Help! Any sewing mechanics out there? Hook won't grab upper thread?

Question

I know what the problem is. There are two thick gears with angled sides that rotate together, and they keep the "time" between the needle's movements and the hook's. When the problem first occured, I heard a KATHUNK and then I couldn't pick up the bobbin thread. I'm positive it's because the gears were moved because the machine was jammed with a big hunk of thread.
Again, HELP!!!
No answers like, " I wouldn't know so I can't help you." It disappoints me when I check to see if my question got any answers and find those crappy answers.

Answer 1

This is only a possible cause and I hope it does not qualify as a "crappy answer" I'm a guy and don't do sewing, but I have worked on sewing machines several times for people.



The engagement of the two bevel gears determeines the timing between the needle and hook. Unless they were very worn, it is unlikely that one gear jumped over several teeth of the other to loose the timing. These gears are secured to their shafts with either set screws or pins driven into cross-drilled holes. Possibly, when the machine suddenly jammed, one of these pins has sheared off (or screws has slipped) allowing one of the gears to spin on the shaft and lose the timing between the needle and the hook. When this happens, the gear often will still be tight enough on the shaft that, when observed, the mechanism appears to be working.



If you are mechanically inclined, you can try to determine which gear has come loose and get it back into the proper alignment. If it was secured with a set screw, there is usally a flat spot on the shaft where the screw was clamped which should give you the original position. (Note: sometimes 2 set screws 90 degrees apart are used). If it was a roll pin that sheared, and it was set in a hole drilled through the exact center of the shaft, there will be 2 possible orientations. Drive the broken pieces out and try each way with a wire or nail in the hole until you get the proper orientation and then install the pin. If it is a taper pin driven in a tapered hole, there will be only one way the new tapered pin will fit in.



I hope this is of help to you.



Added:



I was assuming you had already tried all the "easy fixes" and eliminated the problems described in the other answers. Also, you stated that you were fairly certain the gears were causing the problem, that's why I gave instructions for dealing with the gears. If the mechanism became suddenly jammed stopping the motion, the inerta of the rest of the mecanical parts wanting to keep moving might have been enough to cause one of the gears to get out of timing as I already described. Depending on the design of the machine, there may be other places besides where the gears attach, where something could have slipped and be causing the problem. Most of the machines have a catch you can release which lets the machine flip over sideways so you can oil & clean the various linkages and shafts underneath. Since the machine jammed near the bobbin, if something has slipped or sheared off, it will be between the bobbin and the upper shaft (where the belt attaches). Try doing the timing test which one of the answerers gave a link to and if it doesn't help, start looking for places where an allignment pin or set screw might have failed and allow part of the mechanism to get out of sequence with the rest of the machine.

Answer 2

I hope this isn't crappy but, I'm trying. We have about seven machines, we make quilts and etc, I just put a singer together and remade the cabinet for my grand daughter. All that said and done.



The thread may have pulled the bobbin out of sinc, and loosened it or tightened it, take the bobbin out and hang it by the thread, a slight jerk will let it fall about one inch. If it doesn't adjust it slightly.



Take the entire unit out and check for excess thread trash, it happens. When the bobbin comes around the thread is moved around the bobbin loosely and is picked up by the upper thread, then looped and it starts over. Make sure you wined the bobbin thread right or it will affect it, when it comes off the bobbin.



Use a new needle, a very slightest bend, sometimes you can't see it, will stop this action. Make sure you have the same size thread in both the bobbin and the upper thread. Make sure all the tensions are correct.



You shouldn't have anything real serious happen, to do what the one guy says you'd have to really have a problem, a thunk could be just the thread getting caught in the bobbin area. Take it all apart, clean it out, then oil it good and wipe off the excess.

Answer 3

Sounds like it's out of time -- the loud thunk is almost diagnostic. What kind of hook?



Did you replace the needle with a brand new one of the correct size and needle system? Do that if you haven't... even a slightly bent needle looks like an "out of time" machine. Make sure it's inserted correctly -- needles do have front and back sides. Home machines are typically timed with a size 80/12 sharp needle.



http://www.sewusa.com/Sewing_Machine_Repair/Sewing%20Machine%20Hook%20Timing.htm