Thread: Torqueing screws for cheapskates

I've finally got around to getting my first scope mounts and am in the process of mounting them. I've read a lot about the importance of correct torque on the screws. The thing is, I'm too cheap to buy a torque driver I'll use a handful of times and hate borrowing tools so I've had to contrive a way to get the correct torque with a high degree of accuracy once I've leveled the optics etc. I thought I'd share it for fellow cheapskates.

Based on the engineering toolbox idea of using a luggage scale on a crescent spanner, I'm using the allen key supplied with my mounts with a exercise weight attached by fishing line near the end. Since T=Fa, where a= the length of the lever, with a given weight I can vary the torque by shifting the point along the Allen key it's attached (it's 60mm long). A quick cut with a file so the fishing line doesn't slip off, and I can get the torque within about 1 in-lb. This will work equally as well as the luggage scale method.

I've made a spread sheet to make the calculations easy. In my case, I need to torque the ring screws to 2Nm / 18in-lb. So I enter in 2 in the torque cell, 5kg in the weight cell and it gives me 41mm (0.041m) for my attachment point.

Link

Of course I could pay $10 to get a luggage scale delivered but I already have the fishing line and the weight. With the savings from not buying a wrench I can buy a box of ammo!