T Nut and End Cap Basics for 8mm T-Slot Sim Rig Builds
By Racing Simulators - World's Best Sim Rigs | Published: 2026-11-02
Category: How-to Guides
Learn how to install T nuts and 120x40 end caps on 8mm T-slot extrusion. Follow a simple step-by-step process to avoid loose joints and sharp edges.
Quick answer
Install T nuts by dropping them into the 8mm slot before joining profiles, then secure end caps by pressing them into the 120x40 extrusion ends. Always check that the T nut is seated perpendicular to the slot and that the end cap is fully flush to avoid rattles and sharp edges.
Why T nut orientation matters more than torque
A T nut that sits slightly rotated in the slot will not clamp evenly, even if you tighten the bolt hard. The ball-bearing design in some T nuts helps them self-align, but you still need to confirm the nut is square to the profile before final tightening. If the nut binds, back it out and reseat it rather than forcing it.
When to use end caps on 120x40 profiles
End caps are not just cosmetic. On 120x40 extrusion, exposed ends can catch cables or clothing and leave sharp edges. Caps also keep dust out of the slot. However, if you plan to add a joint plate or corner bracket later, leave that end uncapped until the build is final.
Step-by-step installation for T nuts and end caps
- Insert T nuts before joining profiles: Slide the T nut into the 8mm slot from the end of the profile before you attach any corner brackets or plates. If the slot is already closed, you may need to disassemble the joint to add nuts later. Checkpoint: confirm the nut slides freely and sits square to the slot.
- Seat the T nut perpendicular to the slot: Rotate the T nut until its flat sides align with the slot walls. A ball-bearing T nut will usually self-center as you tighten the bolt, but start it by hand to avoid cross-threading. Common mistake: over-tightening before the nut is seated, which can jam it sideways.
- Tighten bolts gradually in a cross pattern: When joining two profiles, tighten the bolts in an alternating pattern (like wheel lug nuts) to keep the joint even. Final torque should be snug, not extreme, to avoid crushing the extrusion slot. Checkpoint: recheck all T nuts after the first few hours of use, as they can settle.
- Press end caps into 120x40 profile ends: Align the cap with the profile opening and press it in firmly with your thumb. It should sit flush with the end. If it feels loose, check that you have the correct 120x40 size and that the slot is free of debris. Common mistake: forcing a cap that is not fully seated, which can leave a sharp edge exposed.
- Leave access for future adjustments: If you plan to add accessories or joint plates later, leave those profile ends uncapped until the build is complete. Caps can be removed, but repeated removal can loosen the fit. Checkpoint: mark capped ends that may need future access with tape or a label.
Product facts
- 120 X 40mm Plastic Extrusion End Cap - Pack of 2: Pack of two ABS plastic end caps sized 120 x 40mm for 8mm slot extrusion. These caps fit the common 120x40 profile used on many sim rig bases, giving you a clean finish on two ends.
120 X 40mm Plastic Extrusion End Cap - Pack of 2 - T Nut for 8mm T-Slot - Pack of 40: Pack of 40 carbon steel T nuts with ball-bearing design for 8mm slot. A 40-piece pack covers a typical rig build with spares, and the ball-bearing helps the nut stay aligned during installation.
T Nut for 8mm T-Slot - Pack of 40
