GLAST LAT Projecttitle - MRB 21 June 2005 R. BAGAGLI 1 Threads on flexure MRB Meeting – 21 June 2005

GLAST LAT Projecttitle - MRB 21 June 2005 R. BAGAGLI 2 Description and reference documentation Description of nonconformance –Some flexure was sent back to SLAC to clean holes, the dirty inside the holes was supposed to be the cause for which the Bolts don’t stop on the sidewall’s washer Instances –Dry tests with shorter bolts and cleaning of threads flexure hole Suspected Root cause –Missing countersink on the flexure hole due to a lack of specification in the flexure drawings

GLAST LAT Projecttitle - MRB 21 June 2005 R. BAGAGLI 3 COMPARISON PICTURE SOME HOLES ALLOWS THE BOLTS TO STOP ON THE SIDEWALL’S WASHER, SOME HOLES DON’T TOO HIGH BAD CASEGOOD CASE

GLAST LAT Projecttitle - MRB 21 June 2005 R. BAGAGLI 4 Detail on the bolt THE PROBLEM CAN NOT BE SOLVED USING A SHORTER BOLT LOOKING AT THE MICROSCOPE THE BOLT, THERE IS A NO-THREADS ZONE AT THE END OF THE THREADS, THIS ZONE HAS A DIAMETER GREATER THAN THE MINOR DIAMETER OF THE THREADS l

GLAST LAT Projecttitle - MRB 21 June 2005 R. BAGAGLI 5 Considerations on the threads hole d d d l HOLE BAD CASE HOLE GOOD CASE THE BOLT HAS A ZONE, “l” IN WICH THE DIAMETER “d“ > “d min ” THE MINOR DIAMETER OF THE THREAD, THIS MEANS THAT SCREWING THE BOLT IN TO THE HOLE, THE BOLT WILL BE STOPPED OUTSIDE THE HOLE OF A “l” DISTANCE IN THE WORSE CASE d min WORSE CASE, THE BOLT WILL BE STOPPED OUTSIDE THE HOLE GOOD CASE, THE BOLT WILL BE STOPPED ONLY BY ITS HEAD

GLAST LAT Projecttitle - MRB 21 June 2005 R. BAGAGLI 6 Proposal d l HOLE WITH COUNTERSINK REWORK ALL THE HOLES IN THE WORSE CASE, MACHINING A COUTERSINK DEEP ENOUGH TO REMOVE THREADS ALL ALONG THE “l” DISTANCE, THAT IS APPROXIMATELY mm, IN ORDER TO ALLOW THE BOLT TO STOP ON THE WASHER