Expanding Yarn Swift

Nowadays it’s not just hand-dyed yarn that comes in hanks or skeins. Even commercially spun and dyed yarn is often sold skeined, presumably to make it look "artisanal". So, like our grandmothers before us, we must wind it into a ball before we can knit or crochet with it. Unless you possess a swift, that means persuading your nearest and dearest to stand with their arms out (like many of us did as children) while you wind the yarn, or trying to do it on your own by looping it around the back of a chair or even over your knees. After buying 5 large skeins of yarn and spending a tedious half hour winding the first of them off my knees, I decided to make a swift.

A swift holds a hank of yarn and rotates to deliver it smoothly when the yarn end is pulled. It makes life a lot easier, whether you’re winding the yarn by hand or using a mechanical ball winder. Swifts come in two main varieties: the umbrella type which expands (like an umbrella does) to accommodate different skein sizes, and the simpler Amish style with movable pegs. Making an umbrella-like frame seemed far too complicated, but I didn’t really like the idea of pegs either, I was afraid they’d get lost. I had a look online to see how people had made their own swifts, and a solution based on a pair of expanding coat racks and a lazy Susan looked promising, as did nindespin's DIY Yarn Swift Instructable built around an expanding wine rack. I’d rather make something from scratch though, and have it just as I want it.

I started the design process in Tinkercad but I found it hard to visualise how the finished swift would look as it moved. I switched to Fusion 360 – this was one of my first Fusion projects and it was a useful learning exercise. I was then able to insert joints between the various parts to make the swift articulate, produce drawings and rendered images, and even set up animations (like the one above) and motion studies (like the one in Step 8) to watch it move. See Step 8 for more info on the advantages of Fusion 360 over Tinkercad.

A piece of stiff, thin (about 5mm / ¼”) plywood at least 120mm by 450mm, or a 2.8m / 3yd length of 18mm / ¾” wide hardwood strip of the same thickness

0.7m / 28” of 9mm / ⅜” wooden dowel

A piece of 18mm / ¾” thick plywood or hardwood about 320mm x 160mm / 12½” x 6½” for the base

A short length of brass, copper, aluminium or stainless steel tube with an inside diameter very slightly bigger than the dowel

A small offcut of 18mm / ¾” thick plywood or hardwood

7 M3 or M4 (about ⅛” diameter) bolts at least 20mm / ¾” long, 12 matching nuts and 6 matching washers

2 woodscrews with countersunk heads, about 6mm / ¼” diameter and 35mm / 1¼” long

4 smaller woodscrews with countersunk heads, 3mm / ⅛” diameter and 25mm (1”) long

A saw

A drill and bits to suit the bolts and screws used, plus a countersink bit and 22mm (approx. ⅞”) and 13mm (½”) spade bits

Wood glue

A 608 ball bearing (22mm outer diameter, 8mm bore, 7mm width)

Sandpaper

Duct tape

Wood finish

A small round or half-round file

A hammer

A router and roundover bit – optional

A hacksaw or Dremel with a metal cutting disk

Loctite or similar threadlocker

The Tinkercad design I came up with first is shown in the screenshot (red and green swift) attached to this step. Its rotor is made from 6 wooden strips arranged in an expanding coat rack-like (or pantograph-like) structure. Its centre is bolted onto a shaft that rotates in a bearing sunk into the base. The idea was that the swift would fold up small for storage like an Amish one, but could be quickly expanded like an umbrella swift to suit different hank circumferences without the need for adjustment by placing removable pegs in the right holes. When I’d made it and used it for the first time I discovered four things:

1. There’s no need for any fixed pegs other than the four at the outer corners;
2. Those four pegs need to be positioned a little way in from the tips of the wooden strips to allow space for the yarn, otherwise the skein tends to fall off;
3. The shaft needs to be supported where it emerges from the base to prevent the rotor from wobbling in use, particularly when it's fully extended; and
4. The rotor needs to be attached to the shaft by more than just a central bolt, or it will rotate around that bolt instead of the shaft rotating in the bearing that’s hidden in the base.

The version described in the following steps incorporates these modifications. It will accommodate hanks with a circumference between 90cm (36”) and 2.6m (102”) but could easily be made larger or smaller by varying the length and/or width of the 6 wooden strips.

My swift has four unnecessary holes (the ones near the outer tips where the pegs were originally going to go), which I’ve filled with extra bolts to try and make my mistake less obvious. This explains why the photo of the finished item (with parts labelled) shows 11 bolts rather than just 7.

The rotor and shaft can be pulled out of the lower shaft support to disassemble the swift for storage.

As explained in the Intro, I started my design in Tinkercad and just picked a half-expanded state to model. But I worried that I might be missing unexpected interferences between the parts when it was opened and closed unless I also modelled the swift in the fully open and closed states, and that just seemed like tripling the effort. So I changed to Fusion 360 which allowed me to articulate my swift model and watch what happened as the rotor expanded and contracted. This was particularly useful when I found that I needed to move the pegs (as per point 2 above) because I was able to work out how far in they could move without preventing the rotor from closing fully for storage. The third image in this step is a rendering of my first F360 model before I made changes 1-4, and the final image is the actual swift, part way through the changes.

Cut the thin plywood or hardwood strip into 6 lengths, each 18mm / ¾” wide and 450mm / 18” long. (See Step 8 for a PDF drawing which gives most of the dimensions for this swift.) If you're starting with a piece of ply then cutting it into strips is easiest done with a table saw or bandsaw, but it can be done by hand. First, check whether the plywood bends more in one direction than the other and cut it so that the bendier direction is across the strips rather than along them, to prevent rotor droop.

Smooth all the edges with sandpaper and round off the corners. The rotor needs to be perfectly smooth so yarn doesn’t catch on it.

Mark the centre of each strip and drill a hole through it that’s the same diameter as a bolt. In addition, drill holes as follows on the (longitudinal) centre line:

• on two strips, 10mm / ⅜” from each end
• on the other four strips, 10mm / ⅜” from one end and 40mm / 1⅝” from the other end.

Recess the holes that are 40mm / 1⅝” from an end, on the underside, to suit the small screws with countersunk heads. (These holes are where the fixed pegs will be attached.)

Bolt the strips together as shown in the photo, leaving the nuts slightly loose for now. (Ignore the holes in the photo that don’t have bolts in, these were drilled before I realised that the upright pegs are best moved in from the tips to stop the yarn falling off.) Check that the rotor expands and contracts, folding up neatly when the strips are pushed right together.

Cut five 120mm / 4½ ” lengths of dowel. A hand mitre saw is my tool of choice for this sort of job, but a bandsaw would be quicker. (Again, ignore the fact that there are too many lengths of dowel shown in the photo, I took it before I modified the design as explained in Step 1.)

Sand the cut edges smooth and round one end of 4 of the dowels. These 4 will be the fixed pegs that hold the yarn, the 5th dowel will be the shaft.

Drill a small hole in the centre of the un-rounded end of each peg, big enough to allow one of the small woodscrews to be screwed in but not so big that it won’t grip tightly. If you have a pillar drill, the best way to drill a hole that’s exactly on the centreline of the dowel is to put the un-rounded end of the dowel in the chuck, lower the drill press until the rounded held can be held and clamped vertically in a vice, release the chuck, raise the drill press, fit a drill bit and then drill.

You could screw the 4 pegs in place on the rotor now, but that makes it more awkward to handle and is best done later.

Also drill a hole in one end of the shaft that will take a bolt, again without it being loose. The other end of the shaft needs to be reduced in size (diameter) so that it will fit tightly into the 8mm hole in the middle of the bearing, ideally with a shoulder - see photo - that will rest on the top of the bearing’s inner ring rather than a more gradual reduction in diameter. Unless you have a lathe and can turn down the last 7mm of the shaft (the width of the bearing) to a diameter of 8mm, it’ll have to be done by sanding.

Draw a line 7mm from the un-drilled end and wrap a length of gaffer tape above it. Then just sand the zone below the tape, either by hand or by putting the shaft in the chuck of a drill, turning it on and gently holding sandpaper against it. Be careful if you do it the powered way, it’s easy to take too much off. Keep trying the shaft in the bearing and carry on until it will just fit in to the full 7mm depth.

The base needs to be quite heavy to keep the swift stable when it has 100g / 4oz or more of yarn on it, rotating fast. That’s why I suggest making it quite large and from relatively thick wood, although you could make a smaller one and clamp it to a table before use. Assuming you’d rather not bother with clamps, cut a piece of thick ply or hardwood measuring about 320mm x 160mm / 12½” x 6½”. I rounded over the upper edge with a router, but that’s not essential.

Draw in the diagonals on the top surface to find the centre point. This is where the bearing will go, in a recess so that it sits slightly below the surface.

Measure the diameter of the outside edge of the inner ring/race of the bearing you’re going to use. Mine was about 12mm so I used a 13mm spade bit to sink the first hole – it needs to be big enough to ensure that the inner ring can rotate freely without rubbing on the base of the hole the bearing will sit in. Drill the hole a little deeper than the bearing’s width of 7mm, say 3mm / ⅛” more.

Now drill a second, concentric hole with the larger spade bit. Make it just slightly deeper than the bearing, say 1mm / 1/32” more. The bearing should be a good tight fit in this hole so that the outer ring is held fixed and won’t rotate, and when you place it in there it should sit just below the surface of the wood. (If it’s a loose fit, don’t worry for now, you can glue it in place in the next step.)

To keep the shaft vertical and prevent the rotor wobbling in use, the modified version of the swift has a support that fits over the lower part of the shaft where it emerges from the bearing in the base. This is the truncated cone in the photos – but it doesn’t have to be that shape, I just happened to have a piece of turned scrap that would do the job. A square section would work just as well, and I suggest you cut a piece of wood to about 50mm x 50mm x 45mm tall / 2” x 2” x 1¾” tall.

At the top of this support is a metal bushing which is a reasonably close fit onto the shaft to hold it vertical. Cut a length of tube about 18mm / ¾” long with a hacksaw or Dremel, file off any burrs from each end, inside and out, and then try it for size on the shaft. The shaft needs to be able to rotate freely within the bushing without binding, but the clearance should be such that it can’t wobble much, if at all. If the fit is too tight, then either lightly sand the lower part of the shaft or file out the inside of the bushing.

Drill a hole vertically through the centre of the support using a bit that matches the outside diameter of the bushing – the bushing should be a tight fit in it or you’ll need to glue it in place. The shaft needs a good clearance below the bushing so drill out that part of the central hole to a larger diameter if necessary. Then hammer the bushing into place at the top of the support – put a piece of wood over the bushing to protect it if it’s made from a soft metal such as brass – until it’s flush with the surface.

Feed the shaft down into the support from above, leaving just enough shaft protruding from the underside to fit into the bearing. Place the support down on the base, pushing the shaft into the bearing and holding the support down firmly. Check that the shaft can rotate freely – if it can’t, it’s probably because the support isn’t in quite the right position and the shaft is being forced out of alignment, so just move it around by tiny amounts. If that doesn’t work, then it can only be because the axis of the bushing isn’t aligned with the axis of the bearing, in which case you’ll need either to pack something under one side of the bearing (and possibly deepen its recess) to tilt it a little, or else adjust the underside of the support to tilt that very slightly. If the bearing is a sloppy fit in its hole, glue its outer ring into the curved face of the hole, taking care not to get any glue anywhere that could prevent the inner ring from rotating or stick the shaft into the bearing.

Once you're happy that everything is positioned so that the shaft can spin freely, draw in pencil on the base around the support and mark both base and support as necessary to show exactly where the support needs to be placed, and which way around.

Remove the shaft and support. Mark the base, within the support outline but clear of the bearing, where the holes should go for the two large woodscrews that will hold the support in place. (Screws are used for this, rather than glue, so you can get at the bearing in the future in case it should ever need lubricating or replacing.) Drill holes right through the base big enough for the screws to just fit through them.

Holding the support in its marked position and working from the underside of the base, drill a pilot hole into the support through one of the screw holes in the base. Before drilling the second pilot hole, fit the bearing into its recess (if it isn't already there) and the shaft into the bearing and the support, then screw the support in place with the first screw. Check that the shaft still rotates freely. Drill that second pilot hole (through the base again) and fit the screw. As long as everything is still OK, remove the screws, countersink their holes on the underside of the base and refit them.

For the upper support, drill a dowel-sized hole in a small offcut of thick ply or hardwood to take the upper part of the shaft. The hole should be at least 25mm / 1” from adjacent edges of the material. Then cut the support down to create a block the same width as a rotor strip (18mm / ¾”) and about 50mm / 2” long, with the hole through its centre. Sand it smooth.

Check the whole length of the shaft will slide through the hole in this support. If it doesn't, enlarge the hole a little using a piece of sandpaper wrapped around something like the shaft end of a drill bit.

Apply a wood finish of your choice to all the wooden parts, bearing in mind that you don’t want to risk leaving an oily residue that could get onto the yarn.

All the pivot-point bolts except for the central one that goes into the shaft will be fitted with a washer and two nuts. (The washer is there just to prevent the nuts from digging into the wood, and using a pair of nuts makes them less prone to working loose when the rotor is opened and closed repeatedly.) Work out what length they need to be to pass through two rotor strips as well as the washer and nuts and then cut them down with a hacksaw or Dremel. Remove any burrs and sharp edges with a small file. Wind two nuts onto each bolt before shortening it, both to make it easier to hold it in a vice and to clean up the thread at the cut when the nuts are unscrewed. The swift will look best if the bolts barely protrude below the second nut.

Once that’s done, screw the 4 dowel pegs in place on the upper side of the relevant rotor strips using the small woodscrews. Then assemble the rotor by bolting the strips together through the holes in their tips and centres, remembering that each bolt goes through from top to bottom with a washer and two nuts below the strip to fasten it. Just put a single nut on the central bolt for now and leave it fairly loose, but all the others need to be fastened tightly enough for the rotor to stay in whatever expanded position you put it in, but not so tightly that it’s a struggle to move it. Add a drop of threadlock to make sure they don’t undo themselves.

Remove the nut from the central bolt and screw it into the pre-drilled hole in the top of the shaft, thereby attaching the rotor’s two middle strips to the shaft. Then slide the upper shaft support onto the lower section of the shaft. Apply glue to both the upper section of the shaft and the top face of the support, then slide the shaft support up into place and clamp it onto the underside of the lower of the two middle rotor strips (see 2nd photo) until the glue is dry.

Finally, push the shaft down through the bushing in the lower shaft support and into the bearing beneath it. (The shaft can be removed just as easily when the swift needs to be disassembled for storage or transportation.)

To use the swift, place an untied hank of yarn around the 4 pegs and expand the rotor to the right size. Position the swift on a table of the correct height, such that the free end of yarn is pulled off the rotor horizontally, either by a mechanical ball winder or a person winding a ball by hand. The rotor will spin as the free end is pulled, allowing the yarn to unwind smoothly.

Tinkercad is great for newcomers to CAD and can be used for even quite complex designs. But if you want to create assemblies with moving parts then you need a more sophisticated CAD system. I chose to move my design from Tinkercad to Fusion 360 primarily so that I could insert joints between the various parts of the model and check that it would move as expected before I'd even built it. The first 2 images of this step are renders of the initial version of the swift in two different partially open states. I was able to download standard parts like nuts and bolts from the McMaster-Carr catalogue, saving a lot of time while ensuring that the photo-realistic images gave a very good impression of how the actual swift would look.

Having made the first version of the swift and discovered its limitations, it was easy to make the necessary amendments to the Fusion 360 model. Then I discovered that I could use contact sets to stop the CAD model behaving in odd ways, like rotor strips moving through each other instead of stopping when they touched. Later, I had fun creating animations (like the one in the Intro showing the swift rotating from different camera angles) and motion studies (like the 3rd image in this step, showing the swift expanding/contracting and rotating), and I was able to produce a dimensioned drawing as a PDF - see below.

The final 3 images above are Fusion 360 renders of the "as built" version of the swift. You can see how closely they resemble the actual swift shown in the photo that comes before them.