Subject: Re: Drilling thick cast iron help, please?

From: anderson <[email-masked]>
Date: 19 Sep 1996 01:53:12 GMT

[email-masked] (Jens) wrote:
>
> [email-masked](Wm. Congreve (Sr.) ) wrote:
> 
> >I need to drill a 3/8" or 1/2" hole through a hunk of cast iron about
> >six inches thick, which was cast using scrap in a small cupola and
> >doubtless has a hard skin and hard spots throughout.  Should I attempt
> >it with a cobalt steel drill, or a solid carbide?  Any lubricant as I
> >get deeper, or simply do it in small steps, clear the chips,  and let
> >everything cool down?  Any practical advice will be much appreciated. 
> >Next time I'll somehow rig a core for such a hole!
> >
> >                                    --Alan Heldman
> 
> Don't know the answer to most of your questions but I found that
> drilling cast iron in the lathe (horizontally) will clear the chips
> out really nice - it allows you to do the job much faster.
> (Oh, this is assuming you drill dry - which you should)
> Jens

Alan- HSS drill, 90 degrees with 12 degree relief is prescribed 
for cast iron.
For a list of recommended drill point angles see:
http://www.darex.com/m&mtech.htm  for more info see also
http://www.darex.com/links.htm  (machinist's cgi scripts and tables)
-Curt Anderson
Darex

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From: [email-masked] (MARK CENTER)
Date: Wed, 18 Sep 1996 23:39:13

>six inches thick, which was cast using scrap in a small cupola and

A masonry type carbide-tipped drill will work espcially if you sharpen it 
with an oilstone or green wheel. If you use HSS you will need to sharpen each 
time you hit an occlusion. A combination of both may work best. Drill outside 
with carbide, use HSS until you hit an occlusion, drill through the occlusion 
with carbide, re-sharpen the HSS and drill until you hit an occlusion.
With that length to diameter ratio it would be eaiser to dill from both sides

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From: [email-masked](Wm. Congreve (Sr.) )
Date: 17 Sep 1996 15:07:09 GMT

--Alan Heldman

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From: [email-masked] (Jens)
Date: Tue, 17 Sep 1996 12:18:40 -0700

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From: [email-masked] (Bruce Holder)
Date: 20 Sep 1996 01:24:36 GMT

Jens ([email-masked]) wrote:
: Alan Heldman (posting as [email-masked](Wm. Congreve (Sr.))?) wrote:

: >I need to drill a 3/8" or 1/2" hole through a hunk of cast iron about
: >six inches thick, which was cast using scrap in a small cupola and
: >doubtless has a hard skin and hard spots throughout.  Should I attempt
: >it with a cobalt steel drill, or a solid carbide? 
                                      ^^^^^^^^^^^^^
  If I owned a 3/8 or 1/2" solid carbide drill with 6" flute length, I'd
sell it and buy a nicer car.

[snip]

Bruce

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From: [email-masked] (Ian R. Howcroft)
Date: Thu, 19 Sep 1996 11:57:16 GMT

>                                    --Alan Heldman

During my apprentiship ( too many years ago to mention) I worked a
radial drill, and literally drilled tons of cast iron.  However, it
was all good quality stuff, so there may be problems with the stuff
you have which I have not encountered.  I can't see that you should
have too many problems though.
Firstly, you shouldn't need any lubricant, there is normally
sufficient free carbon in cast iron to give the drill or cutter all of
the lubrication it needs.  Sand inclusions can give you problems, and
this does happen even in good quality cast iron, as do the odd chilled
spots, but they are fairly rare in my experience.  Personally, I would
start off with just a normal high speed steel drill bit, but you know
the piece of metal you have better than I do, so if you have any
doubts, I would suggest you grind a masonry drill (carbide tipped)
closer to the  profile of a metal working drill and try that.  They
can be the answer to a whole lot of drilling problems, and they are
pretty cheap too.  You just need to have the right wheel on your
grinder to deal with them.  If you use the hss drill bit, keep the
revs fairly low, but if you use the masonry drill, you should be able
to get through with quite high revs.
			Good luck.
					Ian.