Loopy from creativesewing.com
With this chapter of our Technician's Outpost we examine loop lift. This may be a completely new topic to you and if your machine isn't sewing well because of a problem with "lift" there's really not a lot you can do about it. That's encouraging isn't it? The solution will have to be found at a technician's workdesk. But these bits of information will help you understand what's going on.
First, what is loop lift? When your needle goes into the fabric all the way and then starts back up, the friction of the fabric against the needle causes the thread to "bubble" on the back of the needle. instead of using "bubble", us technology minded technicians call it, "Loop lift"
There are several factors in play here, including the height of the needle, the size of the needle, the timing of the feed system, the timing of the hook, the distance between the hook point and the needle, the size of the scarf of the needle, and a whole list of other things that we'll not get into here.
This picture shows the formation of the
loop. The arrow is pointing to it and,yep, it's about that size in better
machines, much bigger in other machines. The loop is a really important
part of how your machine sews. If your machine is coughing up skipped
stitches, one of the problems is highly likely to be connected to this.
Now, the tip of the hook, the point, has to strike this loop as it
is forming. The scarf, a small---for lack of a better word--"Dent"
allows this point to have a teeny, tiny larger target to hit. On this
needle the scarf is to the left of the arrow point..rather small, isn't it?
For a bit more info about the scarf check our award
winning chapter on Sharp Pointy Things.
To work correctly the fabric friction has to be correct which is why your needle size has to match the fabric...In addition, the groove on the front of the needle has to match your thread so it creates the loop and doesn't ball up under your project. So when you purchase a size 16 needle instead of a size 12, you are, among other things, getting a deeper and wider groove in the front. This is one reason, only one of many, why you have a collection of different needles in the top drawer of your machine cabinet. If you think about how fast your machine works then you have an idea about how often the hook and the loop lift have to meet.
Some machines, Singers for example, wobble around in this area a bit and so they have a hard time making the hook and lift connect all the time. So Singer has a special needle that has a much larger scarf. This provides a larger target and results in fewer skipped stitches particularly on stretchy fabrics. Think about it...if the machine is not quite as precise then the stretch fabric clings to the needle like a rubber band and the lift is smaller. The hook misses its target and you growl a lot cause you're getting skips. More accurate machines don't have that problem. Singer calls this special needle a "Gold Band" and if you examine one of those beside a regular needle you'll be able to readily see the larger scarf. This many times will cure skips in those and similar machines but don't use a Gold Band needle in a more precise machine because damage could result, especially to your sewing project. That's another chapter in this series.
