How to make screw fit snugly in a hole

[andrew700andrew]

Hi, I've made a T-joint recently between two sections of aluminium box section and I rivited a sheet aluminium triangle between them to try and prevent rotation, with two rivets in each corner, and a machine screw actualy through the two aluminium box sections. While this did a good job at preventing large rotation, there is still some movement in the joint. I've figured that this is because the screw is slightly smaller than the hole and so the joint is rotating about the two rivets. So does anybody know of a decent way to reduce wobble in a loose screw, one which is a bit too small for the hole? So far all I've though of is wrapping some tape arround the screw, which doesn't sound perticularly durable.
Thanks.

 

[Burnerman]

There will always be a pivot around one screw....the secret is to use two, as per the rivets.
Consider some adhesive too? How about a pic?
John

 

[andrew700andrew]

I don't have it on me but here's a drawing. It might make it clearer now, if the screw in the middle is too small for the hole, then the two box sections can pivot arround the screw a little but, until the screw hits the edge of the hole.

Untitled

• andrew700andrew
• 28 Feb 2015
• 1

 

[Burnerman]

Nothing wrong with your triangulation, Andrew!
I suspect the screw has a clearance hole that is too big.....is it possible to get another screw in, or is the space a bit tight?
Likewise, two rivets at the top of the web could help.
John

 

[Dave54]

If you can use a bolt, (with a plain shank above the thread that is), that would be even better I'd think. You may have to alter existing bolts though to get them that short. Holes need to be accurate to the diameter or you will still get the movement.

 

[longdogs]

what about swapping the triangle for two of these?

http://www.diy.com/departments/bq-s...89_BQ&ef_id=UwZZ1wAABEB4aSup:20150228163733:s

 

[cajar]

Does your machine screw have a bolt on the end of it, or did you cut the thread into the aluminium?

 

[Burnerman]

I think we are dealing with very thin section aluminium here....1mm thick has been mentioned somewhere so crushing is going to be likely.
John

 

[Dave54]

Seems to me that it's going to be difficult to get any real strength in the joints to stop that movement as they are. Sort of the same limitations as Meccano. Thin sections that rely on friction for location. You could put bigger washers, or made up slightly thicker alloy plates in, which might help increase the clamping area, but my mind keeps coming back to John's suggestion of using adhesive of some kind.
The only other thing that occurs to me would be to use rigging wires somehow to triangulate the whole frame, rather than just triangulating the corners.

 

[foxhole]

For loose screws into metalwork I use a piece of wire around paperclip diameter. Hook thru hole and screw will bite.