Singer 431G Length Stitch Lever Knob

In the past time, I saw several Singer 431G Slant-O-Matic sewing machines on auction sites missing Length stich lever knob. I have bought myself a such one, a friend of mine too. The same lever is on following Singer machines: 401, 402, 403, 404, 411, 412, 421, as well as on some later models). 

At first time I tried to identify thread of this knob and finger, than to make 3D models of missing parts. 

After my measurement, I got: 

• The knob has a length of 15,7mm and LEFT thread ¼"-28UNF
• The finger thickness is 1.1mm, and the same thread as above
• The washer, ID5, OD9.4mm and thickness of 1.25mm. NOTE: this washer is very important, otherwise you can't screw the front screw on the lever. The washer is sitting on the lever behind the knob. 
• The original front screw, with 4-40 thread and length of 3.3mm. A HDD screw may help here with added an extra washer, as my picture shows. 

3D models are sliced in PLA at 0.15mm layer height and than printed. I need to clean finger's thread, i.e. to get more pronounced ‘V’ shape, by help of a magnifying glass and a scalpel. When I screw it on the knob, I was surprised: it works very well. Put some vaseline or silicone grease on the threaded surfaces. When assembling all parts, remember that you are dealing with left knob thread!

I was very surprised and pleased with the result: it looks nice and works very well, without any intervention on the sewing machine. It is always easy to replace printed details, when you get original parts. Print time is short, with a very little amount of filament used. Print several set to have it as a spare parts. 

Other printed details and accessories for the same machine may be found here and here.