Hand crank conversion – Vintage Singer

So far, the most notable omission from my collection of sewing machines is a hand crank. For some reason, it is much easier and cheaper to buy old electric machines here in NZ than hand cranks. Having just serviced 6 electric motors in a week, I can maybe see why.

I’ve wanted a handcranked machine for a while, so I looked at machines, and looked at second hand cranks (rare and expensive) and new reproductions, which vary in price from a few dollars up to $100 or so. With the reproductions you hear both good and bad things about quality and usability.

There is an issue of hand cranks needing a spoked balance wheel, rather than the solid balance wheel 6 of my machines have (my 1911 28K is a treadle machine with a spoked wheel). You can easily change the balance wheel, with either a second hand authentic or a reproduction wheel depending on the type of hand crank. Some bobbins winders might work with both spoked and solid wheels, but some definitely don’t. Going for a full conversion can be a bit troublesome and expensive.

You can also modify your existing balance wheel by notching it at the rim, so that the finger can register in a similar way to when the finger goes between the spokes of a wheel. I have also seen various methods using drilled and tapped holes in the big chrome clutch knob, or near the rim of the balance wheel, to hold rods or similar.

All I wanted to do is try a hand cranked machine to see if I want one in the long term. I thought I might buy a very cheap example off the web, and modify one of my balance wheels to suit, choosing the scruffiest most expendable example.

The hand crank was ordered, costing the princely sum of NZ$22.56 including delivery from China to  New Zealand! I regretted it immediately when I looked at the photos on the TradeMe advert, you definitely get what you pay for!

I also reconsidered the modification of the balance wheel. The least attractive example is on my favourite 1960 99K31 which I did a bare metal restore on a few months ago, and the second least attractive is on a 201K23 I intend to give to my daughter. All the others are perfect, 3 with chrome rims!

I took a wheel off one of my machines and used my digital calipers to measure up a few aspects of the wheel. The most notable thing I discovered is that the central boss of the wheel, the part behind the clutch knob is not a random tapered shape! It is 28mm (1 1/8″) in diameter for the first 20 mm of it’s length, the last 2 millimetres at the dish end curving out to 29mm. So a properly sized device could clamp to this boss. What I see as the perfect solution is a two part clamp milled from billet aircraft aluminium, with recessed torque head set screws clamping the two part to the boss, and two fingers attached elegantly towards the edge of the wheel for the hand cranks finger to register in. Unfortunately, I can’t do that, so I bodged something that works.

1 1/8″ stuck in my mind, and I remembered that the smallest exhaust clamp (muffler clamp to some) you can buy was exactly this size. Honest, I really did know that. I am sure there are other types of clamp that would also work, worm drive hose clamps, wire hose clamps, maybe even bicycle handlebar clamps or similar, but I can buy an exhaust clamp for $9!

What I produced has evolved over 3 attempts, and while it looks a bit scruffy and unfinished, it fits to the balance wheel very well, and the hand crank registers in it very well (more on the hand crank coming up).

What you see in the pictures above is a modified exhaust clamp. The threaded ends have been shortened, the folded metal part has been truncated at both ends, and the washers behind the nuts have been omitted, all these things allow the bracket to be fitted into the dish of the wheel without interference. The two steel fingers are actually a 100mm (4inch) nail, both ends removed and bent into a square U shape 38mm long and 15mm wide internally. I put a Rivnut into the folded metal part of the bracket, and a M4 screw and a couple of washers holds the two fingers firmly in place.
This fits into the balance wheel like this:

Two things to note here are that the two pins clear the clutch knob by a couple of millimetres, and that the clamp is below the level of the top of the boss, so that the clamp does not interfere with the clutch operation.

These pictures show the bracket and flywheel on the machine, and the hand crank attached and registered in the bracket.
This machine is a 1947 99K13 in a knee controller case, with a bentwood top.

Let’s see what we get for our $22.56.
The pictures above will give an idea of its appearance and functionality, it’s obviously not a singer, it’s obvious it’s not even a good reproduction, but it looks functional and useful.
What you won’t see above, because I tore it off and threw it away as soon as I got the box open, is the decal. Badly printed on a piece of clear vinyl, removed from its backing and stuck haphazardly to the top surface, it really was ugly. It was peeling from the middle outwards, and took 2 seconds to remove and left no residue. Most of it was taken up by ‘Made in The Peoples Republic of China”, with probably the same in Cantonese or Mandarin above it, and there were a few random Singer like squiggles stuck on the end.
The quality of the case and gears is actually quite good. The case and mounting bracket appears to be aluminium, and quite accurately made, the gear mounting bolts are well located, and the gears mesh well. The gears themselves appear to be cast iron, but are machined accurately and look quite good. The case is painted in a black paint straight onto bare metal, and the surface seems delicate at best. The mounting bracket fits the machine well, and hold the unit firmly.

The handle is a different matter. The main part is a thin strip of steel, which is quite flexible and easily bent. The knob is small, just 2 inches long (50mm) and as would be expected is plastic. The pin holding it on is flimsy, and was bent out of the box. The handle is loose on its attachment to the main gear, with a simple loop of the handle wrapped round the pin.The handle folds away when not needed, but there is nothing to keep it out of the way. When in use there is a sprung pin to hold it in place. This can be fiddly to use, and does not make the handle any less wobbly.

Finally, the really disappointing part of the whole deal, the finger. This is attached to or part of the smaller gear. Incidentally the gear ratio is 1:3, one turn of the handle makes 3 stitches. Attached to the end of the finger is a small phalanx, and we can call the joint the knuckle, OK? This phalanx is supposed to hinge towards the sewing machine and slot between the spokes of the balance wheel, transferring drive to the machine. When not required it can be folded straight, disconnecting the drive. The main part of the finger is actually OK, but the phalanx is very badly cast. It sits at an angle to the main finger, and it bends as much sideways as it does to and fro. Out of the box it would not move at all, the spring that is supposed to latch the phalanx in each place would not let it move. I had to remove the spring, bend it slightly and put it back on pointing slightly to one side before the phalanx would move, and now it doesn’t latch very well in either position, so it flops around and sometimes goes from engaged to disengaged without warning. This is of no use on a machine with a spoked wheel, good job that’s not what I am using it for!
You get what you pay for. I could probably make it work better, and may do that eventually. Some fibre washers between the gears and the case would probably be a good start. At the moment it does what I want it to do, which is let me experiment and play with a hand crank machine.
Of course I have just delayed the day when I decide whether to get a real Singer hand crank of a better reproduction.

Using this working version as a template I have designed a version that could be made from aluminium stock, or possibly 3D printed. There is a PDF below, those parts identified as M5 on the diagram are threaded holes to take 5mm metric threads. If someone were wanting to stay traditional, these could be in a UNF or UNC thread, maybe 3/16″.
handcrank adapter

The threaded bit the pinch bolt threads into may need to be a recess for a suitable nut if 3D printed in plastic.
handcrank adapter with nut

I sent these designs to my son, who improved them slightly and printed them up. It will take few days for them to travel the 20,000 KMS back to NZ, so it may be a while before I test them.