Luca Dassa – 01/05/2015 1 / 5CRAB cavities meeting

Bolts

Titanium Grade 6 bolts

Jeveka has found a supplierThey say the cost is very high but on offer is possibleThey 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 22nd and the 23rd

Luca Dassa – 01/05/2015 2 / 5CRAB 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

Luca Dassa – 01/05/2015 3 / 5CRAB cavities meeting

Washers (2)

Luca Dassa – 01/05/2015 4 / 5CRAB 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?

Luca Dassa – 01/05/2015 5 / 5CRAB 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 washersWe make 10 cycles 300 K – 4 K with instrumented bolts

We use the same set-up for test on anti-galling coatings