Consew 225 loose stitches on circle

[Cihowe]

Any suggestions on how to resolve this? While sewing leather in a straight line it sews perfectly but at random times on radius it starts loosing tension on bottom. Makes a slight noise when it’s starts. 
Thanks for any help.

[Wizcrafts]

Check to make sure that the top thread is staying all the way inside the tension disks. Add some more top tension. Verify that the check disk is properly threaded and that the spring tension is good, the bottom stopper holds the thread taut until the needle pierces the leather, and that the little set screw is either in the center, or to the left in the curved slot. Finally, change needles.

UPDATE

One way to ensure that the top thread has a fighting chance of staying seated inside the top tension disks is to twist it around a top post counterclockwise, feeding it through a top and bottom hole in the post. You can turn the post with pliers to get a good angle coming out of the bottom disk. This provides back pressure before the disks and helps keep the thread seated down in them. It also tends to counteract twisty thread that may act like a coil spring coming off the spool.

[Cihowe]

I can’t understand how it sew so good going straight but somehow looses tension when turning a radius. 
Check disc spring is holding pressure on thread until needle enters material. Adjustment screw in check disc is just left of center. Also change needle and retreaded with no help.

[AlZilla]

I don't know if I'm seeing it right or if it's some kind of optical delusion, but the stitches on the bottoms of your circles look much longer than the lead in stitches at the top. None of the stitches really look taut to me, anyway.

In these pictures at least, it doesn't look so much random as it seems to happen when the circle gets really tight.

The holes look a little big, too. Are you using the right size needle?

No answers, just an observation. Definitely looking forward to the solution.

[kgg]

2 hours ago, Cihowe said:

I can’t understand how it sew so good going straight but somehow looses tension when turning a radius. 

 

1 hour ago, AlZilla said:

I don't know if I'm seeing it right or if it's some kind of optical delusion, but the stitches on the bottoms of your circles look much longer than the lead in stitches at the top

To many unknowns to start with. 

i) what model of sewing machine are you using??

ii) what thread size are you using??

iii) what size of needle are you using??

iv) is the machine threaded correctly??? Need photo's showing thread from spool to the eye of needle??

v) Did you do a drop test or use some other method of setting the bobbin tension????

My take:

When you make a circle type seam manually without using a circle guide the sewing speed and controlled movements both have to be properly matched. Particularly with drop feed machines there can be a tendency to twist / turn / move the material to quickly. With drop feed and walking foot machines there is definitely points in the sewing cycle where there is no downward pressure on the material. If you move the material at one of those points you can drag up from the bobbin extra thread and get poor stitches. Those poor stitches do not necessarily appear at that stitch point but in the following stitches because there is so much slop / extra thread in the bobbin thread which then can become a self compounding issue. 

My observation:

At your starting point of the seam you did not lock your stitches and the knot / loop is visible. The knot / loop should be buried in the leather which usually indicates a tension problem. If you don't lock your stitch it will cause a tension issue. Typically 3 stitches (4 holes) forward and then reverse back through those holes and then do your seam. Another method is start your seam the distance 4 holes in would be and reverse back 3 stitches then forward. The second method reduces the amount of thread in each hole by 1/3.

kgg   

 

[AlZilla]

This shows the difference in stitch length. But, style points for hitting that stitch hole in the middle twice!

[Cihowe]

1 hour ago, kgg said:

 

To many unknowns to start with. 

i) what model of sewing machine are you using??

Consew 225

ii) what thread size are you using??

v92 a&e polyester 

iii) what size of needle are you using??

size 20

iv) is the machine threaded correctly??? Need photo's showing thread from spool to the eye of needle??

No photos for now. It’s in my shop

v) Did you do a drop test or use some other method of setting the bobbin tension???

Just by feel 

My take:

When you make a circle type seam manually without using a circle guide the sewing speed and controlled movements both have to be properly matched. Particularly with drop feed machines there can be a tendency to twist / turn / move the material to quickly. With drop feed and walking foot machines there is definitely points in the sewing cycle where there is no downward pressure on the material. If you move the material at one of those points you can drag up from the bobbin extra thread and get poor stitches. Those poor stitches do not necessarily appear at that stitch point but in the following stitches because there is so much slop / extra thread in the bobbin thread which then can become a self compounding issue. 

My observation:

At your starting point of the seam you did not lock your stitches and the knot / loop is visible. The knot / loop should be buried in the leather which usually indicates a tension problem. If you don't lock your stitch it will cause a tension issue. Typically 3 stitches (4 holes) forward and then reverse back through those holes and then do your seam. Another method is start your seam the distance 4 holes in would be and reverse back 3 stitches then forward. The second method reduces the amount of thread in each hole by 1/3.

kgg   

You are probably right. After messing with tension and slowing down while turning leather it seem to do better.

 

[kgg]

@Cihowe

I would do the drop test for tension on the bobbin thread. If it needs to be adjusted turn the tension spring screw a 1/8 of turn at a go. If you over tighten that screw it will flatten the bobbin thread tension spring and you will have to replace the spring. Once those have been over tighten they are never right afterwards and you will never get consistent bobbin tension.  

kgg

[friquant]

43 minutes ago, AlZilla said:

This shows the difference in stitch length

I used to get longer (or shorter) stitches when turning tight circles on my pfaff 535. I was driving it like a racecar, meaning taking the corner at a constant, appropriate speed and rotating the fabric (cardboard, actually) at a smooth, constant rate. The center of pressure of the feed dog was not concentric with the needle, but rather more aft and off to one side. So when the needle was in the air, the fabric (cardboard, actually) would rotate around that offset center of pressure. It would make one length of stitches going straight. But longer stitches turning left, and shorter stitches turning right.

Edited Wednesday at 12:03 AM by friquant

[Cihowe]

3 minutes ago, kgg said:

@Cihowe

I would do the drop test for tension on the bobbin thread. If it needs to be adjusted turn the tension spring screw a 1/8 of turn at a go. If you over tighten that screw it will flatten the bobbin thread tension spring and you will have to replace the spring. Once those have been over tighten they are never right afterwards and you will never get consistent bobbin tension.  

kgg

I have to get another bobbin spring because I have over tightened it.