This Guide will show you how to replace the PLASTIC GEAR on TOP for any Singer models 413, 416, 418, 457, 466, 477 and 478 series. This PLASTIC GEAR can break at any time on these machines by sewing heavier fabrics. Such machines were not made to sew heavy fabrics at all.
STEP 1: Remove the 2 top cover screws, as well as the left side cover. Remove also the needle, the needle plate and the bottom cover (one screw in the middle). You will have to remove what we call the "face plate", a plastic panel where the model number is printed. Keep all the face plate screws in a small container for reinstallation.
You will have access to the mechanism once the face plate will be removed. Remove also the bobbin case by lifting the (black color) bracket. You have to lift it up first (approx. 1/4") and move it to the right. You will be able to remove the bobbin case. Be sure to clean the bobbin case slot as explained in my Guide "How to make a tune-up on your Singer 457 sewing machine". You are now ready to remove the broken gear.
STEP 2: REMOVING THE BROKEN GEAR. First, you will have to remove the timing belt tensioner and the timing belt underneath. Then, by inserting a long flat screwdriver in the illustrated opening, you will be able to remove the gear set screw. Please keep that screw because if the one with your new gear was made in China (as well as the gear itself), many chances are the set screw will break in few parts when tightening it. Note that I removed also the Needle Position Lever which is retained by one screw, to gain access when removing the old gear and to reinstall the new one. This lever serves also to adjust the center position of the needle.
Once the gear set screw is removed, you will have to pull the vertical shaft underneath. The broken gear will slip out of the shaft. Do not remove the entire shaft. By pulling it approx. 2 inches will be enough to release the gear.
You are now ready to install the new gear. Replace its set screw with the old one. Be sure also to clean the bigger (white color) gear which match the top gear. Check for any debris between the teeth.
STEP 3: INSTALLING THE NEW GEAR. Reinsert the vertical shaft so it is flush with the gear surface. With your long screwdriver, slip the new gear in it, and put your screwdriver blade in contact with the gear location (on top of the vertical shaft). Slip the gear to its original position while inserting the shaft slowly. This method is recommended instead of trying to place the gear with your fingers. The gear can fall at the back of the mechanism or fall down in the motor.
Hold now the gear with your fingers on one hand, and with the other hand, push the vertical shaft in place. Be sure the flat side of the shaft comes in contact with the gear set screw. Tighten the set screw firmly when the vertical shaft is completely inserted.
STEP 4: INSTALLING THE TIMING BELT. Before reinstalling the timing belt, check for severe cracks or missing teeth. Replace if necessary, this timing belt should not cost more than $10 and is available at any Singer store. Part Number 37977. When the timing belt is placed around the 2 sprockets (left and right), install the belt tensioner. The belt do not have to be too tight or too loose, you should be able to depress it 1/2".
You will now loosen the 2 set screws on the left sprocket to be able to move the rotating hook freely to make the hook-needle timing.
STEP 5: THE NEEDLE POSITION. First, you will reinstall the needle position lever and the face plate. The face plate serves as a guide for the needle center position. If you have the straight stitching needle plate, install it as well as a brand new needle. DO NOT move the needle down as it could hit the hook. Position the needle (by turning the hand wheel towards you) so the needle comes slightly over the needle plate opening. By pulling or pushing on the needle position lever, you will be able to position the needle in the center. Be sure the lever is at "center" position and tighten the lever mounting screw.
STEP 6: THE NEEDLE-HOOK TIMING. You will have to rotate the hook so the point will face the back of the machine. Then, turn the hand whell slowly (towards you) so the needle will goes completely down. You should be able to see the LOWER timing mark on the needle bar. By turning the hand wheel a little more, the lower timing mark will be flush with the bushing, as illustrated.
When the LOWEST needle bar timing mark is EXACTLY flush with the bushing, the rotary HOOK POINT should be in front of the needle. Tighten the bottom sprocket set screws firmly. Make a few revolutions with the hand wheel to be sure the needle does not hit any part of the hook.
The needle should be exactly beside the hook point.
STEP 7: REINSTALL THE PANELS. Reinstall the side panel, the bottom cover and make a sewing test. Use the widest and the longest zigzag on a piece of cotton. The zigzag stitch should be equal on both sides.
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