Tightening torque for Scoket Head Cap Screw 1

[feng09]

Hi,

Can anybody tell me how to find tightening torque for socket head cap screw.

I am sure tightening torque for hex head bolt and socket head cap screw will be different

I think the procedure mentioned in machinery's handbook is for hex head bolt.

Please comment on this

Thank you..! ! !

 

[KENAT]

While for some head forms the strength of the head has to be taken into account, typically tightening torque is usually based more on the thread and related factors.

faq725-536

faq725-600

You can use

http://www.boltplanet.com/

to check your math.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[feng09]

Thank you very much Kenat,

it is a good help for me at this initial stage, but still confused as thread forms are universal around the globe

and irrespective of the bolt head so the bolt manufacturer should design the bolt head to withstand the tightening

torque for that particular thread form, only one can change only bolt material. so i presume there will be same

tightening torque for M10 Hex Head bolt and M10 Socket head cap screw...

can you advice me on this..?

Thank you once again.. ! ! !

 

[MintJulep]

Feng,

Read the material provided in Kenat's FAQ links. I suggest that you start with the NASA reference.

After that, please come back and ask more specific questions if necessary.

 

[hydtools]

feng09, hex head and socket head capscrews are generally different strength materials unless you specify higher strength hex head capscrew to match strength of hex head capscrew. Different strengths, therefore different torques(tensions) permitted for same thread.

Ted

 

[swall]

Look at the head for markings. Socket head cap screws, at least the ones I've seen, have the grade designation on the head between the hex and the head rim. You will need to know this before you can make an intelligent decision on tightening torque.

 

[hydtools]

For a particular clamp load, torque(capscrew tension) will be the same for a given thread. For the capscrew maximum capability, that is material dependent.

Ted

 

[Cockroach]

Unbrako is a good reference.

Regards,
Cockroach

 

[MintJulep]

Oh yea, that is a good reference too, and available online.

http://www.unbrako.com/dnloadengg.htm

 

[Screwman1]

All things like the head OD, plating material, nut material, lubrication and heat treat (strength level) will result in differing seating torque levels. You can use the Unbrako numbers and get reasonably close, but if you really need accurate clamp loads you will have to do some torque tension testing to determine the K factor for your joint in question.
Socket head screws were designed for tool and die work (hence the small head diameters) and they have 'undersized' bearing surface area for their load capacity so you need to watch out for embedment at high clamp loads (esp. with aluminum).

 

[desertfox]

http://www.unbrako.com/docs/engguide.pdf

Regards

Desert fox

 

[feng09]

Thank you very much all...

 

[geesamand]

The amount of torque to be used for a given fastener depends on many things. This is why it's (so very) dangerous to download torque tables from the Internet and use them for other applications.

Most companies have standard torques that relate to the assumed load carrying capacity for each size of fastener. For example my company uses many stainless fasteners in an environment where thread sealants and lubricants are not permitted. As a result our torques for this situation are much lower than they could be, to ensure things don't gall.

David

 

[feng09]

Hi all,

Based on the above discussion.. can anyone advise me how to find torques carrying capacity of bolting head such as soceket head cap screw and hexagonal head ..

Thank you in advance...

Regards
feng09

 

[Screwman1]

A quick and dirty way to get a seating torque number (assuming that your goal is maximize clamp load in the joint; not obtain a specific clamp load) is to take a valid sized sample of assemblies to failure (failure of any part of the assembly, not necessarily the fastener) and then set your seating torque at 65% of the failure torque. This will get you at about 75% of yield, which is a good general target.
There are many cases where this is not a good strategy, but it works well in many general purpose applications.
Make sure when you are running the test that you use all virgin components for each test; performance may vary dramatically on reuse.

 

[Tmoose]

Most recently You say you are interested in the torque limit of the fastener "head".

For hex head cap screws it seems the strength of the thread (based on material) is typically the limit.

For socket head cap screws I'd compare MintJulep's unbrako link, pages 7 and ll for conventional non Stainless and low head types.
They say their "recommended seating torque" is based on a particular thread stress, but for low heads is 50/120 of the SHCS despite similar material properties.
I've wrecked a few hexes by overtightening or, much more often, when attempting to removed seized fasteners , when as you seem to suspect at some point the female hex became the limit by starting to yield.

http://diyhousehelp.com/wp-content/uploads/2012/06/stripped_screw_removal_th.jpg