tapping very short blind hole

I want to tap a blind hole about 4mm deep in 5mm aluminium plate, without disturbing the other side. M5 thread, or so. Any ideas how to go
about it?
ta
Peter Fairbrother
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"Peter Fairbrother" wrote in message

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
Andrew
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On 06/08/2018 22:41:06, Andrew Mawson wrote:

Good advice, also keep a blast of air over the hole to keep any swarf from getting under the bottom of the tap.
--
mick

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On Mon, 6 Aug 2018 22:41:06 +0100, "Andrew Mawson"

I might go as far as using a spiral flute tap for both operations, but that might be overkill since you're only looking at five turns!
Mark Rand
--
RTFM

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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
http://www.engineershandbook.com/Tables/metrictapdrill.htm
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?
Alan
Alan
--
snipped-for-privacy@argonet.co.uk
snipped-for-privacy@riscos.org
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On 08/08/18 12:39, Alan Dawes wrote:

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 far.
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, yippee!
-- Peter Fairbrother
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Peter Fairbrother wrote:




Our showmen solder the sides of aluminium drink cans.
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