Torque values?
Torque values?
(OP)
As a free lance mechanical designer I often specify torque values for machine screws for assembly drawings. More often than not the customer questions my use of "lbs-in" as a torque value. They insist on "in-lbs". I usually change the drawing to "keep the customer happy" but is this the right thing to do? Thanks for the feedback





RE: Torque values?
I rarely see lb-in; almost always in-lb.
http://www.EsoxRepublic.com
RE: Torque values?
RE: Torque values?
Torque is defined as a a force applied at a distance, which is consistent with pound-inch.
I bet your customers would never ask to change Newton-meters to meter-Newtons.
RE: Torque values?
Inch-pounds is the standard way in US industry to present torque values. There is no particular standard or guideline that covers this subject, as far as I know. One pound times one inch (or one pound-inch) is equal to one inch times one pound (or one inch-pound), so it isn't a question of wrong answer but presentation preference. This is one of the problems that occurs with the Inch-Pound system used in the US - there are no standards that cover abbreviations, etc. I have read that some people like to differentiate rotational energy (pound-inch, pound-feet, etc.) and static torque (inch-pound). Because of the info above, and many more reasons, I recommend the conversion to and use of SI units.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque values?
One small correction regarding SI units - you shouldn't use a dash to separate units. Rather, use a space or a dot: e.g., N m or N·m.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque values?
Torque or moment is commonly expressed in pound-feet, pound-inches, kilogram-meters, etc. Metric (SI)is newton-meters.
Work is force times distance and is expressed in foot-pounds, inch-pounds, meter-kilograms etc. SI metric is the Joule.
Because there are two systems using the same units, to differentiate it is common to show torque as lb-in as you do.
RE: Torque values?
how do you type the dot?
RE: Torque values?
Mil-Hdbk-60 uses pound-inch (Newton-mm),
Mil-B-7838 uses inch-pound.
"View-Source" on my browser reveals that you must type "_&_m_i_d_d_o_t_;_" to show a · on the screen. (I had to put the underscores in to prevent the browser from automatically converting the characters to a dot on its own)
STF
RE: Torque values?
Alt 250 ·
Alt 248 ° 100°C
Alt 241 ± ±100°C
RE: Torque values?
Please review
http://www.xcalcs.com/docs/symbolinfo.htm
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque values?
in-lb in Imperial units and
N-m in metric
RE: Torque values?
in metric units the torque is measured in N·m
The metric units suppose to correspond with the way how they were derived/calculated.
" · " means "multiplied by" while " - " means "minus".
In Imperial units I have seen any combination of in lb (lbf).
RE: Torque values?
Very few of my classmates found it as funny as I did.
STF
RE: Torque values?
both your units are acceptable. If logical, it's a different story.
In the automotive industry we use the torque in N·m, the numbers are reasonable.
By the way - the 1988 GM metric standard properly defines the N·m as a unit of torque. (The same standard always shows "lbf" as the unit for pound(force) to make the difference between the mass and force, what is the main reason why we have the Newtons in metric system...)
How did you make the dots bold?
RE: Torque values?
= ia Alt 243. These are ascii codes for the symbol. To get a complete list of symbols accessible this way do a search for ascii codes and pick a table that is easy to read.
Some tables don't show the extended ascii codes (above 127)so find one that does.
RE: Torque values?
RE: Torque values?
How does one know the difference between a hyphen and a subtraction sign? You can't guarantee which is which, so SI style guides state that compound units are separated with a space or a dot, not with a hyphen.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque values?
I have have never seen "-" used in place of "·" in any metric standard. The convention youre talking about is non-metric and can lead to confusion, therefore I would not recommend it with metric units. Obviously most important is to know, what we are doing.
While in the college (in a "metric" country), when we calculated some engineering problems, at the very end we usually performed the same calculations symbolically with units, using the same formulas (sometimes very complex) just to prove that the results are valid values, making sense for the given problem.
Is there any standard allowing using "-" in place of "·"?
As I already mentioned, the GM standard uses "·"
Regards
gearguru