Saturday, May 4, 2013

Tired of Tension ?

The 401/403/404 tension assemblies are a bit different from the 201/221/301.  The thumb nut on the 201 merely screws on to the tension stud.  On the 401 etc there are extra pieces.  Who knows why the engineers changed the design.  Boredom, maybe.

The 401 and 403 accept twin needles.   Twin needles require two spools of thread feeding through the tension assembly and thus, into each needle.  Hence, an additional disc is required for the added thread.  I don't know if the 404 can take a twin needle.  If not, Singer just used the same tension assembly as a cost effective measure.  (Maybe?)

Start by locating the set screw inside the face plate on the machine.  Loosen this.  It is not necessary to remove it. 
Once the set screw is loosened, the tension assembly should pull out.  If it doesn't, try twisting it as you pull.  It may be stuck with ages old dried oil.

Identify the small set screw in the knob
Loosen it. Don't remove it.  You might lose it and it is a teeny, weeny screw that might not be replaceable.
The inner collar can now be removed
And the knob will screw off ( Did I really type that?)
The numbered dial comes off next.  It is important to note the tab on the inside of the numbered dial.
Next remove the threaded nut.  It should just twist off.
The stop washer will likely fall off.  That's ok.  Don't lose it.

Take note of the position of the tension spring as you remove it.  The first coil should wind around the bottom prong of the stub
The indicator cup comes off next. I take the TRP (tension release pin ) out now too.  Otherwise it will fall out and is at risk of getting lost.  (AMHIK)
I mark the tension stud where the tail of the check spring sits.  This prevents me from having to adjust it afterward if, and only if, the original setting was good.  Usually it is.

Pull the check spring and the discs off of the tension stud.  I don't know why there was a washer in there as well.  It certainly is not OEM.
Now you can clean your parts and reassemble them.

Remember the tab on the inside of the numbered dial?  That must sit on the right side of the stop washer when you put it back on.

Replace the chrome collar and tighten the set screw and you are now ready to put the assembly back into the machine.
When you place the assembly into the machine be sure that the check spring sits above the notch on the thread guard.  Orient the -/+ as shown and tighten the set screw. 

Oh, not quite. When you test stitch your machine you may want to set the numbered dial so that your balanced stitch on test fabric (I use light weight cotton that has been starched a little) with white thread is at about 3 or 4.  To do so, loosen the set screw on the knob and turn it to the desired setting.  Tighten set screw.
June 10, 2014

In the photo below: 1 points to the end of the tension release pin.  When the presser foot is raised, the lever pushes on the end of the TRP and releases the tension on the tension discs. 


  1. just catching up on blog-reading,and enjoyed your tensioner posts. I finally got the nerve up to disassemble, clean and reassemble them within the past couple of months. feeling oh-so-empowered now, lol!

    great blog, keep it up please!
    Cheryl Warren

  2. Heed the advice of not losing the knob set screw. Done that. Never did find it.


  3. Thank you for the easy to understand tutorial with pictures. A Singer 404 is now in my collection.(What a great machine) The tension was set to 9 and sewed beautifully, but turning the knob at all it would fall off. With your help I had it adjusted and sewing beautifully again at a setting of 4 and the knob not falling off.

  4. Thanks for this. I don't need it this minute but I'm glad to know it's here. Tension scares me. I'm still laughing over this line: "And the knob will screw off ( Did I really type that?)". Honestly I had to read it a few times before I got it. BTW, I would guess that the 404 can't accept 2 needles, but maybe it's hiding something? Maybe if you put a zz plate on a 404 it can handle 2 needles? That would be so weird.

  5. I'm trying to figure out the behive spring, how long/thick/tall should it be? I think it had been set tight for sometime and lost its spring so to speak. Would stretching it out work?
    Also I have slop/play between the 3discs, should there be slop/play/wobble?

    1. The tension discs should be sloppy with the presser foot up but tight enough to put tension on the thread when the presser foot is down. I don't know if stretching it will work.

    2. If you can take a photo of the bee hive spring next to a ruler, I can compare it with one I have. Likely I have one that is not too compressed. Please email me directly. See address at top of page under Contact me.

    3. OH! Ok. Just put the foot down and the took care of the slop. Didn't know the foot did that. Lol now I'm curious how the foot position does that.
      I like learning/knowing how things do what they do.
      I'll get a picture to you after I test things, may be a couple days.
      Thanks for the fast response. Very much appreciated.
      One other thing would it be good practice to decrease the tension when not in use for extended periods?

    4. When the presser foot is up, the Tension release pin pushes in from behind to release the pressure. Open the side of the machine, raise the presser foot and watch what happens.

    5. See the photo I added at the end of the post.

  6. Thank you, Thank you, THANK YOU for posting this!! I was at my wits' end trying to fix my tension issues. Hours of cleaning and oiling and, at one point, the top tension knob popped off (as you point out above) and the manual wasn't helpful describing how to put this back to together. I was at the end of the line and DREADING lugging this lovely, beast of a machine into a repair shop until I gave it one more go and searched for a site to help with re-assembling this tension dial. Sorted and I now have lovely, perfectly straight stitches that don't pull the fabric. Saved probably at least £50 and learned a lot about my machine in the process. Many thanks for posting such an obscure topic with incredibly helpful photos! Liza

  7. I just received a 404 yesterday with this tension assembly! Too bad I didn't see this before spending an hour today adjusting. There was nothing wrong with the tension, I just thought the discs were backwards, because they didn't look like my other tension assemblies.

  8. I just received a 404 yesterday with this tension assembly! Too bad I didn't see this post before spending an hour today disassembling and reassembling and adjusting. There was nothing wrong with the tension, I just thought the discs were backwards, because they didn't look like my other tension assemblies. Thanks so much for your blog.

  9. Thank you - I followed your instructions and clear pictures. I now have a clean tension assembly. I just purchased the 401a last week. I don't think it had ever been cleaned. Now on to the next area to clean.

  10. I'm so glad I found this! However, I'm reassembling everything on my "new" 401 and I don't know how far to screw on the threaded nut that sits behind the number wheel.

  11. Thank you for posting this with such detailed photos. I was able to disassemble my tension assembly and for the first time since having this machine I am able to sew a nice long stitch. I just found your blog and really enjoyed reading about your vintage machines as well and love your references to cars of the same era.

  12. Thank you for all the info on your blog. I recently was gifted a 403a and have some issues with the tension assembly. It seems that the TRP is too short and doesn't reach the horizontal bar on the dial with the +/- symbols when presser foot is up and thus doesn't release the tension. Considering making a TRP like you did on another blog post but was wondering if you had any other insight. Thanks again!

    1. I can't think of any other solution.