Torque wrenches lie!

Dellortoman said:
I don't reckon there's much that can go wrong with that type. I'd be surprised if its calibration changes.

I still have an old torque wrench that's even less high tech. It just has a scale and a pointer on the handle. The handle deflects as you put force on it and you read off the torque on the scale. It's about as simple as you can get, and it works both ways. I can't imagine how it would ever lose its calibration during normal use.
Click to expand...
OK - here you go... I tested it and - as already assumed by you and Pat, it is surprisingly accurate! That said, mine goes up to 200Nm/20mkp and therefore the scale is in 10Nm/1 mkp steps. Everything between the 10Nm steps is guesswork. Adjustment is subject to the pointer of the scale being accurately at 0 before you start. easy to adjust that way though.

so - good for fastening the tires on the car but not accurate enough to fasten a Laverda cylinder-head...
 
ah,yes, but,
its only as good as the measuring device!
maybe you need a measuring device checker? and a checker checker etc, lets got get too anal, I love my 40 year old Snap on Stuff, thats why I never let anyone else touch them, borrow it? you are having a tin barf pal!
someone asked me if they could loan my 40 year old Snap On timing light the other day, very short answer, "NO" and before you open your gob its still "NO" so don't ask me why not.

CLEM
 
rowdypat said:
Wired up some new 12.5MW (12500kW) aeration blower motors at a sewerage treatment plant. The HV terminations were M16 brass nuts on brass studs. The manufacturer specified 110nm. We had two freshly calibrated Kinchrome 1/2” drive torque wrenches. I stopped before the click occurred as it already was so bloody tight I felt I was going to break the stud, in which case I may as well have thrown myself in the shit tank. I tried the other wrench and it hit 110nM well before it got to the point of the previous wrench 🤨
Click to expand...
The second try would need to overcome the stiction present from the initial tightening. Normally, you'd back the nut off before re-torquing. Often, lube or not is specified, a oiled/greased threads can go a frighteningly long way... often just that little bit too far! :rolleyes:

piet
 
Never seen 'lubed or not' in any Laverda manual!! It's not a nice feeling when the bar keeps swinging and that click isn't forthcoming. Sometimes I just trust my instincts.
 
piranha-bro2 said:
Never seen 'lubed or not' in any Laverda manual!! It's not a nice feeling when the bar keeps swinging and that click isn't forthcoming. Sometimes I just trust my instincts.
Click to expand...
The switchboard manufacturer provided specs for lubed/non lubed. In our case, was bolting onto epoxy insulators….3 Assembly of the switchgear panels.JPG
 
Laverdalothar said:
so - good for fastening the tires on the car but not accurate enough to fasten a Laverda cylinder-head...
Click to expand...
You're dead right there, such a large wrench does not give you the requisite resolution for a 34Nm bolt. As Piet said, you need to use the right tool for the job.
A surprisingly long time ago (realised it's probably 25 years!) I bought a Norbar 20-100Nm wrench to work on Laverdas. Norbar are a torque tools specialist, it's a lovely thing to use, but was expensive. At the time it seemed a good range compromise and I only had 1/4 and 1/2" drive sockets so got the smallest 1/2" drive torque wrench they made.
More recently I've expanded the range of wrenches as small and large jobs came along, so now have a 1-20Nm 1/4" drive and a 60-340Nm 1/2" drive - both by Norbar also. I also got a 3/8" drive Gedore wrench which is 10-55Nm and that is now my favorite wrench for working on bikes as the range is right for a lot of things (especially heads).
I like to use a wrench somewhat in the middle of it's range. A wrench at its lowest end of scale doesn't give any feel or resolution as mentioned above, and usually at the top of the scale you can feel the wrench is too small simply by the effort to reach the setting due to the length of the lever. Doing 100Nm with my 20-100 wrench is uncomfortable whereas it's nice and easy on the 60-340Nm one.

As an aside all my wrenches are the click type, two have a reversible ratchet and two have a 'push through' drive square. The push-through style is great because it can torque up both right and left hand threads.
 
With ya on the Norbar gear Gear, Steve...........only way to fly. Mate of mine was a rep for Norbar in a past life, chewed his ear off and I ended up with a nice Torque wrench 8-60Nm 3/8" Drive, Boooodifull :cool:
 
As I wasn't really sure about my torque wrench after re-tightening the cylinder head last time (which drove me off to this experience of getting a testing device and test all I had), I re-torqued the head again yesterday evening (haden't started the engine between last time and now). I used the 10-40Nm, short Gedore torque wrench that was tested as very close to the adjusted values on my device. The nuts all could be tightened much more than before... :oops: I am so glad I did not start the engine in between...

The feel was totally different, the 35Nm ones did really make me swet and pray - just like it should be... 😂

none of them though was feeling wrong though and so I hope the head is now correctly tightened.

Again, I can only recomend getting you a proper tool for the job if you do not have one. Worth the money if you compare the hassle of a wrongly tightened head...
 
The Sock said:
.View attachment 57889
Click to expand...
Even if that was just fake info on this topic.

No 48 Nm !!!
Correct would be between 10-12 Nm depending oiled or not (see list below on the right side).

The "4.8" on the screw shows the (poor) quality of the screw. It is only a M8.

Tensile strength yield pointTensile strenghtStretch limit
4.84 x 100 = 400 N/mm²4 x 8 x 10 = 320 N/mm²

1626247859820.png

Thomas aus LAU
 
Last edited:
Laverdalothar said:
I think this was more meant a s a joke, Thomas... ;)
Click to expand...
Can be - or not.

I believe not everyone knows what 4.6, 8.8 or 12.9 means on a screw head.

Likewise, I regularly see that motors with normal threads are screwed into the frame (e.g. last weekend).
But this only works permanently with screws, that have a fine thread.

Apparently there is still some clarification to be carried out here.

Thomas aus LAU
 
for Hamish, I never torque the drain plug, and nor do I tighten it much, I use a new doughty washer every time its out and I lockwire it to the frame
CLEM
 
And just for the newbies, the green book head toque numbers are wrong. From someone who did big damage using them. It didn't help that the case studs were upsidedown as well
 
As the pictured item is an oil drain plug, I very much doubt it is an M8 thread. More like 9/16" or M14 fine. Flanges on such plugs can cause loads of stiction, the small hex is meant to discourage the use of huge spanners that might exaggerate the the specified tightening torque. I also doubt the numbering to be a tensile spec, more an assembly code for production line workers 4.8 spec screws/bolts shouldn't be used on any vehicle, their tensile strength only slightly exceeds that of parmesan cheese...

Busting out a piece of alloy sump requires serious force, did King Kong complete an automotive apprenticeship? :oops:

piet
 
Vince said:
And just for the newbies, the green book head toque numbers are wrong. From someone who did big damage using them. It didn't help that the case studs were upsidedown as well
Click to expand...
I am not using them, I always use something posted on the German Laverda-Page and which I think is somewhat "Laverda-Specialist approved":

Cylinder-Head Torque figures Laverda 1000/1200

I think it is from Thomas, but am not 100% sure. At least - as you can guess from the german text on it - from a German Forum member.
 
sfcpiet said:
4.8 spec screws/bolts shouldn't be used on any vehicle, their tensile strength only slightly exceeds that of parmesan cheese...
Click to expand...
I reckon sump plugs are an exception, given that the crankcase material is softer than the parmesan cheese plug (maybe a nice cheddar).

I'm with Clem on the tightening of sump plugs in alloy cases. I just nip them up enough to seal, then wire 'em.
 
Problem with sump plugs is once the thread has stretched in the casting the plug threads are not touching evenly.
Old mechanic taught me to use copper slip on sump plug- it seems to even up the pressure over the whole thread and prevent stretch and galling. New washer every time.
 
You must log in or register to reply here.
Back
Top