Start with a bottoming tap, and finish off with a second bottoming tap that
you have ground the end off to get full threads all the way. It will need a
bit of care to get the first tap started plumb - best done in a tapping
stand or drill press without power
Before you can use the M5 tap you must make a blind flat bottomed hole
either 4.2 mmm diameter for metric course or 4.5mm for fine
So once the "body" of the drill goes down 4mm the "point" will have broken
through the remaining 1mm! How have you drilled this hole? did you use a
4.2 or 4.5mm slot drill or centre cutting end mill or did you grind off
the point of a standard drill?
Thanks all, I decided to "solder" a threaded bit on instead. I am using
Sven's aluminium soldering/brazing wire, and so far it works really well.
Sven is a guy who sells wire at model engineering shows - on that
subject, anyone else going to Bristol tomorrow?
Sven has a showman's act I suppose you'd call it, soldering bits of ali
sheet, making holes in them then filling them again, selling by the
"Sven meter" which is two outstretched arms worth.
I don't know the name of the product he sells. but it is light years
better than the usual aluminium brazes, ie it actually works!
I have had it for ages, bought 2m and gave one as a christmas present,
but this is the first time I have used it, wire brushed and "tinned" the
surfaces before joining - well, as I said,it actually works, at least so
I's quite a bit more expensive - like 5x the price - than the usual
aluminium brazing type rods, but the difference in performance is - wow,
best thing since sliced bread!
Of course it will all probably fall apart tomorrow .. but for today,
-- Peter Fairbrother
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