Sunday, September 07, 2014

Singer 401/403/404 Tension Adjustment

Today I dug out a Singer 403 that I haven't used in a long time (maybe never).

I'm not sure I ever serviced this machine when I got it because there's some tape residue on the vertical pillar that I would've cleaned off if I had ever cleaned and oiled The machine.

As I was sewing on my project, I noticed suddenly I was getting loops on the underside of the fabric. It had me stumped for a minute until I saw that my upper tension dial was at zero. The tension knob was so loose that just the slightest bump moved it from its desired setting.

As I was getting ready to correct that situation, it occurred to me that maybe some others would like to know how that's done so I got the camera out and took some pictures of the process.

  There are many styles of tension assemblies, this is the one used on the Singer 400 series. Once you get the external knob off, you find that all upper tension assemblies are very similar inside.

Here is a clip from the service manual telling how to disassemble the 401/403 tension assembly.  To merely tighten the knob, you only need to perform these two steps.

After the thumb nut L5 is removed and the split stud is exposed, insert the blade of a flat screwdriver in between the two halves of the split stud Q2 and spread the two halves slightly apart. That will tighten up the thumb nut L5 when you screw it back on.

If you get the stud halves spread too far apart and the thumb nut L5 will not go back on, squeeze the stud halves back together a bit with pliers and try again until you get it where you want it.

 I had previously noticed that the +|- indicator was skewed off to one side so while I had the tension assembly open, I thought I would fix that also.

There is a set screw inside the nose door that holds the entire upper tension assembly in the machine. Loosen that set screw and you can turn the assembly to any position you desire. When you have it where you want it, tighten that setscrew and you're ready to reassemble.

Assembly is the reverse of disassembly.

After the tension assembly is reassembled, you want to adjust the tension so that you have a good balanced stitch with no regard to the numbered dial.

Once you have a good stitch, push in the numbered disc D5 and rotate so that the number 4 appears at the top of the dial at the +|- indicator. Release the numbered disc and make sure the pin C5 is seated in one of the holes in D5 and you're done.



Anonymous said...

Hi Ed,

I just recently found your blog and it's a wealth of information.

I'm wondering if you can help me. Recently, the original rubber belt on my Brothers Alt-Omatic sewing machine broke and was replaced by a lug belt (per store employee) instead of the rubber belt I had on this vintage machine.

After about 3-4 hours of sewing, machine wheel completely locked up. Do you think it's possible that the machine locked up because the lug belt replacement?

This machine has been used throughout the family for the past 42 years without any major issues.

Also, any tips for unlocking the wheel at this point?

Thanks much!


Jonathan said...

I have a Singer 401 and a 500 but I've always wanted a 403. I would buy one a in a heartbeat if I found one locally that was reasonably priced in good cosmetic condition.

Rawyah said...

Thank you so much for this information.

Anonymous said...

Hi, can you help me out? I have the 404 model and the bobbin section keeps tangling. It would start off with beautiful tight stitches, then start to make a clicking noise, and ultimately tangles. I also noticed the tension disk isn't working and is a bit rusty. Do you have any advice on how I can fix these issues or buy replacement parts? Thank you in advance! My email is marcellalharris[@]yahoo[dot]com...there are too many spammers.

Kind regards,

never mind said...

Excellent information, thanks for sharing.
I am trying to tighten the tension stud on my Singer 317 but I don' t see the screw that is visible in the above picture,the one with the red arrow....Any ideas where I can find this screw on a Singer 317 ? Thanks

Betty said...

Thank you for this info. I just got a 404 and someone had reassembled the tension mechanism incorrectly. I was able to put it back in the correct order thanks to a YouTube video, but still had issues. Nothing was mentioned about the set screw inside the machine. I loosened that and followed your instructions for reassembly, tightened the set screw and now I am getting a good stitch.

Unknown said...

I want you to know that this post solved a problem that I had been having for over a year, even after taking it to a repair shop and telling them that I had tension problems. I was thinking of chunking this machine and sewing with something different. I am SO glad that I found this because I really do love my 403. I really really really appreciate you! Thank you so much.

Maria Akpoduado said...

Amazing post! I had been battling with my singer 7110 which had tension issue for weeks. The tension dial just wouldn't fit until I applied your solution to widen the screw and that corrected the problem. Thank you so much!

Anonymous said...

I bought a Singer 403a off of craigslist about 2 months ago, it started out sewing fine the I started to get bird's nests on the bottom. Knowing that upper tension controlled this,I adjusted the tension to avail. After finding this column on how to disassemble, clean and assemble the tensioner, it is working beautifully again. Thank you and keep up the great work.