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Bolt Torque Charts- needed
2

Bolt Torque Charts- needed

Bolt Torque Charts- needed

(OP)
I have been tasked to create a centeral database for all fastner types and their torque values. This table should be specific as to the material with the threads, if oil is used or not, etc. Any ideas where to collect this type of information on the web, via a downloadable chart?

RE: Bolt Torque Charts- needed


A good search engine and a few well placed words should get you what you need.

_______________________________________
Feeling frisky.........
www.tailofthedragon.com

RE: Bolt Torque Charts- needed

Please use this site's search function.  This question has been asked many times.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Bolt Torque Charts- needed

Fasteners do not have torque values.  A fastener, used in a joint has a required value of pre-load.  This value of preload is specific to the joint configuration.

There is a weak correlation between torque and pre-load, hence torque measurement is sometimes used as a method to control the amount of preload.  Torque control may be adequeate when a joint can tolerate a wide variation in pre-load without unacceptable consequences.

RE: Bolt Torque Charts- needed

Here we go again ! Fasteners do not have recommended torque values. Joints have recommended torque values once you know how much tension you need in the joint. Then you have about ten further parameters as variables so a correlation table in three dimensions is not going to be enough.

RE: Bolt Torque Charts- needed

I didn't realize that torque had so many bitter enemies.  If extremely precise loading is needed, then there are obviously better methods. In our industry (refining), we use bolt (or stud) stretch to put a more precise stress on a fastener.  However, stretching is much more complicated and takes much longer.  Considering that we tighten hundreds of thousands of fasteners each year, the investment would be too great and not justified by the benefit.  For most routine fasteners in applications with a substantial margin for error, torque is a good alternative.  For many applications, we can't even justify the time and expense to use torque.  Those fasteners are tightened by "feel."  Precision, best practice and detailed engineering are wonderful things.  But overapplied, they simply drive up cost.  I use a spreadsheet that is probably the same as referenced by diamondjim above.  Based on material, thread pitch, lubricant and desired stress level, you can get a reasonably accurate loading.  The most commonly neglected parameter is lubricant.  There is a very large difference between Moly lube and oil.

RE: Bolt Torque Charts- needed

different industries,
different loads,
different consequences,

i guess fatigue effects are more significant for airplanes than they are for refineries,
and i guess that the consequences of a failure (due to fatigue) are more significant at 30,000 ft ...

RE: Bolt Torque Charts- needed

In a recent article, torquing and relaxing
the tension 2 times gives very good results
using the torque method, but what a pain.
Sometimes in the field, this is the only
method that is practical.  I think that this
means that you would have to apply a greater
safety factor when using the torque method.

RE: Bolt Torque Charts- needed

Look @ ASME PCC-1 for a start

RE: Bolt Torque Charts- needed

eng1234,

   You can easily create a bolt torque chart using Microsoft Excel, or some other spreadsheet.  You need to research your bolts and materials.  

   Especially, you need to state all the assumptions you made in your calculations, just in case somebody makes a bunch of other assumptions.

   When I made my torque chart, somebody printed it off, cut out the torque section and taped it to the wall of our assembly shop.  Excluded from this printout were the fact that I was analyzing for 300 series stainless, 90% of yield, and lubrication from Loctite_242.  

   It pays to write out torque values on your drawings, torque chart or no torque chart.  

   The nice thing about the spreadsheet is that if somebody wants to use different materials and loading assumptions, they can copy your spreadsheet and hack with it.

                        JHG

RE: Bolt Torque Charts- needed

1. Tightening torque values are calculated from the formula T = KDP, where T= tightening torque. lb-in. K=torque-friction coefficient;                                                 
    D = nominal bolt diameter. in; and P = bolt clamp load developed by tightening. lb.                                                
2. Clamp load is also known as preload or initial load in tension on bolt. Clamp load (lb) is calculated by arbitrarily assuming usable bolt strength is                                                 
    75% of bolt proof load(psi) times tensile stress area(sq in.) of threaded section of each bolt size.                                                 
    Higher or lower values of clamp load can be used depending on the application requirements and the judgement of the designer.        
3. Tensile strength (min psi) of all Grade 7 bolts is 133,000. Proof load is 105,000 psi.        
4. Tensile strength (min psi) of all Grade 8 bolts is 150,000 psi. Proof load is 120,000 psi. Ref.:Fastening Reference, Machine Design, Nov 1977.        
Captured  from:          Lamson & Session s Co. Chart


SAE Grade 8            
Clamp    Torque        
Load    lb.-ft. or lb.in.above dotted line    
P (lb)    Dry    Lubricated    
540    12    9    4-40
600    13    10    4-48
820    23    17    6-32
920    25    19    6-40
1260    41    31    8-32
1320    43    32    8-36
1580    60    45    10-24
1800    68    51    10-32
2860    144    108    1/4-20
3280    168    120    1/4-28
-------------------------------
4720    25    18    5/16-18
5220    25    20    5/16-24
7000    45    35    3/8-16
7900    50    35    3/8-24
9550    70    55    7/16-14
10700    80    60    7/16-20
12750    110    80    1/2-13
14400    120    90    1/2-20
16400    150    110    9/16-12
18250    170    130    9/16-18
20350    220    170    5/8-11
23000    240    180    5/8-18
30100    380    280    3/4-10
33600    420    320    3/4-16
41600    600    460    7/8-9
45800    660    500    7/8-14
54500    900    680    1-8
59700    1000    740    1-12
68700    1280    960    1-1/8 7
77000    1440    1080    1-1/8 12
87200    1820    1360    1-1/4 7
96600    2000    1500    1-1/4 12
104000    2380    1780    1-3/8 6
118400    2720    2040    1-3/812
126500    3160    2360    1-1/2 6
142200    3560    2660    1-1/2 12

RE: Bolt Torque Charts- needed

a word of caution about diamondjim's table.

preload can vary by a third when using torque control ...
ie on a 1.5" bolt (his last line) a torque of 142,200 ft.lbs. is expected to produce a preload between 2400 to 4800 lbs (on dry threads, round numbers)

RE: Bolt Torque Charts- needed

rb1957,

   All the more reason to fire up Excel and then read your Machinery's Handbook, or Bickford's Handbook if you have it.

   I have a Stock Drive Products design handbook with screw torque charts, but all it lists is the material.  It does not indicate what the author thought the maximum stresses were, or what the torque friction coefficient was, or why it was for that matter.  You cannot trust these things until you do the calculations for yourself, and figure out how the author did them.  It is not as if diamondjim's calculation is difficult.

                           JHG

RE: Bolt Torque Charts- needed

(OP)
Thanks to all that have given suggestions on where to find valuable information regarding torque values for various fastener sizes and materials.  It sounds like my best bet it to create an excel spreadsheet, list all pertinent assumptions and post it in a location where other engineers can access it.  In fact maybe I will password protect the sheet once completed to make sure it can't be changed.  

Thanks Again to all.

RE: Bolt Torque Charts- needed

Many good points raised.

Couple more observations:

Tightening by torque is generally regarded as accurate to about +/- 30%.  Tightening by FEEL by an experienced mechanic is generally regarded as accurate to about +/- 35%.

Due to the larger o.d. and cone angle, a flat head screw will require significantly more torque to induce a given tension than a hex head or socket cap screw.  

RE: Bolt Torque Charts- needed

Please read the following FAQ: How Do I Make Files Available For Download? ... No Emails Required

FAQ559-1177

Hope you could share the files with the rest of us.

Thanks.


RE: Bolt Torque Charts- needed

(OP)
fwc

Once I have added additional information to an Excel spreadsheet, I will share it through this thread if found useful.  I will heed your advice about posting to a downloadable site instead of through email communication.

Thanks Again to all

RE: Bolt Torque Charts- needed

I think that general torque charts or databases should be made available to maintenance staff.  However, my personal preference is to build up a more detailed database on each bolted joint in the facility.  It may seem like a large task, but the end result is worth while.  Each joint should be treated as a unique joint and identified that way.  The database includes info on bolt/nut grades, sizes, torque and number of passes, lubricant, torquing sequnce, quality verifications, testing requirements, etc, etc, etc.  Maint staff can quickly track down a joint in the databse, print a "single page" and go do what is necessary ... a quality job.
 

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