Stainless can be quite frustrating if you are not used to working
It can still be frustrating even when you ARE used to working with
Ill prempt all of this by saying this is only my experience…and I
only resort to free hand drilling when the piece cannot be solidly
clamped in the milling machine.
One thing that has helped me a lot when free hand drilling small
holes with a foredom unit in stainless steel (300 series) is the use
of a 2 flute 140* straight carbide drills. You can get these in wire
size bits down to #60 (0.040"). thru mscdirect.com (big book page
The main advantage of these particular bits is the geometry of the
bit itself. The 140* point is pretty darn strong, Using a center
punch, or starter dent, is highly recomended as the tip will tend to
wander on start due to the wide angle.
The straight flute design lends itself to making a sturdy bit as
well, it can take more side load abuse than a standard twist carbide
drill before it fails. I say this with the understanding that almost
all small carbide twist drills snap with the slightest side load
applied, and drilling freehand, this will happen. Honestly, this was
a huge suprise, I was expecting this bit to shatter when a side load
was put on it, but to my amazement, it kept on trucking, major bonus
points here…all things considered, these bits are extremley
With the point geometry, the cutting action is more akin to muscling
thru the stainless, especially at slow rpms, without a spiral flute,
chip extraction is almost non-existant, so peck drilling is
advantageous with this bit to clear out the chips created. Lastly,
the point geometry doesnt grab the material like spiral flutes tend
to do, its more of a scraping action that achieves the cut, this
bit WILL CUT through work hardened stainless as well. I run these at
a medium rpm with my fordom and the chips are tiny flecks, not spiral
strings most people are used to.
Now the disadvantages of these bits…they are pricy…starting
at $10 USD each, a hand full will run you a small fortune, I dont
recomend free hand drilling at high speeds with these either, you can
generate enough heat to break down the carbide, causing them to dull.
If your needing smaller sizes (pg. 119 of the big book), MA Ford
makes the same thing with a 135* point down to #68 (0.031"), but
these start at $17 USD each.
Sorry to say this isnt the least costly solution, but it is a great
solution none the less, and I work with stainless all day, the
upfront cost is scary, but the long term payback is well worth it. Id
imagine using these bits on softer metals, they would last a