Causes of Upper Thread Breaking
Machine improperly threaded.
Tension too tight.
Needle bent or having a blunt point.
Thread too coarse for size of needle.
Needle too fine for size of thread and material to be sewn.
Burr on the needle hole in throat plate. (Caused by breaking needle in pulling material from machine.)
Burr on needle hole in presser foot. (Caused by sewing over pins or breaking needle)
Needle is not insert right in clamp.
Needle to long for the machine, or not all the way up in the clamp.
Take-up spring bent or broken.
Tension discs worn so that the thread works in groove.
Cause of Lower Thread Breaking
Improper threading of bobbin case or shuttle.
Tension to tight.
Thread wound unevenly on bobbin or bobbin wound too full.
Spring on bobbin case or shuttle worn to sharp groove.
Burr on underside of throat of plate. (Sometimes caused by sewing over pins or breaking needle.)
To Avoid Braking Needles do not sew heavy seams with a needle too fine.
Use proper size of needle for thread and material to be sewn.
See that the presser foot or attachments are securely fastened to the bar and that the needle goes through the center of the hole.
Do not pull the material to one side when taking it from the machine. The needle may become bent and strike the side of the hole when starting to sew.
Do not pull material when sewing. The needle may become bent and strike the back of the needle hole.
Do not bend the needle when pulling out the material before cutting the thread.
Do not use a needle that is too long. It is liable to come in contact with the bobbin case and break, probably spoiling the case and requiring replacement.
Do not leave pins in the material after basting and sew over them with the machine.
Needle not accurately set into the needle bar, blunt or bent.
Needle too small for the thread used.
Needle too short for the machine.
Looped stitches are usually caused by an improper tension.
If the loop is on the upper side, it may be corrected by tightening the under tension.
If the loop occurs on the underside, it may usually be corrected by tightening the upper tension. See that both the upper and lower threading is correct, that the thread is of good quality and the correct size for the needle.
Test both tension and stitch on the same material to be sewn.
Looping of stitches is sometimes caused by the placing of the bobbin in the bobbin case or shuttle so that the thread pulls from the wrong side of the bobbin, or the bobbin being wound too full.
Machine Not Feeding Properly
Improper feeding is often due to the pressure being too light for the material being sewn.
The feed dog may be worn smooth. This may be determined by running the finger over the teeth.
If they are not sharp, the feed dog should be replaced by a competent adjuster.
The stitch regulator may have been turned back so far that the feed is entirely out of action.
Needle may be bent.
Machine Working Heavily
If the machine works hard after standing it is probably gummed and needs a general cleaning.
The belt may be too tight and hence putting excessive pressure on the bearings.
When the belt is too loose it slips on the balance wheel and causes the operator to treadle more than necessary.
Sometimes thread becomes wound around the hub of the balance wheel and the ends of the band wheel crank.
With constant running and contact with oil the threads work in next to the bearings so tightly that it makes the machine run heavily.
When this happens, remove the thread with a stiletto or other sharp instrument.
Sometimes the bobbin winder snaps down, putting pressure against the balance wheel.
Be sure to see that the bobbin winder in released.
Thread may be tangled in the shuttle race.
Tension too tight
Stitch too long for the material being sewn, especially on fine material.
Wind the Bobbin Evenly
A bobbin must be wound evenly to work properly in the machine.
Great care should be taken in winding bobbins to have the thread placed on the bobbin smoothly and evenly, and the bobbin should never be wound so full that it is tight in the bobbin or shuttle.
If the thread winds to one side of the bobbin, the guide which carries the thread from the bobbin winder to the bobbin must be adjusted away from the side at which the thread piles up.
Always make it a point to have sufficient quantity of bobbins on hand so that it is unnecessary to wind one color thread on a partly wound bobbin of another color.
Bobbins wound in this manner are often uneven, and the ends of the threads become tangled, causing no end of trouble in the bobbin case.
Proper Needle and Thread
A perfect stitch can be obtained only when the thread is selected to suit the fabric which is to be stitched and the needle is the correct size for the thread.
If the needle is to fine for the thread and the material to be sewn it is quite likely to beak when crossing a seam.
If a large needle is used on fine material the perforations made by the needles will show on the finished work.
A table of correct needles for the various sizes of silk and cotton is given in the instruction book for each machine.
This table should be carefully followed when ordering needles and when changing them for various classed of work.
Testing a Needle
An important essential for good work is that the needle be perfectly straight.
A straight needle can be determined by placing the flat side of the needle on the slide plate of the machine or any other perfectly flat solid surface.
Hold the needle flat to the plat and the plate up to the light. A straight needle will show an even amount of light under it and the point will be in line with the shank, while a crocked or bent needle will show closer to the plate or further from it at the point.
Setting the Needle Properly
Turn the balance wheel over towards you until the needle bar rises to the highest point.
Loosen the thumb screw of the needle clamp, release and remove the old needle.
Place the new needle in the needle clamp, make sure that the flat side of the needle in against the needle bar.
Push the needle up as far as it will go and tighten the clamp.
You will note that the side of the needle with the flat on the shank has a shorter groove at the eye while the other side has a long groove.
The thread must lie in the long groove when sewing. If the needle is not placed correctly in the machine it will not sew.