Bolt Connection to resist vertical Slip 2

[daelo]

Hello all,
First time poster here, couldn't find an introduction forum so I'll introduce myself here instead. 26 year old product designer working in the construction industry(partitions).

And here's my problem, I'm trying to design a bolted connection that uses dowel pins to provide shear strength but which also uses socket screws to withstand slip in the vertical plane. If you take a look at the attached scan you see how and see the detail of how the two blocks are clamped together with a frame which is in the middle. 2 or perhaps three socket head screws sunk into block A will screw into block B with or without helicoils if ally 6082 T6 is not suitable for the threads strength. A vertical load of 1962N or 200kg is what the clamping force will have to over come, the material between the blocks will be powder coated aluminium.

I understand that preloading of *bolts* will need to be at 75% of their proof strength,but how do you work torque into a force that can be applied to clamp the two items together without slipping. In the worst case scenario I will just settle with the dowel pins doing all the shearing work with the screws just holding the blocks in place to avoid any prying.

The dowel pin calculation has been include below, would someone mind checking? I work it out to be 2 8mm A4-80 stainless pins fitted into an m6 hole tolerance (press fit).

I've been banging my head against a brick wall all day trying to work out the clamping force equation but just cannot simply get my head around. Surely the clamping force just have to overcome a 1962N force x coefficient of friction in order for no slip to occur?

Thanks for taking the time to view my thread, and hello again!

 

[KENAT]

Is this the kind of thing you're talking about faq725-536

Posting guidelines faq731-376

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

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[CoryPad]

You are correct, the clamping force must be greater than the vertical force divided by the friction coefficient.

If the structure will be exposed to the outdoor environment with any possibility of corrosion, then I recommend property class 8.8 or 10.9 screws to avoid stress corrosion cracking of 12.9 screws. The screws should use a multilayer coating such as ISO 10683.

 

[daelo]

Fortunately this item is designed to be used indoors and as such shouldnt need any considerations for corrosion bar galvanic, which i believe steel + aluminium shouldnt have a problem. I'll take a look at the assembly torque faq and see if I can work it out from there, wish me luck!

 

[Tmoose]

Fitted dowels in a door frame? is that standard practice in commercial doors?
Roll pins don't require precisely sized and finished holes.
With good engagement in both sides I'm guessing the shear strength would approach 1/2 the double shear strength.

http://www.spirol.com/library/main_catalogs/cldp_us.pdf

one torque vs preload chart

http://www.spaenaur.com/pdf/sectionD/D48.pdf

The fixed block part A's yield strength may limit the allowable bolt head's bearing stress, and the torque that should be applied.

With the "right" bolt the unthreaded body could be considered acting as a pin.