Rivet nuts

[daedalusminos]

I have a need to bolt a 4-hole flange bearing to a couple of pieces 25mmx25mmx1.5mm ERW square tube...

The bolt holes are sized for 10mm and my first thought was countersunk rivet nuts but the countersink is as thick as the 1.5mm wall thickness and standard rivet nuts have a standoff. I could put a thickening plate between bearing and ERW to countersink into or scrap the rivet nuts and go for anti-collapse tubing and nut/bolt or weld in a threaded tube.

Any other ideas?

 

[hotponyshoes]

You can still countersink them.
Just go steady so you don't enlarge the hole too much.
Might be worth drilling the first hole 1mm or so undersized then countersink to the correct size.

 

[hotponyshoes]

Or if you can get to the back side to put them in place you can get a reverse type rivet nut that you can either rivet or tig into place

 

[Agroshield]

How far from the end of the tube are the holes?

A Unistrut zebedee (with spring) might fit inside the tube.

Edit:

If the length is too far to poke a spring zebedee, a plain one could be encouraged into place with a piece of string. Secure temporarily with a piece of threaded stud until the first bolt is in.

 

[daedalusminos]

How far from the end of the tube are the holes?

A Unistrut zebedee (with spring) might fit inside the tube.

Edit:

If the length is too far to poke a spring zebedee, a plain one could be encouraged into place with a piece of string. Secure temporarily with a piece of threaded stud until the first bolt is in.

ERW is about 375mm long, bearing is fitted in the middle. That Unistrut nut looks interesting, bit concerned they may move when the bearing is removed though....could potentially spot it in place from the front when it's in situ.

 

[daedalusminos]

You can still countersink them.
Just go steady so you don't enlarge the hole too much.
Might be worth drilling the first hole 1mm or so undersized then countersink to the correct size.

I'll give one a go, measuring up the countersink on the M10 is 1.9mm deep so it's definitely going to enlarge the hole.

 

[Agroshield]

...bit concerned they may move when the bearing is removed though....

You could make one out of some thick strip with two tapped holes. Drill a small hole in the tube midpoint between the holes and plug weld the insert into place.

 

[daedalusminos]

You can still countersink them.
Just go steady so you don't enlarge the hole too much.
Might be worth drilling the first hole 1mm or so undersized then countersink to the correct size.

I may even try pressing the countersink in.

 

[bricol]

I have a need to bolt a 4-hole flange bearing to a couple of pieces 25mmx25mmx1.5mm ERW square tube...
View attachment 527979

The bolt holes are sized for 10mm and my first thought was countersunk rivet nuts but the countersink is as thick as the 1.5mm wall thickness and standard rivet nuts have a standoff. I could put a thickening plate between bearing and ERW to countersink into or scrap the rivet nuts and go for anti-collapse tubing and nut/bolt or weld in a threaded tube.

Any other ideas?

I've done all of those. Is the bearing taking a fair load that needs a decent amount of the strength of M10 bolts? If it is, then welded in threaded bosses, or welded tubes through. But by the time you've dropped a length of bar or tube through 25 box, there's not a lot of box left.

Steel rivnuts should be okay, although with some of the stuff at work where I use a rivnut, I sometimes add note to TIG it in a couple of spots, stop them spinning. Used for lifting eyes on machine guards.

 

[Maxakarudy]

I've drilled & tapped a strip of 5mm plate long enough for 2 holes & taped it to a bit of bar, then slid it inside until lined the holes up, then got the bolts to pick it up.

 

[daedalusminos]

Made up a press tool to press the countersink in, works a treat...

 

[Windy Miller]

Nice job!

 

[Agroshield]

Made up a press tool to press the countersink in

Superglue the female threaded part to a piece of pallet strapping, then you can poke it inside a long piece of box and position it fairly easy.

Is there any way to make the male part captive (but rotatable) on the bolt as that would speed up the process?