The good old flange nut

[BuggyDad]

Building my Falcon née Blitzer recently I got reacquainted with the good old flange nut from my 1980s Tamiya days, used for bolting gearbox halves together and the front bulkhead to bumper and the like. Never seen on modern kits but it stays tight, no chance of failure on a zillion reassemblies, pretty versatile. So next time I headed off to my bolt supplier I bought a load because I reckon they're sure to come in handy for the kind of mods I come up with (and I lost a Falcon one, inevitably to find it again once the parcel arrived). And a bag of M4 ones too, figuring serrated wheel nuts are probably exactly the same anyway (subsequently confirmed) and I might as well stock up.

So why is it not used anymore I wonder? I can of course see why not on higher end kits where we're threading into tougher plastics without issue, but on the weak plastics often used in Tamiya's most basic kits and for applications above, I think it might often be better than a self tapper, taking the load right through to the other side and then spreading it vs just pulling on the internal plastic. Especially with the frequency of reassembly I get up to. 

[TurnipJF]

1 minute ago, BuggyDad said:

I think it might often be better than a self tapper, taking the load right through to the other side and then spreading it vs just pulling on the internal plastic. 

I agree. In places where self-tappers are known to pull out and/or crack the surrounding plastic, if possible I typically drill out the hole to 3mm and run a bolt through it with a flange nut on the other side. Upper shock mounts on TL-01s, WR-01s and the like are prime candidates for such treatment.

In other scenarios where I can't get a bolt all the way through and put a nut on the opposite side, I like to tap the hole with an M3 tap, run a long grub screw into it, then secure the piece with a flange nut on the grub screw.

[Willy iine]

Would it have something to do with keeping the BOM (bill of materials) as minimal as possible for the kits?   I too agree flanged nuts and longer machine crews can come real handy where 3mm tappers stripped out.  

[Pylon80]

I run a long though bolt and a nut on the steering bridge of the TT-02's for that reason.

For lower stress areas I found that tapping the threads with a rolling tap and grease makes for a durable attachment that can be dismantled hundreds of times and never cracks.

[alvinlwh]

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[BuggyDad]

2 hours ago, TurnipJF said:

I agree. In places where self-tappers are known to pull out and/or crack the surrounding plastic, if possible I typically drill out the hole to 3mm and run a bolt through it with a flange nut on the other side. 

Ah yes. Falcon/Blitzer chassis front being a classic example. I remembered my childhood and did exactly this on assembly this time. In that instance they had gone for opposing self tappers top and bottom so all you have to do is drill to join the holes.

2 hours ago, Willy iine said:

Would it have something to do with keeping the BOM (bill of materials) as minimal as possible for the kits?   I too agree flanged nuts and longer machine crews can come real handy where 3mm tappers stripped out.  

Above little mod is far stronger than stock, and a screw and a nut pair replaces two self tappers, so in that example even the bill of materials is perhaps hardly altered?

[Kpowell911]

This method should certainly be on the TL-01 shock towers.

[Honza]

10 hours ago, alvinlwh said:

These had been suggested before. You melt them into the plastic and you have a M3 thread to screw into.

These are not much stronger than a self-tapper - they are quite often used in laptops and I've seen numerous times that plastic boss around them cracked and disintegrated as the plastic became more brittle.

[Willy iine]

14 hours ago, BuggyDad said:

 

Above little mod is far stronger than stock, and a screw and a nut pair replaces two self tappers, so in that example even the bill of materials is perhaps hardly altered?

I was thinking more in terms of if the flanged nut and longer machine screws not even included in the BOM and just use general 3x10 self-tappers that can be used on many other areas of the chassis.   That means less material to buy for Tamiya, less to qualify, less cost at the end.  

Looking at the MB01, if that is the trend for budget RC, then they are pushing minimalist approach to use as much plastic as possible and the simplist most general hardware that can be used across many platforms. 

Back 40 years ago if we take a look at the M38.. wow does it come with many dedicated metal bits that is unnecessary by today's standards. But that is the coolness of these vintage kits so I don't mind it at all (rather prefer it as you).   I think if Tamiya rere'ed the original M38, it would cost like 3x or more (in today's dollars) with all the misc parts they would need to re-tool.

[Pylon80]

16 hours ago, alvinlwh said:

These had been suggested before. You melt them into the plastic and you have a M3 thread to screw into.

I would only use this as a very last ditch attempt to save an old model; probably not as an improvement.

In any case, I think most thread problems come down to re-threading existing threads when reinstalling a screw (always turn counterclockwise until your hear the click, then start turning clockwise) especially in soft plastic, as well as installing the screw without grease in hard or brittle plastic the first time around.

[Willy iine]

When my vintage car's plastic strips out I try 2 things first..  First is using Tamiya's plastic cement (orange top) as thread lock on the screw and screw it in, let it set over night.   If that still comes loose (which it shouldn't as it reshapes the hole), next would be super glue.  Same approach, apply as thread lock and screw in.

Then last ditch is the mighty flanged nut + longer machine screws.

[ad456]

8 hours ago, Honza said:

These are not much stronger than a self-tapper - they are quite often used in laptops and I've seen numerous times that plastic boss around them cracked and disintegrated as the plastic became more brittle.

Yup, we are regularly repairing these in laptops at work, Acers are a particularly bad one for shedding plastic but there isn’t a brand I can think of that is free from that. Laptops generally have an easier life than rc so I’d probably not bother putting them in. Better than a gaping hole I guess.

 
Helicoils are an alternative but I’d expect they’ll have their own issues. I have seen them used with success on here, a CC01 build maybe? Can’t remember as it was a year or two ago.