Rule of thumb of placing a center of a bolt hole from the edge of steel 2

[Metallic007]

I had drilled a bolt hole of 8mm diameter into a solid steel that was so close to the edge (around 2mm to the edge) of the steel. After sometime, the steel had fractured across the bolt hole. Does anyone know a rule of thumb of placing a center of a bolt hole from the edge of steel? Is there any reference standard or specification?

I have done some research online and some of the articles stated the rule of thumb would be placing the center of the hole 1.5*Diameter from the edge? Does anyone know if there is any reference for this rule from any metal handbook or standard?

Many thanks.

 

[hydtools]

Rule of thumb usually does not appear in standards. It is an opinion based on practice and experience.

Ted

 

[desertfox]

Hi

distance from edge rule of thumb 1.5 times bolt diameter.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[JNieman]

There is a table in the AISC Steel Construction Manual I recall seeing back when I was still doing structural steel design.

A quick google shows that it apparently is based off of:

http://www.boltcouncil.org/files/2004RCSCSpecification.pdf

However, it depends on your context. I can tell you that these numbers do not hold true in tooling design and machinery. They have much different considerations and "norms" that allow for ignoring those numbers found in the RSCS Spec.

The structural connections are likely based upon the assumption that one is using A36/A500 type steels, for one. Plus, you're unlikely to see anything thinner than 1/2" thk being used in any ply. Additionally, there are much different load considerations. Different grades and types of bolts, and I would guess the structural steel erectors are more likely to properly, fully torque a bolted connection than any typical machine/mechanical application, unless specifically controlled.

I expect you won't find much help with a "rule of thumb" unless you are working to a particular industry standard, company standard, or design manual. In the tooling/fixturing world, most major companies have design manuals/standards that will specify PREFERRED fastener spacing, or MINIMUMS, and almost always include exceptions are allowed as needed, if justifiable.

Plus, as an educated designer/engineer, you should be able to evaluate the special cases to decide if they are adequate or if they will fail so quickly.

 

[swertel]

The rules of thumb that I practiced are 1.5X Bolt Dia for Steel and 2.0X Bolt Dia for Aluminum.

But, in any load bearing case, I always analyze the tear out strength of the material when I'm that close to the edge.

--Scott
www.aerornd.com

 

[CWB1]

I cringe when I hear the phrase "rule of thumb" during design bc as a rule of thumb it leads to bad decisions. I would recommend following a design standard or understanding the part's clamp load.

 

[3DDave]

I worked with a guy who slammed me over edge distance on a box cover. I pointed out that similar boxes often use open end slots. He just whinged that it was bad practice anyway. I dislike rule-of-thumb. It's a poor shortcut.

 

[Tmoose]

X2 on Much more info being needed, as to sheet metal cover, vs thru bolt in housing securing heavily loaded components, vs tapped housing, vs something else altogether.

drawings, pictures, intended use, etc, etc, etc

It may be your design was fine, but the bolt(s) were not tightened adequately.
Or, something else altogether

 

[racookpe1978]

True, but "rule of thumb" can also mean simply "lessons learned - without getting too fancy".

 

[dvd]

The 1.5 diameter rule of thumb derives from punched holes. Material is displaced during punching with less edge distance. Plates thicker that (1) punch diameter will not punch well, also, so the rule of thumb depends on plate thickness in some degree with drilling required based on plate thickness. Drilled holes might be able to get closer to the edge - it would depend on visual appearance with the fasteners used in my opinion (along with function and strength).

 

[SwinnyGG]

I don't think the 1.5D 'rule' has anything to do with punched or not punched holes- its about tearout strength.

It's also situational. If the bolt is loaded in bearing, 1.5 x hole diameter is the absolute MINIMUM I would accept. Depending on loading I might still be uncomfortable at that number.

If the assembly load is taken up by shear force between the faces of the two parts or in tension parallel to the bolt axis (as in a flange connection) then distance from the edge matters less, in my opinion. You'll see a LOT of flanges in various applications where hole distance from the flange OD is less than 1.5D.

As with everything else... the rule of thumb only applies in the right situations.

 

[dvd]

My opinion is that the 1.5 'rule' originated with punched holes.

 

[JNieman]

Like all rules of thumb, they typically arise from a specific context (maybe even the one @dvd suggests) and are over-applied to places that don't even require or benefit from it. Thus the failing of rules of thumb. They are no replacement for knowledge and experience of specific applications.

They can mostly save young/inexperienced people from completely boggling up simple stuff, though, and the young/inexperienced likely aren't being charged with very critical responsibilities yet, anyways. Otherwise, I'm sure we all develop our own 'habits' or 'idiosyncrasies' when applying typical placement. To write out calculations for allowable edge distance for common situations would be a waste of time. Rules of thumb, when intelligently applied, save time, money, and allow for more focus on more important things.

I find edge-distance of fasteners to be one of the most fundamental basics, though, personally.

 

[SwinnyGG]

Arguing about the origin of the 1.5D 'rule of thumb' is definitely semantics, but in the image above, the phrase 'material web should be larger than material gauge' is indicative- material gauge and hole size are different things. If I'm punching 1 inch holes in 1/4" material, the graphic above tells me that the edge of my one inch holes need only be 1/4" from the part's edge, which means the hole center distance is .75 x D. Whether or not that results in a bulge on the part's edge depends on the material being punched.

[rules of thumb] are no replacement for knowledge and experience of specific applications.
Rules of thumb, when intelligently applied, save time, money, and allow for more focus on more important things.

To get back on topic... a star for J.

 

[CWB1]

Bolted joint analysis should take all of about 30 seconds in one's head if they don't have a CAD plugin, and there's a gazillion online and phone apps if the math is over someone's head. JME but most joints with a relatively high clamp load are easy to design and hole placement is merely a matter of attractiveness, low-load/torque joints OTOH where tearout is a valid concern are often a PITA and should be properly analyzed and understood.

 

[SandCounter]

You need to run tear-out and bearing stress checks, P/A.
[ul]
[li]For tear-out area (A), use twice the product of the total link thickness and the dimension from the edge of the hole to the outside of the part.[/li]
[li]For bearing area (A), use product of the bolt diameter (I prefer 75%) and the link thickness.[/li]
[/ul]

If both of these check out in less than the diameter of the bolt, use the bolt diameter as the distance of the edge of the hole to the edge of the link. See Norton, Machine Design.

I used to count sand. Now I don't count at all.

 

[RolMec]

In metric country one could check / design by Eurocode 3 part 1-8 for the appropriate spacing of fasteners to edges and within rows as well as some background.
The 1.5 x dia are a standardized design criteria to achieve a maximum transmissible bearing stress for a given fastener. If this is not the guiding value, one could go down to 1.2 x dia.
But nevertheless: There's no design w/o specific analysis ;-)

Roland Heilmann
Lpz FRG

 

[drawoh]

Metallic007,

thread725-267581

This is discussion of lifting lugs, but the David T. Ricker reference discusses the thickness of flanges next to screws. To heck with rules of thumb.

R.I.P. unclesyd

--
JHG

 

[tbuelna]

With most situations I have seen, there was no excuse for not providing a 1.5 e/D margin around fastener holes. Doesn't add weight or require much additional space.