Molecular--Bob Posted May 18, 2014 Share Posted May 18, 2014 I have the mechanical sympathy of an ape and have managed to snap one of the seatbelt anchor bolts flush with the mounting face. I will have to drill it out and then retap so two questions. How hard are the bolts What size of bit will i need to cut the bolt to the point where i can pick out the remains of the bolt? Link to comment Share on other sites More sharing options...
garybee Posted May 18, 2014 Share Posted May 18, 2014 Bolts will be 12.9 grade. I wouldn't be happy re tapping after drilling it out. There may not be enough material left if your threads are 'out of sync' with the originals. How did the bolt shear? Was it cross threaded on the way in or seized on the way out? Link to comment Share on other sites More sharing options...
Wrightpayne Posted May 18, 2014 Share Posted May 18, 2014 Unless its bottomed out it may not be in that tight. Have you tried un-doing with a centre punch? I did this on a shear bolt on a mini steering column many years ago. Tap it straight on a few times to create a divot then slant the punch and see if it will hammer undone. Obligatory plusgas / penetrating oil first. BTW which one is it - can you get to the other side of it? Ian Edited by - Wrightpayne on 18 May 2014 20:26:07 Link to comment Share on other sites More sharing options...
Molecular--Bob Posted May 18, 2014 Author Share Posted May 18, 2014 Its the one in the tunnel. I was trying to remove it, and it was tight as, so i applied the aptly named breaker bar. I do have access from the other side as the other bolt came out easily. Guess i could use the other side as a drilling guide and then use a longer bolt to hold both sides. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 18, 2014 Member Share Posted May 18, 2014 While the penetrating oil is soaking in... what's the full list of options for this: * Drill and destroy the bolt * Drill and apply a left-handed extractor, discussed here, with recommendations for drill bits * Weld a lever on the bolt * Cut a slot in the remnant and use a screwdriver bit * Centre punch, as above ... what else? Jonathan Edited by - Jonathan Kay on 18 May 2014 20:52:42 Link to comment Share on other sites More sharing options...
garybee Posted May 18, 2014 Share Posted May 18, 2014 You know it's not cross threaded then. I would weld a half nut to the remainder of the bolt then, once it's cooled, heat up the chassis rail with a blow torch before attempting to turn the remainder out. Link to comment Share on other sites More sharing options...
Molecular--Bob Posted May 18, 2014 Author Share Posted May 18, 2014 It may have been crossed prior to my ownership, as the belts are not original. Welding may not be possible as it is flush with the face of the mounting boss. Link to comment Share on other sites More sharing options...
Birkin S3 ZA. Posted May 19, 2014 Share Posted May 19, 2014 I use left hand drills to remove broken bolts, if its loose enough it will spin itself out as you drill. If its tight after drilling the hole, heat the bolt until red with a small gas welding torch. If done quickly without the nut getting red the bolt will shrink as it cannot expand, Once cool it will just turn out with a screw driver. Chris. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 19, 2014 Member Share Posted May 19, 2014 Quoting Birkin S3 ZA.: If its tight after drilling the hole, heat the bolt until red with a small gas welding torch. If done quickly without the nut getting red the bolt will shrink as it cannot expand...I think that heat causes expansion and subsequent contraction which breaks the bond between the two threads. I don't know if heat weakens thread locking compounds. Jonathan Link to comment Share on other sites More sharing options...
Grim Reaper Posted May 20, 2014 Share Posted May 20, 2014 Heat does soften thread lock. I have seen figures for the required temperatures somewhere and they are not that high that you'd need to get the bolt/nut glowing red. Heat is often used to release threadlocked bolts into alloy where it's not desireable to heat those up too much. Found Loctite Red succumbs at 550F/287C Edited by - Grim Reaper on 20 May 2014 11:36:17 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 20, 2014 Member Share Posted May 20, 2014 *arrowup*Thanks Jonathan Link to comment Share on other sites More sharing options...
Birkin S3 ZA. Posted May 20, 2014 Share Posted May 20, 2014 I think that heat causes expansion and subsequent contraction which breaks the bond between the two threads. As long as there is a hole in the centre and the wall is not to thick, when heated quickly the bolt will try to expand outwards but collapses inwards. If its heated slowly it will brake the bond and kill the Loctite but will expand the same rate as the outer part, and when cooled both will return to there original size. The new KTM four stroke cranks have no web to hold onto for removing the big end pin, the pin is hollow for the oil passage so I remove the plugs and heat the pin. Once cooled the pin just taps out and the hole is left the original size to press the new parts together. Chris. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now