Transforming T-Shirts: Crafting Custom Onesies

There are several ways to make a T-shirt into a onesie, and it can be a fun and easy project. The process involves tracing and cutting the T-shirt according to the shape of a onesie, and then sewing the pieces together. Some methods involve using a sewing machine, while others can be done by hand. The type of T-shirt and onesie used, as well as the desired style, will determine the specific steps and materials needed. For example, one method suggests using a small adult T-shirt or a child's shirt, along with a store-bought onesie as a guide, while another method recommends using a youth-sized T-shirt and a pre-made romper. Ultimately, with the right tools and guidance, anyone can create a unique and personalised onesie.

Cut and leave the T-shirt as is

If you want to cut and leave the T-shirt as is, the process is very simple. First, lay your T-shirt on a flat surface and straighten it as much as possible. Then, find the lowest point on the T-shirt where it starts to curve down into the snap area and cut the shirt horizontally at this point. You can also cut off the sleeves if you want to make it into a vest.

If you are using a child's shirt, you can cut only the bottom of the shirt, shaping it into a onesie while keeping the rest of the shirt intact. You can also cut a U-shape at the bottom of the shirt to create a harem pant-style onesie.

If you are using a larger shirt, place a onesie that fits your baby on top of the T-shirt, making sure the neckline is centred. Cut about 1 inch outside the lines of the onesie, so you have a seam allowance. You can then cut the back underwear panel of the onesie and make the front panel shorter.

Cotton doesn't fray, so you can leave the T-shirt as is without sewing or using hem tape. However, if you want to neaten the edges, you can use hem tape, sew the edges, or use a coverstitch machine.

Cut and finish seams using hem tape

To cut and finish seams using hem tape, you will need to prepare the fabric or clothing you are using. Mark where you would like the hem to be using a pin or any other means, and then turn the clothing article inside out to expose the inside of the garment. Using a ruler and a marking pen, mark where the pants will be folded. If you don’t have a washable pen or air-erasable pen, chalk is a good substitute.

Next, cut the item a little longer than your desired length, as you will need to fold it and then apply the hem tape. Depending on your tape width, this will vary, but it is usually about 25mm or 1 inch.

Now, fold the part you want to hem with the tape. All of the item should be inside out except the bottom where you will iron on the hem tape. Make sure the item is the length you want it to be. Cut your adhesive tape to the length of the hem of the pants you will be covering, cutting a little more than necessary. Half an inch is more than enough.

Depending on your hem tape, you will soak the tape in water. It is recommended to soak for 3-5 minutes. After it is soaked, take it out and apply the adhesive side over the raw hem. The adhesive side is the one with the white woven strings. It will look shinier on the sides than on the non-adhesive side. Other hem tapes do not need soaking, so check the instructions that came with the tape to confirm.

Place the adhesive side down over the raw hem. Place the tape near the edge of the cut hem, straight and covering all of the edges. Press the hem tape. If your material is not cotton, it is recommended to use a press cloth between the iron and your item. Using your iron on medium heat (150°C or 302°F), press on the hem tape. Do not slide the iron; only press, applying your weight for about 10 seconds. Move on to the next section.

After you have completed the iron presses, wait for the material to cool. If you happen to make a mistake, take a damp press cloth and iron over the hem tape. After it has heated, you may peel the tape off gently. There may be residue left, so it is best to try again with fresh tape.

Cut and finish seams using a sewing machine

To cut and finish seams using a sewing machine, first cut out your T-shirt pieces. Place your two T-shirt body pieces back-to-back, so the wrong sides are facing out. Align them as neatly as possible, focusing on the neckline and shoulders. Pin them in place along the shoulders, aiming to pin every 1 inch. Sew along the pinned shoulder edges to join the two pattern pieces together. Remove the pins as you go.

Next, open out the two pieces so they are only joined at the shoulders. Take an arm pattern piece and find the centre point of the curved side. Line this centre point up to one of the shoulders and pin it in place, with the right sides facing in. This pin will be at the point that will lie on the very edge of your shoulder. Now, pin the rest of the arm to the armhole. Starting at the pin you just added, work outwards along the curved edge of the arm and pin it to the body piece. Be very careful here, as it's tricky to pin curved edges together! Don't be afraid to go crazy with your pinning—more is definitely merrier!

Carefully sew the pinned arm piece to the body pieces, along the curve you have just pinned. Remove the pins as you go. Repeat this for the other arm piece.

Then, fold the T-shirt back together along the shoulder seam (right sides facing in), so the front and back line up neatly again. Pin the sides together, starting at the underarm and working your way down to the bottom edge. Sew in place, removing the pins as you go.

Now, it's time to add the neckline. Cut a strip of fabric, measuring 4cm wide by approximately 45cm long. Make sure you orient your cutting so that it will stretch lengthwise, not width-wise. With a medium-hot iron, press the fabric strip flat. Carefully and neatly, fold the strip in half along the long edge. Press this fold in place.

Find the midpoint of the neck binding strip. Turn your T-shirt the right way round. Line the midpoint of the neck binding with the midpoint of the neck hole, on the front of the T-shirt. You'll need to align the raw edges of the binding strip (i.e. not the folded edge) with the raw edge of the neck hole. Pin them together.

The next step involves pinning the binding to the neck hole. For this, the binding must be at greater tension (i.e. more stretched) than the neck hole. This will ensure it sits flat when you wear it. Make a mark on the binding strip 10cm to one side of the pinned midpoint. Pin this marked point of the binding to the shoulder seam of the neck hole. The length of fabric between the pins should now be shorter for the neck binding than it is for the neck hole.

You now have the neckline pinned in two places. Carefully add more pins in between the two existing pinned points. You'll need to gently stretch the neck binding as you pin, so that it lines up against the neck hole without any gaps. When finished, you'll have a quarter of the neckline pinned in place. Repeat this step for the other quarter of the neckline that sits on the front of the T-shirt. Then, repeat this for the back of the T-shirt, so that the entire neckline is pinned in place.

Set your sewing machine to a zig-zag stitch. Sew along the neck binding, removing the pins as you go. As you sew, ensure that you gently stretch the neckline so that the binding is at a higher tension than the neck hole. When you get to the back of the neckline, where the two ends meet, stop sewing. Remove any last pins. Unfold the two ends of the neckline and lay them flat against each other, right sides together. Pin them together and sew in place (with a straight stitch). Trim any excess, then fold the neckline in half again (along the line that you pressed earlier). Then simply sew this to the T-shirt, in the same way that you sewed the rest of the neckline (make sure you use a zig-zag stitch!).

At this point, it's a good idea to try on the T-shirt. Make sure the neckline can stretch over your head. If it's too tight, simply unpick the neckline and cut the hole larger, then repeat the previous steps. If the neck strap does not sit flat against your neck, it's probably because the binding was not held at a high enough tension when you sewed it. Unpick the neckline and repin it, but this time stretch the neck binding more tightly against the neck hole.

Finally, put the T-shirt on and use tailor's chalk to make a small mark on the waist section, at the length you would like to cut it. Do the same for each of the arms. Take the T-shirt off and find the three marks you made. At each point, add an extra 3-4cm as a seam allowance. Then cut off the excess fabric.

Starting at the waist section, fold the raw edge (that you've just cut) over by approximately 1-2cm. Then fold it over another 1-2cm, so the raw edge is hidden. You can fold it either inwards or outwards, depending on the finish you would like your T-shirt to have. Then, starting at the side of the T-shirt, sew over the folded edge. Keep sewing all the way around the waist, until you loop back on yourself. If your T-shirt has a slightly loose fit, then you can use a straight stitch for this step. However, if your T-shirt is a tighter fit, make sure you use a zig-zag stitch. The most important thing with this step is to ensure you do not stretch the fabric as you sew it! Gently guide the fabric through the machine, without stretching it.

Finally, repeat the exact same process for each of the arms.

Use a coverstitch machine to finish the edges

Using a coverstitch machine to finish the edges of your onesie will give it a professional-looking hem. This technique is especially useful for hemming knit fabrics as it maintains the stretch in the fabric and doesn't pucker, unlike a sewing machine. Coverstitch machines are primarily used to cover raw edges of fabric while retaining fabric stretchability.

To start, make sure the edges of your fabric are evenly cut. You can use a rotary cutter to help achieve this. Then, prepare for hemming by clipping the side seams at the fold and laying the clipped seam in the opposite direction. Make sure the cut is small and that the seam is sturdy enough to withstand the clip. If your fabric can take a little heat, it is recommended to iron the fold to make hemming easier.

When you're ready to start sewing, always begin at the back of the garment, just after the side seam. Pull all the threads back and to the left before you start to ensure they don't get snagged. Use a seam guide for an even hem if your machine doesn't have a built-in ruler. You can also use a piece of Lego attached with sticky pads or Blu Tack to help you sew in a straight line.

As you sew, gently guide the fabric without pulling to ensure it is evenly fed and to avoid twisted seams. If you are sewing in a circle, sew over the beginning stitches for a couple of centimetres, then lift the presser foot to release the tension. Check your machine manual for specific instructions on how to release the threads and tension.

When you're finished sewing, it's important to secure the coverstitch seam to keep the threads from unraveling. Refer to your machine's manual for instructions on how to do this.

Using a coverstitch machine will give your onesie a neat, professional finish that will stretch with the fabric. With a little practice, you'll be able to create beautiful, durable garments.

Hem the armholes for a more finished look

Hemming the armholes of your onesie will give it a more finished look and feel. The armhole, or armscye, is the circular edge that extends from the tip of the shoulder to the underarm. This edge can be sewn to connect a sleeve to a garment, or it can be left sleeveless.

There are a few different methods you can use to hem armholes, depending on the fabric and the shape of the armhole. The two most common techniques are shaped facings and binding. Facings provide a more tailored finish and work well with medium-to-heavy fabrics, while binding can be machine or hand-stitched and is a good option for lightweight fabrics.

One method for hemming armholes is the double turn-under hem. Here's a step-by-step guide:

• Sew a baste stitch 1/4" in from the raw edge.
• Turn the fabric towards the wrong side and press under along the stitch line.
• Turn under again 1/4" towards the wrong side and finger press.
• Sew the hem in place, massaging the fabric into the curve as you go. You may need to put tension on the fold to navigate tighter curves, like at the bottom of an armhole.
• Your completed double turn hem should be neat on both sides.

Another option is the single turn-under hem. This method can be done with an overlocker/serger or with a zig-zag stitch. Here's how:

• Use an overlocker/serger, or sew the raw edge of the fabric with a zig-zag stitch to prevent fraying.
• Turn under 3/8" once, press, and top stitch in place.
• You may need to narrow the hem where the curve gets steeper, as it can be challenging to get the fabric to bend.

For a more professional finish, you can also use bias binding (tape). You can buy bias tape or make your own. This method involves:

• Opening out one side of the bias tape and pinning the right side of the tape to the right side of the garment along the first fold line, matching the raw edges.
• Sewing "in the ditch" of the first fold line to attach the bias tape to the garment edge.
• Pressing the garment towards the bias tape on the inside.
• Deciding whether to conceal the bias tape by turning it to the inside or making it a visible feature by bending it along the midway fold line.
• Sewing the bias tape in place.

By following these steps and choosing the appropriate method for your fabric and armhole shape, you can achieve a neat and professional-looking hem for the armholes of your onesie.

Frequently asked questions