Screws & Nuts

Find the Right Screws and Nuts for Pinball Machines

Pinball machines use a wide variety of fasteners. Screws and nuts securely hold components such as plastics, ramps, posts, metal guides, switches, coil mounts, cabinet parts, and mechanical assemblies in place. These parts differ not only in length and head shape, but also in terms of thread type, diameter, material, and surface finish.

Inch sizes such as #4-40, #6-32, #8-32, #10-24, or #10-32 are particularly common in American pinball machines. The first number indicates the screw size, while the second number specifies the number of threads per inch. A screw designated #8-32 therefore has a different thread than a #8-36 screw or a metric screw with a similarly appearing diameter.

If an incompatible screw is forced into place, threads, T-nuts, metal brackets, or delicate game components can be damaged. Before replacing a screw, you should therefore always check which size, length, and thread type was originally intended.

🔧 Workshop Tip:

During repairs, store removed screws separately by assembly. Small sorting boxes or labeled bags prevent screws that look similar but have different threads or lengths from being mixed up.

U.S. inch threads are not compatible with metric screws

Many pinball machines were developed and manufactured in the U.S. Accordingly, manufacturers such as Williams, Bally, Data East, Sega, Gottlieb, and Stern Pinball predominantly use screws that comply with the American Unified Thread Standard. These differ fundamentally from the metric threads commonly used in Europe.

Even if a metric screw appears to have roughly the same diameter, the thread pitch and thread profile usually do not match. A screw that seems to fit may therefore jam after just a few turns or damage the existing thread. This is particularly true for metal posts, brackets, switch mounts, coil assemblies, and T-nuts installed in the playfield.

For a reliable repair, you should always use the original screw size or a technically identical version. Existing part numbers, the pinball machine model’s documentation, or a careful measurement of the removed fastener can be helpful here.

Which screw is used where?

Depending on the application, different types of screws are required in a pinball machine. Machine screws are screwed into existing metal threads, nuts, or T-nuts. Wood and sheet metal screws, on the other hand, have a coarser thread and are often used directly in the playfield wood, in the cabinet, or on specific brackets.

Hex screws can be quickly installed and removed using matching socket wrenches or so-called nut drivers. Phillips, slotted, hex socket, and Torx screws are used depending on the manufacturer, year of manufacture, and assembly. Screws with an integrated flange or a permanently attached lock washer distribute the load and prevent the connection from loosening too easily due to vibrations.

The screw length must also be correct. A screw that is too short may not engage sufficiently in the thread. A screw that is too long can press against underlying components, damage cables, or protrude from the visible side of the playfield. With ramps and plastics, there is also a risk that delicate plastic parts will crack if screws are tightened too tightly or if unsuitable screws are used.

🔧 Workshop Tip:

Tighten screws on plastic parts, ramps, and other plastic components only enough to hold the part securely in place. Excessive torque can cause stress cracks or damage existing drill holes.

Lock Nuts, KEPS Nuts, and Spring Washers to Prevent Loose Connections

During play, constant vibrations are generated by spools, flipper fingers, bumpers, kickers, and the moving ball. As a result, standard nuts can loosen over time. For connections subject to heavy stress, nylon lock nuts, KEPS nuts, or additional lock washers are therefore frequently used.

A nylon lock nut, also known as a Nylock nut, has a plastic insert that engages with the thread as it is screwed on. This makes it more difficult for the nut to loosen on its own. KEPS nuts feature a pre-mounted toothed washer that presses against the surface when tightened. Spring washers and lock washers serve a similar purpose and help maintain the preload of a screw connection.

The type of locking mechanism to be used depends on the specific assembly. In the case of moving mechanisms, care must also be taken to ensure that a nut is not tightened so tightly that levers, joints, or guides become blocked.

Washers protect playfield components and distribute pressure

Washers may seem unremarkable, but they perform important functions in pinball machines. They distribute the clamping force of a screw or nut over a larger area, thereby protecting wood, plastic, paint finishes, and sensitive components. At the same time, they can compensate for misalignments or prevent screw heads from slipping through larger drill holes.

If a required washer is missing, a screw connection can cut into the material. This can cause visible pressure marks, cracks, or damage, especially on plastic parts, ramps, and painted cabinet components. When replacing a part, therefore, you should consider not only the screw itself but also the washer or lock washer originally intended for that application.

What to Do If a Screw No Longer Holds?

If a screw spins freely or can no longer be tightened securely, the problem is not necessarily with the screw itself. For wood screws, the hole in the game board or cabinet may have become worn out. For machine screws, the internal thread, the nut, or a T-nut inserted on the underside may be damaged.

First, check whether the correct screw size was used and whether the thread shows signs of wear, corrosion, or deformation. A longer or thicker screw should not be installed without first checking, as it may damage the component or adjacent parts. In the case of defective threads, a professional repair or replacement of the corresponding nut, T-nut, bracket, or post is usually the better solution.

If a screw gets stuck in the thread, do not force it further by applying excessive force. A damaged screw head or a broken screw usually requires significantly more effort to remove than stopping the disassembly process in time.

🔧 Workshop Tip:

Use tools that are exactly the right size. Especially with small Phillips, Allen, and hex screws, the heads can be easily damaged if an improperly sized screwdriver or socket wrench is used.

Screw Sets as Basic Equipment for the Pinball Workshop

For regular maintenance work, it’s worth keeping a stock of frequently used screws, nuts, and washers on hand. A suitable pinball screw set provides a practical basic kit for typical repairs on the playfield, mechanical assemblies, and the underside of the playfield.

Especially with older or previously restored pinball machines, individual original screws are often missing or have been replaced in the past with incompatible fasteners. With an assortment of common US sizes on hand, such connections can be properly restored without having to source individual parts for every minor repair.

Screws and Nuts for Repair and Restoration

A careful restoration is not just about a functional connection. The head shape, color, coating, and visible finish can also be crucial for achieving an authentic overall look. Black, zinc-plated, white, or color-anodized screws and washers allow you to select fasteners that match the specific location and design of the pinball machine.

At PU-parts , you’ll find an extensive selection of screws, nuts, nylon lock nuts, KEPS nuts, T-nuts, washers, spring washers, and other fasteners for classic and modern pinball machines. By selecting the correct size and type, you can reliably secure loose assemblies, repair damaged connections, and perform repairs professionally.

Frequently Asked Questions About Pinball Screws & Nuts