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Robw_z Samba Member
Joined: April 28, 2007 Posts: 983
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Posted: Wed Aug 07, 2013 3:48 pm Post subject: Tapping out an M11 to M12? Seat belt bolt question. |
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Failed attempt at replacing rear bench seat. The z-bed in non campers is held to nuts welded to the body which are M11 x 1.25, the same pitch and thread as the seat belt bolts. I knew going into the project that these bolts love to cross thread, and was careful but somehow crossthreaded one severely, and two just a little.
I'm not even sure an M11 x 1.25 tap could save the day, but they are certainly not available locally and reasonable cost shipping on Amazon is at least two weeks.
I have an M12 x 1.25 tap but have never used a tap for anything other than thread cleaning. Is upsizing these bolts to M12 using the tap I have a bad idea? These nuts are welded to the body so I don't want to screw it up. Thanks for any input I'm not exactly sure how obscure a question this might be.
-Rob |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9939 Location: Orbiting San Diego
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Posted: Wed Aug 07, 2013 3:56 pm Post subject: Re: Tapping out an M11 to M12? Seat belt bolt question. |
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Strange as it sounds, I think you may find that those are really 7/16" bolts. Take a good one down to a decent hardware store and match one up. Then buy a 7/16" tap of the correct pitch.
Mark
Robw_z wrote: |
Failed attempt at replacing rear bench seat. The z-bed in non campers is held to nuts welded to the body which are M11 x 1.25, the same pitch and thread as the seat belt bolts. I knew going into the project that these bolts love to cross thread, and was careful but somehow crossthreaded one severely, and two just a little.
I'm not even sure an M11 x 1.25 tap could save the day, but they are certainly not available locally and reasonable cost shipping on Amazon is at least two weeks.
I have an M12 x 1.25 tap but have never used a tap for anything other than thread cleaning. Is upsizing these bolts to M12 using the tap I have a bad idea? These nuts are welded to the body so I don't want to screw it up. Thanks for any input I'm not exactly sure how obscure a question this might be.
-Rob |
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nepawesty Samba Member
Joined: April 08, 2013 Posts: 108 Location: CO
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rubbachicken Samba Member
Joined: October 05, 2004 Posts: 3058 Location: socal
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Posted: Wed Aug 07, 2013 4:01 pm Post subject: |
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tap it out carefully, once you have it started, i always turn turn in 1/4 turn, then back off 1/2 a turn, use cutting grease or some kind of lubricant, and don't hurry.
turning back after each cut will clean the tap, and shold leave you with a decent thread when you are done.
i have watched people just wind the tap through the hole and end up with a mess.
take your time, be sure you start off square, and take your time. _________________ lucy our westy
lucy's BIG adventure
meet 'burni'
markswagen {mobile mechanic} san diego area all early VW's cared for.
619 201 0310 or 617 935 4182 |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32632 Location: Reading Pennsylvania
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9939 Location: Orbiting San Diego
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Posted: Wed Aug 07, 2013 4:12 pm Post subject: Re: Tapping out an M11 to M12? Seat belt bolt question. |
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They are so close that the factory VW Parts data says they are 7/16" bolts.
Mark
djkeev wrote: |
crazyvwvanman wrote: |
Strange as it sounds, I think you may find that those are really 7/16" bolts. Take a good one down to a decent hardware store and match one up. Then buy a 7/16" tap of the correct pitch.
Mark |
They are actually metric 11 x 1.25 threads
Darn close to 7/16 fine used by the USA
So close that they will thread into each other.
Dave |
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Christopher Schimke Samba Member
Joined: August 03, 2005 Posts: 5391 Location: PNW
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Posted: Wed Aug 07, 2013 4:16 pm Post subject: |
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If you end up needing to tap them to M12x1.25 (which should work just fine), make sure you run a 27/64" drill bit (actually, the proper drill bit diameter for tapping a M12x1.25 is 10.80mm, but a 27/64" drill bit is 10.72mm which will work fine) through them before attempting to tap them. Otherwise you could end up breaking off the tap inside the nut and then you would have a real mess to deal with. _________________ "Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)
*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected] |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32632 Location: Reading Pennsylvania
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randywebb Samba Member
Joined: February 15, 2005 Posts: 3815 Location: Greater Metropolitan Nimrod, Orygun
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Posted: Wed Aug 07, 2013 4:29 pm Post subject: |
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all seat belt anchors made on Planet Earth are spec'd to be SAE bolt threads
dunno re the seats themselves _________________ 1986 2.1L Westy 2wd Auto Trans. |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9939 Location: Orbiting San Diego
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Robw_z Samba Member
Joined: April 28, 2007 Posts: 983
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Posted: Thu Aug 08, 2013 1:24 am Post subject: |
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Thanks for all the suggestions and input!
From what I've read I am tempted to try a 7/16 x 20 tap, which is available locally, and try and re-use the factory bolts. If not plan B is M12. Thanks to Chris for the tip to drill and the size!
I also saw a trick on some muscle car forum to thread the tap through a nut first(in this case a 7/16 nut) and washer, and hold them against the surface to help with starting it straight, which is the part I'm most worried about.
This whole thing happened because I thought since I could pull a Z-bed from a junkyard van solo, easily, I could also install it solo... Not so! Not the whole assembly at least. You can only hold up one side at a time, and that angle tends to force the bolts to cross thread. If installing alone, unbolt the cushioned sections first!
-Rob |
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furrylittleotter Samba Member
Joined: May 19, 2008 Posts: 1506 Location: West Seattle
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Posted: Thu Aug 08, 2013 1:32 pm Post subject: Re: Tapping out an M11 to M12? Seat belt bolt question. |
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crazyvwvanman wrote: |
They are so close that the factory VW Parts data says they are 7/16" bolts.
Mark
djkeev wrote: |
crazyvwvanman wrote: |
Strange as it sounds, I think you may find that those are really 7/16" bolts. Take a good one down to a decent hardware store and match one up. Then buy a 7/16" tap of the correct pitch.
Mark |
They are actually metric 11 x 1.25 threads
Darn close to 7/16 fine used by the USA
So close that they will thread into each other.
Dave |
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Robw_z Samba Member
Joined: April 28, 2007 Posts: 983
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Posted: Sun Aug 11, 2013 2:27 pm Post subject: |
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For thread posterity I will confirm that a 7/16 x 20 tap works very well in place of an M11 x 1.25, which is hard to find.
I would call the difference between the two "negligible but existent" meaning you can tell there is a bit of a difference, as evinced by a more than usual amount of metal carved out by the tap, but nothing to worry about.
-Rob
Last edited by Robw_z on Sun Aug 11, 2013 4:05 pm; edited 1 time in total |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32632 Location: Reading Pennsylvania
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syncrodoka Samba Member
Joined: December 27, 2005 Posts: 12008 Location: Santa Cruz, CA
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Posted: Sun Aug 11, 2013 2:55 pm Post subject: |
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They are definitely 7/16 bolts, all of the seat belt bolts in the van are that size just like crazyvwvanman said. |
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