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Old 28th Dec 2017, 6:11 pm   #1
Ian - G4JQT
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Default Chassis-fixed nuts

Apologies for the vague title but I don't know what they're called!

I'm looking to fix some bolts to a bracket via nuts that are fixed to the bracket. I could use self-tapping screws, but they become unreliable after a few un-doings and re-tightenings. Soldering nuts to aluminium...? Possible I guess but tricky.

I vaguely remember from school drilling holes and pushing in interference-fit nuts. These nuts had a machined round top third or so. This was pushed into the holes and knocked tight with a round hammer.

The result was a row of nuts attached to the bracket that never loosen.

What are they called?

While I'm trying to get names for stuff, I have some strange bolts. Where the slotted head should be, it's flattened and drilled with a hole about the diameter of the bolt thread. Probably not a very elegant solution to fixings, but used by some of the older Heathkits and handy to mount metal sheets at 90 degrees to each other, amongst other things.

Has anyone ever heard of those and know what they're called?

Thanks.

Ian
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Old 28th Dec 2017, 6:25 pm   #2
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Default Re: Chassis-fixed nuts

Rivnuts?
They are usually fitted using a tool rather like a pop-rivet gun, though, rather than hand riveting.
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Old 28th Dec 2017, 6:32 pm   #3
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Default Re: Chassis-fixed nuts

Clinch-nuts? https://uk.rs-online.com/web/p/products/0827647

Hank-nuts: https://uk.rs-online.com/web/p/rivet-bushes/0505252/

Or Bohlhoffs? https://uk.rs-online.com/web/p/products/0138893/

Both really need to be installed using the proper setting tool. I've used the Bolhoff type for fitting threaded inserts into thin aluminium-alloy car body panels and they work OK provided they're not subject to much vibration.
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Old 28th Dec 2017, 6:39 pm   #4
Ian - G4JQT
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Default Re: Chassis-fixed nuts

Thanks guys!

Neither are what I'm thinking of but probably worth looking into for the first type I described. They look like some sort of tool is required, although maybe a Youtube video will show how they can be easily knocked in with a nail and jam-jar lid or similar!

Cheers, Ian

Edit: Just had a look on Youtube and for rivet nuts it looks like all you need are a couple of spanners to fix them in place:

https://youtu.be/3Og-tHIR_0I

Last edited by Ian - G4JQT; 28th Dec 2017 at 6:52 pm.
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Old 28th Dec 2017, 6:46 pm   #5
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Default Re: Chassis-fixed nuts

Hank Bushes are the usual riveted type: - https://uk.rs-online.com/web/c/faste...74206275736826

Clinchnuts can be fitted from one side - with the fitting tool :-https://uk.rs-online.com/web/c/fasteners-fixings/sheet-metal-panel-fasteners/self-clinching-nuts/

Self Clinching Fastners can be pushed in with a press, rather than being riveted over :- https://uk.rs-online.com/web/c/faste...linching-nuts/ - standoffs and pillars are also available.
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Old 28th Dec 2017, 7:43 pm   #6
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Default Re: Chassis-fixed nuts

I have used the self clinching nuts in the past, using nothing more than the screw that assembles the parts to pull the bush into place - quick and effective, but you must use the correct diameter drill for the bush.
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Old 28th Dec 2017, 9:36 pm   #7
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Default Re: Chassis-fixed nuts

What size/quantity do you need? I have a selection of what look like Clinch nuts and Hank nuts that I saved from the skip many years ago when the Marconi site I was at was closed, and I can't see myself using them all myself. Large quantities of some sizes, only handfuls of others, metric M3 to M10.
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Old 28th Dec 2017, 10:59 pm   #8
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Default Re: Chassis-fixed nuts

Hank bushes are the ones that the sheet metal people use for my psu brackets and U bracket encl stand offs. They punch a slightly undersized hole in the sheet metal then by hand insert the hank bushes and fix them in place by a low power fly press.
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Old 29th Dec 2017, 12:13 am   #9
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Default Re: Chassis-fixed nuts

Also "PEMs"

David
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Old 29th Dec 2017, 12:14 am   #10
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Default Re: Chassis-fixed nuts

I have a few of your "strange bolts", although I can't help with a name. I've seen similar ones used to retain old school IF transformer cans.

The earlier RS clinchnut system (now discontinued) was similar to threaded pop-rivet.
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Old 29th Dec 2017, 1:22 am   #11
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Default Re: Chassis-fixed nuts

For tools remarkably similar to the RS one pictured above, searching "rivnut", "rivet nut" and "nutsert" tool in the usual places will produce 1,001 returns, typically with M3-M8 fitting studs and for not that much money. One of my favourite gizmos, I prefer the serrated steel inserts.
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Old 29th Dec 2017, 7:30 am   #12
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Default Re: Chassis-fixed nuts

Quote:
Originally Posted by Ian - G4JQT View Post
Apologies for the vague title but I don't know what they're called!

I'm looking to fix some bolts to a bracket via nuts that are fixed to the bracket
Self tapping screws in my view are always a poor option compared to proper machined threads.

However, you have not provided enough data to know what the better solution is.

What diameter screws are you considering ?

What is the thickness of the aluminium plate you are attaching to ?

What is the mass/forces of the objects you are are attaching ?

How many fixing points do you think are required ?

Pressed nuts into the receiving plate might be a good option, but it might be beaten by another option.

If your receiving plate is at least 1mm thick, you might be better off tapping it with a roll tap (not an ordinary tap) with a coarse thread such as a 4-40 or 6-32 UNC. If you can give more data on the project would help.

I can also direct you to the suppliers of pressed stainless steel captive nuts, which simply require a round hole, which I use in many of my projects where the receiving panel is too thin and multiple removals of threaded screws are required.

Hugo.
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Old 29th Dec 2017, 11:48 am   #13
Ian - G4JQT
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Default Re: Chassis-fixed nuts

Thanks for the info. It's just for a raised chassis in a box and the sheet material is aluminium. Thickness about 1/16 inch as near as I can measure - same gauge as a DAC90A (and most other) chassis.

Not much pressure/weight, just a few valves and a small 15VA transformer with tagstrips etc. underneath. M3 threads will be quite sufficient at six fixing points - three front and back.

Quote:
Originally Posted by AC/HL View Post
I have a few of your "strange bolts", although I can't help with a name. I've seen similar ones used to retain old school IF transformer cans.

The earlier RS clinchnut system (now discontinued) was similar to threaded pop-rivet.
Yes, that's the thing! Very handy if you don't mind rather ugly fixings.

Maybe I missed something, but the video in my link showed rivet nuts being fixed into place without any special tools. I assume smaller ones are available so I'll be off looking for some.

Thanks for all the help.

Beast wishes and good health for 2018.

Ian

Last edited by Ian - G4JQT; 29th Dec 2017 at 12:01 pm.
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Old 29th Dec 2017, 2:24 pm   #14
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Default Re: Chassis-fixed nuts

I have some M3 Hank Nuts to spare and and almost 2000 M3 press nuts!

http://www.autonic.co.uk/Datasheets/AutonicPressNut.pdf

If they are of any use, PM me your address and I can put them in the post FOC.
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Old 29th Dec 2017, 7:55 pm   #15
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Default Re: Chassis-fixed nuts

What about tri-lobular thread forming screws? 1.6mm chassis thickness will allow the minimum 3 threads at M3 and in steel this will be enough. In aluminium it should also do, with care as the thread is formed, not cut.

These screws form a standard machine thread and ordinary screws will fit the formed, tapped hole. They are widely used in industry and superior to self tapping screws.

The drilling size is quite critical so you will need the correct size of drill.

https://www.google.co.uk/url?sa=t&so...3c8rOmLEeWcaTa

PMM
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Old 30th Dec 2017, 12:57 am   #16
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Default Re: Chassis-fixed nuts

Hi,

There are various designs of pressed nuts and some are not as good as others I'm afraid.

For thin materials it is best to use the type attached in the photos, these have been cleverly designed so most of the thread is in the thickness of the nut behind the panel, where you want it in a solid cylinder (rather than down a longer tube with a small flange like the Hank nuts) Notice how the binding part has been created in the 90 degree recess. These are more complex to manufacture than the other design nuts.

They are very easy to fit, by drilling 4 or 4.5 mm holes, depending on the size screws you want. I drill the hole undersize by 0.5mm first, then finish with the correct size helps to ensure its not over size and that the hole bur is minimised. A screw & washer is then used to press in (pull the nut) to the panel. The ones in the photos are stainless steel.

They are available in stainless steel from PSME (Precision scale model Engineering) www.psmescale.com Don't be put off by the USA, they arrive quickly with air post. If you email them they will sort out it out. They also have very attractive slot binder head screws etc.

Your other option, depending on how many times your panel might be removed, & since the aluminium is 1.5mm or thereabouts thick, is to tap a thread. I would oppose the notion of a 3mm metric thread in aluminium, it is far too fine, not wear resistant enough and prone to cross threading, so I never use this thread in thin panel material.

The ideal threads are UNC and for this thickness panel material 4-40 is an ideal size (about 2.75mm OD and a similar thread pitch to 1/8 bsw). The important thing though is it gets tapped with a "roll tap" not a tap that removes/cuts material from the thread area. The metal gets compressed and it creates an extremely strong thread compared to what is created by a standard tap. Over the years using these I have found that just starting the thread with a standard taper tap about 2/3 to 1/2 of a turn, helps to get the roll tap started.
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Last edited by Argus25; 30th Dec 2017 at 1:06 am.
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Old 30th Dec 2017, 6:27 pm   #17
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Default Re: Chassis-fixed nuts

The 'traditional' D-i-Y way of clinching the small-bore 'stub' of the clinch-nuts shown above was to drift them through the panel using a tube (or a small socket-spanner) so the splined-part was tight in the hole, then 'set' the thing by whacking a suitable sized ball-bearing into the end of the splined-part to splay it out slightly.

Ball-bearings are really hard! be careful though, whacked too vigorously and they can shatter!
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Old 2nd Jan 2018, 11:18 pm   #18
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Default Re: Chassis-fixed nuts

My weapon of choice is the rivnut (with proper setting tool!). A complete kit with pack of various rivnuts, replaceable mandrels and tool is as little as £12 off ebay. (mine came from CPC).
I've seen too many clinchnuts work loose and fall into equipment when the screw is allowed to get slack.
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Old 30th Mar 2018, 3:47 pm   #19
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Default Re: Chassis-fixed nuts

For something that will not need to be dis-assembled, I sometimes find that pop rivets can be useful.
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