hi. no matter what machine you use, you always have to adjust the tension when you change the thickness of the leather. i would recommend not to mess with the lower tension if possible. use the upper tension to adjust. some machines have more than one option to adjust the top tension. take a piece of the leather you wanna use and try it first out until you have the look you like. it has also a foot pressure that is very important. as thicker the leather, as lower the foot pressure should be. if the foot pressure is to much, you will get ugly marks on the leather. if you have the problem, that the loops from the sewing are showing on one side, then it is for sure the tension that is not right. if the loops are showing on the back side, get more top tension. if the loops are showing on the top, lower the top tension. you also have to make sure, that your tension is right to the thread you are using. hope this helps
i'm using a juki flatbed and i cowboy cb3200......depense on the work i do and what i have to sew.....but i always have to play with tension and pressure foot adjustments...... i always say ...... it is a little bit like this ...... before you saw projects you like to sell or show, get first in touch and have a relationship to your machine. i know.....it looks like a simple machine ..... but you still have to learn how to work with it .......
