[TCL]

Will white high heat loc-tite or similar thread locking compounds affect the torque specs of engine case bolts? I know with plumbing fittings, teflon or pipe dope allows you to get an extra half turn or so due to the lubrication. However, an extra half turn could crack an engine case. Just curious if anyone has any info on this.

 

[ohiorider]

TCL - This is an interesting question. I can only back up your question with additional information. I do not think the Triumph Manual calls out different torque values for dry or lubed bolts, but a small Pocket Reference Guide I purchased years ago has a small table in the 'bolt torque' section that provides widely varying torque values depending on how the bolt is coated. Here's a section from that table for one size bolt.

I'm not suggesting you deviate from the torque specs Triumph provides in their Manual. Just wanted to add this info to TCL's question, and get it in front of a few of you guys who wrench more than I do for your comments.

EFFECT OF LUBRICATION ON TORQUE
Using only one bolt size in this example ..... torque is in foot/pounds
5/16" with 18 threads per inch
No Lube - steel: 29
Plated and cleaned: 19
SAE 20 Oil: 18
SAE '40 Oil: 17
Plated and SAE 30: 16
White Grease: 16
Dry Moly film: 14
Graphite and Oil: 13

I don't know exactly how I'd use this info, but it probably explains why bolts sometimes get stripped before they reach max torque reading on a torque wrench. However, it'd be a bit scary to be riding with my fork tubes attached at 50% of their torque value.

I do recall one of my old BMW manuals providing different torque specs for lubed or dry spark plugs, and a different spec if one was reinstalling the old plug where the plug gasket had already been crushed, but that's a different animal.

Shorty from Dallas .... are you out there? You know this stuff!

Bob

 

[Wooly]

Interesting topic, I've often wondered about this.
On a fairly trivial point I noted that the torque value for the sump drain plug is 25nM and had a go at it with the torque wrench to see what it felt like.
It seemed to require far more effort to get the wrench to click that I would have otherwise applied to that particular bolt being in an alloy case, so I backed off to what I thought was a safe value.
Makes me think that the presence of lubrication can over-torque a lot of the threads on our bikes.

 

[Ventura]

Application of a specific torque to a nut, bolt or stud is purely a means of applying a roughly controlled amount
of pre-tension (stretch) in the bolt/stud.
This pre-tension, dependent on the application, bolt/stud length, thread specification and materials in question,
will be sufficient to ensure correct tightness but be within the limits which would be required to snap the bolt or strip the thread.

This all applies to, for instance, the likes of casing bolts, cylinder head studs, bottom end bolts etc etc where two components are being forced together.
I use the words roughly above as the accuracy of this pre-tension is certainly effected by friction between the threads.

The exception to all this would be the likes of a sump/spark plug which is more akin to a plumbing application where you need
enough tension to crush the washer to create a seal AND to ensure it doesn’t fall out/pop out due to vibration etc.
It also importantly ensures you dont strip the thread.
What you’re not doing in this case is pulling two separate pieces of material together i.e a cover to an engine casing.

Torque wrenches etc are fine for use on small applications such as bikes and cars/trucks etc, but when the application gets bigger
then the means of applying this pre-tension differs due to the higher tensions/increased stretch required..
Generally hydraulic jacks are used to pre-stretch the studs in an axial direction (no turning involved), then the nuts are tightened purely by hand.
But that’s a different subject entirely!!

Loctite and the likes only “goes off” (sets) after the pre-tension is applied.
While it is still in its liquid form it will act as a lubricant.
This aids in ensuring that the specified torque is accurately applied in that increased friction is not a factor which effects it.

So I guess that, in answer to the question, any medium which reduces friction will ensure that the correct torque is more accurately applied,
without risking snapping the bolt or stripping the thread.
Every effort should always be made in ensuring that the threads (both male and female) are as clean (and well lubricated) as possible and are also without damage.

All a bit long-winded I know, but thats me!!..................


V.

 

[ohiorider]

Before I retired, I worked for Rockwell Automation. One of our divisions several years ago had integrated some of the Rockwell air tools used in engine assembly into a (now this will date it) DEC VAX. These tools were being used to assemble cylinder heads to blocks, big end and crankshaft mains, etc. The primary purpose of the computer interface was to support an algorithm that took into account the frictional properties of the bolts It also logged all torque readings automatically as the engine was being assembled.

That division is probably long gone, but I'll ask a few of my old buds still working at RA if they can find any info that might shed more light on this topic. If so, I'll post it.

Bob

 

[reflectedstatic]

Of course there would be a huge difference in the amount of bolt stretch and/or washer crush obtained for any given torque value for fasteners installed wet versus those installed dry, but you would never install dry fasteners in an engine anyway. Published torque values are generally slightly higher than is theoretically necessary to accommodate the extra torque required to overcome friction, assuming that some sort of lubrication is used. If you didn't use lubrication, in addition to risking damage to the threads, you wouldn't get anywhere close to the necessary bolt stretch.

When used on steel bolts, high quality threadlocking compounds generally have similar lubricant properties to whatever weight oil or grease would normally be used to lubricate the fasteners they're intended for. The fact that you will (I assume) be using previously installed- and thus previously stretched- bolts will probably have a greater effect on the actual amount of bolt stretch you get than using threadlocker instead of oil or grease will. As always, applying the torque progressively and evenly across all the fasteners is much more important than hitting an exact value anyway.

 

[norse]

Tread lubrication

The Bonneville Service manual says: "Unless specified, threaded fixings must always be fitted dry (no lubrication)."
"Warning: Never lubricate a thread unless instructed to do so. When a thread of a fixing is lubricated, the thread friction is reduced. When the fixing is tightened, reduced friction willcause overtightening and possible fixing failure."

This can be found on page 1.6

Norse

 

[Ventura]

I guess it all boils down to the specific application in question, and the use of good engineering practice.

For instance, you wouldnt treat the exhaust manifold bolts/studs in the same manner as the bottom-end/main bearing bolts/studs.

With an application such as the manifold bolts, the use of (copper-based) lubricant is not so much to ensure correct torque, but to protect from the elements and to make sure they come off next time without them snapping!
There are many applications where the use of lubrication is more to ensure ease of disassembly rather than the assembly itself.

In case of the running gear bolts, especially those subject to constant stress reversals during engine running, the correct application of torque is far more critical than protection from the environment they are used in.

Commons sense being the prevailing factor in it all I think......

V.

 

[mikeinva]

The Bonneville Service manual says: "Unless specified, threaded fixings must always be fitted dry (no lubrication)."
"Warning: Never lubricate a thread unless instructed to do so. When a thread of a fixing is lubricated, the thread friction is reduced. When the fixing is tightened, reduced friction willcause overtightening and possible fixing failure."

This can be found on page 1.6

Norse

that about tells you what you need to know .loctite can be good or it can cause more trouble then you want dont use it unless its called for .Some of it must be heated to remove bolts .The factory guys know what it takes to get the right bolt strech they want and what the bolts they use are made of .just like you will find over the years they have used 2 types of main bolts one takes more torque then the other.Alot of the bolts they use are coated and need no lube.

 

[Geimer]

You can strip thread with less torque when it is lubed. Just had experience with that this past Thursday. The info given on the earlier posts is interesting too.

We have been, this past week, qualifying new suppliers for gas valve bodies. We ran torque to failure tests on old supplier vs new supplier. Running without lube I torqued a 3/4-18 UNS thread plug into the tapped aluminum gas valve body and it stripped at 106 ft/lbs. When lubed they ran down to about 90 ft/lbs before stripping (or breaking the casting). Thus quite a difference. The thing is that ANSI standards for gas valve fittings the size I was testing require 16.7 ft/lbs before damage occurs. Thus my lowest reading was over 5 TIMES STRONGER than the ANSI spec.
We build stuff that we want to be reliable even if it is in the field for 30 years or more. Its important!

I hope Triumph is calling out torque specs that have a built in factor of safety too.

 

[why II]

Torque wrench quesiton

I'm hoping that this sticks close enough to the tread here.
How many torque wrenches should one have in their tool box to work on these bikes? Two? What ranges and which are the best brands and types?

why2