Bottom stitch is loose - Sailrite Ultrafeed LS

[CarrieReneHall]

I have done everything and cannot figure out why - at random times - my bottom stitch is loose. It seems to happen more often when I am sewing my leather onto my zipper (handbags). I am wondering if it is the glue I use to get the leather in place. I did not have any issues with this until now. I am desperate for some help. I have so many orders and cannot send these out like this. I will take any advise! I am using leather glue and not very much of it. 

[Northmount]

17 hours ago, CarrieReneHall said:

I have done everything and cannot figure out why - at random times - my bottom stitch is loose. It seems to happen more often when I am sewing my leather onto my zipper (handbags). I am wondering if it is the glue I use to get the leather in place. I did not have any issues with this until now. I am desperate for some help. I have so many orders and cannot send these out like this. I will take any advise! I am using leather glue and not very much of it. 

Moved to leather sewing machines.  You'll get more help here where the machine guys hang out.

What are you sewing when the stitches are good?  Makes a difference to helping you figure out the full cause.  Thickness and type of materials, needle size, thread size?

Most often loose threads on the bottom are a result of not enough top tension to pull the thread up.

[nylonRigging]

Also, double check the tension you winding thread on your bobbin winder . things happen, and bobbin winder gets looked at very little when you working repetitious day after day.

.

[Deanr]

I use a lsz ultrafeed and I make bags.

I don't think it is the glue. I use seamstick tape as it is not as messy and allaround easier.

My experience is it is usually the tension. I have mine pretty much cranked down all the way and back off about 1/2 turn.

You didn't say what type of leather. I have much better luck with Chrome tan.

Also try putting in a new needle and remove your bobbin and make sure there are no pieces of thread down there.

[kgg]

20 hours ago, CarrieReneHall said:

at random times - my bottom stitch is loose.

Typically top tension issue. This also crops up when using dull, incorrect needle size, thickness of leather, worn hook, incorrect tension on bobbin tensioner spring. The correct needle for leather in the Sailrite is a 135 x 16, the max thread size is V92, the max needle size is #22 and the max thickness is about 1/4" in chrome tan leather. Are you doing a drop test on your bobbin / bobbin case to get the tension correct. Keep in mind these machines were designed for sewing sail cloth on the open water.

What needle are you using??? What thread size you are using??? What type of leather and in what thickness???

kgg