1. Luca Dassa – 01/05/2015 1 / 5 CRAB cavities meeting Bolts Titanium Grade 6 bolts Jeveka has found a supplier They say the cost is very high but on offer is possible They ask for Quantity for a pilot production Quantity for the final application My suggestion: M6x20 ISO 4762 avec trou pour le dégazage de 1.5 mm de diamètre (+/-0.1 mm) -> 200 pour la qualification + 5500 pour la série M5x16 ISO 4762 avec trou pour le dégazage de 1.3 mm de diamètre (+/-0.1 mm) -> 100 pour la qualification + 2800 pour la série Jeveka could be at CERN in June, the 22 nd and the 23 rd

2. Luca Dassa – 01/05/2015 2 / 5 CRAB cavities meeting Washers (1) Washer function: Locking effect Bearing surface function (Pressure under the screw) Spacer function Spring function (Preload regularization) Washer function: Locking effect: NO (when it is fully compressed it is equal to a plane washer) The designer says that a locking effect is slightly present Spring function (Preload regularization): stiffness not well- known / valid only if the washer is not fully compressed or when untightening slightly release the washer Titanium washer: only plate washer or “spring lock” washer

3. Luca Dassa – 01/05/2015 3 / 5 CRAB cavities meeting Washers (2)

4. Luca Dassa – 01/05/2015 4 / 5 CRAB cavities meeting Washers (3) BUT… If the washer is 2 mm in height, the differential contraction wrt the stainless steel is 3 um (the stainless steel contracts more). For a Belleville washer compressed by 0.3 mm, this is negligible Stainless steel washers?

5. Luca Dassa – 01/05/2015 5 / 5 CRAB cavities meeting Thread Spiralock thread: Used in space application Used in Titanium grade 5 (Ti4Al6V) Special tool for the thread No washer needed Reusable up to 50 times (at least for stainless steel) Tightening torque increases Maybe some tests? Case 1: with bolts and Ti washers Case 2 without bolts and with Spiralock Case 3: with bolts and StSteel washers We make 10 cycles 300 K – 4 K with instrumented bolts We use the same set-up for test on anti-galling coatings