Sewing Techniques with an Overlock Machine
Constance Kratzer, Family Resource Management Specialist
College of Agriculture, Consumer and Environmental Sciences New Mexico State University. (Print Friendly PDF)
Sewing with an overlock machine is a bit different from sewing with a conventional sewing machine. Some of the sewing techniques used will require practice to become proficient. Here are a few tips to help you:
- When sewing with an overlock machine, be sure to
fit the garment before it is stitched. Because seams
are trimmed as they are sewn, it isn’t possible to
let out seams if the garment is too snug.
- Check your machine’s use and care manual for instructions
about how to adjust the thread tension.
To get the feel of good stitches, try using a different
color thread in each looper and needle. Adjust
each tension dial as needed to achieve a balanced
stitch. Stitch through a variety of fabrics to determine
how fabric weight affects the stitch quality.
- When the stitch is properly adjusted, the upper
looper thread will be smooth against the right side
of the fabric and the lower looper will be smooth
against the wrong side of the fabric. These threads
will meet and interlock evenly along the edge of
the fabric. The needle thread will be seen as a long
straight stitch on the right side and a shorter
straight stitch, which is more widely spaced, on the
wrong side (fig. 1).
If needle thread is too loose, increase the needle tension and/or decrease either or both looper tensions (fig. 2).
If upper looper thread is too loose, tighten the upper looper tension and/or loosen the lower looper (fig 3).
If the lower looper thread is too loose, tighten the lower looper tension and/or loosen the upper looper tension (fig. 4).
- The stitch width of an overlock machine is determined
by two or three factors. On some machines
the stitch finger or the cutting knife can be moved
by turning a dial or loosening a screw. Or, change
the throat plate to one that has a wider or narrower
If the overlock uses two needles, the stitch width can be adjusted by removing one of the needles. This can be done only when a three–thread stitch is used. The stitch length of an overlock machine may vary from 0 to 5 mm. The stitch can be adjusted by turning a dial, moving a lever or loosening a screw.
When sewing medium weight fabric, use an average stitch length—3 mm (about 9 stitches per inch). Delicate fabrics or fabrics that ravel should be stitched with a shorter stitch—2 mm (about 12 stitches per inch). A 1 mm setting will produce a satin stitch and is used for rolled hems.
- If your machine does not have a seam allowance
guide, use masking tape to indicate the seam
widths desired. Be sure to measure from the stitching
on the seamline, not from the cut edge of the
- At the beginning of a seam, it is not always necessary
to raise and lower the presser foot. At the end
of the seam, continue running the machine until the
thread chain is long enough to bring under the
knife blade to be cut.
- When seaming many sections of a project, stitch
from one piece to the next without raising the
presser foot or cutting the threads.
- To secure seam ends try one of the following
– Thread the chain end into a large-eyed needle and slip the needle under the seam’s stitching until the chain end is buried inside the seam (fig. 5).
– Stitch a few stitches, then fold the loose thread chain so you stitch over it. At the end of the seam, stitch off the fabric about 1/2 inch, raise the presser foot and turn the fabric over. Place the fabric back under the presser foot lower the foot and stitch about 1 inch before stitching off the fabric (fig. 6).
– Use a seam fixative to glue the thread ends at the end of each seam. This is especially useful when seams are crossed by other stitching (fig. 7).
– Tie a knot in the thread chain close to the fabric edge (fig. 8).
- Seams should be pressed directionally over the
stitching to smooth them, then pressed in the correct
position. To avoid an impression of seam allowances
on the right side of the garment, a piece
of paper can be placed under the seams as they are
Because seam allowances of overlocked seams are finished together, they must be pressed to one side. Horizontal seams usually are pressed up and shoulder seams are pressed toward the back. Vertical seams usually are pressed toward the center front or back. The seam of the sleeve cap should be pressed toward the sleeve.
To avoid bulkiness, seams in hem allowances should be turned in the opposite direction. When seams incorporate fullness, they appear less bulky when they are pressed toward the smoother side of the seam.
- Its best to avoid stitching errors when using an
overlock machine because once the seam edges are
trimmed off, there’s little you can do to remedy the
situation. If you have to rip out seams, here is how
to do it:
Two-thread overlock–Use scissors or ripper to cut stitch loops along fabric edge. Pull out cut threads.
Three- and four-thread overlock–Use scissors or ripper to cut stitch loops along fabric edge. Pull on needle thread to remove. Pull out all cut loop threads.
Chainstitch–Clip the needle thread, then pull the looper thread.
Special Tips for Overlock Sewing
- Pin, glue or hand baste seams together as you sew.
Pins should be placed parallel to the edge inside
the seamline. Place the pin heads so they can be
removed easily as you sew. The knife blades will
be damaged if they hit a pin as you sew.
Glue baste fabrics together with a water soluble glue stick. Lightly dot glue along seamline about 2-3 inches apart. Then, stick the seam allowances together with edges matching. Glue stick is especially helpful when matching plaids and stripes.
Hand basting may be necessary on loosely woven fabrics or when edges are very bias.
- When selecting thread for the overlock, match the
color of the needle thread because it is the one that
may show along the seam on the right side. You may
use a basic color, such as beige, white, gray or black,
on the loopers since these threads should not show.
- When changing thread, tie machine thread to new
thread using an overhand knot (fig. 9). This will make
the threading process simple. Remember to loosen tension
dials to allow knots to pull through easily. Cut the
needle thread before the knot gets to the eye of the
needle. Remove knot and thread the needle.
- It is better to use all one type of thread when possible,
all on spools or all on cones. Once a spool of
thread starts to break, discard it and get another.
- To begin stitching at a specific point other than a
corner, pull threads off the stitch finger and place
fabric under presser foot to begin stitching. After
stitching around edges to beginning, overlap stitching
about 1/2 inch and then sew off fabric edge.
Secure threads with a knot by threading thread
ends under stitches or use a seam fixative.
- When sewing curved seams, sew slowly. On outside
curves, push the fabric into the presser foot so
the edge seems to be straight. On inside curves,
pull the fabric gently to straighten the edge. Be
careful not to pull the fabric out of shape in the
- To turn outside corner, stitch one stitch past the
edge and raise the needle and presser foot. Carefully
pull the thread chain off the prong that forms
stitches and turn the fabric to stitch the next side.
Locate the fabric, lower the presser foot and the
needle and stitch. Stitch each corner in the same
manner. Or stitch along one side and off the fabric.
Then, stitch the next side until all sides are sewn.
Secure chain ends using one of the methods discussed
- To sew an inside corner, trim away all excess seam
allowance. Stitch to the point where the knife
blade reaches the exact corner and stop. Pull the
fabric toward you so the corner is straightened out
and finish stitching (fig. 10).
- Stabilize seams that need to keep their shape by
stitching twill tape or seam binding into the seams.
Place the tape so the needle stitches into the tape
without cutting it, or place a piece of cording (crochet
yarn, perle cotton, buttonhole twist) along the
seamline and sew over it. Let the ends extend so
they will be caught when the seam is crossed by
another row of stitching.
- Seams sewn with a combination of conventional and
overlock stitching can be used in a variety of fabrics
and garment styles. Finish seam edges first using a two- or three-thread overlock stitch. Then, sew the
seams using conventional stitching. Press the seam
allowances open after they are stitched, unless otherwise
instructed. (Not recommended for sheer fabrics
where seam allowances may show through.)
- When finishing facing edges, sew facing seams together and press in the recommended direction, then overcast the outside edge so it is smoothly finished and the facing is the recommended width.
Orginally written by Susan Wright, Extension
Clothing and Textiles Specialist.
Darlene Dictson, 4-H/Youth Specialist, assisted in revision.
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Revised and electronically distributed February 2003, Las Cruces, NM.