Bolt spacing horizontal/vertical

There’s a rule on the net about bolt spacing should be 24 x the thickness of the material but not more than 12”? Is there any validity to this?


So is there any rule as far as bolt spacing?

In a different context there is an answer. I cannot judge the applicability to your work because you haven’t said what you are designing. A bridge, an excavator,

In aircraft, fasteners can’t be too close together, or the holes eat up the “meat” of the joint. They also can’t be too far a part because that would allow the joined pieces to wrinkle between the fasteners. Most sheet-metal structures in aircraft can be subject to tension, compression and shear, so we’re always checking for buckling failures analytically. We don’t need a rule of thumb.

The first part of your rule of thumb isn’t far off the typical spacing that’s used in aircraft sheet metal structure. However, for the 12" limit to apply, the material parts would have to be over an inch thick. Structure this thick in aircraft are DEFINITELY NOT designed to a rule of thumb.

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Thanks Steve, that makes sense for sheet metal. My application involves 3/4 plate and the structure is equally robust. Thanks again.

You’re welcome!

Have we met?

Is that sarcasm or is it a serious question?

I meant the question seriously. Since I go by “sparweb” on the forum, and it’s not immediately obvious looking at a discussion like this one that my real name is Steve, I wondered if you happen to know me in real life. I’ve worked with a number of "Tony"s and at least one of them would know I use forums like this one. So I wondered if…

You may be seeing a different screen interface than I am, and may be able to see “Steven” printed somewhere although I normally don’t see this on forum postings and I don’t see it now.

If he touched your icon, your public profile showed:

Steve Who?

Hi Steve (SparWeb),

Is there anything out there to determine a bolt pattern?
I saw there are several topics covering this but, no


Hi Steve,

lm in the Boat industry, I was referring to the mounts. Normally the mounts have 2 5/8 bolts on each end (Gr. 8). & the base plate is 7” wide x 22” x .75 thick.
I designed one a little longer (7 x 26 x .75) & there was a discussion wether or not to add extra bolts. I added 4 more bolts just to pacify the ones asking the question.
So instead of 2 sets of bolts there are 4 sets.
The higher ups here think things have to be to support the Titanic.

The boats I prefer may have different “mounts” than the boats you prefer.

If you’re mounting an outboard on a transom, then you need a bolt pattern to match the motor, so that can’t be what you’re talking about.

If you’re mounting a mast, then it’s anybody’s guess what you need depending on if it’s an 8’ long Sunfish or a 30’ catamaran.

If you’re mounting the wheels on a trailer, the typical bolt pattern has five 1/2" studs, unless for some reason you want a 4000+ pound axle.

So perhaps you could be more specific…