UAirLtd wrote:This is going to be slightly off-topic, but it's related to the thing you said about "small rim pushed inwards to provide more threading area", don't know what that's called, but it reminds me of flow-drilling, which uses friction from a rotating tip to melt a hole, and this provides a big rim inside that is very useful for extending the threading area, here's a video: http://www.youtube.com/watch?v=NhkWINPRK3A Don't know if you can do this yourself, perhaps the one you showed is caused by drilling or punching.
semicolo wrote:Also it looks like the original screws have high pitched threads, maybe if you use fine threaded screws/taps you won't need the rim
k-ww wrote:Poor mans way:
[try these somewhere you do not mind an extra hole first!]
1) drill hole about 1/2 dia of thread in metal.
2) find nail with dia less than that of hole size needed for tap.
3) place block of wood behind sheet metal.
4) hammer nail into hole.
To tap hole,
1) find steel screw of desired thread
2) grind conical taper on tip, and a flat on one side
3) with drop of oil, thread screw into hole
semicolo wrote:I'm not at ease myself with imperial stuff, being born in France and moved to canada when I was 28, don't get me started on that subject.
But just by looking at the pictures the screws seem to have higher pitch than M3 that are supposed to have 0,5mm pitch (that's still half your 1mm pitched screws), so if your sheet is 1,5mm you should be able to have 2-3 threads holding the screw, that might be enough depending what you're doing.
By the way you could measure 4 spaces between threads and divide the length by 4 to get a better measure of the pitch (or more, the more the better)
my threads are like:
the original ones are
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