Frame mounting bolts

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Hugo
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#1 Frame mounting bolts

Post by Hugo » Thu Aug 24, 2017 11:40 am

I just discovered something that is probably common knowledge, but I'lll mention it anyway - the bolts that hold the front frames to the bodyshell were apparently machined down a bit, so that the pointy bits of the hexagon didn't come into contact with the paintwork and scratch it. In other words, they had the appearance of a bolt with a small flat washer glued to the underside of the head, if that makes sense. Does anybody know if these can be bought? Barratts sell ordinary bolts for the frames. Simple enough to turn them down a bit, but easier to buy a set if they exist.
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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Heuer
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#2 Re: Frame mounting bolts

Post by Heuer » Thu Aug 24, 2017 1:14 pm

Almost everything you need to know about bolts used by Jaguar can be found here: viewtopic.php?p=56692#p56692
David Jones
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#3 Re: Frame mounting bolts

Post by Hugo » Thu Aug 24, 2017 1:56 pm

Everything except whether these special frame bolts still exist and if so who sells them! I remembered where I found them mentioned;- http://owenauto.ca/tag/etype/page/4/ This is a very useful photographic guide of how to put an E type back together when you have bits all over the place like I do.
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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#4 Re: Frame mounting bolts

Post by Heuer » Thu Aug 24, 2017 2:40 pm

Use standard bolts with washers, which are meant to be sacrificial. You can buy a complete frame bolt set from Monocoque Metalworks: http://www.monocoque-metalworks.com/mai ... bolt-kits/

These are the bolts of which you speak, which are pretty standard IIRC:
Image

I don't think they have a specific name but those pictured come from here: http://www.westfieldfasteners.co.uk/A2_ ... .3125.html
David Jones
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#5 Re: Frame mounting bolts

Post by Gfhug » Thu Aug 24, 2017 3:03 pm

What always surprises me about the bolts used by Jaguar and even the Monocoque set is how often shear load is taken on the threaded part.
From an aviation background, only the plain shank should have any sort of shear load; the threaded part, never. Some of the Monocoque bolts are the correct length to do the job, but the threaded section is too long meaning, say on the IRS mounts, shear load is taken on the threads.

Geoff
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#6 Re: Frame mounting bolts

Post by Hugo » Thu Aug 24, 2017 3:18 pm

Perfectly true - but they never shear, do they? Unless you overtighten them.
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#7 Re: Frame mounting bolts

Post by Hugo » Thu Aug 24, 2017 3:20 pm

Heuer wrote:Use standard bolts with washers, which are meant to be sacrificial. You can buy a complete frame bolt set from Monocoque Metalworks: http://www.monocoque-metalworks.com/mai ... olt-kits/l
That's them - but if you use washers, they will be bigger than the bolts - these bolts have the advantage of not needing washers but not damaging the paint either. Why that should be an advantage over using washers I'm not sure, but on this application I just don't think washers would look right.
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#8 Re: Frame mounting bolts

Post by Heuer » Thu Aug 24, 2017 3:31 pm

Yes, Jaguar only used washers under the nuts. Interesting to find out if the stepped bolts have a specific name.
David Jones
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#9 Re: Frame mounting bolts

Post by norman m. macleod » Thu Aug 24, 2017 4:18 pm

Hugo,
Clarification herewith. I wrote a long dissertation on this subject some years back, on this Forum...
1.0 The bolt heads you describe, with the machined relief under the head, are in fact in conformance with relevant BS and AS Standards for fasteners on a structure of this nature. On the E-Type frames, they are in fact set-screws, not bolts (no plain unthreaded section).
2.0 Jaguar did not use washers with the original installation, nor do quality suppliers of replacement frames (e.g. Uryk of E-Type Fabs) supply them, in set-screw kits for their frames.
3.0 The set-screws used should be Class 5 at minimum. The use of Class 8 items may help the owner to sleep better at night, but it should be borne in mind that the receiving fastener (captive plate or nut on the other side) should be of the same class. Not possible with a 50-year old plate.
4.0 Again, should the owner feel compelled to use washers, the stamped-out variety from the High Street hardware store or the "usual" suppliers should be avoided at all costs. Machined washers of a thickness of O.O70" to 0.100" can be used.....

I trust this may assist,
Best regards,
Norman :Scotland: (in Antipodean exile.......)
1967 S1 2+2

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#10 Re: Frame mounting bolts

Post by Gfhug » Thu Aug 24, 2017 7:44 pm

Hugo, by shear load I mean that across the diameter of the bolt, not tensile load by over tightening. Thus if you look at the IRS bolts I mentioned you have part of the shear load on the threads not the plain shank.
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#11 Re: Frame mounting bolts

Post by Hugo » Thu Aug 24, 2017 8:00 pm

Of course - sorry.
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#12 Re: Frame mounting bolts

Post by steve3.8 » Thu Aug 24, 2017 8:49 pm

Hugo,

Buying a bolt kit from Uryk will save you all the grief and save any confusion on what is right or wrong , plus being the correct length and grade .
Your question about the base diameter under head , i would be surprised if you could buy bolts/set screws without , unless they were from some old ironmonger that used to sell paraffin etc .

One important point to note is that the picture frame bolts have deeper nyloc nuts , type P i think [with washers] , another reason to buy from Uryk.

Steve
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#13 Re: Frame mounting bolts

Post by Hugo » Thu Aug 24, 2017 8:56 pm

Thanks - what is his trading name?
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#14 Re: Frame mounting bolts

Post by Series1 Stu » Thu Aug 24, 2017 9:01 pm

No Geoff, a correctly fastened joint should never put the bolt (or screw) in shear. The fixing is there to provide a clamping load and all forces are transmitted by the joined faces, not by the fastener. The only load on the fastener is tensile.

If the bolt is in shear then the joint has failed and you have serious problems. Especially in the case of the engine frames.

Interesting what David said about Jaguar not using washers under screw heads. There should always be a washer at both ends of the fastener.

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Stuart

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#15 Re: Frame mounting bolts

Post by steve3.8 » Thu Aug 24, 2017 9:27 pm

:wavegreatbritain: Steve3.8

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#16 Re: Frame mounting bolts

Post by abowie » Fri Aug 25, 2017 12:39 am

A few comments.

The original bolts are GKN grade R bolts. These are high tensile and the R grade is approximately the same as grade 8.8 metric bolts. So if I were to use new bolts I would use grade 8, not grade 5.

I have personally stripped probably a dozen E Types for restoration including 3 of my own. You do not see broken or bent frame bolts, or any other GKN bolts for that matter. The only things I seem to break are manifold studs.

With 2 exceptions the frame fasteners are all bolts, not setscrews.

We routinely replate and reuse the GKN bolts that came with the car. They look good, are correct and we do not have problems with bolt failures. I own a car restored 13 years ago by the guys I work with that has done 12k miles since restoration. All the original fasteners were used. They are all fine.

We usually use new nylocs. I personally put a 1/16" thick washer under both the bolt head and the nut, even though these were not used at the factory. Otherwise you damage the paint on the frames which looks bad on a car being restored for a small fortune.
Andrew.
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http://www.projectetype.com/index.php/the-blog.html
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#17 Re: Frame mounting bolts

Post by 288gto » Fri Aug 25, 2017 7:02 am

Or if you really do need to get out more :lol: you use the ones supplied by Uryk but get some 0.5mm titanium washers cut the same size as the shoulder on the bolt and use those. This way you still get the unwashered original look but with less chance of damaging the paint.





If only I could get all the high tensile markings on the heads to line up. :lol:


Simon

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#18 Re: Frame mounting bolts

Post by Gfhug » Fri Aug 25, 2017 8:42 am

Series1 Stu, I agree the bolts are there to provide a clamping force. However all the bolts on my IRS mounts had damage to their threads because instead of having plain shank through all the mount and frame, the inner part of the mount only had thread going through the hole. Side/shear load was on those threads to damage them, however tight you do up the bolts. I replaced mine with the same length bolts which had shorter threaded section such that the thread is only there to hold the nut not have any side load on it. The same could be seen on my engine frame. That is where I have seen the great difference between aviation and motoring bolts, that's all my point is.

Cheers

Geoff
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#19 Re: Frame mounting bolts

Post by Hugo » Fri Aug 25, 2017 9:12 am

It's a valid point, but of course it's not nearly so critical in cars, so we can afford to be a bit sloppy about practises like this. Frankly I never cease to be amazed at how safe commercial aircraft are. I wouldn't have thought it was humanly possible to achieve such a high degree of safety. I'm guessing that they are very much over-maintained though. In a commercial road-going vehicle, the ideal is to replace an item just before it breaks or wears out. If you get it wrong you end up stuck on the side of the road. You obviousy need a greater margin with things that fly through the air though.
I'm puzzled that your bolts were worn though - were they not as tight as they should be? I was surprised when dismantling my Series II at how 'un-tight' many of the fixings were. The frame bolts were not much more than hand tight. Nothing had actually come loose though, which was a surprise in itself.
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#20 Re: Frame mounting bolts

Post by Gfhug » Fri Aug 25, 2017 11:01 am

Not worn through, just side pressure on the threads had flattened them a bit. Every bit as tight as they should have been.

Geoff
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