Motors

Measuring up for a hand-crank

It is very easy to switch between a treadle, a motor and a hand-crank provided you’ve got the right stuff. So how do you determine whether that lovely hand-crank you’ve seen, would fit your machine?

We’re just going to look at using hand-cranks as is, without modifications to the hand-cranks or to the machine. If you have an unusual machine, you may have to go with the best available fit and make adjustments.

Clockwise or anti-clockwise?

First of all, determine the direction of rotation of the balance wheel on your machine. Look at the balance wheel head on and see which way it is turning during sewing: clockwise or anti-clockwise?​​

Some people think that all domestic machines are the same and rotate anti-clockwise. Well, most Singer machines are anti-clockwise, but not all, and Singer is not the only maker out there. There are plenty of machines with clockwise rotation, so just check yours, please, don’t assume things.

Regardless of what the machine is doing, the handle of a hand-crank will always turn clockwise, because it’s much easier to work it this way. Nothing to do with machine construction, but rather with human arm construction. πŸ™‚ This means that hand-cranks for anti-clockwise machines will switch rotation, while the others won’t, so we’ve got two major classes of hand-cranks.

Make sure that the hand-crank you’re looking at, is of the correct rotation class for your machine.

Balance wheel size

Balance wheels come in different sizes, and your hand-crank has to fit around it. There are two important measurements here: the diameter and the depth.

The easiest way to measure it, is to take off the balance wheel and measure it up on the table.

Most machines have a locking nut, it’s that shiny (or rusty) circle in the middle. It’s got a little screw in it – remove that screw. Now hold the balance wheel with your hand and unscrew the locking nut as you would for winding the bobbin. But now you unscrew it all the way and take it out. That little screw was preventing that. Ah.

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The clutch ring falls out suit, or if it doesn’t, remove it. If it’s stuck, it’s only with gunk, so be forceful. It’s supposed to be loose like that.

Now take off the balance wheel. Again, if it doesn’t come off easily, it’s gunked up. But if it is really, really stuck, especially if your machine is not an anti-clockwise Singer, then may be there is a holding screw of some sort preventing it from coming off. Have a good look!

Ok, assuming you managed to get the balance wheel off, put it on the table face down. The “face” is the side on the outside of the machine, not the bit that sits against the machine body.

To measure the diameter, simply slide a tape measure or a ruler under the wheel, making sure that zero is at the edge of it and you can see the ruler through the shaft hole. This makes sure it’s centred. Now you can read off the diameter measurement at on the ruler.

​This one is 5.5″ or 14cm. It’s a Singer 9-spoked wheel.

To measure the depth, put something flat onto the wheel, then measure the distance between the table and that flat thing.

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This one is 1.3″ or 3.3cm.

Mount point to shaft distance

The next important measurement is the distance between the centre of the shaft that the balance sits on, and the mount point or points, if you have two. The mount point will usually be a raised ridge below the balance wheel with one or two screw holes in it.

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Stick a pencil into the (top) hole making sure it is strictly horizontal and measure the distance between the pencil and the centre of the shaft.

On this Singer 127K we have 3 3/4″ or 9.5cm.

If you have two mounting holes, measure the distance between them to compare with the hand-crank later.

Putting the balance wheel back on

It’s pretty simple but also easy to get it wrong.

First, put the balance wheel back onto the shaft and reinstate the positioning screws if you had them.

Now look at the clutch ring. It has two prongs that extend towards the centre and stick up on one side of the ring.

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There are two matching cut-outs on the shaft. Slide the ring onto the shaft with the prongs facing out.


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There are two ways to put on that ring determined by which prong goes into which cut-out. It is impossible to tell in advance which way is the right way, so pick one to start with. Remember the position of the three outer dimples on the ring, or mark prong and cut-out – do something so you would be able to reproduce this position if the ring was to fall out. You’ll see why in a minute. πŸ™‚

Next, screw on the locking nut. When it’s in, put in the little screw. If you look from the top between the spokes of the balance wheel, you can just make out that little screw on the other side of the nut.


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If it sits between two of the three outer dimples on the clutch, you got lucky – this is the right way around. However, if it sits on top or very close to one of those dimples, it’s the wrong way around – remove the little screw, unscrew the nut, catch the clutch ring as it falls out, put it back in the opposite way of what you did before (you remember how it was before, right?), then in with the locking nut and the little screw, look through the spokes, and all should be exactly right! If not, start again, this time really making note of how that ring goes onto the shaft. :-p​

Measuring the hand-crank

Now let’s turn to the hand-crank itself.

A hand-crank can have several centres of rotation, depending on its construction and the class of machine it is meant for (clockwise or anti-clockwise). A hand-crank for anti-clockwise machines typically has two centres of rotation: one for the balance wheel and one for the handle.

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The centre for the balance wheel is of interest, it’s where the bit that latches onto the balance wheel is attached. It must align with the centre of the shaft on the machine. So the distance between the (top) mounting screw hole and this rotation centre must be the same as what we just measured on the machine.

Use the same pencil trick and stick it into the mount hole to help you take the measurement:​

​Yes! It is the same. If it’s not, you could drill a new mount hole in the machine, it is surprisingly easy with a metal bit on a slow speed. Then you cut the thread into it – done.

But before you take a drill to it, check the other measurements.

Will the hand-crank fit around the balance wheel? Check the distance between the wheel rotation centre and the mounting arm – it must be larger than half of the diameter of the balance wheel.

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Check the distance between the back of the hand-crank and the mounting surface. It must be larger than the depth of the balance wheel.

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The differences in those measurements give you the clearance around the hand-crank.

In this photo you see two different hand-cranks mounted onto the same Singer 127K. They both have the same vertical distance between the mount point and the wheel rotation centre, but the difference in design of the mounting arm allows for a larger balance wheel to be used with the low mounting hand-crank.

Does it fit?

Compare the measurements of the hand-crank with the machine and check the clearances to decide whether or not the hand-crank fits. Don’t rely on it if it comes from a machine of the same make and model – there may be differences between machines of the same model that will make them incompatible. Look at these two seemingly identical Vesta VS3 machines:​

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And now look at their balance wheels:

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Not quite so identical any longer, are they?

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