A sewing machine is a machine that uses one or more sewing threads to form one or more stitches on the sewing material, so that one or more layers of sewing material are interlaced or sewn together. The old-fashioned pedal sewing machine uses artificial pedals to provide power. Due to the relatively backward production process, it is easy to have jumpers, broken needles, broken threads and other faults during use. So, how to repair the old-fashioned sewing machine? Come and find out with me.
Jumper thread
Features of failure: the bottom thread cannot be drawn
Cause: The hook thread is too short, the hook The thread is caught in the shuttle door, the needle is too high, and the shuttle cannot catch the thread loop.
Treatment: Lengthen the hook thread, check whether the lower thread of the sewing machine is stuck, and remove it. Needle bar connecting shaft firm screw loosens the needle bar and moves up, the needle bar should be lowered, re-align the needle, and tighten the fastening screw.
Failure characteristics: needle bar movement
Causes: Needle bar hole, needle bar wear, needle bar connection The screw is loose and the needle bar is displaced.
Treatment method: Replace the needle bar cover, or select a new needle bar, re-align the needle; and tighten the set screw.
Features of the fault: skipping a stitch after several stitches
Cause: The shuttle is worn, the shuttle tip is too blunt, The sewing machine needle is too high or too low.
Solution: Change the shuttle, adjust the height of the needle bar or needle, and realign the needle.
Characteristics of failure: continuous jumper or stitches cannot be sewn
Cause: Poor quality of needles or needles Bending does not normally create wire loops. The sewing machine needle is too high to hook the thread loop, and the three sewing machine needles are not properly matched. Long-term use of shuttle, swing bed and other parts are seriously worn or broken.
Solution: Replace the qualified needle or straighten the needle. Adjust the needle bar or sewing machine needle height. Under normal circumstances, the shuttle or shuttle bed can be replaced and overhauled if necessary.
Failure characteristics: thin seam without jumping, thick seam jumping
Cause: Insufficient presser foot pressure, sewing machine The needle is too thin, the thread hooking mechanism and other parts are seriously worn.
Treatment method: Adjust the presser foot pressure, change needles, replace parts, and carry out repairs.
Failure characteristics: thick jumper, thin jumper
Cause: The needle hole of the needle plate is worn Too large, the sewing machine needle is too thick, the bottom of the presser foot is worn, or the presser foot pressure is too low.
Solution: Replace the needle plate, fine needle, presser foot, presser foot, or adjust the presser foot pressure.
Feeding failure
Features of failure: wrinkling of sewing material
Causes: Broken needle tip, excessive bobbin thread tension, The differential mechanism is improperly adjusted.
Treatment method: Replace the needle of the sewing machine with a new one, loosen the bobbin spring screw, and readjust the differential mechanism.
Failure characteristics: grid teeth marks formed under the sewing material
Cause: The feeding teeth are too sharp and the presser foot too much stress.
Treatment method: Grind the tooth tip with oil stone and loosen the pressure adjusting screw.
Characteristics of the fault: There is a thread under the sewing material, and the sound of the fiber breaking during sewing
Cause: Needle Broken tip or too blunt.
Remedy: Replace the sewing machine needle.
Failure characteristics: sewing material stagnant
Cause: The feed dog is too low, the presser foot pressure is too high .
Solution: Raise the feed dog and tighten the pressure adjusting screw.
Failure characteristics: sewing material goes back and forth
Cause: The feed dog is too high.
Solution: Adjust the feed dog.
Failure characteristics: the sewing material cannot be sewn due to backward movement
Cause: The feed cam is displaced.
Solution: Adjust the position of the feed cam.
Characteristics of the fault: the sewing material slants irregularly
Cause: The feed dog is installed crookedly or the feed dog Screw loose.
Solution: Align the feed dog and tighten the screw.
Irregular stitches
Features of failure: upper thread is floating
Cause: Thread tensioner The pressure is too low.
Treatment method: Tighten the tension thread and increase the tension of the cotton thread.
Characteristics of the fault: The bottom thread is floating
Cause: The bobbin spring is too loose.
Solution: Tighten the bobbin spring screw to increase the lower thread tension.
Characteristics of failure: long and short stitch length
Cause: The pressure of the presser foot is too small.
Solution: Tighten the pressure adjusting screw.
Failure characteristics: Each stitch under the sewing material has a thread sleeve in the form of a towel thread sleeve
Cause:Feeding It is inconsistent with the thread take-up action, and the cloth feeding action is fast.
Treatment method: Adjust the feed cam screw to make the feed and thread take-up consistent.
Basic knowledge of sewing stitches>>
Operation failure
Features of failure: sluggish machine head rotation
caused Reason: The wrong oil is added, especially vegetable oil. There is too much dirt in the shuttle bed, and the connecting rod screws and cone screws are too tight.
Disposal: After rinsing with kerosene, refill with sewing machine oil. Clean the shuttle bed and loosen the screws to ensure a certain clearance.
Failure characteristics: half-circle stagnation, half-circle slipping, or a stagnation point per revolution
Causes : When the thread head of the inner wheel of the shuttle is running, it is not only half-circle stagnant, but also accompanied by violent shaking and noise. The position of the feed dog is too high or dirt accumulates in the gap between the teeth, so that the feed dog collides with the needle plate when it rises.
Solution: Clean the shuttle and add a little sewing oil. Clean or lower the feed dogs. Replace or straighten the needle bar.
Failure characteristics: the machine head is stuck and cannot move
Cause: The position of the feed dog is too forward or too far Back up, touch the needle plate. The needle bar is installed too high, and the needle clamps against the casing.
Solution: Adjust the position of the feed dog, re-align the needle, and adjust the height of the needle bar.
Failure characteristics: the noise comes from the needle mechanism
Cause: The needle bar, needle bar sleeve, small connecting rod, etc. are worn Send too much. Small connecting rod screw Needle bar crank screw loose.
Handling method: Replace with a new one and screw it tightly.
Characteristics of failure: the noise comes from the feeding mechanism
Cause: The large apex conical screw is worn or loose, and the feeding teeth When touching the needle plate, the stitch length adjusting mechanism is loose.
Treatment: Grind or readjust, readjust, readjust or tighten screws.
Failure characteristics: the noise comes from the shuttle mechanism
Cause: The wear of the shuttle and shuttle bed causes the gap to be large and the pendulum The gap between the shuttle and the shuttle holder is too large, resulting in an impact.
Solution: Replace with new piece, adjust or replace with new piece.
Fault characteristics: general noise
Cause: The upper shaft, lower shaft and bushing are worn, causing the upper and lower shafts to move Move, the machine is out of oil.
Treatment method: Replace new parts, or adjust the clearance between the upper and lower shaft planes, pay attention to maintenance, and refuel on time.
What kind of oil is sewing machine oil>>
Broken needle
Failure characteristic: broken needle for sewing thick material
Causes: The needle is too thin or bent, the thickness of the sewing material is uneven, and the needle bar moves too much.
Treatment method: Change a new thick needle, adapt to slow down the sewing speed and help feed the material by hand, change a new needle bar or needle bar cover.
Failure characteristics: short stitches keep stitching, long stitches break stitches
Cause: The action of the feed dog lags , The feeding dog is unqualified, the needle touches the rear end of the feeding dog and the needle is broken.
Treatment method: Adjust the position of the feed cam, shorten the stitch length properly or replace the feed dog.
Failure characteristics: sewing machine needle is broken under the needle plate
Cause: The needle position is too low, the needle touches The shuttle, the shuttle bed is not installed properly, the tip of the shuttle touches the needle, the clearance between the shuttle holder and the needle end is too small or too large, the shuttle holder touches the needle or loses the needle protection function.
Treatment method: Adjust the position of the needle bar or needle, re-install the shuttle, and adjust the clearance between the shuttle holder and the needle.
Failure characteristics: The needle of the sewing machine broke on the needle plate
Cause: The sewing material was pulled too hard, causing the sewing machine The needle is bent and the presser foot screw is loose, causing the presser foot to slant and touch the needle. The displacement of the feed cam causes the sewing material to break the needle, and there is a hard object in the sewing material that causes the needle to break.
Handling method: Strengthen the operation practice, adjust the presser foot to tighten the screw, and adjust the position of the feed cam screw.
How to deal with the broken needle of sewing machine>>
Thread break
Failure characteristics: the first stitch is broken, and the broken thread ends in a cut shape
Cause: The sewing machine needle is too low because the sewing machine needle is installed backwards or the machine needle is not installed enough. The sewing material is too hard, the sewing machine needle is too thin or the pressure of the presser foot is too high.
Solution: Check whether the sewing machine needle and the needle bar connecting shaft screw are loose. Change the needle or adjust the presser foot pressure.
Characteristics of failure: suture curled at both ends of the severed end with short whiskers.
Cause: The thread is too tight or the thread is tangled during sewing. The thread is squeezed into the shuttle bed guide groove by the shuttle. The quality of the suture is poor, and there are burrs in the thread passing area.
Treatment method: Replace the tension of the wire clamps and check the wire-passing line to eliminate the entanglement. Check the shuttle for wear and replace if necessary. Sand the area over the thread and replace the suture.
Failure characteristics: The lower part of the sewing material has a heavy line, and the stitch cannot be formed and the thread is broken, and the broken thread is in a ponytail shape
Causes: The feed dog is too low, the sewing material does not stop and the thread is too much and breaks. The cloth feeding and the thread are out of step and are cut off. The presser foot and needle are loose, preventing the sewing material from running.
Solution: Raise the feed dog, adjust the positioning angle of the feed cam, and tighten the presser foot and needle screw.
Features of the fault: Sudden thread breakage during sewing, and the upper thread fluctuates in a curved manner
Cause: The shuttle bed position is not Install the upper thread and roll it into the shuttle bed. The bobbin case does not lock tightly or suddenly shifts during sewing. The quality of the shuttle is poor. The shuttle center spring is too long or the center sleeve is oval.
Treatment method: Re-adjust the shuttle bed position, re-install the shuttle, and replace the shuttle with the core sleeve.
Characteristics of malfunction: The bobbin thread suddenly breaks during sewing. The bobbin sleeve is unqualified and the inner diameter is oval
Cause: The bobbin sleeve is unqualified and the inner diameter is oval, resulting in the failure of the bobbin rotation. The bobbin spring screw is overtightened and the bobbin case pressure is too low. The bobbin winding is too full or too loose and messy. The bottom thread is brittle and has knots, so that the bottom core cannot pass through the bobbin spring.
Treatment method: Replace the bobbin case, loosen the bobbin spring screw, rewind the bobbin thread, and replace the lower thread.
