[Dougal]

Thanks for pointing that out, I didn't think about the aluminum. I'm thinking that since I wedged the "custom engine support device" under the front before I let the weight of the engine off the hoist when I put it on the stand I'm hoping it will be alright for now. I'm close to test fitting my tranny so I'll check out the adapter for any problems.

Just make sure you've got enough thread in contact. 3 x bolt diameter is the most you'll ever need.

 

[Dougal]

The first three threads will carry up to 80% of the load. It will get to a point where the bolt will break before the threads shear, but I think it will be a lot less than a depth of three diameters.

Based on what assumptions?
Thread fit?
Material strength?
Fastneer strength?
Fastener torque?
Coarse threads or fine?
Mismatching elastic modulus of the bolt and socket?
What level of friction between threads (any lubrication)?
Linear elastic thread behaviour or yielding?

Three threads in 6061 aluminium can be stripped out very easily. Try it if you don't believe me.
Three diameters for reusable aluminium threads is a safe level for the worst case. It holds after bolts have been removed and refit many times.

In contrast one of the designers at my last job had M6 cap screws threading into 4mm of mild steel. Several of them stripped out during assembly of the brand new machine.

 

[Dougal]

Dougal;
Is 3x diameter a engineering standard ? Is it for Aluminum and steel or both ? Not being an engineer, I am always trying to learn more.
So for a 1/2" bolt your suggesting the tapped hole be 1.5" deep ?

Thanks
Paul

Not a standard, just a "best practice" rule. 3 thread diameters deep in aluminium and 1.5 diameters deep in steel.

Of course it's for non-replacable threads. Most nuts only contain 3/4-1 diameter worth of thread, but they're harder than mild steel and usually easily replacable.

If you're restricted to less thread depth than that, you can improve things by helicoiling the thread from the start. The Kuka industrial robots I've worked with have this done to them to create a stronger thread in light aluminium parts.