Instructables
Picture of How to make arm warmers from a sweater
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Arm warmers are great for regulating your body temperature while bicycling and many other activities.  They keep the wind from coming up your sleeves while cover the area under your wrists and elbows where the blood flow is close to the surface and body heat is easily lost.

This instruction includes five files:
Choosing a sweater;
Spatchcocked sweater cutting instructions and layout; and
Arm warmer patterns, 3 pages

I make the arm warmers out of merino and cashmere crewneck sweaters.  You can make them out of fabrics with other fiber contents like cotton and silk, or blends.

Wool should be washed gently, by hand or machine (short cycle) in cool water with mild soap.  Do not soak, wring or scrub.  Lie flat to dry.  Wool is naturally resistant to staining, is antimicrobial and antibacterial, so does not need frequent washing, and can be spot-cleaned in between washings.  If you are not sure if your garment needs laundering, give the sniff test!

- Large or extra large mens merino, lambswool or cashmere sweater, clean and in fair to good condition.  Smaller sizes can be used for short arm warmers or childrens sizes. The wool should not be pilling.  Small holes can be mended.  Larger holes can be creatively patched.

-Heavy paper or manila tag for a hard copy, if desired.

-Sewing machine that includes zig-zag stitch and an overlock (also called a serger or babylock) if you have one.

-Sewers chalk or wax for outlining the pattern

-Fabric scissors

-Paper scissors

-Hand sewing needle

-Thread

1. Wash sweater by hand if it needs it.  Cool water, mild soap, do not soak.  Do not scrub or wring.  Dry on a towel on a flat surface.

2. Repair all holes.  Small holes can be darned from the inside of the sweater, by using a running stitch (that is the stitch most people think of when they think of sewing by hand, a simple over/under), making small stitches encircling the hole.  Gently pull the thread to make the circle smaller, without bunching the fabric too much.  Then sew in a crosswise pattern, alternating opposite sides of the circle like drawing a star, until the hole is filled in. Use matching thread!  Large holes should be patched with a scrap of wool cut into a small circle, square, or any fun shape.  I like red hearts!  Patches should be sewn onto the good side of the sweater using a wide and short stitch length zig-zag stitch. Contrast colored thread is fun.

3. Carefully cut the sweater open at the side and sleeve seams. Stay close to the seams with the scissors so you don't loose any of the unseamed surface area of the sweater.  You will need it all.

4. If the sleeves and/or sweater bottom are very blousy where the regular knit meets the ribs, you should press with steam, with the iron on med-high to flatten it out a bit.  It does not need to be totally flat.  It can be flattened with the pattern using a little pressure when you draw the outline of the pattern onto the sweater with chalk (see below).

5. If you plan to cut a helmet liner, too,  make sure your sweater is long enough to allow at least 5” below the neckline of the sweater at the center back, and 1.5” below the neckline of the sweater at the center front after you have drafted and cut out your arm warmers.  Of not, proceed to the next step.

1. Prepare the pattern by printing it or copying it.  There are three pages.  Pages 2 and 3 have a ½” bleed, so overlap the previous page by placing on the bleed line.  Tape inside the pattern lines with scotch tape on both sides of the paper.  Once all three pages are attached, cut it out with a paper scissors.  Never use a fabric scissors on paper!  If you want to adjust the patter for size, measure your bicep, and the length of your arm, compare to the note about fitting on the top of page three, and add or subract to the length and bicep accordingly.  The hand, wrist and foream may also be adjusted.  I suggest you make one the size of the pattern first, to experiment with fit on your own.  Once the pattern is ready, and tested, you might make a hard copy out of heavy paper or manilla tag, if you plan to reuse it.

2. If the sweater is big enough and you want to use the entire sweater, you will cut 6 arm warmers (to make 3 pair), and a helmet liner as shown in the file “Spatchcocked sweater cutting instructions and layout”.  I like to start with the sleeves of the sweater (one arm warmers from each sleeve), and then draft and cut four more from the front and back body of the sweater.  When drafting and cutting the body of the sweater, place the pattern as far over to one side as possible, so you can cut another next to it. You can let the pattern cross over seams at the armhole (i.e ignore that seam).  Leave space near the neckline for the helmet liner, as detailed above.

a. Place pattern on the sweater with the top of the hand at the ribbed (or otherwise finished) edge of the sweater.  This placement saves a sewing step, as you wont have to hem the arm warmers here, and also makes the nicest finish.  If you want to hem the edge at the hand, add 3/8” for a hem allowance.

b. Align the grainline of the pattern (the line that is the center of the pattern if you fold it in half lengthwise) with the ribs of the sweater.  You can fold the pattern to align the grainline with the ribs. If you don't place the pattern in line with the ribs, the arm warmers will twist on your arms.

c. Chalk around the pattern, gliding the chalk half way on the sweater, half on the pattern so the chalk isn't stretching and tugging at the fabric.

d. Cut out one at a time, or cut two at a time by layering another part of the sweater under the part you chalked. Repeat until you have used the sleeves and the body of the sweater to make 3 pair.  Be careful when cutting to leave room and to not damage the shoulder and neck area if you plan to make a helmet liner.

e. (Optional.  See instructables for the helmet liner). Cut helmet liner according to instructions, if desired and the sweater allows for it.

First, mend or patch all holes, if you haven't already.

When the instructions say to sew a seam, use the an overlock machine if you have one, or used the zig-zag stitch on your home machine, set to the widest setting, using a short stitch length.  Place the fabric right sides together.  Do not let the fabric stretch as you sew.  All seams are sewn with a 1/4” seam allowance.  If you are using an overlock, do not trim as you go.  Be sure to catch a full 1/4” of the cloth as you go, so the seam does not come apart with wear.  (The sweater knit structure, though fine, is loose enough to come apart easily, if you don't catch all the yarns.)

1. To make the seam from the top of the hand to the thumb (this is the short, curved seam), fold the arm warmer in half lengthwise, good sides together.  Pin and/or baste.  (Baste the seams by hand if you are a beginner or a perfectionist.*)

2. Overlock the thumb opening, that is, the straight line about 3-1/2” long that was formed from the first seam.  If you don't have an overlock, skip this step.

3. To hem the thumb opeing, turn under ¼” and baste,or pin along the very edge of the wrong side of the fabric.  Sew the hem from the wrong side of the fabric using a zig-zag stitch with the stitch width set at wide, the stitch length set at medium. The zig-zag should flank each side of the raw edge of the cloth to prevent the hem from curling.

4. If you added 3/8” hem allowance, hem the hand opening turning 3/8” and sewing as you did the thumb opening. If you are utilizing the finished ribbed edge of the sweater for the hem (i.e. the waistband or cuffs), skip this step.

5. To sew the seam from the thumb opening to the bicep (this is the long seam), fold the arm warmer in half lengthwise, good sides together, pin and/or baste.  Sew the seam with a 1/4” seam allowance, as you did the first seam.  Turn arm warmers right side out and put them on.  Check for any holes in the seams where you may have missed the yarns.  Check for fit.  Fix or adjust as necessary.

6. Cut two lengths of ½” wide elastic the same length minus a half inch as your bicep measurement.  No need to add allowance for this sewing step, as that bit of loss of length helps provide a little snugness to the fit, so they don't slip down as you wear them.  Sew each piece separately into rings with 1/4” overlap making sure not to twist the elastic into a Mobius strip!  With the arm warmers in a right-side-out position, place one of the rings inside of one of the arm warmers, folding the hem allowance over to cover the elastic.  Hand baste in place, placing the stitches close to the raw edge.

7. Using a wide and long stitch setting, zig-zag over your line of basting stitches,  making sure the stitches flank both sides of the raw edges so the hem doesn't curl.

8. Hand-sew the ends of the thumb seams, laying them flat to one side, and tacking them down.

You are done!  Congratulations.  Make another pair!

*To baste, use an hand-sewing needle, and matching thread, so you wont have to rip out the basting thread, which will get caught in the machine stitches later.  Use large stitches (about an half inch apart) running along the line of the seam or hem.  It is always wise not to skip hand-basting, if you care about how nicely your sewing looks!  It also prevents painstaking ripping out of bad work.