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Cleaning & Repair for Secure Thumb Screw Placement


NOTE:  This tutorial is for the Singer Featherweight 221 model in original black, white or tan.  It will work for the Featherweight 222 as well, but the throat plate on a 222 is made of steel, so this technique will rarely be necessary.

Products and Tools Referenced:

  1. Thumb Screw (Vintage)
  2. Thumb Screw (New)
  3. Throat / Needle Plate (Vintage)
  4. Throat / Needle Plate (New with Measuring Lines)
  5. Amoeba Embroidery & Darning Plate & Screw
  6. Buttonholer Feed Cover Plate & Screw
  7. Underbraider
  8. Featherweight Accurate Seam Guide
  9. Kerosene (Empty Oil Bottle works great for this)
  10. Drip Pan Tray
  11. Felt Drip Pad
  12. Presser Bar
  13. Presser Foot (Vintage)
  14. Presser Foot (New)
  15. Screw, Tap & Tool for Truing Mid-Bed Threads

There are many kinds and styles of Featherweight Attachments that can handle any number of sewing tasks.  To secure many of these attachments to the Featherweight, Singer machined two threaded holes directly into the bed of the sewing machine, just to the right side of the needle plate.  Attachments such as the amoeba-shaped embroidery & darning feed cover plate, buttonholer feed dog coverplate, underbraider, as well as new accessories like our ever-popular Featherweight Accurate Seam Guide are all secured to the bed of the machine via a thumb screw and one of these threaded holes.

Sometimes, there can be some difficulty in the process of securing an attachment or accessory by way of the thumb screw.  When a screw will not screw all the way down into the bed of the machine, one can quickly troubleshoot the thread holes by using the vintage original thumb screw used for the presser foot (the one originally supplied with the Singer Featherweight).  The presser foot screw and thumb screw for the mid-bed holes are meant to be interchangeable for size and thread pitch.  Most of the time the vintage original Singer Presser Foot Thumb Screw will turn down easily when screwed into the mid-bed holes, but occasionally, the screw will get stuck and not screw down all the way to the bed surface.

This can happen for a few reasons:

  1. Crystallized or varnished oil down inside the threads

  2. Threads that were not properly threaded at the time of manufacture or damaged from a wrong screw being used in the past

  3. Improper masking during a repainting process, causing paint to build up in the holes

The threads can easily be cleaned using a few drops of kerosene in the holes.  This will help soften any old oils or varnish build-up.  The holes are open all the way to the bottom underside of the machine, so any excess kerosene, oil and grime will be collected on the felt drip pad.  Gently thread the Featherweight thumb screw back into the hole, back and forth.  Usually, after a couple of kerosene applications, this will completely clean any old residue.

If after several attempts to clean out those holes, the screw still resists being screwed down any further, then it may be that the threads were not properly threaded at the time of manufacture or perhaps even damaged from a wrong screw being used in the past.  To remedy this, the holes will need to be re-threaded back to their original design.  To tap or "re-true" the threads in these holes, then the Singer Featherweight Tap Screw & Tool will return the mid-bed screw holes to proper and easy functionality.

The machining world has, what feels like, an innumerable count of different screw thread pitches.  For the Singer Featherweight and many other Singer models, Singer Manufacturing used a fairly unique thread pitch - one that cannot be sourced very easily.  Although, that has not stopped the handyman and / or helpful-husband in trying to help by using a common screw from the local hardware store.  "If it looks like it would be a close fit, it should work, right?"  Unfortunately, no.   

The Featherweight, being made of cast aluminum, is comprised of a relatively soft metal, and common hardware screws forced into the thumb screw holes can actually damage the machine.  But, hold on for the good news!  With the Featherweight Tap Screw & Tool, the thumb screw holes can now be tapped easily!  The new Singer Featherweight Tap Screw has the exact thread pitch and angle as the holes Singer originally designed.  It also has a cutting edge to make sure that the threads are tapped properly.  If the threads on a Singer Featherweight are in good shape, then the tap will simply follow the threads down with little to no resistance.  However, if the threads are not fully formed in manufacturing or even damaged, the tap will restore the threads to an original smooth pitch.


To do this, simply start the tap into the bed hole like you would any screw and when resistance is felt, place the allen wrench (which works like a handle) into the screw head, and gently but firmly screw the tap all the way into the hole.  Be sure the tap is not angled or offset.  It needs to be straight up and down.  The Singer Featherweight Tap Screw cuts and cleans away any crossed or damaged threads, any crystallized oil or varnish and restores the correct thread pitch with each turn downward. 


As soon as the tap is all the way down, back it out of the hole and clean the hole and the tap with a little bit of kerosene.  

 The Featherweight thumb screw should now easily turn down to the bed surface for a secure fit of any attachment or accessory.



But, what if is the screw that came with the attachment is actually the damaged part?  You can test this by removing the presser foot thumb screw again and reversing the troubleshooting process.  Very gently, try threading your attachment screw into the presser bar.  As indicated before, the mid-bed screw hole and the presser bar hole are designed to have the exact same pitch.  If the screw does not easily and smoothly turn in the presser bar hole, then the screw should probably be replaced.  

If you have any additional questions on repairing the mid-bed threaded holes on the Singer Featherweight, feel free to contact us.