This is the second part of the article written by Bill Tarplee about how he reconditioned his favourite motorcycle jacket and covers his comments regarding using the sewing machine and installation of the zipper.
The Sewing Machine
Sewing machines are noted for being temperamental. Frequently this reputation is wrongly deserved. If you know a few basic rules you shouldn’t have too many problems.
The best idea would be to talk with your mum, wife or girlfriend. They will actually show you what I’m Describing here.
Clutch
Most sewing machines have a clutch on the driven wheel. This is a chrome knob that rotate a half turn to lock the driven wheel to the sewing mechanism.
The idea is that you de-clutch before winding cotton onto the bobbin. This way it doesn’t disturb the thread line, or cause any tangles around the needle.
Winding Bobbins
Have a second reel of thread for winding bobbins. This reel sits on a post on the machine bed. The thread goes from a reel, under a tensioning clip, and up to the bobbin mechanism. You make several turns around the bobbin and pass the free end through one of the holes in the side of the bobbin. Fit the bobbin into the bobbin holder, and run the thread over or through the line laying mechanism. There is usually a chrome lever under the bobbin holder. Lift the lever until the tyre on the bobbin winder comes into contact with the driven wheel. Start the machine and wind the bobbin(s). It is better to have too little cotton on them than too much.
Thread Run
When machines go temperamental it is usually because the thread has been run incorrectly.
Thread runs along form the reel at the right to a metal hook at the top left. From there the thread passes down and around between two metal discs held together by spring and tension nut. (This is the Tensioning Device, which I will mention in a minute). The thread passes clockwise around and between the plates, until it come up to a spring wire loop. This will elevate and allow the thread to pass over a notch on the front tension plate. Release the spool and the wire will revert to its state of rest.
The thread then passes through the eye in a rocker arm at top left. It passes through from right to left.
The thread runs down the end of the machine, going under several thread guide clips. There will be at least one on the oscillating sewing leg. The thread then passes through the needle eye.
MOST IMPORTANT – the thread must pass through the needle eye in the correct direction! This is usually from right to left. You will have untold sewing trouble if you run the thread the other way.
Bobbin Holder
The bobbin holder is concealed beneath a sliding plate alongside the sewing foot. . The bobbin should unwind anti-clockwise. Drop the bobbin in its holder, holding the thread end. Clamp the bobbin with one finger to stop it from turning and run the thread through a little slot at about 8 o’clock. Pull 50mm of thread from the bobbin and leave it loose.
You then hold the loose end of the top cotton, and turn the machine over by hand. Once the needle has bottomed and lifted, pull on the loose end. This will raise the loose end from the bobbin. Pull both cottons until you have a good 100mm of cotton beyond the sewing foot. Always start with at least 100mm free, or the needle will invariably unthread.
Tension
Tension is the one area that can have you tearing your hair out. It should not be a problem if adjusted properly AND PROVIDING THE THREAD RUNS ARE CORRECT. You often find that ‘tension’ troubles are actually thread runs that are incorrect.
The top thread is under variable tension. This is to allow the top thread to pull the bottom thread to the centre of the material. In simple terms there are three thread forms. If the lower thread runs straight with the top thread looped across it at each stitch, then there is sufficient tension.
Ideally the tension knob should be set around 4 or 5 on most machines. You should not be able to see the thread from the other side pulled up to the side you’re looking at. I found that I needed no adjustments between sewing leather and sewing flannelette. I did find though that I couldn’t use one reel of thread that was extra thick and strong. I just couldn’t get the tension right. So much for the theory!
Zippers – What to Use
Zippers are one of those devices that you never think about until they give trouble. Then, of course, it’s too late.
The best current range of zippers seems to be those used on diver’s wet suits. These are a large toothed nylon zipper. They seem to be at least as strong as any metal zipper, and give far less trouble.
I bought a replacement zipper from my local dive shop. It cost me $5. It was too long, being designed to run from crotch to throat. It is better to be too long than too short.
I calculated the length I needed from the old brass zipper. I marked the teeth I wanted removed, then split them off with wire cutters. The nylon breaks away, leaving the underlying material intact.
I made up a pair of stops from aluminium sheet. You must have something to stop the closer running off the end of the track. Aluminium is easy to use and it doesn’t rust.
Sewing the Zipper in
The first insert is easy. The zipper material is sandwiched between the jacket and the lining. You actually sew it in twice. First time you sew the zipper material to the inside of the jacket, going almost to the top. This will locate it against the jacket. Then you sew the lining leather onto the zipper material. This gives you the two lines of sewing, and you won’t have the zipper getting out of line. I found that you just can’t control three pieces of material if you try to sew them at the same time.
You must start from the bottom and sew up the jacket. Be sure to allow the zipper teeth to project sufficiently. I found that the first time around I had the teeth in too close to the edge of the jacket. It was a nice, neat looking job, only I couldn’t do it up! Make sure the teeth are a good mm or more from the edge of the jacket. You now have to work out where the zipper must be located on the other half of the jacket. It is important to make sure that they two halves line up. It is possible (but highly undesirable) to insert a zipper so that one side of the jacket is lower than the other.
Once you know where the zipper goes, sew it in as with the first insert.
Finishing the Zipper Off
There are two things to do. Firstly, the material at the top of the zipper should project beyond the stop for at least 30mm. When you have sewn almost to the top, this tail is turned at right angles and tucked inside between the facing and the jacket. The sewing machine then sews beyond this point, locking the tail in.
The second point is to double, or even triple sew the leather at the start and finish of the zipper. These are usually the areas to give way first. Double stitching should prevent this.
