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mxk

Tips for adjusting bobbin thread tension

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Just playing with my Singer 401A and I'm having a bit of trouble finding the right setting for the bottom thread tension. I understand that the goal is to sew with the lowest tension that still gives you a good stitch. Am I correct in assuming that a good stitch, among other things, is one where you cannot tell the top side from the bottom?

I don't have any problems adjusting the top thread tension so that the stitch locks in the middle of the material. However, I can easily tell the two sides apart because the bottom thread has a noticeable S pattern to it, while the top is completely straight. This seems to indicate that the bottom tension is insufficient, but the pattern remains even when I tighten the bobbin spring to the point where it feels too tight. At this setting I can easily lift the bobbin case by the thread and bounce it up and down without the case dropping at all.

I've attached photos of what my top and bottom stitches look like with the loose and tight bobbin thread tension. I'm using E thread with size 18 needle, the material is two layers of 1000 denier cordura. Would appreciate any tips you may have on proper tension adjustment.

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My first impression of your question + pictures: any of those is acceptable, so you're just doing some very fine tuning here. It's good that you care enough to be picky.

I prefer "medium-tight" top and bottom with cordura. That's my own description and I realize there's no easy way to get that tension feeling across over the net :-p. Maybe if I were adjusting the settings, top and bottom would be backed off just a smidge from your tight top and bottom pics.

Also for e thread with most any materials I prefer 20-21 needle sizes. Bigger holes seem to disturb the fabric less during stitching.

Another consideration when adjust thread tensions is how much it changes the dimensioms of your parts. You'll always get some shrinking effect along a seam line because of the top and bottom thread pulling at the insertion points. In some projects that shrinking matters more than others. You can't really tell how much effect is happening until you make about an 8" or longer seam and look at the whole picture, or measure it before/after. The tigher the tensions, the more bunching and shrinking will occur.

Chris

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I have always referred to the article below when adjusting tension on the bobbin. Seems to always give me a good starting point.

http://usapr.com/files/Posts/1/bobbins.pdf

Your top and bottom tension look good, it also depends on material thickness. Since your sewing with two layers of 1000 denier corder, you may always be able to "see" either the top or bottom threads on the opposite side. Ultimately you would want both the top thread and bottom thread to meet in the middle and not be visible, but material thickness plays a great part in that.

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Since we're on the subject of tension (sorry...don't mean to highjack this) but I have issues with my machine in reverse only. It goes very tight on the top pulling the thread thru the material. Otherwise I feel I have the rest of the machine dialed.
my pics & stuff!

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Since we're on the subject of tension (sorry...don't mean to highjack this) but I have issues with my machine in reverse only. It goes very tight on the top pulling the thread thru the material. Otherwise I feel I have the rest of the machine dialed.



What machine specifically? I've owned 2x 20u's (and -33 and -73, blue and green respectively) and I've had that issue with both machines. Timing the hook with the needle bar in the furthest position to the left takes care of that, but on All machines I have worked with that have a reverse, the stitch characteristics differ slightly in forward and reverse. For that reason, I use reverse only to lock the stitch, and not for general use.
=========Shaun ==========


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Thanks to everyone for your suggestions. I did try the hemostat and a bunch of other tricks that I found online. The problem with them is that there was still significant variation between the resulting tension settings (what is a small hemostat, what is the weight difference between my bobbin case and the smaller vertical ones with a plastic bobbin, etc.). That's why I was trying to judge the tension purely based on the resulting stitch.

The one thing I didn't try was a bigger needle size. Unfortunately, the 401A wasn't designed to handle anything bigger than size 18. I was able to sew with a 19 needle, but it was scraping the throat plate just a bit. Even so, the resulting stitch was noticeably better, with the top and bottom almost identical.

I have the service manual with the instructions for centering the needle, so I'm going to try making some adjustments for the machine to work with bigger needles. I suspect that 19 will be the limit anyway due to the clearances between the hook, needle, and position finger, but we'll see.

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Unstable


What machine specifically? I've owned 2x 20u's (and -33 and -73, blue and green respectively) and I've had that issue with both machines. Timing the hook with the needle bar in the furthest position to the left takes care of that, but on All machines I have worked with that have a reverse, the stitch characteristics differ slightly in forward and reverse. For that reason, I use reverse only to lock the stitch, and not for general use.



I have the same issue with my 20U -73. I think it's just one of the limitations of their design. I believe that timing it the way you describe works well except that it will then start dropping stitches on the widest zig-jag pattern. That's what mine dues but fortunately I don't need a lot of super-wide zigzags.

Back on the original topic and to back up what others have said, there is a "range" of adjustment that will produce an acceptable stitch. While i find the hemostat trick gives an idea for the inexperienced, you soon get a "feel" for what the bottom tension should be and adjust as needed for the material you're sewing.

-Michael

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Hey, I actually just stumbled on this thread while searching for bobbin tension suggestions for my singer 401A! I am doing some sewing for the first time in years on a used jumpsuit I just bought.

The lady at the sewing store suggested "Topstitch" Needles. The eye is slightly larger, allowing for the nylon thread I'm using to work in this home, non-industrial machine.

I still haven't gotten my tension right, I've got the top thread tension all the way up, so, I'm working on the bobbin, but it's close

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I still haven't gotten my tension right, I've got the top thread tension all the way up, so, I'm working on the bobbin, but it's close



The golden rule for tension is this:

1.Always start with the bobbin tension first.

2.The bobbin tension should be as loose as possible, This means you should only fell slight (..and I mean slight tension) when pulling the thread with the bobbin case out of the machine. When you install the bobbin case into the machine,the tension will increase somewhat. The direction of the bobbin being unwound makes a hugh difference also. Make sure it is rotating correctly when pulling the thread.

3.You adjust the top thread to balance the two.

4.If you cannot balance the top thread, add tension to the bobbin. Then and only then.


MEL
Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

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masterrigger1

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I still haven't gotten my tension right, I've got the top thread tension all the way up, so, I'm working on the bobbin, but it's close



The golden rule for tension is this:

1.Always start with the bobbin tension first.

2.The bobbin tension should be as loose as possible, This means you should only fell slight (..and I mean slight tension) when pulling the thread with the bobbin case out of the machine. When you install the bobbin case into the machine,the tension will increase somewhat. The direction of the bobbin being unwound makes a hugh difference also. Make sure it is rotating correctly when pulling the thread.

3.You adjust the top thread to balance the two.

4.If you cannot balance the top thread, add tension to the bobbin. Then and only then.


MEL




All good advice in general, but with 401 you don't take the bobbin case out of the machine to adjust the tension. Just thread it through and under the spring and adjust the screw in the spring for slight tension.
Always remember the brave children who died defending your right to bear arms. Freedom is not free.

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All good advice in general, but with 401 you don't take the bobbin case out of the machine to adjust the tension. Just thread it through and under the spring and adjust the screw in the spring for slight tension.



That is correct, it has a drop-in bobbin. I failed to mention that, but other than the non-separable bobbin case, everything else is still applicable.

As previously posted before on these forums, the 401A was my first zig-zag sewing machine that I ever had. I kept it in the loft until about 2-3 years ago. I finally gave it back to my Ex-wife (it was previously her Grandmother's machine). It was a great machine that would sew through 4 layers of type IV with no problem.


MEL
Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

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As previously posted before on these forums, the 401A was my first zig-zag sewing machine that I ever had. I kept it in the loft until about 2-3 years ago. I finally gave it back to my Ex-wife (it was previously her Grandmother's machine). It was a great machine that would sew through 4 layers of type IV with no problem.




Not only that, 401s are just plain cool. I was refurbishing them and selling them on ebay a couple years ago. They are the most advanced domestic machine Singer ever made. They are precise and intricate and a pleasure to work on. I still have about 5 of them waiting for me to get around to shining them up.
Always remember the brave children who died defending your right to bear arms. Freedom is not free.

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Deimian

What about the 801-z2? For some reason I just get results in Spanish when I look it up in google, but maybe somebody is familiar with it. Is it any good for simple work like tubes?




I just Googled it. I've never heard of it, but it's likely a Spanish or Italian market and made version. It looks a lot like a 237, but it takes 66 class bobbins and uses 401 style cams for patterns. If it has metal gears driving the shafts it's likely a robust machine and good for what you are talking about. But if it has nylon gears, they will be old and hard by now and easily broken.
Always remember the brave children who died defending your right to bear arms. Freedom is not free.

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Sorry...just now seeing this. I have a Brother TZ1-B652 zig-zag. I still have the issues of reverse but after reading some of this I might be putting the bobbin in backwards...gotta try that one. But any other opinions?

Regarding just not using it unless needed...putting a BOC on an infinity....it would be friggin great to run a whole stretch backwards. Kelly was showing me this. I tried it but man the tension sucked and had to unpick all of it. It can be bitch getting the whole container in the machine.
my pics & stuff!

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gowlerk

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As previously posted before on these forums, the 401A was my first zig-zag sewing machine that I ever had. I kept it in the loft until about 2-3 years ago. I finally gave it back to my Ex-wife (it was previously her Grandmother's machine). It was a great machine that would sew through 4 layers of type IV with no problem.



Not only that, 401s are just plain cool. I was refurbishing them and selling them on ebay a couple years ago. They are the most advanced domestic machine Singer ever made. They are precise and intricate and a pleasure to work on. I still have about 5 of them waiting for me to get around to shining them up.



Do you have a recommendation for what type of lubricant to use for the metal gears and the motor worm gear? The Singer lubricant that's still available seems pretty low quality.

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The Singer lubricant reminds me of Vasoline. The machine collector people generally recommend "TriFlow Clear Synthetic Grease" on the bevel gears, but a small amount of any light grease will do. I think the manual says to just oil them regularly. The worm gear I'm afraid of. Not the worm gear itself, but the phoneletic gear on the hand wheel that it drives. It's a potential weak point as is the anti-backlash spring inside the handwheel assembly. If either of these break the only source is a donor machine. Just use a light amount of tri-flow. There is a sealed ball bearing at the top of the motor where the output shaft exits. These often go dry and sometimes need to be replaced. But usually you can drip a tiny amount of oil onto them from up top and that will renew the grease inside and save them.

Sometimes the motors need new brushes. You can split the case and remove the armature to polish the commutator. I have the service manual with instructions somewhere, but no time to look right now. If the motor seems to operate and drive the machine, just oil that bearing, very lightly. The biggest mistake people make is trying to oil the motor itself. That always ends badly and the motor then needs to be overhauled. The motor does not want any oil or grease inside of it, and it is downhill from that worm gear. So don't overdo the lubricant there.
Always remember the brave children who died defending your right to bear arms. Freedom is not free.

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