Widened mount hole in control arm pivot shaft. 1

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Hello,

This question is regarding strength reduction in an upper control arm pivot shaft on a 1996 Nissan Hardbody 4x4. The stock holes in it to mount to the frame are 14.3mm in diameter and the stock bolt size is m14-1.5 I discovered someone had drilled one of the holes out to 16mm to drill and tap the frame-side threads to m16-2. I have included a photo of the shaft and the hole on the lefthand side is the widened hole. Do I need to worry about the shaft being weaker and possibly fracturing at that hole? Thank you.

 

[GregLocock]

It does look a bit skinny. I'm assuming it is cast steel? The proper thing to do would be to buy new arms and helicoil the frame back to M14.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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Thanks for the info. As far as helicoil, since helicoil is made out of weak stainless steel, wouldn’t it have the potential to have weak threads? Like if I use a grade 10.9 14mm bolt, wouldn’t the stainless steel threads be quite weak in comparison? Maybe those weaker stainless threads could get pulled out?

Thanks for the help.

 

[GregLocock]

No we helicoil suspension bolts on any car that is regularly dismantled.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[gruntguru]

A helicoiled thread is usually stronger than original. Bringing a 16x2 hole back to 14x1.5 will require something thicker than a standard helicoil.

je suis charlie

 

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Thanks for the advice, everyone.
After researching it, I found these m16 to 1/2” thread inserts made of carbon steel:

https://www.ezlok.com/ezlok-insert-550-8.

(I couldn’t find anyone making a 16mm to 14mm version.)

They would allow me to use 1/2” bolts that would fit the normal 14.3mm stock shaft holes. 1/2” is smaller than the stock 14mm bolts, but I’m ordering the extra strong grade 9 1/2” bolts. They have a higher proof load than grade 8.8 14mm bolts, but a bit less than 14mm grade 10.9 bolts. I suspect the stock 14mm bolts are grade 8.8 as they call for 80-104ftlbs torque per Nissan.

Is it commonly accepted that vehicle frame hole threads are made of plain carbon steel for weld-ability?

 

[BrianPetersen]

Don't know about that particular hole in that particular frame, but a common way of arranging for a threaded hole in an otherwise flat piece of steel involves resistance-welding a weld-nut to the side of the steel opposite the side that the bolt will eventually be installed through. They're carbon-steel for weldability. If someone has drilled out those threads, I'd be investigating how much material is left of the original weld-nut on the back-side of that frame.

 

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Unfortunately, I can’t get to the area behind the threads as they are within a steel “box” that’s welded to the side of the frame in the photo. I did stick a bent paper clip in the holes to feel for how much thickness is left of the interior nut. It seemed pretty thick yet, not like the threads are within a thin-walled nut. There seemed to be substantial mass around the threads.

 

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Here is the finished product with the new control arm shaft, Ez-Loc thread inserts, and grade 9 bolts with alignment washers.