Most effective Torque Wrench size / range?

[Tim Good]

I have a trade account that gets me discount from Norbar wrenches.

I've always been a bit lazy and just tightened things by hand but I want to do things properly during my refit and ideally only want to carry one torque wrench on the boat.

In your opinion from the following what would be the best all round in terms of drive size and range? Boat is a 43ft with an 80HP.

• 3/8in Drive 8-60Nm
• 1/2in Drive 8-60Nm
• 1/2in Drive 20-100Nm
• 1/2in Drive 40-200Nm

 

[VicS]

Check your workshop manual to see what settings you will require
Otherwise
No substitute for a 1/4" or 3/8" drive for small stuff starting at say 5 Nm

And a 1/2"drive going up to 200Nm

You might need 3/4" drive to go up to 300 or 400 Nm.

FWIW I have a cheap, crude, probably not very accurate 1/2" drive one that goes to 150 lb ft . Useful but when I have needed better I have always been able to borrow one

 

[djrussell0]

if you only want one I would get the 1/2in Drive 20-100nm, or if you can have 2 3/8in Drive 8-60 and 1/2in Drive 40-200nm which pretty much what I keep in my tool chest at work. I wouldn't leave on boat unless completely moisture free storage, are they digital or segmental read off.

Dave

 

[RichardS]

8mm - 12mm nuts and bolts are fairly common and are usually less that 20Nm so, in my experience, a wrench starting at 20Nm will be much less useful than the one with the lower range. Whether you go for 3/8/ or 1/2 inch drive depends upon your existing sockets.

I have the low range 3/8 and a high range 1/2 but the high range is rarely used. For high torque nuts (crankshaft and stub axle nuts) you can always do them up to 60Nm and then a bit more with a breaker bar.

Richard

 

[Lakesailor]

I have an old click stop 1/2" Britool torque wrench which is in the 40-200nm range (about 30-150 lb/ft). Unless you have an alloy engine with bolts into the alloy that is the range I would look at. Nuts and bolts at lower torques can be tightened as you are doing at present. The lighter sizes with low torque values never seem right if I use a borrowed torque wrench. With a ring spanner you can feel stretch.

If you are re-using bolts, the recommended settings can sometimes feel wrong.
I have just done up a crankshaft pulley bolt to about 120 lb/ft. It should be 140 lb/ft but I tighten bolts like that in a few stages and the 120lb/ft setting seemed to stretch the bolt enough. I wouldn't have liked to take it further.

 

[dinhtuann123]

Lest anyone believe that they can “guess” whether they’ve torqued a bolt properly, I submit the sad story of the water pump on my late, beloved 1980 Subaru hatchback. I decided to give auto mechanics a try—I was poor then, and figured some DIY would be good—so I replaced my water pump. It leaked, probably because I did a crappy job with the gasket, but I figured I’d just under-tightened the bolts. Nope—snapped one right off with too much torque. If I’d known I’d properly torqued the bolts, I likely would have realized my gasket job was really, really bad. Lesson: always use a torque wrench when the shop manual says so.

 

[RichardS]

Lest anyone believe that they can “guess” whether they’ve torqued a bolt properly, I submit the sad story of the water pump on my late, beloved 1980 Subaru hatchback. I decided to give auto mechanics a try—I was poor then, and figured some DIY would be good—so I replaced my water pump. It leaked, probably because I did a crappy job with the gasket, but I figured I’d just under-tightened the bolts. Nope—snapped one right off with too much torque. If I’d known I’d properly torqued the bolts, I likely would have realized my gasket job was really, really bad. Lesson: always use a torque wrench when the shop manual says so.

No criticism intended but it depends upon how long you've been working on engines. After 45 years I rarely use a torque wrench these days unless it's critical with such things as bearing caps. However, I do occasionally use one to check my judgement and am pretty much spot on from 10 - 50 Nm. From 50 - 200+ Nm it's a lot more difficult but then I always grease and under-torque the big buggers anyway!

Richard

 

[Tim Good]

Lest anyone believe that they can “guess” whether they’ve torqued a bolt properly, I submit the sad story of the water pump on my late, beloved 1980 Subaru hatchback. I decided to give auto mechanics a try—I was poor then, and figured some DIY would be good—so I replaced my water pump. It leaked, probably because I did a crappy job with the gasket, but I figured I’d just under-tightened the bolts. Nope—snapped one right off with too much torque. If I’d known I’d properly torqued the bolts, I likely would have realized my gasket job was really, really bad. Lesson: always use a torque wrench when the shop manual says so.

Blatant spam. He's linked the word "torque" to his website. You'll probably find this exact post or similar versions on other forums.

 

[ghostlymoron]

One thing I've never understood about torque wrench. What is important is the tension in the shaft of the bolt, the torque wrench measures how much force it takes to turn it. Surely this depends on the condition of the threads. If it is old and rusty, it will take more force to turn it resulting in less clamping force than if the threads are clean and well lubricated when it will be easier to turn.
Am I wrong and does it matter?

 

[RichardS]

Blatant spam. He's linked the word "torque" to his website. You'll probably find this exact post or similar versions on other forums.

Ah, now that has answered a question .... when I quoted the post I could see that there were URL tags in the quote but when I looked back at the post I couldn't see any hyperlinks so I though it was just some oddity. I've checked again after reading your post and I now see that the word "torque" is indeed a hyperlink, although how anyone is supposed to accidentally click on it I've no idea!

Richard

 

[RichardS]

One thing I've never understood about torque wrench. What is important is the tension in the shaft of the bolt, the torque wrench measures how much force it takes to turn it. Surely this depends on the condition of the threads. If it is old and rusty, it will take more force to turn it resulting in less clamping force than if the threads are clean and well lubricated when it will be easier to turn.
Am I wrong and does it matter?

You're right. The torque wrench measures how hard it is to turn the nut or bolt which is a close proxy to how much the bolt is being "stretched" (usually at a microscopic level) and therefore how much force is being exerted on whatever the bolt is holding.


The manufacturer usually does their calculations with new clean threads. Anything other than new clean threads will affect the readings. With rusty threads the actual stretch force will be less than the trorque wrench suggests whereas with greased threads the stretch force will be higher that the torque wrench suggests, and hence my phrase "grease and under-torque".

Hope this helps.

Richard

 

[elton]

One thing I've never understood about torque wrench. What is important is the tension in the shaft of the bolt, the torque wrench measures how much force it takes to turn it. Surely this depends on the condition of the threads. If it is old and rusty, it will take more force to turn it resulting in less clamping force than if the threads are clean and well lubricated when it will be easier to turn.
Am I wrong and does it matter?

The amount of resistance created by corroded threads is generally insignificant compared by the resistance imparted by stretching the bolt. If you look at any bolt that's just been removed, it's unlikely to have any remaining corrosion on it in any case. There's a widespread myth that lubricating threads with Coppaslip and such like, alters the required torque application. It's a complete fallacy.

I wouldn't trust any mechanic that didn't use a torque wrench. Some of the old hands are the worst culprits, believing they have "a feel" for torque. Just as important as using one, is using it correctly. Vehicle manufacturers publish every torque specification for every bolt, as well as the specification of every bolt, in terms of materials, torque, and usage.

Incorrect application of torque can lead to all kinds of disasters, from wheels falling off, to brake failure, to warped cylinder heads, snapped crankshafts, or simple oil leaks.

 

[RichardS]

The amount of resistance created by corroded threads is generally insignificant compared by the resistance imparted by stretching the bolt. If you look at any bolt that's just been removed, it's unlikely to have any remaining corrosion on it in any case. There's a widespread myth that lubricating threads with Coppaslip and such like, alters the required torque application. It's a complete fallacy.

I wouldn't trust any mechanic that didn't use a torque wrench. Some of the old hands are the worst culprits, believing they have "a feel" for torque. Just as important as using one, is using it correctly. Vehicle manufacturers publish every torque specification for every bolt, as well as the specification of every bolt, in terms of materials, torque, and usage.

Incorrect application of torque can lead to all kinds of disasters, from wheels falling off, to brake failure, to warped cylinder heads, snapped crankshafts, or simple oil leaks.

I don't trust any mechanic ......... full stop. If I need to use one I always double check their work and in 99.9% of my experience they have done something incorrectly and I usually get a refund when I point out their errors. Last case of a full refund was 3 weeks ago. Best case was £500 refund about 10 years ago.

Torque settings table, dry and grease: http://www.raskcycle.com/techtip/webdoc14.html.

Richard

 

[Tim Good]

Ah, now that has answered a question .... when I quoted the post I could see that there were URL tags in the quote but when I looked back at the post I couldn't see any hyperlinks so I though it was just some oddity. I've checked again after reading your post and I now see that the word "torque" is indeed a hyperlink, although how anyone is supposed to accidentally click on it I've no idea!

Richard

They're not. It is for link building which raises his site on Google. To point he has missed is that doing things like that stopped working about 2 years ago when Google cottoned onto it and now actually works against you.

 

[ex-Gladys]

Reminds me of a video I saw on t'internet of the BSA factory in the 50's. On the engine line they were choosing left and right crank case halves and crankshaft on how the three bits fitted together, and tightening bolts there wasn't a torque wrench in sight. And we wondered why the Japanese destroyed the British bike industry...

 

[ghostlymoron]

Your attached table does seem to support my suspicions as it makes a significant difference.
I don't share your distrust of mechanics. There are good and bad as in all trades.

I don't trust any mechanic ......... full stop. If I need to use one I always double check their work and in 99.9% of my experience they have done something incorrectly and I usually get a refund when I point out their errors. Last case of a full refund was 3 weeks ago. Best case was £500 refund about 10 years ago.

Torque settings table, dry and grease: http://www.raskcycle.com/techtip/webdoc14.html.

Richard

 

[Daydream believer]

Just as important as using one, is using it correctly. .

I think that is a valid point.
When i first borrowed a click type wrench i found I could make it click at what seemed to be different torques for the same setting & bolt. Although the "oil" factor may have been at play which I was not aware of --thinking that the use of oil would make little difference at full load, only when spinning up
True it may not have been a particularly good wrench but clearly i was not up to using one correctly
i also suspect that nuts & bolts must have different settings as a bolt gets the friction through the product being bolted whereas the nut does not

 

[RichardS]

There are good and bad as in all trades.

That's a fair comment. The problem is that what none of them has is time, however good they might be as mechanics.

I replaced the front disks and pads on my XK8 last week and spent 3 days on the job. Whilst I was doing that job I noticed that one of the piston gaiters was displaced and some water had got in. Attending to that required a complete removal of the caliper and piston so I could polish up the corrosion on the piston with wet and dry and replace the gaiter properly which can only be done if the piston is completely ejected. That drains down the fluid so a complete flush and re-bleed is then necessary. All the caliper parts from both sides were thoroughy cleaned and all threads cleaned-up and greased.

If that job had been done by a garage to the standard I did it, it would have cost at least £1000 in labour alone and no-one would be prepared to pay it so a garage would have just done the minimum necessary.

The annoying thing is that the badly fitted cylinder gaiter was actually a botch-up by a garage some years ago as part of a job that I couldn't do because I don't have the two special (very special in fact) tools. I should have spotted it earlier but it wasn't visible until the caliper was unbolted and I've had no reason to do that before now

Richard