Sailrite ultrafeed LSZ-1 stitches come with different tension.

[climent]

Hi

Got a second hand LSZ-1 and the tension on the tension disks seems to be coming and going. As one can see in the attached picture, if I increase the tension all the stitches come similar, bit when I lower it there are some stitches that are deep and some that show the lower thread on the upper surface.

Any hints?

[Wizcrafts]

I would remove and clean/polish the tension disks. Then inspect the bobbin tension spring for a thread fragment. Also check the bobbin to ensure that it doesn't have a thread stub sticking out, or windings crossing over other windings. Check the thread cone for cross-windings, or knotting along the path to the needle. Clean/replace the needle.

[kgg]

Any chance of adding a couple of photo's of the thread path from the thread spool to the tip of the needle as well as the size of needle and thread you are using. Do as Wiz has suggested and check the way you are inserting the bobbin in the bobbin case. If it is inserted incorrectly you can get inconsistent bobbin tension issues.

kgg

[Northmount]

Needle holes look pretty big.  As kgg says, need needle and thread information.

Tom

[Gymnast]

Many issues can cause this to happen as already suggested above. And it might not be just one of them. The machine have got no pretensioner and therefore one issue more is thread twisting problems forming kinks or unstables position of thread to tensioner. I have seens the same problems as you several times, and my good help was the use of dynamometers to measure the upper and lover thread tension. It narrows down where to look for the problem without a lot of test sewing. I like spring dynamometers best:

[Gymnast]

When you have got a Sailrite Ultrafeed LSZ-1, then I like you to read the thread below as well regarding class 15 shuttles. If you have got one shuttle hook with edged thread U-turn and one with smooth U-turn, then you could verify this issue better than me. But from from a theoretical point of view: High friction at this thread U-turn can make very high tensions in the upper thread, that might alter the lock position of the previous stitch. So in this way this tension from hook shuttle can compete with the tension for the tensioner applied by the thread take-up. Higher lower thread tension from bobbin may then be one way to solve the problem, because then you need to increase the tension from upper tensioner, so it will win in this competition.

I suppose that the friction to thread at thread guide edges will be of variable nature.

 

[chrisash]

Have a look at the sailrite web site it has lots of video's to assist you setting up and making items

https://www.sailrite.com/How-To-Projects-Guides/Projects-and-Tips/Learning-to-Sew