Introduction: Pencil/Tool Case From a Bike Inner Tube

About: I'm a chartered mechanical engineer and life-long maker. I especially like making useful things from cheap materials, including waste, and fixing things that would otherwise be scrap. I'll have a go at anythin…

Used bicycle inner tubes are easy to get hold of for free and they can be upcycled (geddit??) into great cases for pencils or bike tools. They're made from butyl rubber which is waterproof, tough and hardwearing. Sewing it is a little tricky, but perfectly possible with a domestic sewing machine when you know how.

You'll end up with a zipped case that measures something like 7½" / 19cm long by 3½ -4" / 9-10cm high. You could make it longer, but the curve of the inner tube starts to become more noticeable the longer it is.

These cases are made from two lengths of inner tube, each slit along its inner fold. They're joined together with a zip / zipper across the front, a seam across the back and seams at each end.


A used bike inner tube (see Step 1 for details)

A zip that's at least 14" / 35cm long (see Step 2)

A sewing machine, ideally with a walking foot, roller foot or Teflon foot

If using an ordinary machine foot, a little vegetable oil

A large leather or jeans sewing machine needle

Strong polyester sewing thread

Scissors and/or a sharp knife or roller cutter and mat

Quilting clips (or paperclips will do)

A soft pencil (eg 2B) and a ruler

Superglue (cyanoacrylate) - not essential

A drill and small drill bit, plus a short length of strong, thin cord (optional)

Step 1: Sourcing an Inner Tube

You’ll need an inner tube meant for a mountain bike (MTB) tyre for this project because they are wider than other bike types. Unless you have an MTB yourself or have friends who do, the best source is your local bike shop. Here in the UK and probably elsewhere, they put punctured inner tubes to one side for recycling and only send them off when they have amassed a few kilos, which will be dozens of them. And you'll be surprised how few of them are patched, it seems that a large proportion of today's cyclists take their bike in for someone else to fit a new inner tube the first time they get a puncture in one. All the more reason to give these waste tubes a new life as zipped cases, reuse being higher up the waste hierarchy than recycling.

With luck, the bike shop will present you with a carton of used inner tubes and invite you to take your pick. To sort through a stash quickly, look for those marked in inches (eg 26, 29) rather than mm (eg 700) because the inch ones tend to be for MTBs (in the UK, at least). You won’t need to use anything like a whole inner tube for a single case, but nevertheless it’s best to choose one for a larger wheel (eg 29”) if possible because the bigger the diameter, the straighter it will be.

After the large number indicating the wheel diameter, there’ll (usually) be a pair of smaller numbers on the inner tube indicating the range of tyre widths for which it’s suitable, eg. 1.50-2.50. So for example, the markings on the CST inner tube I used for the pencil case pictured above show that it was for 26” diameter tyres with a width of 1.5 to 2”. Some MTB tyres are much fatter than this, even 3” or more.

Of course, the circumference around the tube (and thus the width of “fabric” you get when you slit the tube) will be longer than the tyre width, but probably not as much as double the average figure. (The 1.50-2.50 inner tube I used produced a strip about 3¾” wide, a bit less than twice 2.0). The strips need to be sewn across the back of the pencil case with an overlap of at least ¼” which means that the maximum height of a case made from such a tube is 3¾– ¼ = 3½”. If you want a larger (ie taller) case than that, you’ll need to look for a tube meant for a fatter tyre, or else be prepared to sew more strips together.

(Apologies to those who prefer to work in metric units, but it makes more sense to stick to inches for this explanation, given that MTB inner tubes are sized that way.)

Personally, I prefer the inner tubes I use to have some character. If you feel the same, then look for tubes with patches (especially if they're a colour other than black) or printing on them. Also, it's quite neat to use a valve as a zip pull, so find a tube with an attractive (not too battered or dirty) Schrader valve - you'll need to drill a hole through it and the Presta ones are too skinny for that. Bike shops often cut across their old inner tubes either side of the valve and throw it away - presumably the recyclers only want the rubber - but you might find some in the pile that are still whole. It makes the straightening process (see Step 3) a bit simpler if the tube is still a complete circle, but it isn't essential.

Step 2: Zip Choice

You’re probably wondering why you need a zip that’s so much longer than the finished pencil case. That’s because the seam across the back has to be sewn by topstitching it on the outside of the case – an ordinary right-sides-together seam can’t be pressed open in this rubber “fabric” and would be far too bulky - and it’s impossible to do that by machine if it will produce a narrow tube held together at one end by the base of the zip. There just isn’t room to get the foot in there, particularly a walking foot. The case with the darker green zip and a piece of rubber sewn across the base of the zip shown in some of the photos in this 'Ible was made without using a long zip, but it could only be done by hand sewing the rear seam.

So we’re going to insert the zip first, and then open it all the way to the bottom to provide enough space to sew the overlapping seam across the back. Then we can shorten the zip and seam the two ends of the case in the ordinary way (right sides together - a little bulk at the ends of the case doesn't matter) before turning the case the right way out through the opening.

To do this, the zip ideally needs to be, at a minimum, the length of the pieces of inner tube that you will cut to make the case, plus the width of an inner tube that has been slit and opened out flat. (For example, if you cut 25cm long pieces and the width of a strip is 10cm, then a zip at least 35cm long is needed.) You can get away with a zip a little shorter if you don’t mind manipulating the pencil case while you’re sewing the back seam to keep the section under the presser foot flat – not recommended unless you are an experienced sewist.

As to the type of zip, I think the ordinary (ie not invisible) nylon coil type is best as they can be easily shortened and it's possible to stitch across the teeth without breaking a needle. Also, superglue will stick the nylon teeth effectively where you cut off the excess length. Moulded plastic zip teeth, or metal teeth, will just make the task harder and will also create more bulk at the ends of the case. An ordinary #3 zip (ie the width of the closed teeth is 3mm) as is used for dressmaking is fine, but you could use a bigger one.

Bright, zingy colours like lime green, orange and shocking pink look great against the black rubber. Match the zip to the sewing thread colour if possible, and to any coloured patches or printing on the inner tube.

Step 3: Straightening the Inner Tube

This step isn't essential, but is well worth doing to avoid a curvy pencil case that won’t lie flat. Follow the process set out in Waldemar Sha's Straightening/Flattening Bicycle Inner Tubes for DIY Projects 'Ible. Full credit to the author for coming up with this method. I had my doubts that it would work, given that butyl rubber is a thermosetting polymer, but it definitely does.

This is more straightforward if the tube is still a full circle, but all is not lost if you have to use one that's had the valve cut out of it. Instead of stretching the whole tube around a board, just wrap one cut end over the end of the board and sandwich that end between two flat pieces of wood (or one piece above and the bench/table below) that can then be clamped firmly to grip the rubber, both on the top surface and the underside. Then stretch the tube along the board and clamp at the other end in the same way.

In fact, there's an advantage in having the inner tube as a strip rather than a loop: the board doesn't have to be the right length to stretch the whole thing. You can use a relatively short board and just stretch as much of the tube as you think you'll need, letting the excess hang down at one end. So you might want to cut the valve off now, even if you do have a complete inner tube. Do remember to make holes in each end just inside the clamping zone though (see Step 3 of Waldemar's 'Ible), because the air inside needs to be able to escape and it can't do that through the cut ends if you've clamped them properly.

Another advantage of using a strip of inner tube is that you only need to iron one side of the board instead of flipping it over to do the other side. But you will need to ensure that the second board that will be used to clamp the rubber flat after ironing is short enough to fit between the clamping zones at each end.

I recommend stretching and flattening at least four times the length of the pencil case you plan to make, plus say an extra 6" / 15cm for seams. You need twice the length plus seam allowances for each case, but preparing twice this much means you'll have enough to make mistakes on, including some pieces for stitching practice.

Step 4: Cutting and Cleaning

Cut across the tube if it's still a loop, close to the valve on either side of it. Keep the valve to use as a zip pull – see Step 10.

Slit the tube along one of its long folded edges with scissors or a knife to make a flat piece of rubber “fabric” – take your time over this to get the cut as straight as possible. It's usually best to cut along the inner folded edge (ie the shorter edge that went against the wheel) so that the narrowest point of the pencil case is the centre rather than the top and bottom, but before deciding, consider where any printing or patches are on the tube. To make the origin of your pencil case obvious you can make a feature of such things, especially the markings denoting the manufacturer and size. If you want such printing in the top half of the front of the case, above the zip, then cut along the edge underneath the writing because that’s the edge that will then be sewn to the zip. On the other hand, cutting along the fold above the writing will allow it to be positioned below the zip.

Once cut, wash the inner tube in warm soapy water followed by a rinse to get rid of any dirt and the chalk that’s on the inside surface, then hang it up to dry naturally.

Step 5: Practice Makes Perfect

Rubber is an unforgiving material to sew because, like leather, the stitch holes don’t disappear if you have to unpick a seam. That means you need to get it right first time, so it’s vital to practise sewing and find the best settings for your machine and a needle/thread/foot combination that works before you tackle the pencil case. Also, you will have to use clips instead of pins to hold the pieces together ready for sewing.

I used a heavyweight polyester topstitching thread as the needle thread for the visible seams so that it would stand out well against the rubber, and an ordinary weight (but good quality) polyester thread in the bobbin. The upper thread, in particular, has to be strong because it needs a lot of tension to pull it through the rubber. You’ll need a beefy needle that is capable of going through several layers of rubber and has an eye big enough for the upper thread. I used a size 16/100 leather needle because leather needles have a chisel point that’s intended to prevent a seamline from tearing, which must also be a risk with rubber. However, I also had good results with a jeans needle of the same size – jeans needles have a particularly vicious point.

Using the needle and upper and lower threads that you intend to use for the real thing, first try stitching a piece of inner tube to a piece of scrap fabric of a similar weight to zip tape, with the inner tube on top. Draw a seam line along the rubber with a pencil. Set a long stitch length (at least 6-7 sts per inch / 3.5mm) and turn the upper thread tension up high, way beyond the setting you’d normally use. Fit your walking foot if you have one, otherwise try a roller foot or Teflon foot but I found that an ordinary foot with lubrication worked better than those options. To lubricate the seam pour a little cooking oil (eg sunflower or groundnut) into a dish, dip your finger in it and wipe it fairly liberally along the marked seamline. As long as you have ordinary fabric underneath in contact with the throat plate and the bed of the machine, there’s no need to lubricate the underside of the seam, just the upper, rubber surface over which the foot must slide. (And lubrication isn’t necessary with a walking foot because it “walks” across the work rather than sliding.)

Examine the underside of the trial seam. If there are loops of upper thread visible, turn up the tension even higher. I used a setting of 9-10 (on a scale of 1-10) whereas I have seldom gone above 5.5 before.

Assuming you get an acceptable result, the next stage is to try a zip insertion. Find an old or unwanted zip, or use the lower end of the zip you’re going to use for the pencil case – but you will need to leave it attached to the rest of the zip and unpick the trial stitching afterwards. With the zip open and on the underside of the seam, try stitching a length of rubber to it (see Step 7 for further advice on zip insertion, if needed). Without a walking foot you’ll need to lubricate the seamline and use a zip foot. This worked for me but left loops of thread on the underside and I got a better result by using my walking foot, even though its width mean that it rode over the zip teeth. I was able to find a side-to-side position in which the inner tube was held under the foot (ie it didn’t move when I pulled gently on it) and, by moving the needle position from the centre to the side, I could stitch along the marked seamline.

Now try a rubber-to-rubber seam, such as will be used for the ends of the pencil case and the seam across the back. I used ordinary sewing thread for both the upper and lower threads for these seams, because I couldn't get enough tension to pull a thick topstitching thread through two layers of inner tube. But I still needed a very high upper thread tension. To prevent the underneath layer from sticking to the throat plate you may need to lubricate the throat plate and/or the underside of the seam, even with a walking foot, so it’s going to get messy. As an alternative, try putting a strip of tissue paper under the bottom layer of rubber. Stitch through it and then tear it away afterwards – pull each side of the paper away from the seamline at the same time to avoid distorting the stitches.

You might like to try using a triple stitch for the visible rubber-to-rubber seams across the back of the case, if your sewing machine does one, to make stitches in ordinary thread stand out more against the rubber.

Finally, try sewing through 4 layers of rubber to see if it will be possible to insert a tab in the side seam to make it easier to pull the zip open (see Step 9).

Make a note of the settings, presser feet, threads and needles you’ve used for each type of seam, before you forget.

Step 6: Cutting Out the Case Pieces

Decide how deep (tall) you want the pencil case to be. The maximum height will be the width of the strip of rubber (opened out flat) plus the gap between the seamlines on either side of the zip. That gap will be roughly the width of the zip when it’s closed (ie from one edge of the tape to the other) minus about 3/8” / 9mm, because you can’t sew much closer than about 3/16” / 4-5mm from each edge of the tape. But if you make your case to this maximum height there’ll be a gap across the back that will need filling with a third, narrow strip of inner tube to compensate for the width of the zip (see 2nd photo in Step 8).

The alternative is to trim a little off the two front edges before inserting the zip, thereby reducing the height of the front of the case so that there’s enough of an overlap across the back to sew a seam without needing any extra “fabric”. Or else to trim more off the upper edge and none off the lower edge - as shown in the photo above - to produce a case with the zip near the top rather than across the centre.

You decide. There should be plenty of inner tube left to cut an insertion strip to go across the back if that’s the way you want to go. Otherwise, you’ll need to measure carefully and trim the correct amount off one or both of the front edges that will be sewn to the zip, allowing for at least 3/8” / 9mm of overlap across the back in order that your seamline will be no closer than 3/16” / 4-5mm from the edge of each piece of “fabric”.

Examine the slit inner tube to find any punctures (whether patched or not) and decide which sections of it to use. Draw on the rubber with a soft pencil to mark cutting lines. A new pencil is typically no more than 19cm / 7.5” long, which means 21.5cm / 8.5” or a little more is a good length to cut, allowing for the seams at the ends. You need to cut two pieces of the same length, one of which will form the upper half of the case (both front and back) and the other the lower half. While you’re at it, cut a couple of shorter lengths to use for stitching practice. Keep what's left until you decide whether you need an insertion piece across the back (see Step 8).

Trim the cut edges of the pieces for the pencil case to get them perfectly straight and square. You can draw a pencil line along them and cut along it with scissors or else use a sharp knife or roller cutter against a straight edge.

Step 7: Zip Insertion

Draw a seamline in pencil along the lower, front edge of the piece of inner tube that will form the top half of the pencil case, about 1/8” / 3mm from the edge. The instructions below will give a zip that opens from left to right, as is best for right-handed people. Just turn it around if you are left-handed.

Open the zip fully and place the marked seamline over the right hand side of the tape (as viewed with the zip pull at the bottom), with the end of the rubber strip about ¼” / 5mm above the zip stop. (See close-up photo above.) The long edge should be about ¼” / 5mm away from the edge of the zip teeth, meaning that the seamline is about 3/8” / 9mm from the teeth. There’s often a woven line down the zip on each side of the tape that you can use as a guide for where to place the edge of the rubber - see photo in Step 2. Check by looking underneath that the seamline you've drawn isn’t too near the free edge of the zip tape and adjust by reference to this woven guideline if needed.

It’s not possible to pin rubber without leaving holes but you can at least clip the inner tube in place at several points along the zip, using quilting clips or even paperclips

Stitch along the seamline marked on the rubber, from the top of the zip downwards, being careful not to stretch it as you go. Then follow the same process to stitch the second piece of inner tube that will form the lower part of the case to the left side of the zip tape, lining up the top edge with the edge of the first piece. Sew from the top down again, then any minor stretching will at least be in the same direction.

Close the zip and check that it's reasonably flat and smooth and that everything lines up correctly. In the event that the upper and lower halves of the case aren't perfectly aligned at the ends, it won't matter because that misalignment will be hidden in the seam allowance.

Just leave the excess zip at the right hand end of the case dangling for now.

Step 8: Back Seam

Now for the rear, overlapping seam(s). If you're inserting a third piece of inner tube, trim it to the correct width to give you enough of an overlap both for the upper seam and the lower one. I think the upper seam (or the only one, if there’s no insertion piece) looks better if the layer at the top of the case goes over the other layer, and the bottom of the case over the insertion piece for the second seam, but it doesn’t really matter.

The first seam will be easy if there’s an insertion piece because the case will still be flat after sewing it. The second seam (or the only seam for a 2-piece case) is trickier because it makes the case into a tube, but thanks to the long zip you can open that tube out flat to get it under the sewing machine's presser foot as long as the zip is fully open.

It isn’t possible to clip these seams to hold them in place while you sew. Instead, with the zip closed and the case face down, draw a seamline in pencil on the upper piece (after checking by looking under it that the stitching won't be too close to the edge of the lower piece). Then draw a line along the lower piece where the edge of the upper piece needs to be. As you sew, make sure that the overlap stays constant by keeping the upper edge along the line you marked on the lower piece, as well as keeping the stitches on the marked seamline.

The extra zip length has done its job and can be removed now. Close the zip fully and make a few stitches by hand around the teeth just inside the point at which you will cut it off level with the rubber. To be on the safe side, put a blob of superglue (cyanoacrylate) onto the teeth and the stitches in that area, if you have some.

When the glue is dry, cut away the excess zip so that it doesn't protrude beyond the end of the case. But keep at least one of the two halves as you may want to use it for a zip pull - see Step 10.

Step 9: Side Seams

You may wish to insert a tab into the side seam at the top end of the zip, to give something to hold onto when opening the case. But only do this if your practice session in Step 5 confirmed that your sewing machine would go through 4 layers of rubber, and if the tab will not be in the same place as a rear seam. Cut a strip of inner tube measuring 2½” x ¾" / 6cm x 2cm and fold it in half, right sides together. Stitch across close to the ends to keep them together,

You need to ensure that the start and end of the seam you're about to sew coincide exactly with the existing fold lines that form the top and bottom edges of the case. Before turning it inside out, mark the fold lines (top and bottom) with a pencil near each end on the inside of the fold. Then turn the case inside out and open the zip an inch or two – no more because you want the two sides of it to stay level with each other. If you are using a zip tab, lay it over the right side of the zip, with the fold inwards and its cut ends level with the other rubber edges (see photo). Clip the front of the case to the back, catching the zip tab between those two layers. Also use clips to keep the folds in the right place (but right sides together) while you sew, checking that your pencil marks are right on the fold. Stitch a ½” / 12mm seam, going straight over the zip teeth. Stitch again inside the seam allowance for added strength.

Open the zip half way – this is very important, you won’t be able to open it after sewing the second side seam unless you can get your fingers in! Then stitch the remaining seam which forms the right hand end of the pencil case, going over it twice as before.

Trim off the corners then open the zip fully and turn the pencil case the right way out. Ta dah! But see the next step if you want to add a zip pull.

Step 10: Add a Zip Pull

For a zip pull, you can use a valve stem or even some of the excess zip tape that was cut off.

Valve zip pull

Cut away any excess rubber from around the valve you're planning to use as a zip pull. You can either strip the rubber skin off the valve stem itself or leave it on. Either way, it's probably quite grubby so clean it up. Then drill a small hole through the stem, close to the end that was attached to the inner tube. I stuck the valve down onto scrap wood with duct tape to hold it steady and used a 2.5mm (about 1/8") drill bit. If there's no hole already in the pull attached to the zip then you'll need to drill one through that too.

Feed a piece of fine cord about 5" / 12.5cm long through the hole in the valve - use a sewing needle if necessary. Knot the ends together with an overhand knot to make a loop. Attach the new valve pull by pushing the loop through the hole in the existing zip pull and tucking the valve through the loop that emerges (ie a lark's head knot). Now you can shorten the cord to whatever length you like by tying a new overhand knot above the first one. Trim off the excess cord. If you like, drop a little superglue onto the knot to make sure it will never come undone and then pull the knot into the hole in the valve stem - you'll need to loosen and adjust the lark's head knot - and leave it to set there.

Zip pull from excess zip tape

For a pull that matches the zip perfectly, cut the teeth off one of the pair of zip pieces that were trimmed off in Step 8. Then trim away some of the width of this length of zip tape to leave just a narrow strip that's a little wider than the hole in the metal zip pull. Melt both long edges to seal them and prevent the fabric from fraying by passing each edge in turn rapidly through a flame. The easiest way to do that is using a candle in a holder, then you have both hands free to hold the strip of tape taut and horizontal. Guide it through the edge of the flame slowly enough to seal it, but not so slow that it melts or gets sooty. The chances are that some parts of the tape will look better than others after this process, so pick a good section, cut away the rest, seal the cut ends of the piece you're keeping and then tie it onto the metal pull in a lark's head knot.

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