Board logo

Metric fasteners for uniballs/heim joints
mart154 - 6/7/22 at 11:06 AM

As standard DIN 912 / DIN 931 bolts have undersized shanks (M12 bolt is with 11.80mm shank best case).

What are you guys using for mounting metric heim joints?

Going for AN bolts and imperial heims seems, well, a tiny bit absurd when I have to order every single bolt and joint overseas.


nick205 - 7/7/22 at 10:59 AM

Not something I've used before or had to consider.

Does whoever's supplying the joint not supply fastners to suit?


obfripper - 7/7/22 at 11:59 AM

From a mechanical strength view, the bolt you use is a clamping device so should be strong enough to provide the appropriate clamping force, but shouldn't act as a pivot, as that is the purpose of the heim joint.

However from an ease of repair view, it's not ideal to have to redo the geometry every time a suspension component is removed/refitted, and having a tight tolerance here helps to avoid that.

You might want to look at oem (ie ford,vw) suspension bolts, as they tend to use oversized bolt shanks to reduce play during fitment, some also use sleeve shims on standard shank bolts to achieve the same effect.
The oem bolts are more expensive than standard industrial bolt types, but are designed for this purpose.

I have seen industrial cap head bolts with the larger shank profile, but i have no idea if they are to a din standard or a a manufacturer special order, some of the ones i'm thinking of were on large (2-3m cut) guillotines so could be special order items.


Dave


Mike Wood - 8/7/22 at 06:11 AM

You could try contacting LAS Aerospace in Devon: https://www.lasaero.com/products/category/F010IHRIF/

Anything of use: https://www.mcgillmotorsport.com/rod-end-bearings-c-88

Is there no option to use more readily available joints that are more widely used in racing cars, such as by Aurora from companies such as Raceparts or Trident Racing Supplies?

https://race.parts/Catalogue/Steering/Bearings-Rod-Ends

https://tridentracing.co.uk/product/rod-ends/

Cheers
Mike

[Edited on 8/7/22 by Mike Wood]

[Edited on 8/7/22 by Mike Wood]

[Edited on 8/7/22 by Mike Wood]


daviep - 8/7/22 at 01:11 PM

Allen cap with a ground shank is normally called a "shoulder cap screw" ISO7379, however the threaded portion is always 1 size smaller than the shank, see here for an example https://www.spaldingfasteners.co.uk/m10-10mm-socket-shoulder-cap-screw-12-9-high-tensile-steel-allen-bolts/

Personally I wouldn't worry about the clearance on a standard bolt, as has been said already the clamping force should hold the joint in the correct position.

Davie