improved trailing arm studs

[DaveN]

Keenserts UNF Sizes. I’ve used them in the past but for lightweight installations and for a 5/16unf bolt or stud you would need to drill just under 0.4. (My notes say a letter X). That would almost definitely breakthrough the side of the arm.

[astontr6]

20 hours ago, Motorsport Mickey said:

Depends very much on the actual trailing arm Bruce, as pointed out there is considerable variation in the locating block positioning and I've seen some horrors (when buying spare trailing arms for my Stag) especially when "gung ho freehand" drilling and tapping has lead to a lean which leads to the thread breaking through the material wall around almost half of the diameter.

I'm not sure that a helicoil or even these solid inserts will remain in position if a maximum exertion of side force is put through them (happily because there's 6 of them they support in a push me-pull me way). Hence my preference for the 3/8 th UNC hybrid stud into the remaining parent material which if in it's original 5/16th UNF stripped condition offers the maximum remaining material to tap into.  The 5/16th stripped dia holes (.312 thou )being the tapping size for 3/8th UNC taps, and smaller than the 5/16 Helicoil size (it's a fine interior thread inside a coarse exterior thread) of .328 thou, 16 thou bigger on dia. Those that remain unstripped are easily drilled out to 5/16th, and also the virgin material under the bottom of the stud can be drilled and tapped 3/8th UNC (you'll note the hybrid 3/8 UNC -5/16 UNF studs are long on the UNC side) offering another 3 threads of full dia material there.   

Mick Richards  

I see what you mean about wall thickness! My TA must be unusual as it has a good thickness of metal in that area? But it is a 1973 car. I wonder if they (BL) modified the casting? I am still using the original threads?? Mine have not stripped yet?/

Bruce.

[Schnippel]

Hello
the dangerous thing about these small threaded bolts is history - if someone has exceeded the permissible torque. Unfortunately it is possible to pull the bolts including the thread out of the swing arm with a torque of 20 N / m. The torque wrench says click. But the threaded bolt comes out! That's why I always turn the nuts with a short, circular-grip wrench. This means that you can feel very precisely when the screw connection is tight or behaves like a rubber band.
I have to say that it takes a little practice before it works.
It is very helpful to glue in the threaded bolts with Loktite 648!
After hardening, the strength of the thread is increased many times over.

regards
Ralf

[RogerH]

Hi Folks,

there is a great deal to be said about these TRailing Arms and their attachments.

Clearly with such a low torque loading one needs a sympathetic torque wrench.   The reading you want should be towards the middle of the wrench range.

They are not truly linear devices.

I must admit I use a 6" socket wrench and tighten by feel.  This is against all my aerospace TRaining - but !!!!

Loctite will definitely hold the stud in place but will not increase the shear strength of the teeth in the parent material of the hole.

 

Roger