Singer Heavy Duty 4423: threading, bobbin, tension and fixes

Is this your machine?

The Singer Heavy Duty 4423 is a mechanical zigzag machine on a metal frame: 23 built-in stitches picked on a dial, separate stitch length and width dials, a three-position needle dial, a one-step buttonhole, an automatic needle threader and a clear top drop-in bobbin. Singer rates it at up to 1,100 stitches per minute. The manual cover reads "SINGER 4423 Instruction Manual"; Singer also sells color versions such as Meltwater Blue under the same number and the same manual.

The 4411, 4432 and 4452 look similar, but Singer publishes a separate manual for each, so check yours rather than assuming this page fits them. The Facilita Pro 4423 is a different product.

Needles and bobbins that fit

Singer's manual does not state a needle system. It names Singer's own needle styles and asks for genuine SINGER needles:

• Style 2020, standard sharp, sizes 9 (70) to 18 (110), for natural woven fabrics. Singer says not for double knits.
• Style 2045, semi-ball point, 9 (70) to 18 (110), for knits, synthetics, Lycra, swimwear and elastic.
• Style 2032, leather, 12 (80) to 18 (110), for leather, vinyl and upholstery.

Sizes 9 to 11 suit lightweights, 11 to 14 medium weights including denim, 16 heavy canvas and upholstery fabric, and 18 heavy woolens, upholstery and some leathers. With an 18, Singer suggests heavy-duty thread on top, all-purpose thread in the bobbin and a stitch length of 3 or 4. Change the needle about every other garment, after about 16 hours of sewing, or at the first broken thread or skipped stitch.

1. Turn the power switch off.
2. Loosen the needle clamp screw and put the needle in with the flat side of the shank toward the back, pushed up as far as it goes. Tighten.

The bobbin: Singer's 4423 product page says to use SINGER Class 15 Transparent bobbins. Singer's own 4-pack is SKU D2134. You will see "Class 15J" bobbins advertised for Heavy Duty machines; Singer's own Class 15J pages list Futura and Izek machines, not the Heavy Duty, so stay with Class 15. Singer's "Class 15" bobbin case is for front-loading machines and does not fit the 4423's drop-in system.

Threading the top thread

1. Turn the power off. Turn the handwheel toward you until the needle is at its highest, then a little further until it just starts down. Raise the presser foot so the tension discs open.
2. Lift the spool pin. Put the spool on so the thread comes off the back, and push on the matching spool holder.
3. Take the thread through the upper thread guide on top of the machine, then through the pre-tension spring.
4. Bring it down the right-hand channel. Holding the thread between the spool and the guide helps it seat between the tension discs.
5. At the top of the U-turn, pass the thread from right to left through the slotted eye of the take-up lever, and take it back down.
6. Pass it behind the horizontal thread guide, then behind the thin wire guide on the needle clamp.
7. Thread the needle front to back, or use the automatic threader. Pull 6 to 8 inches under the foot to the back and trim it on the built-in cutter.

Automatic needle threader

Thread as far as the wire guide, raise the needle to its highest point and select straight stitch. Press the threader lever all the way down and swing it toward you so the hook goes into the eye. Pass the thread under the guide from left to right, then in front of the needle around the hook from bottom to top. Release the lever and pull the loop through.

Winding and dropping in the bobbin

1. Put the thread and its spool holder on the spool pin and snap the thread into the thread guide.
2. Wind it clockwise around the bobbin winder tension discs, thread the bobbin and put it on the spindle. Push the spindle to the right.
3. Hold the thread end and press the foot control. After a few turns stop, trim the tail close to the bobbin, and keep winding until full.
4. Cut the thread, push the spindle back to the left and take the bobbin off. The machine will not sew while the spindle is to the right.

Dropping it in

1. Raise the presser foot and make sure the needle is fully up. Turn the power off. Slide the small tab beside the bobbin cover plate to the right and lift the cover off.
2. Drop the bobbin in so the thread runs counterclockwise seen from above, as the arrow in the manual shows.
3. Pull the thread through slit A. Hold the bobbin down with a fingertip and draw the thread around until it slips into notch B.
4. Pull out about 15 cm (6 inches) toward the back and replace the cover plate.
5. To bring the bobbin thread up, hold the top thread, turn the handwheel toward you through one full down-and-up cycle, and pull the top thread to lift a loop of bobbin thread. If it will not come up, check it is not trapped by the hinged cover or the extension table.

Top and bobbin tension

Singer's basic upper tension setting is 4, and Singer says 90 percent of sewing falls between 3 and 5. Higher numbers tighten, lower numbers loosen. Zigzag and decorative stitches usually want less tension than straight stitch; on decorative work a little top thread showing underneath is correct.

Singer's quick diagnosis is worth memorizing: loops or bird-nesting on the underside mean the top thread is threaded wrong; loops on the top mean the bobbin is threaded wrong. Rethread before you touch the dial.

Leave the bobbin tension alone. Singer sets it at the factory and says it does not need adjusting. Presser foot pressure is also factory set; if you must change it, turn the screw on top with a coin a quarter turn at a time, counterclockwise for thin fabric and clockwise for heavy.

Cleaning and oiling the 4423

The English 4423 manual has no cleaning or oiling section at all. Its troubleshooting table says a noisy machine has lint or oil on the hook or needle bar and to clean the hook and feed dog, but gives no steps. The Spanish table in the same manual says to lubricate, and the French table says to take the machine to a Singer store. Because Singer gives no oil points, oil type or schedule, this page does not publish any. For a machine that is noisy after cleaning, Singer service is the answer.

What is safe to do: with the machine unplugged, take off the bobbin cover and lift out the bobbin, and brush lint out of the bobbin area with the brush end of the seam ripper Singer supplies. Change the needle while you are there.

1. Brush lint from the bobbin area and around the feed dogs with the supplied brush.

To lower the feed dogs for free motion or darning, use the drop-feed lever. To raise them again, push the lever back and turn the handwheel toward you until they re-engage.

Troubleshooting by symptom

Leave these to a technician

Singer's manual says the 4423 is double insulated, should be serviced only by qualified personnel with identical replacement parts, and that a damaged LED lamp or power cord must be replaced by Singer, its service agent or a similarly qualified person. Oiling the internals, timing and anything electrical go to Singer service. Use only the foot controls Singer specifies (FC-1902A or 4C-316Q in 110 to 125 volt areas).

Singer's manual and support pages

• Singer 4423 instruction manual (PDF, Singer)
• Singer HD4423 stitch applications guide (PDF, Singer)
• Singer 4423 product page
• Singer accessory finder
• Singer customer support