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?
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Bolt Torque Charts- needed 8
- Thread starter eng1234
- Start date
A good search engine and a few well placed words should get you what you need.
_______________________________________
Feeling frisky.........
_______________________________________
Feeling frisky.........
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.
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.
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.
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- #6
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.
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- #7
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 ...
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 ...
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- #8
diamondjim
Mechanical
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.
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.
These are similar threads:
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- #11
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
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
diamondjim
Mechanical
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
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
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)
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)
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
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
- Thread starter
- #15
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.
Thanks Again to all.
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- #16
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.
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.
bearing in mind all the comments above about how carefull you have to be general information, here's a link ...
good luck
good luck
- Thread starter
- #19
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- #20
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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