[Alberg30] Mast Step Bolts

[tristan]

Hi Michael,

Thanks for your reminder about using a bottom tap which has the bottom
taper cut off so that the tap can go to the bottom of the hole.  I have
been away from machining for longer than I thought :)

Good point about tapeeze or any other lubricant and good warning to
clean out the hole well.  Aluminum as a metal is weird since it is
almost like an "earth metal" and had peculiar machining properties...I
don't remember now, but I remember the speed and feed of the drill is
different than for ferrous or stainless metals...check out this site:
http://www.woodweb.com/knowledge_base/Machining_aluminum.html

You can use a tape to mark off where the tap will be even with the top
surface of the mast step when the bottom tap will be at the bottom of
the hole.  Tape the tap just a little below the spot so you don't bottom
out and strip out the new threads...You can use a hand tap to chase the
threads...

Scott

Crufone at aol.com wrote:

> Joe,
> Would like to add a couple of comments.  Mask off the area around the
> mast step carefully.  Once tapeze or cutting fluid mixed with al
> corrosion gets onto your weathered getcote your will not be happy with
> the mess and stains that it will make on your coach roof!!!!!!!!!!!!!!
>
> You will be taping into a blind, dead end hole.  You will need a
> Starter and a Bottoming Tap.  The starter tap has a long lead of
> cutting threads and is used first.  This is then followed by a
> bottoming tap which has almost no lead.
>
> The blind hole also traps all the cuttings and junk.  DON'T BE IN A
> HURRY, YOU WILL ONLY HAVE ONCE TO GET IT RIGHT, SO BE CAREFUL.  Tap a
> little; one or two turns, turn 90 degrees and then back off to clear
> the tap then go the 180 degrees and then back 90 and then 180 and back
> 90 and then 180 and so on.  After your 720, yes your fouled me again,
> remore the tap entirely out of the hole and clean out all debris.
> Compressed air blows stuff all over the place and also on your coach
> roof so a vacuum is better.  When the hole is clean add more cutting
> oil and go in another two turns further and so on.  NB the cuttings
> must be cleared because they will clog the tap and eventually tear the
> metal and ruin the newly cut threads.
>
> Most important off all.  Because you are taping a blind hole measure
> the depth and then mark the tap before you begin.  A real heart break
> is when you bottom the tap and don't realize it, you keep turning the
> tap which begins to turn in place, because it is bottomed, and you
> strip out all the new threads that you have just cut. Be very careful
> as you reach the bottom of the hole!!!!!!!!!!!!!!!!!
>
> This is very easy.  I only mentioned these pit falls because you will
> be taping a relatively soft metal - Aluminum - with a HSS tap and can
> easily tear up the Aluminum.
>
> Michael #133


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