Why and when to disassemble your Kenmore 158

You disassemble a Kenmore 158 Series sewing machine when you need to clean the feed dogs, replace the bobbin case, unstick a needle bar, or reach internal parts that jam or wear out. The 158 is a mechanical machine—no circuit boards—so most of its moving parts are accessible once you remove the outer casing and a few fasteners. Taking it apart yourself saves money on service calls and lets you understand how your machine actually works.

Before you start, know that the 158 has a lot of small springs and screws. A phone camera or notebook to photograph each step as you go is worth more than any written guide. If you are uncomfortable working with small mechanical parts, or if your machine is still under warranty, a Kenmore service center is the safer choice.

Key Takeaways

  • The Kenmore 158 comes apart in layers: the presser foot and needle plate first, then the side panels, then the internal casing that holds the feed dogs and needle bar.
  • You need a Phillips screwdriver, a small flathead screwdriver, tweezers, and a small container to keep screws organized by location and size.
  • Take a photo or sketch after removing each layer so you remember how springs and levers sit before you lift them out.
  • The feed dogs, bobbin case, and needle bar are the parts you will most often need to reach; they sit under the needle plate and the internal cover.
  • Reassembly is the reverse of disassembly, but springs and tension levers must sit exactly as they were, or the machine will not feed fabric or form stitches correctly.

Gather your tools and workspace

You will need a Phillips head screwdriver (size #1 or #2), a small flathead screwdriver, tweezers, a small bowl or compartmented container for screws, and a clean, flat work surface with good light. A phone camera or notebook is essential—the 158 has springs that look identical but belong in specific spots, and a photo taken before you remove them saves hours of frustration during reassembly.

Unplug the machine and remove the power cord, presser foot, and needle. Lay the machine on its right side on a towel so you do not scratch the finish. Have your manual nearby if you have it; the Kenmore 158 manual shows the screw locations, though the steps below will get you to the parts you need most often.

Remove the needle plate and presser foot assembly

The needle plate is the flat metal plate under the presser foot with the oval hole for the needle. Loosen the single Phillips screw on the right side of the needle plate (the side closest to you when the machine faces forward). Slide the plate toward you and lift it out. Set it aside in a safe place—it is straightforward to lose and hard to replace.

The presser foot itself is held by a single Phillips screw from above. Loosen it, slide the foot forward, and lift it away. Below the presser foot you will see the presser bar and the spring that holds it down. Do not remove this spring yet—just note where it sits. Take a photo now if you have a camera.

Unscrew and remove the side panels

The Kenmore 158 has a left panel and a right panel held by Phillips screws. On the right side (the side facing you), remove the three Phillips screws: one near the top, one in the middle, and one near the bottom. The panel will slide out toward you. Set it aside.

Repeat on the left side. You may need to tilt the machine slightly to see all three screws. Once both panels are off, you can see the internal frame and the feed dog assembly. The feed dogs are the small metal teeth that move up and down to pull fabric forward. If they are clogged with lint or thread, this is where you clean them.

Access the feed dogs and internal casing

With the side panels off, you will see a metal casing that covers the feed dog mechanism and the needle bar. This casing is held by four Phillips screws: two on the top edge and two on the bottom edge. Remove all four. Lift the casing straight up and set it aside—it is heavier than it looks.

Now you can see the feed dogs, the needle bar, and the bobbin case area. The feed dogs sit in a metal frame and move side to side and up and down. If they are stuck or clogged, use a soft brush or compressed air to clean them. Do not force them—they are delicate. The needle bar is the vertical rod that holds the needle; if it is bent or the needle does not move smoothly, this is where you will see the problem.

Remove the bobbin case (if needed)

The bobbin case is the small metal or plastic housing that holds the bobbin and the lower tension spring. It sits below the needle bar and is held by a single Phillips screw on the left side. Remove the screw and slide the bobbin case toward you and out. The bobbin case is one of the most common parts to replace on the 158, so if it is cracked or the tension spring is missing, this is where you will notice.

When you remove the bobbin case, a small metal tension spring may come loose. This spring is critical—it controls how tight the lower thread is. If it falls out, note exactly where it was sitting before you put it back. If you lose it, you will need to order a replacement bobbin case assembly; the spring cannot be replaced separately on most 158 models.

Clean and inspect before reassembly

With the machine open, use a soft brush, compressed air, or a lint-free cloth to remove dust and thread bits from the feed dogs, the needle bar, and the bobbin case area. Do not use water or oil unless your manual specifically says to. Most Kenmore 158 machines need only dry cleaning—oil can gum up the mechanism and attract lint.

Inspect the feed dogs for cracks or missing teeth. Check the needle bar for bends by looking at it from the side. Look at the bobbin case for cracks or a missing tension spring. If you find damage, note what part you need to order. If everything looks clean and intact, you are ready to reassemble.

Reassemble in reverse order

Put the bobbin case back in first, slide it into place, and tighten the Phillips screw. Replace the internal casing and tighten all four screws—do not over-tighten, or you will crack the plastic. Replace the side panels and tighten all six screws. Slide the needle plate back in and tighten its screw.

Reattach the presser foot and tighten its screw. Replace the needle and thread the machine as you normally would. Run the machine slowly by hand (without power) a few times to make sure the needle bar moves smoothly and the feed dogs engage. If anything feels stiff or sounds wrong, stop and check that all springs and levers are in the positions you photographed.

Frequently Asked Questions

What if I lose a screw or spring during disassembly?

Springs and screws on the 158 are not all the same size. If you lose one, take a photo of the empty hole or the spot where the spring sat, and bring it to a Kenmore service center or a local sewing machine repair shop. They can match it and order a replacement. Do not guess at the size—using the wrong screw can strip the hole or damage the casing.

Can I clean the feed dogs without taking the whole machine apart?

You can brush lint away from the feed dogs without removing the internal casing, but you cannot reach underneath them or clean the mechanism thoroughly without removing the casing. If lint is visible on top of the feed dogs, a soft brush and compressed air will help. If the dogs are truly stuck, you need to remove the casing to see what is jamming them.

How do I know if the needle bar is bent?

A bent needle bar usually causes the needle to hit the presser foot or the needle plate, which breaks needles or makes a loud clicking sound. With the machine disassembled and the casing off, look at the needle bar from the side—it should be perfectly straight. If it has a visible curve or kink, it needs to be replaced by a service center.

Do I need to oil the machine after reassembly?

Most Kenmore 158 machines do not need oil after cleaning. The manual will tell you if your model requires a drop of sewing machine oil on specific pivot points. If you do oil it, use only sewing machine oil, not household oil, and use very little—excess oil attracts lint and gums up the mechanism.

What if the machine does not work after I reassemble it?

Check that all screws are tight and that no springs or levers are out of place. Run the machine by hand slowly to feel for resistance. If a spring is missing or a lever is bent, the machine will not feed fabric or form stitches. If you cannot find the problem, take a photo of the disassembled state and bring the machine to a Kenmore service center—they can identify what went wrong and fix it faster than you can troubleshoot.