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# Edge distance for a tapped hole

## Edge distance for a tapped hole

(OP)
I need to put tapped holes in the face of a piece of metal plate (316 SS).

Can anyone tell me a good reference - or better yet just tell me the answer - on calculating how close a tapped hole can be to the edge of the metal plate.

My current thought on being sure that I am capable of developing the strength of the bolt is that the tapped hole depth and edge distance would be at least that of the nuts that come with the bolt.

Thanks,

Alan

### RE: Edge distance for a tapped hole

For structural steel applications using drilled/punched holes, AISC uses material thickness as the determining factor for hole-edge distance and hole-spacing. Reference: AISC ASD 9th Edition, Chapter J, Section 5 (or page 5-77).

### RE: Edge distance for a tapped hole

For aluminum, the Aluminum Association recommends 2.5 bolt diameters edge distance from the center of the hole in the direction of the stress.

### RE: Edge distance for a tapped hole

We use 1 times the bolt diameter min. for steel
in the bearing industry assuming you are measuring
from the center of the bolts.

### RE: Edge distance for a tapped hole

(OP)
Thank you all for your quick response.  My bolt is strictly in tension.  It is holding a blind flange on a home-made flat face studded flange which has an rubber o-ring seal (i.e. no moments due to gasket reaction or raised face).  The holes in question are in the home-made studded flange.

The AISC spec and IFR's aluminum recommendation both cover cases when bolt is in shear and towards the edge of the plate.

DiamondJim's standard more closely matches my toughts on a nut; DJ=> 1/2" for a 1/2" bolt; for a 1/2" heavy hex nut =>7/16".

Diamond Jim, are your bolts likewise in tension only?

More thoughts from all are appreciated.

Alan

### RE: Edge distance for a tapped hole

SInce it is for a flange, why not use standard flange edge distances?

### RE: Edge distance for a tapped hole

(OP)
Its a small research reactor, totally machined from solid chunk of metal.  Standard flanges just don't fit application.

### RE: Edge distance for a tapped hole

Alan,
Almost all of our applications are in tension only.
We make large ball and roller bearings where the
bolts fasten our bearings to customer structures
and to the cranes above the bearings.  We recommend
pilots to take any shear loads. VDI2230 has some
good information about end distance for different
thicknesses of material verses bolt clamping length.
The compressive forces make a conical wedge force
much like a stone hitting a window.  The hole is
small on the initial contact side and much larger
on the opposite side.

### RE: Edge distance for a tapped hole

alan54,

Since you state that the hole will react only the joint preload, then your comparison to nut wall thickness is understandable.  View this thread for calculating wall thickness:

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