Eye bolt contacting area 1

[drodrig]

Hi there,

We have to lift a heavy plate, it has existing threaded holes to screw in eye bolts.

The thread is an M64, but it is counterbored with a diameter of 80mm and the counterbored surface is not flat.

The contact area of the M64 eyebolt is 120mm.

So the surfaces touching are from 80 to 120mm. Here a sketch showing it. One image is worth 1000 words...

Is the contact area enough to use the maximum load capacity of the eye bolt?

We will also use it on the side of the load and pull at 90º

I was thinking to manufacture a washer to fill the gap, but since it is very irregular (and not flat) and I am afraid it will stick out and then only touch it and not the area of the big diameter.

Maybe a washer made of rubber? It could stick out a bit, then when screwing in the eyebolt it will deform and maybe help a bit increasing the area?

Are these counterbored holes normal to use with eyebolts?

thanks
regards,

 

[SSCon]

Don't think the slight counterbore causes any issues. If lifting sideways the eyebolt has to be shimmed in order to ensure the sling is in-plane with the eye. This is a real pain in the arse and doing it wrong can lead to premature failure.

It's far easier to use a self-alinging eye bolt like a Rud starpoint (it'll also have more than double the load capacity). Would suggest a washer under the starpoint and then check the length of thread engagement (needs to be 1.5 x 64mm for full capacity in S235JR)

https://www2.rud.com/ext/tmp/B12907...06BB61099//PDF_LINK_PRINT-20210531-131129.pdf

https://www2.rud.com/PHP/php/ecs/web_live/ECS_OBJBAUM_MED/ECS_221_37.pdf

 

[drodrig]

But the washer I was thinking about are 1.5mm and the threaded length of the eye bolt is 90mm

The Rud eye bolts look very nice, but we already have the DIN 580 ones

thanks

 

[desertfox]

Hi drodrig

Well I don’t know how deep the c/bore is to start with but it means you already lose thread engagement even before you put the washers in, remember it’s not only the external thread that can shear, if the plate you are picking up is not the same Strength grade as the eyebolt then the internal thread might fail first.

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

 

[drodrig]

The holes are deep enough for the eyebolt to go all the way in

But I still don't know what torque should we apply

And how to apply it. A bar through the ring?

 

[desertfox]

Hi drodrig

Your original post shows the thread of the eye bolt located about halfway into the tapped hole, if you put washers underneath then the eye bolt thread will sit above midway giving you less thread engagement.

Well I haven’t heard of anyone torquing them up when lifting but in order to calculate the torque you require you would need to know the strength of the plate material and the thread engagement between the female and male threads

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

 

[drodrig]

you are right

I was thinking about the threads on the other end

 

[BrianE22]

Can you design an adapter that fits between the block and the eye bolt?

 

[desertfox]

Hi

Same problem with an adaptor because it’s not physically connected to the plate, yes it will help the contact area but reduces the thread engagement, ideally you would want an adaptor that sits in the counter bore but is perfectly flush with the top of the plate surface which from the OP’s description of surfaces not being flat will be impossible, you would need to make a adaptor for each counter bore and in truth to get them perfect would be impossible.

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

 

[BrianE22]

By "adapter" I was thinking of a thick plate bolted to the block. On top of the block (pointing to sky) is a thread for mounting the eye bolt. So plate mounting hole and threaded hole are at right angle.

 

[desertfox]

Hi BrianE22

The OP stated in a post he couldn’t alter the design so the only hole available to bolt an adaptor to it would be the existing hole, however what could possibly be done is to have a bar with two clearance holes which pick up the existing c/bored holes and then have the bar thick enough to accept the lifting eye threads, only problem with that is we are now creating a structure to lift the plate. I am not sure what you mean by having the plate mounting hole at ninety degrees to the tapped hole, can you elaborate please.

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

 

[Tmoose]

I'd ignore the counterbore. The large diameter of integral flange on the eyebolt is way more important for bending resistance.

I'd bet the lifting eye manufacturer has installation torque specs.

Shims to get the plane thru the inline with the load would require a bit of fussing around.
The labor might well increase the "cost" beyond the price of proper swiveling eye bolts.
I fear a shim that was pretty close might actually orient the eye so the lifting force would tend to unscrew it.

 

[BrianE22]

I was thinking something like this:

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1622575905/tips/Scan_-_Block_dwfpcf.pdf[/url]

BTW, how do you embed the picture in the thread? I can only find the link option.

 

[desertfox]

Hi BrianE22

Thanks for the sketch I see what you mean now, I’m not sure that putting the bolt in shear is a good idea and also if it’s only got one bolt the block might rotate.

I take a picture of what I want to post and then use the image icon on tool bar and then I select the photo file and it puts it in the post.

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

 

[BrianE22]

I'd machine a relief around the bolt hole so that the clamp load is taken up at some radius. The M64 will provide plenty of clamp load for friction.

Thanks on the photo answer. I've been scanning, creating a PDF and linking the PDF.

 

[desertfox]

Hi BrianE22

No problem, there might be an easier way to get a picture in here but I am not aware of it

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