In the previous post, we examined the overall issues of snags that can affect tensions.
In this post, lets take a step by step sewing machine repair course approach.
Our goal is to identify anything that might cause the sewing machine tensions to mess up.
Our tools for this exercise consist of our eyes and our fingers. Isn't it nice to know you do not have to buy a $75 dollar tool for this?
Begin at the thread spool. Look closely at the thread spool itself. Is there any roughness, groove, or irregularity in the top of the spool itself that might snag the thread. Use your finger to gently slide over any questionable spots.
If you find a potential problem, solve it before you proceed. As mentioned in the previous post, you may be able to use a spool cap or alternate (horizontal or vertical) spool pin. You may need to use a file to smooth a rough spot. Be careful that you do not create a flat surface that looks smooth but may catch thread on the end of the flat area. Maintain the curves while you smooth out the rough spots.
Using the same technique follow the entire upper thread line looking for potential snag spots. Examine the thread guides for rust, burrs, old lint, bends or twists that might be problems. Remove rust, burrs, and lint using a small brush or file as needed.
Examine the upper tension assembly. Lint often catches in the tension disc causing snags for new thread passing through. Rust is often a problem on older machines. Make sure there are no obstructions to the flow of the thread.
Change the needle regularly (ever 3 hours of sewing or so). Needles are notorious for developing sticky surfaces, burrs, dull points, and bending. The solution is replacement. If you are having tension problems, the first thing to do is rethread. The second is to replace the needle. You can often save frustration by making this just one quick step.
The bobbin are is very similar to the top thread path, but it is more hidden. You know the problem, "Out of site, out of mind.". Begin by cleaning out the bobbin area using compressed air and a brush. It must be clear of debris before you can properly diagnose it.
Examine the surface of the bobbin itself. Is there rust on that old metal bobbin? Throw it out. Is the edge of the bobbin got a rough spot on it? Throw it out.
Examine the surface of the bobbin carrier. In many cases, you will need to remove the carrier and check all of its surfaces. Metal carrier are more prone to rust, while plastic carriers are more prone to thread scoring and rough spots. Rusty carriers can sometimes be buffed to remove the rust, but usually it is best to replace the carrier. Plastic carriers can sometimes be smoothed with a gentle filing, but again may need to be replaced.
Examine the race. This is the track or groove in which the carrier sits and around which the hook moves. Use your fingers to check for rough spots. Remove the rought spots with emery cloth, file, or sandpaper.
Examine the hook itself. This is a common place to find burrs. The tip of the hook may strike the needle or debris during the course of sewing. Remove the burr and make sure the tip is sharp but smooth.
Sewing machine repair often involves great attention to tension issues. The user must be careful to use good sewing practices to avoid many of these problems. A good sewing machine repair course can help you prevent these problems as well as solve them.