Bottom Stitch Issues

[Yanni]

I think Wizcrafts has said it all.

We make leather bags here in England and the tension is something you set depending on thickness and hardness of leather.

You might have thin leathers but very dry so you need more tension for the needle to get back up etc.

As previously said on the post, most issues are generally related to top tension of the thread.

If too high and the stitch is filling the holes on the top side of leather, then reduce the tension until they disappear but make sure the stitch is not coming from off the back.

Also, make sure the bobbin spring is doing its job and the bottom thread is not too lose, check also tension on bobbin winder..

On older SInger/Seiko flat bed machines, there is a little metal pin behind the tension roller that usually gets stuck in one place and needs oiling or replacing.

This can also be a cause.

In our factory we've got a PFAFF 335 for closing backs(3-4 layers of 1.4-1.8mm leather) and another one for sewing around pockets(2 layers of leather) etc.

The one that is used for pockets has less tension than the one used for closing the bags.

We use 130 size needle as we sew mainly rucksacks. If I see missing stitches and tension problems on harder leather, usually a 140 needle cures that.

This is all UK sizes...we use Schmetz needles type S, although for a more decorative stitch I would use LR type.

Edited November 21, 2013 by Yanni

[Cobra Steve]

Hello. To me, this looks like a needle/thread problem. I see needle holes that appear to be larger than the kno,t which allows the knot to travel up and down in the hole looking like a tension problem. In the instruction book there is a needle and thread reference guide that will tell you what size thread and needle to use for different applications and thicknesses. It is not written in stone because there are so many variances in leather, but it is a good starting point. Also when back tacking, make sure that the needle comes up 1/4 to 3/8 of an inch before you start your back tack. If you are using 346 thread on top, then you cannot use 346 in the bobbin (you must use 1 size smaller), unless you are not back tacking. The reason for this is in every hole that the needle punches there are 4 strands of thread and 1 knot, when you back tack in the same holles then you have 8 strands of thread and 2 knots and all of that thread will not fit in the hole, so always remember to use 1 size smaller in the bobbin when using 346 thread on top. Steve

[ec2121]

thanks Steve... i change the top thread to 277 with a #25 needle and bottom 206 and really helped alot. i do notice that with thicker leather the stitches look better. i've been working with two pieces of 4oz leather...maybe my consew 2050 works best with thicker leather???