Knit Tube Top: A Simple Sentro Project for Every Skill Level

If you have been sitting with your Sentro knitting machine and wondering what to make next, a tube top might be exactly the project you need. It is one of those pieces that sounds too simple to be worth your time until you finish it and realize it fits beautifully, takes barely any yarn, and comes together in an afternoon. Whether you bought your Sentro a few months ago or you have had it sitting in a box since last Christmas, this project is approachable enough for beginners and satisfying enough for experienced machine knitters who want a quick, wearable win.

This guide walks you through everything — yarn selection, machine setup, stitch counts, finishing techniques, and tips for making the top actually fit the way you want it to. By the end, you will have a clear picture of the whole process and enough confidence to cast on without second-guessing yourself.

Why the Sentro Is Perfect for a Tube Top

The Sentro knitting machine is a circular knitting machine, which means it naturally produces a tube of fabric as you crank. This is exactly the shape you need for a tube top. You are not seaming two flat panels together or picking up stitches along an edge — the structure of the garment is already built into how the machine works.

That circular construction is what makes this such a satisfying beginner project. A tube top is essentially a longer-than-usual tube with some shaping at the top and bottom, and possibly a ribbed or folded band at each end. You are working with the machine’s natural output instead of fighting against it.

The Sentro comes in 22-needle and 40-needle sizes (some makers have also produced 48-needle versions), and both can work for this project depending on your yarn weight and the size of top you want to make. The 40-needle machine gives you more flexibility for garment work, particularly if you are making a top for an adult, but the 22-needle machine is absolutely workable with the right yarn.

What You Will Need

Before you sit down at your machine, gather your materials so you are not stopping mid-project to hunt for something.

Yarn: A lightweight to medium weight yarn works best for this project. Cotton, cotton-blend, bamboo, and linen yarns are popular choices because they have natural drape and breathability, which matters a lot for a top you will wear in warm weather. Look for a yarn labeled as sport weight, DK weight, or light worsted. Stay away from anything very thick or bulky — it will make the fabric stiff and too heavy to hold up as a tube top without rolling or drooping. Acrylic works too, especially if you want easy care, but a yarn with some natural fiber content tends to drape more flatteringly on the body.

You will need roughly 200 to 400 yards depending on the size of the top and the weight of your yarn. A petite or small adult top in sport weight might use closer to 200 yards. A medium or large in DK weight will likely use 300 to 400 yards. When in doubt, buy an extra skein.

The Sentro knitting machine: Either the 22-needle or the 40-needle version. Make sure all your needles are in place and moving freely before you start. A needle that is sticking or bent will cause dropped stitches.

The crank handle and any included accessories: Keep your hook tool and latch tool close by.

Cast-on yarn or waste yarn: A contrasting color helps you see where your cast-on ends and your main fabric begins.

Elastic cord or knit elastic: You will use this for the top edge of the tube top to keep it in place. About a yard of ¼-inch or ⅜-inch knit elastic is usually enough.

Tapestry needle: For weaving in ends and any finishing work.

Scissors

A measuring tape

Understanding Gauge Before You Begin

Gauge is the part that knitters sometimes want to skip, especially on a machine project that feels more mechanical than hand-knitting. Please do not skip it. Gauge is the reason your finished top will fit or will not fit, and on a circular machine, gauge is affected by your yarn weight, the tension dial setting on your machine, and even how fast you crank.

To check gauge, knit a swatch of about 20 rows and measure how many stitches per inch you are getting across the width of the tube and how many rows per inch you are getting vertically. Write this down. You will use it to calculate how wide and how long to make your top.

A typical gauge for DK weight on the Sentro 40-needle machine with a medium tension setting might land around 4 to 5 stitches per inch. A sport weight yarn might give you 5 to 6 stitches per inch. Your numbers might be slightly different, and that is completely fine — just use your actual numbers for the calculations below.

Calculating Your Measurements

A tube top needs two key measurements: circumference and length.

Circumference: Measure around the fullest part of your chest or the area you want the top to cover. Then subtract about 2 to 4 inches for negative ease. Knit fabric stretches, and a tube top is meant to fit snugly enough to stay up, so you want it to be slightly smaller than your measurement before it goes on your body. If your chest measures 36 inches, you might aim for a finished circumference of 32 to 34 inches.

Since the Sentro produces a tube, the circumference of your finished fabric is determined by the number of needles in use multiplied by your stitch gauge, then doubled (because the tube is two layers of fabric folded flat, but the circumference is measured around the full circle). On the 40-needle machine with all 40 needles in use and a gauge of 4.5 stitches per inch, your tube circumference would be roughly 40 ÷ 4.5 × 2 = about 17.8 inches in diameter, or about 56 inches in circumference. That is likely too large unless you are making a very oversized top.

This is where tension adjustment and yarn weight become important. A thinner yarn at a tighter tension will produce a smaller circumference on the same needle count. Experiment with your specific setup and measure your swatch tube to know exactly what circumference your machine is producing with your chosen yarn and tension setting.

If the circumference is still too large with all needles in use, you can take some needles out of commission by skipping them during the cast-on. Some knitters also work with the 22-needle machine for smaller sizing.

Length: Measure from where you want the top to sit on your chest down to where you want the hem. A standard tube top might be 12 to 16 inches long, but this is entirely personal. Add an extra inch or two if you plan to fold over a band at the top or bottom.

Setting Up and Casting On

With your gauge and measurements in hand, you are ready to begin.

Set your tension dial to the setting you used for your gauge swatch. Thread your machine with your waste yarn first. The purpose of the waste yarn is to give you a base to knit onto — it is easier to start on waste yarn and then switch to your main yarn than to start on your main yarn directly from scratch.

Crank through about 10 to 15 rows of waste yarn. These rows will be removed at the end, so the color does not matter.

Switch to your main yarn. If you want a simple rolled hem at the bottom, just keep cranking in stockinette. If you want a ribbed band at the bottom, you will need to stop and manually manipulate stitches to create a 1×1 or 2×2 rib pattern. Ribbing on the Sentro requires moving stitches between needles by hand, which slows things down but gives a nice polished edge.

For a beginner-friendly approach, simply knitting in the round in stockinette and relying on the natural roll of the fabric to create a finished edge is a perfectly valid choice. Stockinette rolls toward the knit side, so the bottom edge will naturally curl into a little roll that looks intentional and clean.

Crank the number of rows your length calculation requires. For example, if you need 14 inches of fabric and your row gauge is 8 rows per inch, you need 112 rows. Count as you go or use a row counter if your machine has one, or simply make marks on a piece of paper every 10 rows.

Finishing the Top Edge

When you reach your desired length, the top edge needs a bit more attention than the bottom. This is the edge that will sit across your chest and needs to stay in place.

The simplest and most effective approach is to bind off loosely and then thread elastic through a folded casing at the top. Here is how to do that:

Knit about 8 to 10 extra rows beyond your length measurement. These extra rows will fold over to create a small casing channel. Bind off by removing the stitches from the machine carefully using your hook tool, working one stitch at a time in a basic bind-off. Keep your tension loose — a tight bind-off will pucker.

Fold the bound-off edge down toward the inside of the tube and use a tapestry needle to whip stitch it in place, leaving a small gap of about an inch so you can thread the elastic through. Use a safety pin attached to one end of your elastic to guide it through the casing channel all the way around. Overlap the ends of the elastic by about an inch, sew them together securely, and then sew the casing closed.

This elastic casing method keeps the top in place reliably and is much simpler than other methods like picking up stitches for a band or working with hook-and-eye closures.

Removing the Waste Yarn

At the bottom of your tube, you still have those rows of waste yarn. Carefully cut the waste yarn away row by row, being careful not to cut into your main yarn. The live edge that remains can be left to roll naturally in stockinette, or you can pick up those stitches and add a ribbed band with your tapestry needle and some yarn, working a hand-knit 1×1 rib for a few rows before binding off. This gives a more polished finished look.

Another option is to fold the bottom edge up inside the tube and tack it in place, creating a double-layered hem that is thick and stable without any ribbing required.

Blocking and Finishing

Once your top is assembled, wet blocking does wonderful things for machine-knit fabric. Fill a sink with cool water and a small amount of wool wash or gentle soap, submerge your top, and let it soak for about 20 minutes. Gently squeeze out the water without wringing, then lay the top flat on a clean towel, roll the towel up to press out more water, and then lay the top flat again on a dry surface in the shape you want it to dry in.

Blocking evens out the stitches, relaxes the fabric, and helps the top maintain a consistent shape. Cotton and linen yarns in particular benefit significantly from blocking because they tend to look uneven when fresh off the machine.

Weave in any remaining yarn ends with your tapestry needle, being thorough so nothing works loose when the top is worn and washed.

Tips for Getting a Better Fit

A few extra considerations will make the difference between a tube top that you reach for all the time and one that sits in a drawer.

Think about the fabric’s stretch when choosing your negative ease. A very stretchy yarn like one with high elastane content needs more negative ease than a cotton with very little stretch. If you are unsure, err on the side of more negative ease rather than less — a snugger fit stays up better.

The length of your elastic casing matters. An elastic that is too tight will bunch the fabric and feel uncomfortable. Too loose and the top slides down. Before sewing your elastic shut, put the top on and adjust until the elastic feels firm but not painful at the chest.

If you want a seamless look at the back of the top, keep your yarn joins at the same point in the round so any slight color variation or texture difference from a new skein stays in one discreet spot.

Consider adding boning or a layer of bra cups inside the top if you want extra support and structure. These can be hand-stitched to the inside fabric without showing on the outside, and they transform a casual summer top into something you can wear more confidently at a wider range of occasions.

Variations to Try Once You Have the Basic Version Down

The basic tube top is a template you can take in many directions.

A striped version is easy to achieve on the Sentro by changing yarn colors every few rows. Because the machine is circular, stripes come out as clean horizontal bands all the way around the tube.

An open-work or lace effect can be created by dropping certain stitches intentionally and letting them ladder down the fabric, or by skipping needles at intervals. This gives a more decorative, summery texture.

A longer version becomes a tube dress or a cover-up. The same technique scales up easily — just keep cranking more rows.

You can also experiment with different edge treatments. A picot edge on the top casing looks delicate and feminine. A broader ribbed hem gives a sportier, more structured look. A raw cut edge with just a light seam finish suits an edgier aesthetic.

Caring for Your Finished Top

Care instructions depend on your yarn fiber content. Cotton, bamboo, and linen machine-knit tops can generally be machine washed on a gentle cycle in cold water and laid flat to dry. Avoid the dryer, which can cause the fabric to shrink or distort. Acrylic tops are more forgiving and can handle a regular gentle wash cycle, though air drying is still preferable for keeping the fabric in good shape over time.

Store your top folded rather than hung to prevent the fabric from stretching out of shape under its own weight.

A Final Word

The Sentro tube top is one of those projects that rewards you quickly. Within a single sitting or spread over a couple of evenings, you have a wearable, flattering, handmade garment that genuinely looks like it belongs in a boutique rather than a craft box. The skills you practice here — managing gauge, calculating sizing, adding elastic casing, blocking machine-knit fabric — all carry over to more complex Sentro projects like sweaters, skirts, and accessories.

Start with one simple version in a solid color to get the process clear in your head, and then let yourself experiment with the second one. You will find a rhythm with your machine that makes each subsequent project faster and more intuitive. Knitting on a circular machine is one of those skills that feels steep for the first twenty minutes and then suddenly clicks into place, and once it does, you will find yourself reaching for that crank handle every time you want something satisfying to make.

Happy knitting.