Stretching / Torquing a bolt

little decks · Postby **little decks** » Wed Aug 14, 2013 11:17 pm

Even the best quality rod bolt is worthless unless its stretched properly

Postby **NitroDann** » Wed Aug 14, 2013 11:25 pm

Dude...!

what.?

Postby **orx626** » Wed Aug 14, 2013 11:33 pm

NitroDann wrote:Dude...!

what.?

Read this Dann http://arp-bolts.com/pages/technical_installation.shtml

Cheers,
Danny

Postby **NitroDann** » Wed Aug 14, 2013 11:47 pm

You dont want them to stretch permanently.

Using a stretch guage is fine (didnt read link but get the idea), but suggesting stretching is something done first isnt.

Miscommunication I spose.

Dann

Postby **orx626** » Wed Aug 14, 2013 11:54 pm

NitroDann wrote:Using a stretch guage is fine (didnt read link but get the idea), but suggesting stretching is something done first isnt.

What do you mean by "done first"?

Postby **NitroDann** » Wed Aug 14, 2013 11:56 pm

I know, thats why I responded why I did, I somehow read it that way. Even with a stretch gauge ive only ever heard of people using the term torquing bolts, never heard of people stretching them.

Dann

sailaholic · Postby **sailaholic** » Thu Aug 15, 2013 12:07 am

Yup bolts are stretched when taking them up, makes for a much stronger connection

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Postby **NitroDann** » Thu Aug 15, 2013 12:13 am

I know, miscommunication, never heard someone refer to torquing bolts as stretching them, permanent stretch fucks them and reffering to stretching them sounded backwards to me.

Dann

Postby **orx626** » Thu Aug 15, 2013 12:49 am

NitroDann wrote:I know, miscommunication, never heard someone refer to torquing bolts as stretching them, permanent stretch fucks them and reffering to stretching them sounded backwards to me.

Dann

Torquing a bolt is in fact stretching the bolt. Without bolt stretch there is no bolt tension. In some automotive applications bolts ("Stretch Bolts") are actually designed to be permanently deformed (ie. loaded beyond the material's yield point) when tensioned! Rover V8 head bolts come to mind. But you are correct, they can only be used once.

Cheers,
Danny

Postby **NitroDann** » Thu Aug 15, 2013 1:08 am

Right, Ive just never ever heard anyone refer to it like that, and I know and hang with a few engine builders.

Dann

little decks · Postby **little decks** » Thu Aug 15, 2013 1:22 am

NitroDann wrote:Right, Ive just never ever heard anyone refer to it like that, and I know and hang with a few engine builders.

Dann

It's extremely common but in much more high performance stuff than you might have come across, I've seen a couple of porsche 996 engines getting overhauled and there are specs provided for stretch on more than just the rod bolts, thats why you replace all of these bolts every time you pull the thing down.

Little details like this is why some builders charge more than others, the aviation grade fasteners aren't the cheapest... some try to get away with reusing rod bolts that have already been stretched and you see a lot of the time the end up sheering or snapping the bolt.

little decks · Postby **little decks** » Thu Aug 15, 2013 1:33 am

NitroDann wrote:You dont want them to stretch permanently.

Using a stretch guage is fine (didnt read link but get the idea), but suggesting stretching is something done first isnt.

Miscommunication I spose.

Dann

The bolt can stretch to an extent and still be able to return to its original length, thats the whole theory behind stretching the bolt, the fact that the material tries to pull back to its original shape is how it gets really tight. That's why ARP fasteners are dearer, due to the R&D in finding the optimum material that can stretch a fair bit while still having the elasticity to pull back towards its original shape and maintaining strength.

Postby **NitroDann** » Thu Aug 15, 2013 1:50 am

I think you missed the entire conversation we just had.

My exhaust component supplier has an engine dyno that consistantly has Australian champion dirt track engines on it.

Ive simply never heard anyone refer to torquing a bolt with the use of a stretch gauge as stretching the bolt.
If you were to pull on the bolt and it becomes permanently stretched past spec, it is ruined.

Ive simply never heard anyone say they are stretching a bolt. Only ever heard people use the term torquing, whether they were fitting by torque, angle, or stretch gauge.

Dann

little decks · Postby **little decks** » Thu Aug 15, 2013 10:55 am

NitroDann wrote:I think you missed the entire conversation we just had.

My exhaust component supplier has an engine dyno that consistantly has Australian champion dirt track engines on it.

Ive simply never heard anyone refer to torquing a bolt with the use of a stretch gauge as stretching the bolt.
If you were to pull on the bolt and it becomes permanently stretched past spec, it is ruined.

Ive simply never heard anyone say they are stretching a bolt. Only ever heard people use the term torquing, whether they were fitting by torque, angle, or stretch gauge.

Dann

Oh sorry, i didn't realise you know someone with an engine dyno... how naive of me to think you didn't know everything there is to know. Funny little anecdote actually, my contract law tutor at uni is actually a leader in the area of banking and finance law, I was in his class for 3 months and got a good mark in his exam, it's almost certain that I know everything about banking and finance law.

You are just carrying on as if what i said was so manifestly incorrect, when in fact quite correct. You just seem as though you're embarrassed but just having managed to figure it out yet.