loose topthread only in reverse?

[dana]

Hi Everyone, this is my first post and unfortunately it's about a problem that arose out of nowhere i think. so here it is, as thorough as i can be:

so my problem is I'm getting loose stitches on the underside of whatever i'm sewing *BUT* ONLY when in reverse to backtack ect. My equpiment i'm using is a highlead 618 with a size 18 needle and 69 bonded nylon thread. What's baffling me is that all stitches are nice and tight on top and bottom but as soon as i am at the end of a stitch and want to backtack, the upper thread (black in the photo example) will hang loose on the underside.

so i thought it could have been a tension issue.. but if it was then why does all my forward stitching look OK?

if it was a timing issue, then once again, why only in reverse is it bad? wouldnt timing affect forward and reverse?

i looked over my manual and from what i can tell the timing is ok, but im obviously not a pro.

i cleaned out the bobbin case, needle plate, ect.

so in my image i have 2 layers of canvas. this is the underside. you can see in the top one that i was sewing forward and at the end you can see the black(top thread) coming through to the bottom and not forming the knot in the middle of the piece

the bottom stitch is reverse only, so you can further clearly see whats going on.

sorry for such a long post but anything i can do on my own would be better than transporting it so thanks in advance for any help!

-Dana

[neelsaddlery]

Hi Everyone, this is my first post and unfortunately it's about a problem that arose out of nowhere i think. so here it is, as thorough as i can be:

so my problem is I'm getting loose stitches on the underside of whatever i'm sewing *BUT* ONLY when in reverse to backtack ect. My equpiment i'm using is a highlead 618 with a size 18 needle and 69 bonded nylon thread. What's baffling me is that all stitches are nice and tight on top and bottom but as soon as i am at the end of a stitch and want to backtack, the upper thread (black in the photo example) will hang loose on the underside.

so i thought it could have been a tension issue.. but if it was then why does all my forward stitching look OK?

if it was a timing issue, then once again, why only in reverse is it bad? wouldnt timing affect forward and reverse?

i looked over my manual and from what i can tell the timing is ok, but im obviously not a pro.

i cleaned out the bobbin case, needle plate, ect.

so in my image i have 2 layers of canvas. this is the underside. you can see in the top one that i was sewing forward and at the end you can see the black(top thread) coming through to the bottom and not forming the knot in the middle of the piece

the bottom stitch is reverse only, so you can further clearly see whats going on.

sorry for such a long post but anything i can do on my own would be better than transporting it so thanks in advance for any help!

-Dana

How closely do the stitches match in forward and reverse? What is your stitch length set at? Try setting it to zero and see if the needle bar is stationary in forward and reverse. I had this issue with a drop feed machine one time and it was because of an issue with the reverse not matiching the forward stitch.

Also, check bobbin case positioning finger for correct alignment. If this finger is not set right, then it makes it hard for machine to pull knots into the material.

This is not an easy problem to diagnose, but I do agree there is something not right here. I do not think it has anything to do with timing or thread tension however. If it were timing or thread tension, it would do it sewing forward as well in reverse.

Hope this is of some help to you.

[dana]

alright! thank you! we're making progress. the stitches are longer in reverse. you can see it in the image i posted. i never realized it, but the forward stitches are 3/4 the length of the reverse stitches. I was sewing on length 6.

as for the needle bar. i set it to 0 and there is no movement from what i can tell. it pierces the same hole over and over. is this what we want? or if something was wrong would there be a feeding motion here?

so how did this problem arise do you think? how easy of a fix is this? or something that should be left to the pros?

thank you for the help

[neelsaddlery]

alright! thank you! we're making progress. the stitches are longer in reverse. you can see it in the image i posted. i never realized it, but the forward stitches are 3/4 the length of the reverse stitches. I was sewing on length 6.

as for the needle bar. i set it to 0 and there is no movement from what i can tell. it pierces the same hole over and over. is this what we want? or if something was wrong would there be a feeding motion here?

so how did this problem arise do you think? how easy of a fix is this? or something that should be left to the pros?

thank you for the help

If you have the stitch length dial set at 0 and the needle bar does not move at all when sewing forward or backward, then this tells me that the reverse mechanism in the machine should be adjusted correctly. In other words, at 0 there should be no movement of material in sewing forward or reverse.

If the bar was moving forward or backward with the dial set at 0, then the stitch dial to stitch length relationship would need to be adjusted.

Now for the big problem, you say that the forward stitch does not match the reverse stitch. So we need to find out why. Try this.....

Try running the machine without thread in it, and just poke holes in the material. Check the spacing between the holes in forward and reverse. If the spacing is different, then you have a problem with the calibration of the forward and reverse stitch, and this tells us that the thread/material/needle and other things have nothing to do with the problem. It would strictly be a feed calibration problem at this point.

If the holes are spaced different with no thread in the machine, then we need to look into why this is the case, and that unfortunately is not an easy fix. There is a cam inside of the machine that can be adjusted to control the forward and backward movement of the needle bar and inside presser foot. This may need some adjusting.

Another possibilty to look at is the alternation of the inside and outside feet as the machine sews. Is the outside foot lifting up emough to allow the material to pass underneath it? Most likely this system should be working properly, but it is a possible longshot and I listed it because of this reason.

Additionally, there is a cam inside the machine that controls the front to back motion of the feed dog, and this may need adjustment.

How about the spacing of the feed dog in the slot as well? I have seen some drop feed machines where the feed dog was spaced too far forward in the slot, and this would make the thread hang on it when feeding in reverse. On a compound feed machine, if you mess with the feed dog spacing, you'll need to adjust the spacing of the needle bar so that the needle comes down into the middle of the hole in the feed dog.

The last possibilty (and the hardest to fix) is to examine the geometry of the internal parts the regulate the feed action. This would take a very experienced mechanic, and somebody that knows these machines extremely well. This is the worst case scenario, and it would take someone with a great deal of skill to diagnose this scenario.

Lots of things to think about here. One thing I can tell you is that the specing of the forward stitch should match that of the reverse stitch. Is this the cause of the problem? I can't say for sure. But, you miught want to get that fixed first and see if that does anything to correct the problem.

Hope this is of some help to you.

[dana]

alright, thanks ryan, i'll look into it. i appreciate taking the time to write all that up.

[Cobra Steve]

Hi Dana, what Ryan said is true. I think your hook timing or possibly your feed timing (and maybe both) are off a little bit. If the feed timing is off, then the machine will not pull the thread up. This is also true if the feed dog is too high. A local industrial sewing machine mechanic should be able to take care of these problems. Thanks, Steve

[dana]

thanks steve, i asked for help here first in case it was something i could take care of/adjust because i don't have a car at the moment. i'm hopefully getting it looked at tomorrow morning. thanks for the info

[Saddlebag]

dana, rather than have loopy backstitching why not turn your work and go back along a few stitches. That's how I have to do it with my Union Shoe machine which I wouldn't trade for anything.

[dana]

so i went to my local sewing machine mechanic and i told him everything that was the matter with it. turns out a few things were out of adjustment but nothing resolved that problem. he insisted that it was assembled incorrectly from the factory and that the problem was "too far into the machine". it could have been that i had that problem from the getgo but who knows. he was an older guy so i do trust his opinion. he also had his very own opinion about chinese-made machines in general.

but anyways, i brought it back to the shop i bought it from (different shop than mentioned above) and told him the trouble i was having. he told me if i was that unhappy i could exchange it for another machine he had laying around. turns out he had a pfaff 1245 that ran good so i traded and i am much much happier. it was a "one step back, two steps forward" kind of thing but i feel like it was worth it. so now all i need to do it get the right presser feet and i think i'm set for a while. also, does pfaff have a special knee lift? i adapeted mine as best i could but but when the foot is up and i want the foot to drop it hands free, i cant get more leverage to do so. if someone has a picture of that, then that would help.

saddlebag- i realize i could do the ol' flip and sew but i just figured that since i paid for a machine with reverse, i may as well use it.

[zurialjazz]

I had the same problem. I fixed it by adjusting the Clearance between rotary hook and opener (Thread release finger). Machine works great now