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General Information => General => Topic started by: bbob203 on August 21, 2013, 05:32:23 am

Title: Why do xzn bolts exist?
Post by: bbob203 on August 21, 2013, 05:32:23 am
Especially smaller than 8mm.. Stripped every 1 but 2 (6mm) out of both 020's im taking apart. Im replacing them with flat head 12.9 socket cap bolts. I followed all the steps cleaned out the heads with brake clean made sure they were 100% free of oil and debris... So i drilled the heads off.
Title: Re: Why do xzn bolts exist?
Post by: CRSMP5 on August 21, 2013, 10:13:34 am
 ;D

you tapped socket in with hammer too?? if not thats your fail... ive never had the 6mm xzn in 020 give me such fits.. but id use a impact driver if i felt they would strip.. but at min.. tapping the socket in will mushroom the bolt into case and let them release with lots less work...
Title: Re: Why do xzn bolts exist?
Post by: bajacalal on August 21, 2013, 01:32:12 pm
Especially smaller than 8mm.. Stripped every 1 but 2 (6mm) out of both 020's im taking apart. Im replacing them with flat head 12.9 socket cap bolts. I followed all the steps cleaned out the heads with brake clean made sure they were 100% free of oil and debris... So i drilled the heads off.

I think they do it because it expedites assembly at the factory, by allowing further automation of the process- machine grabs the bolt head, the triple square pattern is self-aligning, the bolt is threaded in and torqued to spec, the tty bolt can't be overtorqued as easily, the amount of wrench turning by individual workers is minimized.

But I hate non-standard hardware on all my cars I've owned and I try to replace as much of it as possible, whenever feasible.
Title: Re: Why do xzn bolts exist?
Post by: smokeinmirrors on August 21, 2013, 05:18:07 pm
triple square bolts: I've had 100% extraction success by using the socket in conjunction with vice grips to spread the load.  I definately still replace them with hex heads upon re-assembly.
Title: Re: Why do xzn bolts exist?
Post by: bbob203 on August 21, 2013, 05:51:34 pm
Any idea where to get m7x1.25 flat head allen or torx bolts to replace these with.
Title: Re: Why do xzn bolts exist?
Post by: Syncroincity on August 21, 2013, 06:08:37 pm
Any idea where to get m7x1.25 flat head allen or torx bolts to replace these with.

FASTENAL, if you have one near you.
Title: Re: Why do xzn bolts exist?
Post by: libbydiesel on August 21, 2013, 07:11:48 pm
I've never had any issues with XZN bolts provided they are actual OEM bolts and not cheap aftermarket copies.  They're actually less prone to stripping than allen head bolts at the same torque.  I thought the axle bolts were 8mm xzn.  Any chance you're using the wrong size bit?
Title: Re: Why do xzn bolts exist?
Post by: CRSMP5 on August 21, 2013, 07:13:58 pm
4 6mm ones behind 5th gear in 020....

i think his socket crap.. i bet i have 4 bbob..
Title: Re: Why do xzn bolts exist?
Post by: 8v-of-fury on August 21, 2013, 07:31:21 pm
I thought the axle bolts were 8mm xzn. 

Correct you are.
Title: Re: Why do xzn bolts exist?
Post by: burn_your_money on August 21, 2013, 07:42:10 pm
They're actually less prone to stripping than allen head bolts at the same torque.

Very true. XZN FTW
Title: Re: Why do xzn bolts exist?
Post by: theman53 on August 21, 2013, 08:09:50 pm
I personally think a good grade socket head "allen head" as some call them are way better. I replace the CV ones every time I switch the cv joints out for a Socket head.

Fastenal...competition to me, but 9/10 times they will not have it in stock no matter how common it is. If you go to a store and they have it consider it lucky, as I don't even carry M7 stuff, they hardly ever do.

If you go the socket head route go SPS Unbrako or Holochrome for the best results.
Title: Re: Why do xzn bolts exist?
Post by: bbob203 on August 22, 2013, 05:42:05 am
Fastenal has no m7 bolts listed on there site in flat socket cap.
Title: Re: Why do xzn bolts exist?
Post by: theman53 on August 22, 2013, 06:35:59 am
Fastenal has no m7 bolts listed on there site in flat socket cap.
Yep, I said 9/10 and I was being nice.
Title: Re: Why do xzn bolts exist?
Post by: bbob203 on August 22, 2013, 07:10:25 am
Fastenal has no m7 bolts listed on there site in flat socket cap.
Yep, I said 9/10 and I was being nice.

So man can you get me some? m7x1.25x15mm


RE:crsmp5 yes i think part of it was junk xzn bit from advance auto only place i could find an m6 xzn same day.
Title: Re: Why do xzn bolts exist?
Post by: bajacalal on August 22, 2013, 09:22:47 am
The problem I find with the triple square is that the torque is applied to the points, which works fine when the fastener is new, but when it is corroded or dirty it doesn't make good contact. The axle bolts are hard to tap in securely with a hammer because of their location. An allen bit applies torque to the flats of the hexagon which I think are less likely to strip, especially if the tool is not perfectly seated in the hole.
Title: Re: Why do xzn bolts exist?
Post by: bbob203 on August 22, 2013, 10:19:47 am
Tracked down the cornwell tool truck getting a proper quality bit and have 4 new xzn bolts on order. seems m7x1.25tx25mm  with a socket or torx head are non attainable..
Title: Re: Why do xzn bolts exist?
Post by: CRSMP5 on August 22, 2013, 10:37:22 am
The problem I find with the triple square is that the torque is applied to the points, which works fine when the fastener is new, but when it is corroded or dirty it doesn't make good contact. The axle bolts are hard to tap in securely with a hammer because of their location. An allen bit applies torque to the flats of the hexagon which I think are less likely to strip, especially if the tool is not perfectly seated in the hole.

ask older air cooled people.. they were allens...


biggest point here.. no dirt.. inside tranny... maybe little oil at bottom for hydro lock effect.. but they do not rust even..

henc my worry on tool.. and telling him that next time you ever see this hit it with a hammer will save time..
Title: Re: Why do xzn bolts exist?
Post by: 92EcoDiesel Jetta on August 22, 2013, 02:15:12 pm
From an engineering standpoint, XZN head has 12 points to transmit torque compared to 8 of the torx and 6 of the allen, thus the XZN is less likely to strip. You need a quality driver bit no matter the type of head.
Title: Re: Why do xzn bolts exist?
Post by: theman53 on August 22, 2013, 05:37:19 pm
I could get them but the boss would want you to order box quantity. I don't know what that is but I would guess minimum of 100.
Title: Re: Why do xzn bolts exist?
Post by: Toby on August 30, 2013, 11:30:39 pm
From an engineering standpoint, XZN head has 12 points to transmit torque compared to 8 of the torx and 6 of the allen, thus the XZN is less likely to strip. You need a quality driver bit no matter the type of head.

Are you kidding me? 12 tiny points are better than 6 larger ones? Perhaps you might explain why the 12 point crap strips aboutv1/3 of the time with a (Snap-On bit) and I can't remember that last time I stripped an Allen head fastener. This nis the problem with most engineers: They have more faith in calcs than actual performance. If your calcs say yes and life says no, you better refigure your calcs.
Title: Re: Why do xzn bolts exist?
Post by: 745 turbogreasel on August 31, 2013, 03:40:43 am
I've broke more than a dozen head bolts, and only stripped one(from trying to drive it t an angle).
More splines is always stronger.
Title: Re: Why do xzn bolts exist?
Post by: 8v-of-fury on August 31, 2013, 06:45:46 am
Snap-on is nothing to write home about lol. Not anymore anyway.

 
Perhaps you might explain why the 12 point crap strips aboutv1/3 of the time with a (Snap-On bit) and I can't remember that last time I stripped an Allen head fastener.

Well if you stripped the fastener.. likely it was a substandard bolt you were taking out.
Title: Re: Why do xzn bolts exist?
Post by: TylerDurden on August 31, 2013, 08:49:16 am


This is torx, but XZN has similar properties.

(https://lh5.googleusercontent.com/-UThDSF-_TEE/UiIMmdLRHBI/AAAAAAAABS0/rm823qlb-58/s800/Torx.png)
Title: Re: Why do xzn bolts exist?
Post by: Toby on August 31, 2013, 10:49:34 am

Well if you stripped the fastener.. likely it was a substandard bolt you were taking out.

You are correct there. All of the dozens that I have stripped were substandard factory VW bolts. They are always a cause for concern when you have to take them out when changing a motor or a trans. The Allen head bolts never are. In other words, it is remarkable when I get all 12 of the 12 point axle flange bolts out without problems. Just as remarkable when I have trouble with the Allen head bolts.
Title: Re: Why do xzn bolts exist?
Post by: theman53 on August 31, 2013, 10:59:39 am
The other part of the equation is the bit has less strength behind it than the Hex key does. Also if the grain of the metal in a torx fastener is questionable as Toby has said happens a ton then the points are more easily rounded and easier to strip than a similar socket head cap screw *Allen* as some call them. The triple square and double hex I have found worse yet when you get a sub par batch of metal in them.
Title: Re: Why do xzn bolts exist?
Post by: burn_your_money on August 31, 2013, 12:40:05 pm

Well if you stripped the fastener.. likely it was a substandard bolt you were taking out.

You are correct there. All of the dozens that I have stripped were substandard factory VW bolts. They are always a cause for concern when you have to take them out when changing a motor or a trans. The Allen head bolts never are. In other words, it is remarkable when I get all 12 of the 12 point axle flange bolts out without problems. Just as remarkable when I have trouble with the Allen head bolts.

I find that very interesting, because it is 100% opposite to the issue I have when working on the exact same engines.
Title: Re: Why do xzn bolts exist?
Post by: libbydiesel on August 31, 2013, 10:47:43 pm
I cannot remember a single time that I have ever stripped an xzn bolt in almost 20+ years of working on VWs.  I have, however broken a couple of the heads off.  I was working with a friend removing the bumper cover from his '99 Golf last night and he broke the head off one of the torx.  Stripping allens is not exactly common, but I can certainly recall quite a few.  Almost every allen that I have stripped, I have then removed by pounding in the tightest fitting XZN bit to remove it...  hmmm....  I wonder why that always works.
Title: Re: Why do xzn bolts exist?
Post by: 92EcoDiesel Jetta on September 01, 2013, 09:27:47 am
it is remarkable when I get all 12 of the 12 point axle flange bolts out without problems. Just as remarkable when I have trouble with the Allen head bolts.

 As I remember, you must have each xzn in the right spot at 6 o'clock to get a straight shot with the bit. If the bit is not straight it will strip the bolt. Also those axle flange bolts are in a pretty dirty spot and must be cleaned out first.
Title: Re: Why do xzn bolts exist?
Post by: burn_your_money on September 01, 2013, 11:59:49 am
Anywhere from 11-1 o'clock works well with long enough extensions. I rarely clean them out, I just hammer the bit in there and hit it with the impact.