Is tension discs wear an issue?

[dikman]

Try using very fine wet and dry paper, used wet, on a piece of glass, you should be able to get them very smooth and then finish off with metal polish. Unless you have a buffing wheel, of course.

[Gymnast]

Well - now I tried the in the DIY way. I do not claim it to be right, but here is what I did. I do have some sandpaper from grit 60 down to grit 400. On the internet I have seen, that you actually can get sandpaper with grit 60000. I have got a drill, so I used that. And I have got some scouring cream. I needed to grind with the sandpaper grit 400 about 5 min to almost get off the previous marks. The result is not perfect - I know. But perhaps somewhat better than before and i think it should be more reliable. And when I measure the thread tension it seems in order.

Result after Work:

I made a Little video on how I use a spring dynamometer for thread tension etc. Do any of you use them? https://youtu.be/NW58ckOU6YI

[RockyAussie]

Checked out your video and well done. I did something a little similar with some fish scales and for the price they work great. I wanted to post some results with these as for people that are new to using sewing machines it could be used as way of setting some idea of the parameters a machine should have in regards to the tension adjustments. Here is a link to the scales I bought and am very happy with.  https://www.ebay.com.au/p/Wh-a05l-LCD-Portable-Digital-Electronic-Scale-10-45kg-10g-for-Fishing-Luggage/15020246737?iid=323005161210

I did a little on this subject in this following post that you may want to check - only good for giggle I guess.....

 

[dikman]

That looks a lot better than it was. You appear to have rounded off the flat part a little, but as long as it works ok is the main thing.

[Gymnast]

57 minutes ago, RockyAussie said:

Here is a link to the scales I bought and am very happy with.  https://www.ebay.com.au/p/Wh-a05l-LCD-Portable-Digital-Electronic-Scale-10-45kg-10g-for-Fishing-Luggage/15020246737?iid=323005161210

Thanks Again

This digital scale looks nifty. But will the minimum weights be in 10 g - NeXT 20 g ? I think you may like to measure the tension from bobbin case at some more accurate small figures. So perhaps a small scale more than this. Perhaps I should link to one supplier of dynamometers. I hope the link Works from another country.

https://www.ebay.com/sch/m.html?_ssn=alpinetopline&LH_PrefLoc=&_from=R40&_trksid=m570.l1313&_nkw=dynamometer&_sacat=0

[RockyAussie]

The scales gives the option to show Kilo's (0.000)and that is in 5gram jumps or pounds lbs (0.00) or oz (0.0) Jin (0.00) and all of these go up in individual units. Possibly on a domestic machine this may not give a fine enough reading but I would be surprised.

[Gymnast]

On ‎5‎/‎2‎/‎2019 at 8:55 AM, Gymnast said:

Well - now I tried the in the DIY way. I do not claim it to be right, but here is what I did.

Just for the record, I think the tension discs became worse after my treatment documented above. So do not repeat that. I compared these discs to two others I have got, that were not that bad. It seems to me, that the thread tension became unstable, and the static friction of the discs to the thread are considerable higher than the dynamic friction.

If you do not have the right tools for grinding and polishing these discs, I think you should replace them with new ones.

[DonInReno]

Your first pictures show marks that are normal from sanding grooves with sandpaper on a flat surface.  600 to 1000 grit paper on a flat surface will quickly take out slight grooving.  It shouldn’t matter if there are flats on the disks - flats don’t effect the consistency of tension, but any grooving is not good.  

I also don’t think a static friction test gives a person any usable information as long as the friction is consistent they are working just fine.  Tension adjustments should become second nature to even an occasional sewer.

[mikesc]

It shouldn’t matter if there are flats on the disks

All the disks that I've ever seen* , including brand new ones from different manufacturers and suppliers, have slight flats "out of the box"..

The reason would be , I presume , to spread the pressure from the "beehive" spring evenly..a flat allows for more adjustment than a round..a round would translate to two very small points of contact with the thread as it passed between the discs of the tension assembly, which would "pinch" it rather than exert tension by "drag" across a the surface of the flats..Force exerted and focused on two points is less adjustable than the same force adjusted over a greater area ( two areas ) as presented by flats..

Note..I don't pretend to have seen all tensions discs from all manufacturers or suppliers, so readily accept that they ( tension discs with no flats ) may exist, and may even be "the norm"..

[Gymnast]

On ‎5‎/‎26‎/‎2019 at 6:46 PM, DonInReno said:

Your first pictures show marks that are normal from sanding grooves with sandpaper on a flat surface.  600 to 1000 grit paper on a flat surface will quickly take out slight grooving.  It shouldn’t matter if there are flats on the disks - flats don’t effect the consistency of tension, but any grooving is not good.  

I got information from another source too, that the praksis of controlled sanding and not polishing is normal. The source called for paper of grit 1000 to 2000. The reason should be, that you want some friction from these discs, and it can be hard to achieve high and stable tension without some controlled roughness of the surfaces providing the friction. Some thread can be very smooth. I noticed three people in this thread with a praksis of polishing the discs. So this seems to vary.

The aim should be, to be able to keep as Little as possible variation in the tension. Due to small differences in the thread and friction internal in the tensioner, you do not have a perfect tensioner. If you look at the pictures above, the direction of the sanding and the Width of the flat area vary around the perimeter. The discs might move around and this could also make some variation in tension.