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Hi Michael,
<P>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 :)
<P>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:
<BR><A HREF="http://www.woodweb.com/knowledge_base/Machining_aluminum.html">http://www.woodweb.com/knowledge_base/Machining_aluminum.html</A>
<P>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...
<P>Scott
<P>Crufone@aol.com wrote:
<BLOCKQUOTE TYPE=CITE><FONT FACE="Arial"><FONT SIZE=-1>Joe,</FONT></FONT>
<BR><FONT FACE="Arial"><FONT SIZE=-1>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!!!!!!!!!!!!!!</FONT></FONT>
<P><FONT FACE="Arial"><FONT SIZE=-1>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.</FONT></FONT>
<P><FONT FACE="Arial"><FONT SIZE=-1>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.</FONT></FONT>
<P><I><FONT FACE="Arial"><FONT SIZE=-1>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!!!!!!!!!!!!!!!!!</FONT></FONT></I>
<P><FONT FACE="Arial"><FONT SIZE=-1>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.</FONT></FONT>
<P><FONT FACE="Arial"><FONT SIZE=-1>Michael #133</FONT></FONT><FONT FACE="arial,helvetica"></FONT></BLOCKQUOTE>
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