhorses. Hopefully others will comment who know more than I do, but personally I’d get it serviced. Good luck!!

activistPnk, 6 months ago (edited 6 months ago)

I want to be self-sufficient enough to “own” my machine (i.e. to be able to repair it myself). OTOH, I see lots of room for user error judging from the service manual steps with difficult measurements. It seems I have a good chance of making it worse by adjusting something that doesn’t need it. I doubt I’ll be able to find a pro who I can watch over the shoulder on in my area, so the risk of making it worse might be my best option.