How do you torque?

[visitam]

Some of us aren't so lucky to have fathers, great grandfathers, or uncles to show us the tricks and the trade of mechanical techniques when working with cars. Apparently I'm one of the more unfortunate ones so I'd like to ask the veterans of the tool world, what is the general principle or the "correct" way to torque a bolt. What's your take on torquing?

Some background:
I am about to be a 3rd year engineering student coming this Fall at UCSC. I thought I'd try to gain more tangible experience (versus the hypothetical knowledge that I know about statics, physics, and such) by taking the responsibility of assembling a new motor and making that as an excuse to start building my tool fetish. So far, the tools I have worth noting are impact grade sockets from IR, proto ratchets, SO CT4850, and my two brand new torque wrenches from PI, c2fr100f (5-100 ft. lbs) and D2F600HM (0-600 in lb). I've been lurking for quite a while, but I hope to be more engage in the participation that goes on this forum.

 

[tatra]

half a turn back after destruction noted.............

 

[Kevin54]

I use oil on the threads (on engine assemblies) to reduce drag and get proper torque reading. And always go by torques specs and torque patterns.

 

[tatra]

school boy, should wheels studs be lubrcated or dry torqued.............personally, contrary to costco"s policy, i elect to use never seize...........did a lot of tire changes in my earlier days, and f$%%^ !Y$%$%^$#$&#$$%&%*&, some were stubborn.........and the occasional one of those was personal property............salt *****............

 

[wbclassics]

If the initial torque spec is given for dry threads, you better be accounting for the reduction in friction by putting lubricant on the threads and then reducing your the required torque value...

Torque wrenches are used for fastener tightening because they're convenient, but not the perfect method to tension a fastener.

 

[FastKat]

One thing to keep in mind is that you want to keep the torque wrench moving at a steady, medium pace as you approach the desired torque AND up until you approach the desired torque. Don't stop when you're almost there, and then start up again to get the last little bit in.

This might take a little practice because you will want to have the torque wrench in the correct position so you can easily sweep up to the desired torque. For this reason, I think a ratcheting flex-head torque wrench is the way to go, if you can justify the cost of buying one.

 

[LoneGunman]

I was always told the threads should not be lubricated when torquing unless you account for the lower resistance. How would one count for the lower resistance, is there a set formula?

Visitam, I think it's great you are trying to learn the hands on stuff. I've ran across a few engineers who wouldn't think of getting their hands dirty. I was told by the owner of a large manufacturing plant that some of his best engineers were guys who knew both sides, the engineering side and the getting your hands dirty size.

I spent a lot of time working in this facility as an outside contractor so I witnessed a lot. This new engineer belittled the head machinist when the machinist asked him for clarification on a print. The engineers response was "Just do what the print says, I made the print and that's what I want, I don't need a machinists input". From what I heard about 20k in titanium was wasted before the mistake was realized. I knew something bad was going to happen, after the engineer insulted the machinist the machinist said "you are the boss" and walked off with a smirk.

The engineer was canned over the incident.

 

[benjamming]

I was always told the threads should not be lubricated when torquing unless you account for the lower resistance. How would one count for the lower resistance, is there a set formula?

One example that assumes the initial torque rating was for dry.

 

[Dodgepu360]

I was always told the threads should not be lubricated when torquing unless you account for the lower resistance. How would one count for the lower resistance, is there a set formula?

do you have the little black "Pocket Ref" book there is a section in there about torquing bolts and has chart showing max torque for varius sizes and grades
it also has a list of theard lubicants and platings with a muiltipiler to figure the correct torque the list is 2 pages long
for example:
black oxide 1.00
WD-40 0.80
cadmium plating 0.80
Moly-50 anti-seize 0.65

so if the recomend torque is 75 ft-lbs and you used Moly-50 anti-seize on the bolt you would only torque it to 75 X 0.65 = 48.75 49 ft-lbs

 

[Teken]

Excellent topic . . .

 

[z28snksknr]

do you have the little black "Pocket Ref" book there is a section in there about torquing bolts and has chart showing max torque for varius sizes and grades
it also has a list of theard lubicants and platings with a muiltipiler to figure the correct torque the list is 2 pages long
for example:
black oxide 1.00
WD-40 0.80
cadmium plating 0.80
Moly-50 anti-seize 0.65

so if the recomend torque is 75 ft-lbs and you used Moly-50 anti-seize on the bolt you would only torque it to 75 X 0.65 = 48.75 49 ft-lbs

Where does one find such book?

 

[Moose-LandTran]

I use oil on the threads (on engine assemblies) to reduce drag and get proper torque reading. And always go by torques specs and torque patterns.

I do the same. I always clean out the female threads as best i can, then dip the bolt threads in diesel before putting them in a torquing them.

 

[Dodgepu360]

Where does one find such book?

I got mine a 6-7 years back at Harbor Freight
I think I saw them at Ace Hardware last time I was there
Amazon has it too

 

[visitam]

Thanks everyone for your input, I didn't expect such quick replies. I will definitely buy that ref book and adhere to the suggestions prior to this post.

About multiple fasteners, say for example head bolts and camshaft retainers, is it wise to break the required torque into smaller equal passes? If so can someone give me an example.

 

[z28snksknr]

Thanks everyone for your input, I didn't expect such quick replies. I will definitely buy that ref book and adhere to the suggestions prior to this post.

About multiple fasteners, say for example head bolts and camshaft retainers, is it wise to break the required torque into smaller equal passes? If so can someone give me an example.

I believe the accepted practice is to torque in steps. Using fake numbers for example only, if desired torque was 100 ft. lbs, torque all to 40 lbs, 80, lbs, then 100 lbs. I've seen this specified for cylinder head bolts as well as main caps, and they specify the steps.

 

[Moose-LandTran]

I believe the accepted practice is to torque in steps. Using fake numbers for example only, if desired torque was 100 ft. lbs, torque all to 40 lbs, 80, lbs, then 100 lbs. I've seen this specified for cylinder head bolts as well as main caps, and they specify the steps.

The engine i'm working on at the moment specifies to torque headbolts to 20NM in sequence, then to 40NM, then an additional 90 degrees in sequence, followed by another 90 degrees in sequence.

Complex shiznit, nah'm'sayin'?

 

[GDA]

I was schooled with a couple simple rules -

Hold and use the tool from the furthest point away from the point being torqued (it will give you the smoothest movement due to leverage)

Hold the tool in your fingers and not in your palm as your fingers provide greater dexterity and your pull will be in a smoother overall movement

Always attempt to use a pulling strategy versus pushing as your body is stronger and more accurate pulling versus pushing

Try to align your pulling movement and your arms to the same parallel plane as the item being torqued

 

[Major Ramifications]

Quite a bit of good advise here.
I just wanted to add, THANK YOU! After having worked with and interviewed many mechanical engineers, it is so refreshing to find one who actually places some value on hands-on learning. I'd take a half-educated, but fully experienced guy over a fully educated guy with no experience any day. I promise that this type of experience will pay off during the interview.

 

[z28snksknr]

Quite a bit of good advise here.
I just wanted to add, THANK YOU! After having worked with and interviewed many mechanical engineers, it is so refreshing to find one who actually places some value on hands-on learning. I'd take a half-educated, but fully experienced guy over a fully educated guy with no experience any day. I promise that this type of experience will pay off during the interview.

I'll second this, but from personal experience. I've succeded past my peers more from my knowledge base I obtained from busting knuckles and diagnosing POS cars then from my engineering experience. And I'm a CHEMICAL engineer! We don't even FIX anything!

 

[chevyboy91188]

visitam you sound like me I'm 3rd year ME student at University of South Florida I did my first two years at Rensselaer Polytechnic playing baseball, but my mom got sick so I came home to help out. I'm in the middle my grandpa know the stuff but he's 1000 miles away so it's not easy to get lessons all the time. This site is a great place for your questions everyone has been a big help for me so far and I'm doing a basket case 66 GTO lol.

But I always torque dry and use one clean sweep like the others have said. I haven't built an engine yet but its next on the list

 

[Teken]

I was schooled with a couple simple rules -

Hold and use the tool from the furthest point away from the point being torqued (it will give you the smoothest movement due to leverage)

Hold the tool in your fingers and not in your palm as your fingers provide greater dexterity and your pull will be in a smoother overall movement

Always attempt to use a pulling strategy versus pushing as your body is stronger and more accurate pulling versus pushing

Try to align your pulling movement and your arms to the same parallel plane as the item being torqued

I knew it was a matter of time for someone to write out the proper steps . . .

 

[georgiadave]

I think torque data is in Machinery's Handbook. That is a reference you should have as an Engineer. A bit pricey, but a wealth of information.

 

[Major Ramifications]

I think torque data is in Machinery's Handbook. That is a reference you should have as an Engineer. A bit pricey, but a wealth of information.

I agree. I got my Machinery's Hanbook on Ebay. My Pocket Ref came from Ace Hardware. You can't be a real engineer or designer without these two books within easy reach.
Now, if I could only find my reading glasses...

 

[caper]

Most fasteners have a dry spec and a lubricated spec.We recently had a training session at work put on by a major fastener sales company and were told to always use the lubricated spec unless you took the bolt out of the bin and cleaned it with brake kleen or some other solvent and then installed it without touching the threads.The oil from your fingers was enough for the bolt to be considered lubricated.The instructor did some demos with a machine which showed what torque was being applied to the bolt,pretty interesting stuff.Pick the spec your going to,break it down into a couple stages,pull smoothly on the torque wrench with your hand centered in the grip and if your torquing a nut and bolt the torque wrench goes on the nut not the bolt.

 

[Mike 47]

I think torque data is in Machinery's Handbook. That is a reference you should have as an Engineer. A bit pricey, but a wealth of information.

Good graduation present

If you want to geek out on fasteners, there's Carroll Smith's "Nuts, Bolts, Fasteners and Plumbing Handbook" available from SAE, and HPBooks' "High Performance Hardware."

 

[Daedalus]

Awesome. I think I was a 3rd year ME student when I took apart my first motorcycle. The knowledge and familiarity gained from that experience came in handy a good number of times before I graduated.
A "best practice" for torquing bolt patterns is to follow an "inside-out star pattern". Assume bolts on a valve cover are spaced as follows:

o o o o o o

o o o o o o

You'll want to torque them in this order:

'9 5 1 3 7 11
10 6 2 4 8 12

Don't forget Mark's Standard Handbook for Mechanical Engineers for your reference set.

 

[Bolster]

Welcome, Slug! Good first posting!

 

[benjamming]

[snip]and if your torquing a nut and bolt the torque wrench goes on the nut not the bolt.

Why is that?

 

[nate379]

I use my "calibrated arm" for most things. About the only thing I torque are some internal engine parts, and things that have many bolts like oil pans, trans pans, valve bodies, etc.

 

[Treeman]

Most wrenches have a pivot point or mark on the handle where the wrench length corresponds to the calibration point.....Not the longest end of the handle to increase leverage.

From all the sites I studied, the consensus is that measuring torque via twisting motion (vs. stretch) can be off +/- 30% due to all the variables......rough threads, dirty threads, poor wrench use, etc.).

Supposedly, the design engineers take this into account regarding fastener strength.

 

[Mr.Nutcase]

you torque with torque wrench.........

 

[00S4Boy]

Mg31 torque works for me lol.