tank mounting stud

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edward

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Does anyone know how thick the boss that the front tank mounting stud screws into is? The stud on my metal roadster tank has broken off and all my attempts to remove the remaining part with a screw extractor has failed, it may be loctited in. I was thinking of drilling and tapping it but am afraid of breaking through into the tank.
 
I don't have the measurements but for memory the thread length of the stud is about 3/8". The boss in the tank is deeper as the thread lock before you feel the stud bottom. Use a good quality sharp drill and go gently and you should feel the drill go into the void the stop again as it meets the tank boss.

If you are unfortunate enough to go through into the tank all is not lost as once the hole has been tapped then sealant or thread locking compound may prevent leakage. I have seen Arlodite epoxy resin hold up against even modern fuels for years with not sign of leakage when used in this way.
 
On my original steel Roadster tank the front threaded boss measures a little bit over 5/8 of an inch deep. The rear threaded bosses measure 1/2 inch deep.

I hope this is of some help,
Peter Joe
 
toppy said:
Use a good quality sharp drill and go gently and you should feel the drill go into the void the stop again as it meets the tank boss.
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Get a hold of the proper sized left-hand twist bit for this operation. As you probably know, a drill bit will grab just as it exits the piece you're drilling. With a left-hand twist, you stand a very good chance of this grabbing action spinning the broken bolt out without incident. It's worked well for me on many occasions.

Nathan
 
Nater_Potater said:
toppy said:
Use a good quality sharp drill and go gently and you should feel the drill go into the void the stop again as it meets the tank boss.
Click to expand...
Get a hold of the proper sized left-hand twist bit for this operation. As you probably know, a drill bit will grab just as it exits the piece you're drilling. With a left-hand twist, you stand a very good chance of this grabbing action spinning the broken bolt out without incident. It's worked well for me on many occasions.

Nathan
Click to expand...
Awesome advice Nate, another reason I love this forum , I learn something new here all the time :)
 
Rather than a left-handed drill bit and an Easy-Out, you might try the screw extractor kit Sears sells. The bits combine both functions; they drill left-handedly into the broken stud or bolt until the bit binds in the hole and then the broken piece should spin out. Much sturdier than either an Easy-Out or twist bit, both of which tend to break and make re-drilling nearly impossible.
 
I've never tried the combination LH drill/extractor but I've done hundreds of screws on aircraft with LH drill bits and had about a 50% success. When the drill went through without grabbing the broken screw the next thing I used was a shoulder type EZ out. They have fine LH flutes and a shoulder so they bury only so deep then apply removal torque. That method got the vast majority of the rest out. Some just don't want to.

If it wasn't on a fuel tank I'd advise welding a nut on the broken part but..........

If you end up drilling it all the way for a helicoil use a drill stop collar and you won't break into the tank. I get them here:

http://www.mcmaster.com/#drill-bit-stop-collars/=z0ecou
 
Be very careful, as boss is pressed in and you may be able to see there is a ring where the outer edge of the tool that was used to press it in came to rest. If it fails it leave a clean cut hole. My boss on my MK3 failed, Metal Magic here in the UK welded it back in no problem at all.
 
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