On Sat, 07 Sep 2013 12:41:00 -0500, dpb wrote:

On 9/7/2013 10:39 AM, N_Cook wrote:
I need to do a hub-pulling type operation on a small piece of equipment
that is not made to be taken apart, so no purpose-made anchor points.
There are 8 off , 1mm tapped holes with 5 threads per hole , in the
aluminium available (used for undemanding normal fixing to the chassis)
, if I drill a plate to take 8 screws . The only screws of that thread I
have are brass, probably preferable to steel anyway. For a similar
hub-pulling where there was purchase , after heating (limited as to
amount that can be used ), required about 4Kg of force to extract. Would
4Kg , assuming even distributed loading over the 8 screws be above or
below the stripping force ?
I found these sites but not applicable for my purpose it would seem

www.tribology-abc.com/calculators/e3_6e.htm
http://www.roymech.co.uk/Useful_Tabl...ead_Calcs.html

The _rough_ back-of-envelope estimate here comes out at only about 20
lbf loading each assuming a soft Al. T6061 w/ a hard fastener might be
closer to 100 lbf.

I get 30 pounds, but maybe your aluminum is softer. And I didn't have
the benefit of a napkin. g

In any case, if the screws are not silicon bronze or some other high
strength alloy, it's probably a toss-up between stripping the threads
and breaking the screws.

--
Ned Simmons