Torque wrench errors

[northwind]

See, I don't quite get teh "don't trust torque wrench" argument, since it's not as though you don't have your sense of feel as a backup... They can be risky if you turn off your brain, but then what isn't?

Originally Posted by northwind

See, I don't quite get teh "don't trust torque wrench" argument, since it's not as though you don't have your sense of feel as a backup... They can be risky if you turn off your brain, but then what isn't?

Trouble is Norfie you dont really get sense of feel with a massive torque wrench - at least not with the 25 year old one that I have got.

[21QUEST]

Originally Posted by northwind

See, I don't quite get teh "don't trust torque wrench" argument, since it's not as though you don't have your sense of feel as a backup... They can be risky if you turn off your brain, but then what isn't?

I hear you but maybe one might as well not be using the torque wrench in the first place. A bit like fitting a gear indicator wotsitthingy and wondering if it's showing the right gear.

I do still use a torque wrench for the odd stuff but haven't sold my soul to the torque wrench god as some people seem inclined to do.


Ben

never used one

Originally Posted by hovi5

never used one

Sometimes that can make you walk funny..

[northwind]

Originally Posted by 21QUEST

I hear you but maybe one might as well not be using the torque wrench in the first place. A bit like fitting a gear indicator wotsitthingy and wondering if it's showing the right gear.

Hmm, I can see what you mean, but if I was to set mine to, say, 23nm (have the bolts on an SV are at 23nm it seems) and it doesn't click, I'm going to know it's not right by 30. But I can't set 23nm by feel, put it that way. So I tighten to the click, or until it feels like I've gone too far. That way I'm no more likely to snap a bolt than I am doing it by feel.

Ive threaded a few in alloy so i think Ive just learnt the hard way.

[embee]

For smaller fasteners into questionable alloy I always work up towards the specified torque in steps.

For example if it says 23Nm I'll probably set it to 15Nm first and see what it feels like. If you don't get a repeatable firm feel then be very cautious. Fine series threads are a pain too.

I've found brake caliper fixings to be especially delicate in this respect, and often use "low torque then feel" so you know it's at least a minimum value.

When I was involved in specifying fastener tightening in production, most commercial fastener suppliers used a "lightly oiled" condition though with environmental issues this practice is more or less phased out. The lubrication and plating etc affects the torque/tension characteristics significantly. If you're using a grease then you might want to reduce the torque by typically 25% anyway (no responsibility accepted! ). This doesn't apply to major fasteners like con-rods or cylinder heads though.

Loctite when still wet doesn't lubricate anything like as well as oil/grease, and can sometimes improve the "feel" as you tighten it due to the extra friction.

I'm not sure I understand this 'I don't trust torque wrenches' concept. I have been involved with aerospace engineering all my working life. Torque settings are quoted by manufacturers for a reason. Its not a case of the general public expect it, there is a sound engineering principal behind it. Designers and stress engineers spends hours calculating what the required torques should be. If the concern is in the accuracy of general torque wrenches then thats another thing. You should always slacken off a torque wrench after use otherwise it will stretch the spring inside and will not be accurate any longer. In the aviation industry torque wrenches are calibrated before every use and the calibration guages are strictly monitored and maintained.

Originally Posted by Fearg

I'm not sure I understand this 'I don't trust torque wrenches' concept. I have been involved with aerospace engineering all my working life. Torque settings are quoted by manufacturers for a reason. Its not a case of the general public expect it, there is a sound engineering principal behind it. Designers and stress engineers spends hours calculating what the required torques should be. If the concern is in the accuracy of general torque wrenches then thats another thing. You should always slacken off a torque wrench after use otherwise it will stretch the spring inside and will not be accurate any longer. In the aviation industry torque wrenches are calibrated before every use and the calibration guages are strictly monitored and maintained.

Well you just answered it yourself. I've a torque wrench in my garage which I haven't used for 20 years. Without getting it recalibrated I wouldn't trust it. When I was working on car engines I always torqued the large area joints to prevent distortion. I had no idea how accurate it was though.