Repair for Singer Model 648 replacing Vertical Shaft Top Gear
11-05-2023, 12:50 PM
#1
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Join Date: Nov 2023
Posts: 4
Repair for Singer Model 648 replacing Vertical Shaft Top Gear
Hello all!
This seemed like a very knowledgeable group so I thought it would be worth reaching out in the midst of my repair of my vintage Singer model 648 (maybe Touch and Sew?) Zig-Zag sewing machine.
As with old machines, I had a broken plastic gear. I was able to isolate the problem to the top gear of the vertical shaft, that connect just below the main horizontal drive shaft of the machine, as viewed from the top. The part I ordered was #16338 if that helps give context.
I have started the repair by following this YouTube video that walks through the same steps I have taken, from removing the bottom horizontal shaft and gears, up until removing the set screw of the gear I am replacing. Unfortunately, when getting to this step, I noticed the gear does not appear to have a set screw but seems to have a series of 2 rivets, along with a screw hole. Despite my attempts, these rivets do not appear to have any hex wrench placements and are simply stuck into the side, preventing the shaft from falling out the bottom as seen in the video.
I’m wondering if anyone has run into the same situation with their broken gears, and if there is a way to either remove it, or take out the gear from the top. I was hoping I wouldn’t have to remove the main drive shaft, but if there are clear steps to do so, I will. I’d prefer to not have to take a dremel to the gear to get it out (mostly because I don’t have one and don’t want to damage the machine!)
I have attached some images in the imgur link below, please let me know how I can help further clarify or if there are other steps I can do to keep this great machine running!
https://imgur.com/a/CdgmUY9
This seemed like a very knowledgeable group so I thought it would be worth reaching out in the midst of my repair of my vintage Singer model 648 (maybe Touch and Sew?) Zig-Zag sewing machine.
As with old machines, I had a broken plastic gear. I was able to isolate the problem to the top gear of the vertical shaft, that connect just below the main horizontal drive shaft of the machine, as viewed from the top. The part I ordered was #16338 if that helps give context.
I have started the repair by following this YouTube video that walks through the same steps I have taken, from removing the bottom horizontal shaft and gears, up until removing the set screw of the gear I am replacing. Unfortunately, when getting to this step, I noticed the gear does not appear to have a set screw but seems to have a series of 2 rivets, along with a screw hole. Despite my attempts, these rivets do not appear to have any hex wrench placements and are simply stuck into the side, preventing the shaft from falling out the bottom as seen in the video.
I’m wondering if anyone has run into the same situation with their broken gears, and if there is a way to either remove it, or take out the gear from the top. I was hoping I wouldn’t have to remove the main drive shaft, but if there are clear steps to do so, I will. I’d prefer to not have to take a dremel to the gear to get it out (mostly because I don’t have one and don’t want to damage the machine!)
I have attached some images in the imgur link below, please let me know how I can help further clarify or if there are other steps I can do to keep this great machine running!
https://imgur.com/a/CdgmUY9
11-06-2023, 08:05 AM
#2
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Join Date: Apr 2020
Location: South of St Louis
Posts: 823
Welcome to the QuiltingBoard.
I have done the gears on a couple of T&S machines, there were always set screws; it looks to me from the close up of the top gear that there is no set screw in the hole pictured. I recall there are two set screws, if both look like the picture try tapping down from the top on the vertical shaft with a punch, see if the shaft moves down.
I have done the gears on a couple of T&S machines, there were always set screws; it looks to me from the close up of the top gear that there is no set screw in the hole pictured. I recall there are two set screws, if both look like the picture try tapping down from the top on the vertical shaft with a punch, see if the shaft moves down.
11-06-2023, 08:13 AM
#3
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Thread Starter
Join Date: Nov 2023
Posts: 4
Welcome to the QuiltingBoard.
I have done the gears on a couple of T&S machines, there were always set screws; it looks to me from the close up of the top gear that there is no set screw in the hole pictured. I recall there are two set screws, if both look like the picture try tapping down from the top on the vertical shaft with a punch, see if the shaft moves down.
I have done the gears on a couple of T&S machines, there were always set screws; it looks to me from the close up of the top gear that there is no set screw in the hole pictured. I recall there are two set screws, if both look like the picture try tapping down from the top on the vertical shaft with a punch, see if the shaft moves down.
Everything I have seen also shows 2 set screws! I’ve only seen the hole for the 1 set screw, and there are 2 of the “rivets” that I had pictured in the album. I’m wondering if a video showing all sides of the gear would help…
I actually have tried hammering down on the top and only ended up denting the shaft. I was worried I’d do more harm than good if I kept at it, as I want to fit a new gear on there if I can help it.
11-06-2023, 05:18 PM
#4
Super Member
Join Date: Mar 2016
Posts: 2,853
Try contacting Terry at TandT repair. He's the most knowledgeable person I know about Touch and Sew machines. He's in American Samoa, so there is a significant time difference.
bkay
bkay
11-07-2023, 08:39 PM
#5
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Thread Starter
Join Date: Nov 2023
Posts: 4
Try contacting Terry at TandT repair. He's the most knowledgeable person I know about Touch and Sew machines. He's in American Samoa, so there is a significant time difference.
bkay
bkay
Essentially, instead of a set screw for some models of the touch and sew, there is a rivet that is technically called a “roll pin”
You can find these frequently in engines, guns, and other machines parts. Makes sense for an old machine I suppose, sturdy parts (except for those pesky plastic gears!!)
You need a 3/32” roll pin punch, which is a pin that has a small half-ball or nipple that helps center the punch into the pin, and pushes it through the other side. I reluctantly bought one, but it was $5. Worth getting.
Now the gear is replaced, BUT I still am having trouble with sloppy gears. The new gear seems too tall and has a kind of crunchy movement with the main drive gear? I can’t figure out why, it almost seems too tall. No washer to be removed to make room.
Additionally, the main motor attaches to a gear on the manual spindle (can’t remember the name) and this seems sloppy as well. Causes the motor to work extra hard and I’m worried I’m going to fry the thing! Any further help on this?
11-08-2023, 09:45 AM
#7
Senior Member
Join Date: Apr 2020
Location: South of St Louis
Posts: 823
As to gear sloppiness, I would not assume that the part you ordered matches what was the original. I've seen rubber like gears, and plastic/nylon looking gears. I don't know if it's too late, but I would consider replacing all the gears with a new set.
The gears have to line up such that there is not too much tension or pressure on the teeth. I can't remember exactly how the vertical shaft adjusts, but I remember trying to lift the gear slightly before tightening to line it up. As to the motor, I think there is a flexible part in the hand wheel, where the worm gear on the motor syncs in, and this creates some "delay" when starting up. This is important because when you are ready to reset the timing you want to cycle the machine in the proper direction to take up all this slack before tightening gears, meaning don't turn it backwards at all in order to line up the needle bar marks.
The gears have to line up such that there is not too much tension or pressure on the teeth. I can't remember exactly how the vertical shaft adjusts, but I remember trying to lift the gear slightly before tightening to line it up. As to the motor, I think there is a flexible part in the hand wheel, where the worm gear on the motor syncs in, and this creates some "delay" when starting up. This is important because when you are ready to reset the timing you want to cycle the machine in the proper direction to take up all this slack before tightening gears, meaning don't turn it backwards at all in order to line up the needle bar marks.
11-08-2023, 01:08 PM
#8
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Thread Starter
Join Date: Nov 2023
Posts: 4
As to gear sloppiness, I would not assume that the part you ordered matches what was the original. I've seen rubber like gears, and plastic/nylon looking gears. I don't know if it's too late, but I would consider replacing all the gears with a new set.
The gears have to line up such that there is not too much tension or pressure on the teeth. I can't remember exactly how the vertical shaft adjusts, but I remember trying to lift the gear slightly before tightening to line it up. As to the motor, I think there is a flexible part in the hand wheel, where the worm gear on the motor syncs in, and this creates some "delay" when starting up. This is important because when you are ready to reset the timing you want to cycle the machine in the proper direction to take up all this slack before tightening gears, meaning don't turn it backwards at all in order to line up the needle bar marks.
The gears have to line up such that there is not too much tension or pressure on the teeth. I can't remember exactly how the vertical shaft adjusts, but I remember trying to lift the gear slightly before tightening to line it up. As to the motor, I think there is a flexible part in the hand wheel, where the worm gear on the motor syncs in, and this creates some "delay" when starting up. This is important because when you are ready to reset the timing you want to cycle the machine in the proper direction to take up all this slack before tightening gears, meaning don't turn it backwards at all in order to line up the needle bar marks.
These are awesome tips, and I’ve actually had some more discoveries before totally putting this to use. Good new is, hard part is over and I think replacing gears will be easier in the future, but bad news is the new gears just may be too large.
To your point, I think replacing gears is a solid start and I’ve ordered some to replace the bottom hook gears. These seem to be working properly, but they may break in the future anyway. The problem I found lies with the connection of the top gear I replaced (image of location found in the link above) and how it attaches to the main drive shaft gear (the clear one in the photo set). It almost seems too tall, causing the gears to almost “chunk” into the next position rather than smoothly rotation. There is no room to move the clear gear backwards towards the manual knob/worm gear side due to the other gears being stuck in place. Really tricky to sort out that one.
But you are totally right about the work gear having some “sloppiness” due to the spring-like connection to the manual knob. That helped, but there was sloppiness due to me removing the whole gear set earlier on when I considered removing the main drive shaft… ended up finding the set screw for the metal piece next to the worm gear connection that removed some of the unintentional slop happening. Now it’s just the chunkiness and grinding of this new gear. Very confusing
