From: Dave Baker
Newsgroups: rec.crafts.metalworking
Subject: Re: Drilling titanium -- NOT!
Date: 07 Aug 1999 05:49:31 GMT

>So, I finally got a chance to make something with a piece of .080" 6Al-4V
>titanium sheet I got at Boeing surplus on a lark.  We're going crabbing, and
>the bait shop was out of the plastic crab gages, so I thought I'd whip one
>up out of the titanium.  To make it easier to cut out, I was going to drill
>the interior corners.
>
>Into the drill press goes the made-in-USA HSS New York Twist Drill 7/16"
>bit, check the speeds and feeds, start the quill down, and meet up with a
>gawdawful lot of resistance.  Pull a little harder on the quill, then harder
>yet, fearing work-hardening, and all at once the metal at the cutting edge
>turns red-hot and starts some of the titanium shavings on fire!  Aack!
>
>Fearing I might have ruined the titanium, I stopped the press and took a
>close look -- the titanium was fine, it was the drill bit that was done for.
>The titanium had worried away about 1/16" of the outside part of the cutting
>edge.
>
>What should I have done then?  The drill bit was brand new, never been used.
>Cobalt?  Carbide?  Run the bit through quick to avoid work-hardening?


Ha ha ha ha ha - laugh? - I nearly did.

You aren't the first person to be stumped by a nasty piece of material and no
doubt you won't be the last. We make special race bits from titanium alloys
from time to time and they need some care to machine properly. Very rigid
machines - i.e. not drill presses - low speed, high feed, copious supplies of
cutting oil. Plenty of buckets of sand on hand for when the dust or chips
ignite explosively !!

btw - "check the speeds and feeds" - how do you set the feed on a drill press
with a hand quill???

Try 100-200 rpm, razor sharp drill, preferably carbide. Lots of neat cutting
oil, press like buggery and hope. Also for thin section stuff like yours
support the piece from underneath - i.e. on a block of aluminium or something
and drill through both or you'll just distort the sheet and never get through
it.

So how many of the above points did you get right?

Get the hang of machining titanium and you are well on the way to being able to
call yourself a machinist.


Dave Baker at Puma Race Engines (London - England)  - specialist cylinder head
work, flow development and engine blueprinting. Web page at
http://members.aol.com/pumaracing/index.htm

From: Dave Baker
Newsgroups: rec.crafts.metalworking
Subject: Re: Drilling titanium -- NOT!
Date: 07 Aug 1999 06:13:24 GMT

Oh - another couple of btw's.

If this stuff has been lying around for ages and has any oxide scale on it
you'll need to grind this off first to get back to clean metal. The oxide is
about 7 times harder than an Irishman's skull and will blunt anything you put
near it.

Also titanium fires, like magnesium ones just love water. Makes em burn really
nicely. So if you get a burning chip in your eye it will sizzle away for ages
until your brains leak out through the hole. So wear protective glasses with a
pair of goggles over them and a face mask over both and a diver's helmet over
the lot and then stand behind a sheet of bullet proof glass - or better still
ask someone you don't like to pull on the drill press handle while you watch
from a safe distance.


Dave Baker at Puma Race Engines (London - England)  - specialist cylinder head
work, flow development and engine blueprinting. Web page at
http://members.aol.com/pumaracing/index.htm

From: Dave Baker
Newsgroups: rec.crafts.metalworking
Subject: Re: Drilling titanium -- NOT!
Date: 07 Aug 1999 23:40:16 GMT

>From: stagesmith@earthlink.net (Ernie Leimkuhler)

>Cutting titanium slowly is useless, all you do is build up a lot of heat
>and burn the bit.

<snip>

Your avin' a laugh me old mate - as we say over here. Well in some parts of the
country we do anyway. I don;t know what you mean by "slow" but the Dormer drill
and reamer handbook recommends 15 to 30 sfpm for drilling Titanium which is
pretty damn slow and works out as 130 to 260 rpm on a 7/16 drill bit.

Even then I'd tend to start at the low end of that as these recommendations in
books are always aimed at optimising volume production. For the hobbyist you'll
nearly always get much better tool life by taking things easy. AFAIK machining
anything slowly doesn't tend to build up heat and burn out drill bits - it's
excessive speed that does that.

Ahhhhhhh - just as I finish writing this I wonder did you mean slow as in the
hand feed or slow as in the cutting speed? Oh well - written it now.


Dave Baker at Puma Race Engines (London - England)  - specialist cylinder head
work, flow development and engine blueprinting. Web page at
http://members.aol.com/pumaracing/index.htm