Spigoting 3mm SS to SS boss

[stuyoung]

I am currently redesigning a joint detail to make it more durable.
I have a 3mm stainless bracket that needs to be spigoted to stop it rotating around a boss.
The current joint has a 12mm diameter boss with a flat surface (5mm from the central axis) to provide the spigot into a "D" shaped hole in the 3mm plate. These were a tight interference fit initially, unfortunately the "D" in the 3mm plate has deformed and the joint has become increasingly sloppy.
I have since tried widening the boss to 16mm, adding two, 4mm pins spaced 11mm apart either side of the central M6 cap screw (that holds the plate to the boss). This still flogged out over time!
I cannot weld the 2 articles together due to assembly requirements.
This component locks the pivot point of a footplate for a device for cerebral palsy children who are capable of putting large reciprocating loads on it.
This pivot is generally located 1/2 to 3/4 of the way along the side of the foot long footplate, (for an idea of scale)
There is a lock on either side of the footplate, and the loads that resists the tilting of this footplate is passed through these joins.
What do they say about a picture being worth a thousand words?
Any help would be appreciated.

Thanks

Stu

 

sounds like you are exceeding the capability of the material. Your only options are to make the part larger or to change to a material with higher yield.

 

[stuyoung]

Thanks,
Those are the lines I am going down at the moment,
I have also re tried the roll pins (with a little more precision,) and this may be an acceptable alternative, they perform much better once the stainless has work hardened a little, unfortunately this is after a little slop has been initiated. I am quite short of space so bulking the component up has its limitations
I appreciate your time,
Thanks again,

Stu