Sewing straight lines, corners and curves, and reading tension

Paper drills before thread, stitch length in millimeters and stitches per inch, pivoted corners and curves, and a balanced stitch read from a tension test.

1. Driving on paper first Understand

A sewing machine moves the fabric for you. The feed dogs, the small toothed bars that rise through the needle plate under the presser foot, step the fabric toward the back of the machine once per stitch. The presser foot holds the fabric down against them. Your hands steer the fabric left and right; they do not push it forward or pull it out the back. NMSU's maintenance guide describes the feed dog teeth moving the material before the next stitch is made (NMSU Guide C-102). Singer's M3200 manual puts the rule for your hands plainly: do not pull the fabric while sewing, let the machine draw it through (Singer M3200 instruction manual).

That split, the machine feeding and you steering, is the skill this section builds. Pulling or pushing is the most common beginner habit, and it has a cost: Brother's LX-3125 safety list says pulling or pushing the fabric can deflect the needle and break it (Brother LX-3125 manual), and NMSU's checklist of machine problems says a pulled fabric can bend the needle so it strikes the back of the needle hole (NMSU Guide C-202). Troubleshooting and care covers what a needle strike does to the machine. Here the point is to learn the steering before anything is at stake.

The License to Drive sheets

Wisconsin 4-H's "License to Drive" activity is the drill we use (University of Wisconsin-Madison Extension, 4-H License to Drive). The PDF has three pages: the leader's instructions, a sheet of straight lines with square corners spiraling inward from a "Start Here" dot to an "End Here" dot, and a sheet of curves. Print the second and third pages on ordinary printer paper. If you have no printer, rule your own: a few straight lines about 1 in (2.5 cm) apart with right-angle turns, and two wavy lines drawn freehand.

The Wisconsin steps, in our words:

1. Raise the needle. Turn the hand wheel (the wheel on the right end of the machine, also called the balance wheel or handwheel) toward you until the needle is up and out of the needle plate.
2. Raise the presser foot with the lever behind or beside it.
3. Place the sheet so the needle is directly above the "Start Here" dot, then turn the hand wheel toward you to lower the needle into the dot.
4. Line up the paper so the stitching will follow the line, and lower the presser foot.
5. Press the foot control gently and stitch slowly along the line, guiding the paper, until you reach "End Here."
6. Raise the needle and the foot with the hand wheel and the lever, and slide the paper out toward the back.

The Wisconsin leader's sheet runs the drill on a threaded machine set to 10 to 12 stitches per inch. We suggest one pass unthreaded first. That is our choice, not Wisconsin's: with no thread, nothing can tangle, and the needle still punches a row of holes you can read. A threaded pass afterward is the same drill with a line of thread you can see.

What to watch while you drive

• Look at the guide, not the needle. The needle moves too fast to steer by. Watch the line where it meets the edge of the presser foot, or a mark on the foot, and keep that point on the line.
• Keep the speed low and even. NMSU's checklist lists irregular sewing speed as a cause of uneven thread tension and of a spool that jerks and catches (NMSU Guide C-202). A slow, steady pace on paper becomes the habit on fabric. Some machines have a speed slider that caps the top speed; Brother's CP100X manual describes one (Brother CP100X operation manual). If yours has it, set it low for now.
• Stop to turn. At each corner of the spiral, stop with the needle down in the paper, lift the foot, turn the sheet, lower the foot, and go on. That is a pivot, and the next section uses it on fabric.
• On curves, make many small corrections. Steer a little at a time and slow down where the line bends hardest. If you drift off, stop, put the needle down, and ease back toward the line over several stitches rather than in one jerk.

Three drills is enough when the holes stay on or touching the line for most of the sheet. Wobble at the start of each line is normal. The drill is finished when stopping, pivoting and starting again feel deliberate rather than rushed.

2. The first seam on fabric

A seam is a line of stitching that holds two fabric edges together. The first one in this manual is a test, not a project: two layers of a cotton scrap, folded, sewn in a straight line. It teaches the start, the finish, the seam guide and the stitch you will later read for tension.

Starting: thread tails and the first stitch

Before the first stitch, bring the bobbin thread up through the needle plate (Needle, bobbin and threading shows how to pull it up). Then lay both threads, the upper and the bobbin thread, under the presser foot and toward the back, about 4 in (10 cm) long. NMSU's maintenance guide gives the same order: pull the bobbin thread up, place both threads under the foot, and hold them to the back as you start (NMSU Guide C-102). Holding the tails for the first two or three stitches stops the needle from pulling the thread end down into the bobbin area, which is one of the ways a thread nest (a tangle of thread under the fabric) begins. NMSU's problems checklist lists threads "not properly pulled back under presser foot when starting" among the causes of a broken upper thread (NMSU Guide C-202).

NMSU also advises starting and stopping with the needle and the take-up lever (the lever that rises and falls above the needle as you sew, carrying the upper thread) at their highest position. If the take-up lever is not at the top when you start, the first stitch can pull the thread out of the needle.

Securing the ends: backstitching

A line of machine stitching can unravel from its ends. To lock it, sew a few stitches in reverse at the start and the end. This is backstitching (some patterns say backtacking). Singer's M3200 manual: press the reverse lever, sew a few reverse stitches, release it, and the machine sews forward again. BERNINA UK's foundation course does the same with a quick-reverse button: a few stitches forward, a few back, then forward down the seam (BERNINA UK 325 and 335 foundation course notes). Utah State's Four Square Pillow project gives a count: backstitch 3 or 4 stitches at the beginning and end (USU Extension, Four Square Pillow). Some computerized machines have a button that ties off with tiny stitches in place instead; the BERNINA UK notes describe one. Your manual names what yours has.

Keeping the line straight: seam guides

Most machines have seam guides: lines etched on the needle plate to the right of the needle. Oregon State's 4-H seams sheet says these guidelines are 1/8 in (3 mm) apart, for seam allowances of different widths, and that a strip of adhesive tape on the machine bed works as a guide where there is no line (Oregon State 4-H, Plain Seams and Seam Finishes). Each line is measured from the needle, not from the edge of the presser foot, so the number on the plate is the distance from the stitching to the cut edge. The seam allowance is that distance: the fabric between the stitching and the cut edge. Seams and a first piece covers which allowance a pattern uses; for the test scrap, pick the 5/8 in (1.5 cm) line, the one BERNINA UK's course starts on.

Keep the cut edge of the fabric running along the line, and watch the line, not the needle. Lay a ruler from the needle to the line once to see what the plate's numbers mean on your machine: a few machines mark centimeters, some inches, some both.

Pins

Oregon State's sheet places pins perpendicular to the cut edge and removes each pin just before it reaches the presser foot. Under its advice on avoiding broken needles, NMSU's checklist describes sewing over pins that sit perpendicular, heads away from the stitching line (NMSU Guide C-202). We follow Oregon State: pins out before the foot. A test scrap on the needle-plate guide usually needs no pins for a short straight line.

Corners and curves

To pivot is to turn the fabric around the needle while the needle holds it in place. Oregon State's sheet gives the method for a square or wider corner: stop with the needle in the fabric exactly at the corner, raise the presser foot, turn the fabric around the needle, lower the foot, and sew on in the new direction. NMSU's guide gives the same steps. Utah State's Easy Hot Pad project uses it on every corner of a square: lower the needle, pivot, continue (USU Extension, Easy Hot Pad).

Two refinements from Oregon State:

• Shorter stitches near the corner. Shorten the stitch length for about six to ten stitches before and after a corner. Short stitches give more control and a stronger point where the seam allowance will later be trimmed.
• A sharp corner gets one or two stitches across it. For a corner sharper than a right angle, sew one or two stitches across the point instead of pivoting exactly on it, so there is room to turn the trimmed seam right side out.

To land the needle exactly at the corner, you need to know when to stop. On a square with a 5/8 in (1.5 cm) allowance, the turn comes 5/8 in before the next edge. BERNINA UK's course notes mention horizontal lines on its needle plate set 1.5 cm from the needle for this; on other machines, a mark on tape or on the foot does the job. Slow down for the last few stitches and finish with the hand wheel if needed.

A curve is a long run of very small turns. Oregon State notes that a seam guide is hard to follow on curves and suggests tracing the seamline and stitching along it. Lower speed, more frequent small corrections, and stops with the needle down to reposition your hands are what the curve drill on paper practices.

3. Stitch length in millimeters and stitches per inch

Stitch length is the distance the feed dogs move the fabric between two needle stitches. Most machine dials and screens show it in millimeters. Many American patterns and extension sheets give it as stitches per inch (SPI), the number of stitches in 1 in of seam. The two are related by the inch: NIST defines 1 in as exactly 25.4 mm (NIST, SI Units: Length). So:

SPI = 25.4 ÷ stitch length in mm, and stitch length in mm = 25.4 ÷ SPI. Physical principle

A 2.5 mm stitch is 25.4 ÷ 2.5 = 10.2 SPI. A 12 SPI seam is 25.4 ÷ 12 = 2.1 mm. The stitch length converter does the division both ways.

The ranges, side by side

Sources agree on the direction: heavier fabric takes longer stitches, finer fabric shorter ones. Oregon State's seams sheet adds that knits, crepes and bias seamlines need shorter stitches, and that you test the length on scraps of your fabric. They do not agree on the numbers, because each is written for a different reader and machine. Convention

Sources: NMSU C-102; Purdue 4-H-929-W; Brother CP100X, page 12; bernette b05, straight stitch and basting; Singer HD4423 stitch reference. Converted columns are our arithmetic (25.4 ÷ the number), rounded to one decimal.

Read the table across rather than down. For medium woven cotton, the extension figure (2.1 to 2.5 mm) sits inside Brother's medium range (2.0 to 3.0 mm). For the quilting cotton most beginners start with, 2.5 mm is inside every range that covers it, which is why it is this manual's starting setting. It is a starting point, not an answer: the sample on your fabric decides.

Basting is long, temporary stitching that holds layers for a fitting or a step and comes out later. Topstitching is a line of stitching on the right side, usually a set distance from an edge, that shows; edgestitching is the same about 1/8 in (3 mm) from the edge, in Singer's HD4423 guide. Both get longer stitches because a longer stitch reads as a cleaner line on the surface.

Counting stitches to check the dial

A dial number is the machine's claim. A count is a measurement. Utah State's Four Square Pillow gives the method: sew a straight line about 1 1/2 in (3.8 cm) long on a scrap, mark a 1 in (2.54 cm) space on it with two pins, and count the stitches between them. That count is your SPI. Test it

The same Utah State page asks for "12 stitches per inch or 2.5 on the stitch length regulator." By the arithmetic above, 2.5 mm is about 10 SPI and 12 SPI is about 2.1 mm, so the two settings are not the same length. The page's own pin count settles which one your machine is sewing. We use this example because it is the kind of small mismatch you meet everywhere: sources round, dials are approximate, and some older dials show numbers with no unit. Count once, and you know what your dial means.

Zigzag: width and length

A zigzag stitch has two settings. The stitch width is how far the needle swings from side to side; the stitch length is still how far the fabric moves between stitches. Singer's M3200 manual gives a maximum zigzag width of 5 mm on that machine, says the zigzag gets denser as the length dial approaches 0, and says neat zigzag stitches are usually at 2.5 or below. A very short, dense zigzag is a satin stitch. Your manual gives your machine's maximum width and any limits for its feet. Zigzag comes back as a seam finish in Seams and a first piece and for knits and mending later.

4. Reading tension

A home sewing machine makes a lockstitch: two threads, one from the spool through the needle and one from the bobbin underneath, that loop around each other once per stitch. Thread tension is the drag on each thread as it feeds. The upper thread passes between the tension discs, two discs pressed together by a spring that the tension dial adjusts; the bobbin thread passes under a small spring on the bobbin case. When the two drags are matched, the threads meet and lock between the layers of fabric. Physical principle

NMSU's maintenance guide describes the result: in a perfect stitch, the threads lock midway between the two layers of cloth, with no loops on top or bottom and no puckers (NMSU Guide C-102). That is a balanced stitch. Seen from either side, it looks like a row of short dashes of a single color.

Reading an unbalanced stitch

The stronger pull wins. If the upper thread is held tighter than the bobbin thread, it drags the lock point up to the top of the fabric, and you see dots or loops of bobbin thread on top. If the upper thread is looser, the bobbin thread drags the lock point to the underside, and you see the upper thread on the bottom. Every source we read reads it the same way:

NMSU C-102, figures 13 to 15; Brother CP100X, page 17; bernette b05, upper thread tension; Singer M3200, page 8.

Threading first, then the upper dial, one step at a time

In the manuals we read, the first cause listed for a stitch that looks like a tension problem is threading. Brother's CP100X manual says it outright: if the upper or bobbin threading is wrong, the tension will not adjust correctly, so check both threadings first. Its troubleshooting pages trace bobbin thread on top to a bobbin threaded wrong, and upper thread loose on the underside to upper threading, and both remedies start by returning the dial to its base setting and rethreading.

The most common threading mistake has a physical cause. Singer's M3200 manual tells you to raise the presser foot before threading "to release the tension discs." With the foot up, the discs open and the thread drops between them. With the foot down, they are clamped shut, the thread rides outside them, and the upper thread then has almost no tension. The result is loops or a nest on the underside. bernette's threading preparation, Brother's upper threading and BERNINA UK's course notes all begin the same way: raise the presser foot. Product-specific (each manual's threading path differs; the foot-up rule appears in all four we read).

Once the threading is right, change only the upper tension. NMSU's guide says to assume the lower tension is correct until proved wrong and to make all adjustments on the upper tension first. Singer's M3200 manual says the bobbin tension was set correctly at the factory and does not need adjusting. NMSU's problems checklist notes that some newer machines have factory-set bobbins that should not be tampered with, and to check your manual (NMSU Guide C-202). This manual follows them: the bobbin case screw is left alone in this manual.

Turn the upper dial one number, or one step on a screen, then sew again and look. Two steps at once makes it hard to know which setting did the work.

The contrasting-thread test

This is NMSU Guide C-102's test, which the Practice section uses. Test it

1. Thread the top and the bobbin in two contrasting colors of the same thread type, so you can tell which thread is which.
2. Set a medium stitch length (2.5 mm in this manual).
3. Fold a 6 to 8 in (15 to 20 cm) square of average-weight cotton.
4. Stitch diagonally across it, at about 45 degrees to the threads of the weave. A diagonal line stretches a little when pulled, which shows a stitch that is too tight.
5. Inspect both sides. Read the stitch against the table above. Pull the line gently along its length: a seam that pops or puckers is under too much tension.

Contrasting thread is for the test only. For the project itself, Singer's manual says to use the same thread top and bottom, and NMSU says the same thread unless you are creating a special effect.

Zigzag and decorative stitches

A balanced stitch is the goal for a straight construction seam. Singer's M3200 manual says balanced tension is usually only desirable for straight stitching; for zigzag and decorative stitches, the upper tension should generally be lower, and a small amount of upper thread should show on the underside. That gives a flatter zigzag with less puckering. When you test a zigzag, a little top thread underneath is the result you want, not a fault.

5. The stitch sample book

A stitch sample book is the set of test scraps you keep, each labeled with the settings that made it. In this manual it has two halves: the scraps themselves, in an envelope or a binder sleeve, and one row per scrap in the stitch sample log. The other chapters each add a sample, and Your project uses the settings you tested instead of a guess.

Write on the scrap itself with a fabric marker or a pencil, or pin a paper label to it. Each sample carries:

• the date and the fabric (fiber and weight, or "quilting cotton, folded");
• the needle type and size (Needle, bobbin and threading covers sizes);
• the thread (type and color, top and bobbin if they differ);
• the stitch, its length in mm and its width;
• the upper tension setting as your machine shows it;
• the result in one phrase: balanced, bobbin thread on top, top thread underneath, puckers or skips.

The log's columns match that list, so each scrap and its row say the same thing. If a later setting does not work, the log tells you what did, on what, and when. If you change machines, the log shows that the old dial numbers do not carry over.

6. See it: Dana's first tension test See it

Free material that shows the same steps:

• Wisconsin 4-H License to Drive: the two printable drill sheets and the leader's steps, used in this chapter's practice.
• NMSU Guide C-102, Sewing Machine Maintenance: page 6 and its figures show a perfectly locked stitch and both unbalanced ones; the test above is from it.
• bernette b05 manual, Adjusting the Upper Thread Tension: a short page with a diagram of each fault and a video, a maker's view of the same reading.
• Oregon State 4-H, Plain Seams and Seam Finishes: the seam guide figures and the corner method with its stitch diagram.

7. Practice: drills, one seam, one square, one test Practice

Minimum: the three paper drills unthreaded, then on one folded cotton scrap a backstitched straight line, a pivoted square and the contrasting-thread test, labeled and logged as one row. Time: about 1 hour, plus 10 minutes to print the drills. Materials: your machine with a universal 80/12 needle (Needle, bobbin and threading), all-purpose thread in two contrasting colors (one wound on a bobbin), printer paper or the printed drill sheets, two scraps of medium woven cotton about 8 by 16 in (20 by 40 cm), a ruler, a fabric marker or pencil, a few pins and scissors.

1. Print and drive the drills. Pages 2 and 3 of the Wisconsin sheets, unthreaded, slowly. Pivot at every corner of the spiral. Repeat any sheet where the holes wander off the line for more than an inch at a time.
2. Thread the machine with the foot up. Upper thread in one color, bobbin in the other (Needle, bobbin and threading, threading). Set a straight stitch at 2.5 mm and the upper tension at your manual's base setting.
3. Sew a straight line. Fold one scrap in half to 8 by 8 in. Tails under the foot and held; backstitch; sew along the 5/8 in (1.5 cm) guide; backstitch; raise the needle and foot; pull the work to the back; cut the threads, leaving tails.
4. Count the stitches. Two pins 1 in apart on the line; count. Compare with the dial using the converter.
5. Sew a square with pivoted corners. On the same folded scrap, draw a 4 in (10 cm) square. Sew around it, pivoting at each corner with the needle down. Shorten the stitch for the last few stitches before each corner if your dial allows it mid-seam.
6. Do the tension test. Fold the second scrap into a 6 to 8 in square and stitch one diagonal line. Read both sides against the table in reading tension. If it is off, rethread the top with the foot up and sew another line. If it is still off, turn the upper dial one step in the direction the table gives and sew again. Repeat until balanced.
7. Label and log. Write the settings on each scrap, and add one row to the stitch sample log for the balanced result (and one for each setting you tried, if you like). Keep the scraps together.

8. Your sewing Your sewing

9. Check your work Check your work

Criteria

• On the drills, do the holes stay on or touching the line through the corners and most of the curves, and did you stop to pivot rather than steer around the corners?
• Does the straight line stay at one distance from the edge, and is it secured at both ends with a few reverse stitches?
• Do the square's corners come to a point, with the needle turn landing on the corner rather than past it?
• On the tension test, is the lock hidden between the layers, with no loops or dots of the other color on either side and no puckers along the line?
• Did you rethread before you turned the dial, and change the dial one step at a time?
• Does the scrap carry its settings, and does the sample log have a matching row with stitch length, tension and the result?

Worked example

Common mistakes

• Threading with the presser foot down. The thread misses the tension discs; the underside shows loops or a nest. Raise the foot and rethread before touching any dial. Troubleshooting and care makes this mistake on purpose so you can see it.
• Turning the dial first. If the threading was the cause, the dial now hides it, and the next rethread throws the balance off again.
• Turning the bobbin case screw. The manuals that discuss it say it is set at the factory; this manual does not adjust it. If the upper dial at either end of its range cannot balance the stitch after rethreading, that is a symptom for Troubleshooting and care, not a reason to open the bobbin case.
• Pulling the fabric through. Stitches turn uneven and the needle can bend. Let the feed dogs do it; guide only.
• Starting without holding the tails. The first stitches tangle or the thread pulls out of the needle. Hold both tails behind the foot for two or three stitches.
• Testing on a single layer. One layer of fabric hides puckering and reads differently from a real seam. Fold the scrap so the test has two layers, as NMSU's test does.
• Not writing it down. A balanced stitch you cannot reproduce next week has to be found again.

What is still unresolved

This chapter settles one setting on one fabric with one thread. It does not settle the setting for your project fabric, which a sample on that fabric settles after Choosing and preparing fabric. It does not diagnose a stitch that will not balance after rethreading and a full sweep of the upper dial: that goes to the check order in Troubleshooting and care, and past it to a technician. A computerized machine that sets tension for you still gets the same test; its manual says whether and how you can override it.

10. Knowledge check and scenario

Checklist

• I drove the straight, corner and curve drills on paper, unthreaded.
• I sewed a backstitched straight line and a square with pivoted corners on a folded cotton scrap.
• I did the contrasting-thread tension test, rethreading before any dial change, and reached a balanced stitch.
• The stitch sample log has a row for the cotton scrap with stitch length, tension and the result, and the labeled sample is kept.
• I sewed the stitch length ladder and the zigzag ladder and logged them. (Go deeper; optional)