Hole size allowance for hot dipped steel

[bluedog225]

I’m having some steel fabricated for a landing support. We’re going to use 5/8“ diameter Simpson Titen HD stainless steel anchors to attach a 1/2“ steel plate to a concrete wall.

The landing support will be hot dipped galvanized after assembly. I don’t know the specs for the hot dip process. I called down to San Antonio where the place is located but didn’t make much progress finding a coating thickness. And candidly, that it is cleaned and dipped is good enough for my purposes.

Simpson specifies a steel hole size of between 3/4 and 13/16 per below.

Does anyone know if an additional allowance should be made for hot dipped galvanized coating? I’m guessing it’s thin enough not to matter. Though some of the stuff I’ve seen out of San Antonio looks like a thick coat of paint.

Thanks

 

[PCustoms]

2-5mils

Run your hole at 13/16 and you'll be fine

 

[PCustoms]

Here's a chart:

 

[bluedog225]

That’s good info. Thanks

 

[manwithtools]

Hot dip galvanizing is notorious for not being held to spec thickness, particularly on hole ID'd where it tends to accumulate. You won't get a galvanizer to commit to coating thickness on a hole. It all depends on the tank setups and the galvanizers process. If this were my project, I'd spec a 7/8" hole and use sturdy washers on the lags or anchors you are using. Last thing you want is to have to drill out the hole as you then loose the galvanizing on the hole ID.

Read this note on the chart provided by @PCustoms, pay attention to the part I bolded below.



"It is important to remember these are minum coating thicknesses the galvanizer must achieve; however thicker coatings are common, assuring conformance to specification.

 

[Old tool guy]

Are you going to pre-drill the holes, or drill with the plate in final location?

 

[manwithtools]

Are you going to pre-drill the holes, or drill with the plate in final location?

Drilling in final location would negate the galvanizing benefit...

 

[bluedog225]

Are you going to pre-drill the holes, or drill with the plate in final location?

Plan is to predrill. Some adjustment of landing is possible if we hit too much rebar. Or core drill.

 

[welder4956]

I’m having some steel fabricated for a landing support. We’re going to use 5/8“ diameter Simpson Titen HD stainless steel anchors to attach a 1/2“ steel plate to a concrete wall.

The landing support will be hot dipped galvanized after assembly. I don’t know the specs for the hot dip process. I called down to San Antonio where the place is located but didn’t make much progress finding a coating thickness. And candidly, that it is cleaned and dipped is good enough for my purposes.

Simpson specifies a steel hole size of between 3/4 and 13/16 per below.

Does anyone know if an additional allowance should be made for hot dipped galvanized coating? I’m guessing it’s thin enough not to matter. Though some of the stuff I’ve seen out of San Antonio looks like a thick coat of paint.

Thanks

The 3/4" to 13/16" hole size recommended by Simpson for a 5/8" fastener is more than adequate to allow for the galvanized coating. A standard size hole for a 5/8" bolt would be 11/16" (1/16" oversize). The Simpson recommended hole size is 1/8" to 3/16" larger than the bolt size and leaves plenty of room for galvanized coatings.

 

[ptt49er]

In my experience we've always designed galvanized weldments with a hole 1/8" over the anchor diameter and never had any problems.

 

[manwithtools]

The 3/4" to 13/16" hole size recommended by Simpson for a 5/8" fastener is more than adequate to allow for the galvanized coating.

Awe ****, I missed this was for a 5/8" fastener, I assumed this was for a 3/4" fastener. I now agree that a 3/4"-13/16" hole size should be fine for the galvanizing allowance.

 

[kwb]

I build a lot of galvanized stuff for my 5/8" bolt holes I drill 11/16" hole with the mag drill.

Between manufacturing tolerance and galvanized build up I rarely need to get the reamer.

 

[PCustoms]

I build a lot of galvanized stuff for my 5/8" bolt holes I drill 11/16" hole with the mag drill.

Between manufacturing tolerance and galvanized build up I rarely need to get the reamer.

Picking on this post but there's others.

Look at the OP, this isn't a standard 5/8" bolt, it's a Simpson titen fastener, the OD may measure larger.

I would follow the MFG hole size, err on the max to account for "shrink" when it gets plated and move on

 

[Old tool guy]

Drilling in final location would negate the galvanizing benefit...

Nice try. I meant pre-drill the bolt holes in the concrete.

 

[manwithtools]

Nice try. I meant pre-drill the bolt holes in the concrete.

Well that post was clear as mud. Thanks for the clarification...

 

[kwb]

My point wasn't that 11/16" is the answer here, just that an extra 1/16" is almost always enough on the unfinished part to be able to get assembled after the galvanize is done.

 

[bluedog225]

Nice try. I meant pre-drill the bolt holes in the concrete.

Yes. We will probably put the assembly against the wall on the forks and mark the holes. Or use a sheet of ply to make a template.

 

[kwb]

Drilling in final location would negate the galvanizing benefit...

Actually not as much as you would think. Galvanize (zinc) protects surrounding metal pretty good even when it gets a penetration through to parent metal. It's not like a paint or powder that lets rust migrate under the coating.

 

[bluedog225]

Edit-I mentioned core drill above. We can’t do that with the Simpson titens.