How can I bolt 2 pieces of metal together when I have no access to the underside?

swag72

swag72

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I need to bolt a large piece of metal to a metal pier. The metal pier is hollow but I can not get access inside, so I have no way of using bolts to connect them both as I have only access to the top side (Does that make sense?)

I have looked at 'through bolts' as you only need to be able to screw them from one end, but they seem to be for bolting into concrete. Can anyone point me to the right fixing to use?

The bolts need to be very big.
 
What about a double hole? Must have a technical name, but you drill a hole big enough to get the head of the bolt through, and next to it you drill a smaller hole just big enough to take the threaded portion. Push the head through the big hole, and slide into the smaller hole. Then all you have to do is find some way of holding it until you can get the nut threaded. That's usually the hardest bit.
 
How thick is the pier Sara?

If fairly thick, you could cut a thread into it and then screw your bolt down into it?
 
mickledore said:
What about a double hole? Must have a technical name, but you drill a hole big enough to get the head of the bolt through, and next to it you drill a smaller hole just big enough to take the threaded portion. Push the head through the big hole, and slide into the smaller hole. Then all you have to do is find some way of holding it until you can get the nut threaded. That's usually the hardest bit.
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I think that's called a keyhole...
Or drill and tap it, or if it doesn't need to be a bolt maybe blind rivets would do?
 
Run a tap through the hole, screw a bolt into the hole, job done
 
I'm at the planning stage of the pier at the moment, so I don't know how think the metal will be. At the moment I have a piece of metal, approx 3/4 inch thick, that needs to be attached to a metal pier. It has screw holes (untapped) in it.

Thanks for the help so far. I am wondering whether to take the plate into the metal fabricators and get them to weld it one when they make the pier. I think that may be the easiest solution.
 
Bolts are only normally used as temporary/removable fixings, if the plate will never need to be removed from the pier then welding as you suggest is the way forward in my view.

Matt
 
Rubbish. No reason why bolts are not a viable permanent fixing option.
 
Agreed. Many, many, large and permanent structures are built with bolts and these would not be classed as 'temporary'.
 
Cost, security and ease of fabrication are all factors but MatBin's comment #10 is generally correct.
 
No More Nails ??

Sounds daft but it's strong as hell, managed to 'stick' on a blow of valve to a car engine with the stuff in the past lol...
 
Weld the nut to one of the bits.
Just remember you will need a nut and bolt that will take the loading. Cant remember how they are specified in the here in the UK (the info I have to hand is all american specs.)
 
Rovers_Andy said:
Run a tap through the hole, screw a bolt into the hole, job done
Click to expand...

It depends on the size of the bolt/screw and the wall thickness of the pier. It may be that the wall is relatively thin, and there will not be enough threads for the bolt to hold.
 
swag72 said:
I need to bolt a large piece of metal to a metal pier. The metal pier is hollow but I can not get access inside, so I have no way of using bolts to connect them both as I have only access to the top side (Does that make sense?)

I have looked at 'through bolts' as you only need to be able to screw them from one end, but they seem to be for bolting into concrete. Can anyone point me to the right fixing to use?

The bolts need to be very big.
Click to expand...

I take it you can't dril completely through the pier?

The blind hole/hollow bolt ideas suggested by wiseman and bass_junkie sound good, but if you don't need to disassemble the thing I would get it welded.
 
mickledore said:
Push the head through the big hole, and slide into the smaller hole. Then all you have to do is find some way of holding it until you can get the nut threaded. That's usually the hardest bit.
Click to expand...


:eek: :eek: :eek:


Just from those three sentences I'm sure you could write a 'Carry On' film. :D
 
lol

albion said:
Rivnuts.
http://www.memfast.co.uk/
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another thumbs here

..big size - 20mm plate with sizes like an 18-16mm bolt thread, 15mm plate 12-14mm thread and so on.


Lots of types available, none are structural, very tough otherwise though we call them Hollow Anchor Bolts or suchlike.

Corrosion can be an issue ...Are you salt water? ..i think the rules is Dont use stainless in salt water.
 
Thanks for the continued suggestions - A lot of ideas here - No salt water involved, maybe just dew as the pier is for a telescope.
 
swag72 said:
Thanks for the continued suggestions - A lot of ideas here - No salt water involved, maybe just dew as the pier is for a telescope.
Click to expand...
 
swag72 said:
Thanks for the continued suggestions - A lot of ideas here - No salt water involved, maybe just dew as the pier is for a telescope.
Click to expand...

Just drill two holes straight through and use two 12 mm stainless bolts (no rust) not forgetting 4 plain washers.

Simple.
 
Hacker said:
:eek: :eek: :eek:


Just from those three sentences I'm sure you could write a 'Carry On' film. :D
Click to expand...

lol.

I did nearly spit tea all over my computer when I read it, but then thought it was just my twisted sick mind.:lol:
 
Did you ever solve your problem?

As for using threaded inserts, dependent on the size of the fixing you need these would be ideal but are really for giving you a threaded hole in sheet steel.

albion said:
Rivnuts.
http://www.memfast.co.uk/
Click to expand...

Rivnut is a trade name of a manufacturer and so far as I'm aware not allied to the company you have linked them to ;)

bass_junkie83 said:
I would not use rivnuts for anything structural.
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Rivet nuts have an optimum strength for use, however that's a pretty sweeping statement. Rivet nuts are found in heavy engineering areas such as tractor manufactors and the like as well as more lightweight applications.

If you want to know more PM me.. :)
 
TheNissanMan said:
No More Nails ??

Sounds daft but it's strong as hell, managed to 'stick' on a blow of valve to a car engine with the stuff in the past lol...
Click to expand...

"note to self" never buy anything from this man
 
I haven't taken it to the metal fabricators yet, but I am going to get them to weld bolts on the underside (that I can't get to) then I can use nuts to screw on the adaptor to the top - Should be nice and secure.
 
I really would not reccomend welding the bolts to the underside, It is all too easy to damage the threads on the bolts. If that happens you will then have to try and run a die down the bolt or grind the bolt and bolt head off. I think the best option will be to run a tap through the holes and then use some thread lock on the bolt with flat washer, spring washer and nut on the other side
 
Col said:
Just drill two holes straight through and use two 12 mm stainless bolts (no rust) not forgetting 4 plain washers.

Simple.
Click to expand...

You've never heard of electrolite corrosion then caused when two dissimilar metals are in contact? Yes, I own a Land Rover...:cuckoo:

If it's structural - weld it. It's the simplest easiest and most durable method. If there is any weight acting upon the part you are fixing to the pier then you are introducing weakness if you use bolts/setscrews/any fixing that requires holes etc. If welding is done correctly then the weld will actually be stronger than the surrounding area of steel.
 
I could get the adaptor welded onto the top of the pier, but it may need to be removed at some time. Thanks for all the continued ideas folks :thumbs:
 
Ste Manns said:
You've never heard of electrolite corrosion then caused when two dissimilar metals are in contact? Yes, I own a Land Rover...:cuckoo:

If it's structural - weld it. It's the simplest easiest and most durable method. If there is any weight acting upon the part you are fixing to the pier then you are introducing weakness if you use bolts/setscrews/any fixing that requires holes etc. If welding is done correctly then the weld will actually be stronger than the surrounding area of steel.
Click to expand...

S/steel is OK in this application - Land Rovers show a distinct lack of thought in this respect.
Welding to can cause problems but. Looking for them will never get the job done!
 
If damage were done to the bolts welded you could simply tap and use a wire thread insert such as a Helicoil which would provide a stronger thread than the original.

With regards to dissimilar materials dependent on coating this could be overcome. However you are getting into the realms of the exotic now :)

It really depends on how structural the application is as to the requirement of the solution needed.
 
can you get access to welding gear
you can weld a stud to the existing pier and then put your piece of metal over the studs which will have clearance holes for the weld area
then use a plate washer and a spring washer and nut to finish
i can show you a sketch
but this all depends on being able to weld
high strength apoxy resins may suffice instead of welding but this depends on the loading on the joint...shear tension bending or a combination of all three
cheers
geof
 
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