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Newsgroups: rec.crafts.metalworking
Subject: Re: Making holes in spring steel
From: John De Armond
Date: Sun, 15 May 94 22:20:09 GMT (f.w.kerfoot..iii) writes:

>I am getting ready to make leaf springs for the tender of my 1 1/2"
>per foot live steam locomotive. The prototype used leaf springs,
>where the anchors at the ends were formed by oblong holes in the
>leaves, with the link passing through these holes and a cross-wise
>pin inserted through a hole in the link. I want to make the appearance
>of the model as close as possible to that of the prototype.

>I have found a source of suitable spring material (Power Model supply),
>which is hardened, tempered and blued spring steel, 1/2" by .032"
>and 1/2" by .050" (I am using two different thicknesses to allow
>myself some flexibility in overall stiffness after everything is
>built by substituting thicker or thinner leaves in selected places).
>This material is roughly Rockwell C48-51 in hardness. I am looking for
>insights on making the holes. 

Trivially easy.  Ring up Truebite in new york (they have an 800 number,
try 800 DA) and order a couple of diamond drills.  They have them all
the way up to about 6" in diameter.  The smaller ones, typically up
to 1/2", are designed to be used in die grinders and cost in the $12
range.  They look like cylindrical grinding burrs and are designed
to drill glass, ceramics and other hard materials.  They work like
a champ on hard steel.  Drill using an air powered or battery powered
die grinder and a steady stream of water.  The drill will shed its 
diamond in no time at all if allowed to run dry.  Wet, it drills
so fast as to be unbelievable.


From: John De Armond
Subject: Re: Best way to drill hole in glass?
Date: Tue, 24 Aug 1999 02:56:07 EDT

Vince wrote:
> What is the best way to drill small holes in cold glass?  I tried using a
> diamond Dremel bit and putting the glass in a shallow pan of water.  This
> worked, but it wore out the bit after only 3 or 4 uses and the bit cost $7.
> Any suggestions?

That's the best way.  You're probably using too much pressure and
not allowing enough water to access the bit.  Those are the mistakes
I made in the beginning.  Touch the bit to the glass for no more
than a second at a time and then withdraw.  this allows fresh water
into the hole.  The Dremel drill press stand makes this easier.  An
alternative approach which I use a lot is to rotate the bit in a
small circle inside the hole.  This makes the hole about half again
as large as the bit but it lets plenty of water in.  Water, both for
cooling and for removing grinding debris, is absolutely vital for
long life.

It is possible that you have a defective or poor quality bit.  If
you have access to a microscope, look at the bit.  The best bits
have the diamond particles bonded to the mandrel using nickel
plating that covers most of the particle.  This bonding method
allows the diamond to fracture (exposing new sharp edges) several
times before it finally either loses its bond or the bond is abraded
away.  With cheaper bits, the diamonds look like they are perched on
top of the substrate with the bonding nickel just sorta forming a
meniscus at the base.  These diamonds quickly break off.


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