Singer 7-33 Stitching problem & parts

[hackish]

I bought a 7-33. It's actually for stitching harness webbing. As soon as I try to stitch heavy material it will randomly skip stitches or make giant loops of top thread on the top of the material. This happens even when slowly hand-wheeling it and the bottom thread is not pulled into the material when it happens. I've never seen this sort of problem before.

I replaced the hook with a real singer one and adjusted the spacing so it barely touches the needle - reduced but didn't eliminate the skipped stitches.

I think the problem is in tension. Since parts are hard to come by I've started machining a few new parts to try and correct the problem. Although helpful the only supplier I've been talking to is really hard to buy from. I've probably spent 4h trying to get through on the phone to give a visa number!

The original upper tension assembly was bent to hell and the sewing thread was catching the metal threads slightly so I made a new one using a junk chinese mill. I'm not proud of the result but it's serviceable.

Thread is 348 weight using an organ #27 needle. Needle size and thread are well established standards for sewing this material as is the machine.

The timing is not adjustable and there is nothing to indicate it's grossly out. I've played with a lot of needle bar height settings without making any progress. Any insight into what else I should be looking at?

-Michael

 

[Constabulary]

I don´t know the Class 7 machines but can you try to adjust the needle bar hight or is the needle bar pinned? I would guess you have to lover the needle bar a little bit.

[CowboyBob]

You might need to adjust the hook closer to the needle,there's a large screw underneath to loosen ,you want it as close as you can get w/o touching the needle.

[hackish]

1 hour ago, Constabulary said:

I don´t know the Class 7 machines but can you try to adjust the needle bar hight or is the needle bar pinned? I would guess you have to lover the needle bar a little bit.

As mentioned, I've adjusted the needle bar height a number of times but with little difference.

13 minutes ago, CowboyBob said:

You might need to adjust the hook closer to the needle,there's a large screw underneath to loosen ,you want it as close as you can get w/o touching the needle.

Just spent the last 2 hours playing with the hook distance. Too close and the top thread gets cut, too far and the loop gets missed.

This is the top layer and I can see no reason why the big loop is occurring - it doesn't coincide with a start/stop or anything I can see. You can also see a few where the tension is not quite optimal but the stitch is still well formed.

 

This is the bottom of the same piece. Again, the tension here is OK and teh stitches are formed somewhere near the center of the sample.

On these there is still a tiny bit of thread nicking so I may try backing the hook off by maybe 0.010".

Next step, maybe I will grab my gopro from work and see if I can record the shuttle to see if there is anything catching or jamming.

-Michael

[Gregg From Keystone Sewing]

3 hours ago, hackish said:

 

 

 

-Michael

 

Sweet, that's a nice job on the upper tension stud for sure.  If you can do it yourself, your ahead of the game for sure.

[TinkerTailor]

Just a thought, are you sure the bobbin is turning the right direction? And there is no thread in there hanging the bobbin up?  I have had a similar problem due to this, flipping the bobbin around fixed it. Worth a try.

[hackish]

22 minutes ago, TinkerTailor said:

Just a thought, are you sure the bobbin is turning the right direction? And there is no thread in there hanging the bobbin up?  I have had a similar problem due to this, flipping the bobbin around fixed it. Worth a try.

I'm used to bobbins that turn in the reverse direction but I followed the manual which shows it coming off the top of the bobbin and to the carrier. Pretty sure this is correct...

[Gregg From Keystone Sewing]

On 10/6/2016 at 8:39 AM, hackish said:

 

20 hours ago, hackish said:

I'm used to bobbins that turn in the reverse direction but I followed the manual which shows it coming off the top of the bobbin and to the carrier. Pretty sure this is correct...

 

-Michael

 

Here's an image from Seiko's owners manual showing how to insert a wound bobbin into the bobbin case.

Edited October 7, 2016 by Gregg From Keystone Sewing

[hackish]

Oh so much fun! Have a look at this one from the Singer manual.

I wonder which is better? I can play around a little with it reversed and see what happens.

[CowboyBob]

The Seiko way will keep the thread in the tension better.BUT either way doesn't make a difference in the way it sews(won't stop it from skipping) You might want to try alittle more foot pressure.

[hackish]

I tried more and less pressure on the foot. No difference. I re-adjusted everything including the hook. This time I dropped the needle bar so the eye of the needle is far below the 1/32" the manual says - more like 1/8" below the hook tip. It's not dropping stitches anymore but the loops forming on the top are more pronounced now. It seems to me that it could be related to bottom tension but it's like a loop of loose thread is forming on the bottom and then is being pulled through the material by a "kink" in the thread as the needle rises.

 

I need a transparent sewing machine so I can see what's happening while it sews!

[Yetibelle]

Here are my .0002 cents. 

First that stich-per-inch looks a little tight for Size 27 needle and 346 thread.  See if you can max out the stich-per-inch (I think it is like 5) then try it.  Also sometimes the needle gets a little bent, you can't see it with the eye, so swap out the needle for a new one.  If that does not help....then.  Try a smaller needle like a 22- maybe some smaller thread like 277 and 207?  Try the 277 on top and the 207 on the bottom again with the longer stich.  Then test that out on the lighter material and see if that stops the skipping.  I typically find skipping is a bad needle, or your pulling or pushing the material and the needle ever so slightly misses the hook. 

Also send over a pic of how your threading the top town, and the head of the machine. 

Its not that far off

[hackish]

The harness that I'm sewing specifies that many SPI as well as the thread and needle type. These machines are industry standard as is the needle size. It has to be sewn to spec. I've tried changing the needle.

 

You can more or less see the thread path. The thread goes all the way around the lower tension disc before exiting through the spring.

[Yetibelle]

Yeah nothing looks obvious from that, looks like a great machine.  I understand the specs your trying to get.  I was just wondering if going slightly smaller made and difference?  Could be a loose screw on the feed dogs assembly, causing some play left or right?  I had that, when I used a bolt down there that was not standard it didn't pull right untill I had it all correctly tighten down.  

 

[hackish]

There is a good amount of right/left play in the feed dogs but I haven't figured out how to tighten it. The shaft is in there firmly but I think the only way to tighten up the feed is to shim it since the assembly that holds it is cast. Although not ideal, I'm not feeling like that is the issue because I can feed it smoothly. It has to be something in the tension. Any suggestions on how much tension to use for the bottom?

[Evo160K]

50 minutes ago, hackish said:

There is a good amount of right/left play in the feed dogs but I haven't figured out how to tighten it. The shaft is in there firmly but I think the only way to tighten up the feed is to shim it since the assembly that holds it is cast. Although not ideal, I'm not feeling like that is the issue because I can feed it smoothly. It has to be something in the tension. Any suggestions on how much tension to use for the bottom?

Coincidently my 45K53 had the same problem recently with the feed dog screw, it wouldn't tighten down enough on the feed dog, letting it drop.   The mechanic who's helping me restore the machine put a small, copper shim in behind the feed dog screw, the copper, of course, crushed and held the dog and screw tight.  He said there were singers that he maintained for his employer that used small, serrated, copper washers; I don't remember if he mentioned where they were used. Others may know.

Hackish, does the shuttle cylinder tension spring in the picture above look a bit rough or distorted?  If so, could it be snagging the needle thread occasionally as it comes around creating an issue or perhaps interfering with the bobbin thread in some way?

Edited October 8, 2016 by Evo160K

[Constabulary]

How it the thread coming off the thread spool? Is it a X-wound cone of straight wound spool? Sometime thread keeps hanging when the thread is not coming off the spool properly . The thread guide arm of the thread stand should be straight above the spool. I´d also leave out the wax pot when you do not sew with waxed / oiled thread. At least worth giving it a try.

[TinkerTailor]

Is the thread snapped into the second tensioner? It looks like it may be riding around the outside. Give it a firm tug and make sure it is all the way between the discs.

Second, the thread  looks a little tighter coming out of the thread lube pot than it is going in, its it catching up in there? What happens if you sew without the lube pot in the path, does it still act up?

[hackish]

6 hours ago, TinkerTailor said:

Is the thread snapped into the second tensioner? It looks like it may be riding around the outside. Give it a firm tug and make sure it is all the way between the discs.

Second, the thread  looks a little tighter coming out of the thread lube pot than it is going in, its it catching up in there? What happens if you sew without the lube pot in the path, does it still act up?

Don't quite understand what you mean about the second tensioner. It's wrapped all the way around the tension disc to make sure it doesn't slip. The manual was printed in 1918. That was before nylon was invented so I expect old cotton thread only needed a single loop.

The lube pot does add some tension to it but it's consistent. I expect that would be at most a tiny change while the problems I'm having are not tweaks to stitch quality, they're major problems. The thread is coated (resin perhaps) and that's what the white flaky stuff is - I could omit the pot.

18 hours ago, Evo160K said:

Coincidently my 45K53 had the same problem recently with the feed dog screw, it wouldn't tighten down enough on the feed dog, letting it drop.   The mechanic who's helping me restore the machine put a small, copper shim in behind the feed dog screw, the copper, of course, crushed and held the dog and screw tight.  He said there were singers that he maintained for his employer that used small, serrated, copper washers; I don't remember if he mentioned where they were used. Others may know.

Hackish, does the shuttle cylinder tension spring in the picture above look a bit rough or distorted?  If so, could it be snagging the needle thread occasionally as it comes around creating an issue or perhaps interfering with the bobbin thread in some way?

I can try shimming it. It would be nice to eliminate slop, but the feed dogs fit so well in the needle plate that the slop is only there when I've taken the plate off.

The shuttle tension spring is not really rough but I feel like its related to the problem because it is limited on the amount of tension it can apply. I'm not sure how much is necessary when sewing such thick material. I might spend a few more hours this evening to see if I can make any headway.

[Evo160K]

The shuttle tension spring is not really rough but I feel like its related to the problem because it is limited on the amount of tension it can apply.  Hackish it looks like the spring has been bent down to try to create more tension on the thread.  If so, that may be because a groove has been worn into the shuttle underneath the spring?  I salvaged one of my shuttles by having a welder fill in that groove with a spot of weld......smoothed it down with a dremel tool....worked fine after that.

I'm not sure how much is necessary when sewing such thick material.  Aren't the needle and bobbin threads supposed to cross in the center of the goods, is that the case for the 7-33?

 

[hackish]

3 hours ago, Evo160K said:

The shuttle tension spring is not really rough but I feel like its related to the problem because it is limited on the amount of tension it can apply.  Hackish it looks like the spring has been bent down to try to create more tension on the thread.  If so, that may be because a groove has been worn into the shuttle underneath the spring?  I salvaged one of my shuttles by having a welder fill in that groove with a spot of weld......smoothed it down with a dremel tool....worked fine after that.

I'm not sure how much is necessary when sewing such thick material.  Aren't the needle and bobbin threads supposed to cross in the center of the goods, is that the case for the 7-33?

The shuttle is not worn. It's a 50 year old new part that was never used.

The threads are supposed to cross in the middle of the material but it's going to be a ratio between top and bottom tension. At this point I'm feeling like I should just return the machine to the seller and go buy a consew 7-33 or something like that instead.

[Constabulary]

You say the thread is resin coated. I have not worked with this type of thread but maybe it needs a certain lubrication. To eliminate a thread issue I´d try an uncoated polyester thread instead just to make sure that THIS spool of thread is not causing the issues. I know you have to use this thread because of certain specs but maybe you have just a spool of poor thread. Sewing machines sometime act different with certain threads.

F.I. I wanted to use a pure cotton threads on my DVSG / BUSMC #6 and by the lord it did not form a loop and I have no clue why. I tried different tensions and needles but no change. Then switched to a Polyester thread and it sews like a dream right away. I still want to use the cotton thread but cannot see where the problem is. Sounds stupid but thats how it is.

When your machine came from a dealer tell him to setup the machine for the material and thread you want to use.

Edited October 9, 2016 by Constabulary

[hackish]

5 hours ago, Constabulary said:

You say the thread is resin coated. I have not worked with this type of thread but maybe it needs a certain lubrication. To eliminate a thread issue I´d try an uncoated polyester thread instead just to make sure that THIS spool of thread is not causing the issues. I know you have to use this thread because of certain specs but maybe you have just a spool of poor thread. Sewing machines sometime act different with certain threads.

F.I. I wanted to use a pure cotton threads on my DVSG / BUSMC #6 and by the lord it did not form a loop and I have no clue why. I tried different tensions and needles but no change. Then switched to a Polyester thread and it sews like a dream right away. I still want to use the cotton thread but cannot see where the problem is. Sounds stupid but thats how it is.

When your machine came from a dealer tell him to setup the machine for the material and thread you want to use.

The thread is not the issue. I've tried 3 different cones of it and it's the identical brand and type the factory uses on the identical machine. I have fixed the skipped stitch issue, it's just the mystery loops forming on the top of the seam now.

 

[mikesc]

Any chance that you have a speck of dirt inside of the spring tensioner ( the barrel part that it sits in ) or even in the spring coil, that would make it stick just ever so slightly from time to time and give a "loop"..had that problem with a totaly different machine, was driving me nuts until I thought strip and clean it and maybe inspiration will come to me whilst I do that, there was the tiniest amount of dirt on a cotton bud when I cleaned it, put it back together and its sewed perfectly from then on..then again maybe I just let the gremlin out when I stripped it.

Edited October 9, 2016 by mikesc

[Singermania]

When these type of problems occur its a good idea to swap the thread for a completely different brand or type, replace the needle.   Some machines simply don't like some threads.   Also both of your top tension units are wound up tight, I'd back them right off and try again.   Overtight on top will drop stitches.