Every part of a sewing machine, how a lockstitch is made, and how to get from a cold machine to a straight, backstitched seam. Study Cards name the parts, Helpful Hints holds the troubleshooting chart, the Practice Quiz checks your reasoning, and the Workshop puts you at the machine.
Two layers of cloth, cut through. The needle brings the top thread down. The bobbin waits below the plate with the bottom thread.
That is a lockstitch: two threads knotted together inside the cloth. The knot sits in the middle when both threads pull evenly. Loose loops underneath mean the TOP thread never got its tension — not that the bobbin is broken.
Four things people get wrong
⚠️People often think…
Loose loops under the fabric mean the bobbin is the problem.
The mess shows up on the side OPPOSITE the fault. A nest of loops underneath is spare top thread that nothing held and nothing lifted — it missed the tension discs or the take-up lever. Raise the presser foot and rethread the top.
Loops below, look above. Loops above, look below.
⚠️People often think…
You can thread the top with the presser foot down. The thread still reaches the needle.
With the foot down the two tension discs are shut, so the thread lies across them instead of dropping between them. It reaches the needle holding nothing back, and every stitch comes out slack underneath.
Foot up opens the discs. Thread with it up, every time.
⚠️People often think…
Watch the needle to keep the seam straight.
The needle sews in one fixed place and cannot be steered. The width of the seam is set by where the cut EDGE of the fabric runs, so watch the edge against the 5/8 line on the throat plate.
Eyes on the edge and the line, not on the needle.
⚠️People often think…
Sewing over a pin is fine as long as you go slowly.
Speed is not what decides it. The needle comes down on hardened steel and one of the two breaks, and it is never the pin. A piece of a broken needle can fly. Take the pins out as they reach the foot.
The pin wins. Pull each pin before it reaches the foot.
Read the seam, then fix the machine
1Watch one
A seam looks neat on top. Underneath is a nest of loose loops. What went wrong?
A lockstitch needs both threads pulling even.
Here the loose thread is all underneath.
The mess shows opposite the fault — so it is the top thread.
Foot up, rethread the top: tension discs, then take-up lever.
2Do one with me
Fill these in before you sit down at a machine.
Before you thread the top, this part must be UP:
The thread must pass through this lever:
A lockstitch’s knot should sit here:
💬One sentence, then you move on
Why do loose loops under the cloth point to the top thread?
3Try one
The machine skips a stitch every third or fourth stitch. The thread is seated right and runs smooth. Name the part to check first.
I want a hint first
Which part actually touches the cloth, and is the cheapest thing on the machine to replace?
💬Last one — then you’re done here
A seam looks the same from both sides. What does that tell you about the two tensions?
Where this goes
Where this lives
A hem taken up the night before a job interview. A costume finished the night before it is worn. Both times the machine has to work on the first try, and reading the underside is how you get it there.
What this feeds
Next unit is Fabric, Fibers and Patterns — which cloth you are sewing, and which needle and thread that cloth asks for.
Name one thing you would sew, and say which side of the seam you would look at first.
One card at a time — tap “Show me” to check yourself, then Next. Start at Foundation; when those feel easy, climb.
Helpful Hints
🧭 The unit in one line
Know the parts → wind a bobbin → thread the top in order → bring the bobbin thread up → foot down, backstitch, sew on the 5/8 line → pivot at the corner → backstitch again → and when something goes wrong, read the underside of the seam.
Off, up, up — spool, guide, tension, take-up, guide, needle.
🔑 The one idea
A machine stitch is two threads locked together inside the cloth: the top thread from the spool, the bottom thread from the bobbin. Almost everything you learn here — tension, the take-up lever, threading order, the look of a bad seam — is about keeping that lock in the middle.
⚠️ Traps to avoid
Threading with the presser foot DOWN. The tension discs are closed, the thread never drops in, and you get a nest of loops underneath.
Skipping the take-up lever. It is the one step almost everybody misses, and nothing pulls the stitch tight without it.
Watching the needle instead of the fabric edge. The needle sews where it sews; the width of the seam is set by where the EDGE runs.
Pulling the fabric to help it along. The feed dogs move the cloth. Pulling bends the needle and snaps it.
Sewing over pins. The needle hits the pin and one of them breaks. It is never the pin.
Blaming the bobbin for loops UNDER the fabric. Loops underneath are a top-thread fault; loops on TOP are the bobbin.
Changing a needle with the machine plugged in. Unplug it first, every time.
📐 What went wrong — the chart
What you see
Look here first
What to do
Loose loops in a nest UNDER the fabric
the top thread
raise the presser foot and rethread the top, all the way
Small loops ON TOP of the fabric
the bobbin
take the bobbin out and drop it back in the way the picture shows
Stitches missing every few stitches
the needle
fit a new needle, flat side to the back, pushed all the way up
Thread on top, nothing at all underneath
the bobbin
check the bobbin has thread and that the thread is in its slot
The needle broke
your hands, and the pins
stop pulling the cloth, take the pins out, fit a new needle with the machine unplugged
The fabric does not move
the presser foot
lower it — the feed dogs cannot grip cloth that is not pressed down
🎯 How you will be asked
“Name this part and say what it does.”
“Put the threading steps in order.”
“Here is what the seam looks like. What went wrong, and how do you know?”
“Explain how a lockstitch is made and why both tensions matter.”
“Describe how to sew a 5/8 inch seam and turn a square corner.”
✅ Before the test, can you…
Point to the take-up lever, the tension dial and the feed dogs?
Thread the top of a machine in the right order, without a card?
Bring the bobbin thread up and lay both threads back?
Sew a 5/8 inch seam with a backstitch at each end?
Say the four steps of a pivot, in order?
Tell a top-thread fault from a bobbin fault from a needle fault?
📚 Go to the sources
These open another website and need the internet. Start with the lockstitch page: it has a moving diagram of the loop being caught and wrapped around the bobbin thread. Watch it twice before you read anything else.
Look back at anything you missed — the hint that appeared is exactly what to reread tonight.
How sure did you feel?
Workshop
Work like a sewer: name the parts of the machine, put the threading steps in the right order, sort fourteen things that went wrong, then argue from the lockstitch what caused a bad seam.
Your practice never leaves this device. There is no account and no sign-in. Your work is saved in this browser only, and you can erase it whenever you want.
Your practice record — saved on this device
This is your record of the module on screen — it stays here and goes nowhere. Independent means you got it right on the first tap; supported means you got it after the explain-and-retry, or marked ‘I had it’ on a revealed answer. Both count, and neither is a grade. If your teacher asks, copy the row or show them this screen.
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Supported
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Hints used
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Cards studied
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Lab
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Traps met
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Explained in own words
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The answer key is for a teacher: it prints only from here, for the unit on screen. Print the study packet prints the study pages and a blank quiz — never the answers.