Another thing is to use a center drill to start the hole for the small bit.
This is the same center drill you use in a lathe or on a mill. It has a 60
degree angle. Some steel has a case hardening, or the skin is harder than the
internal steel if through hardened. The center drill should be a carbide type
for really hard stuff, or a hardened high speed tool steel. Titanium Nitride
(TiN) coating is the best (the ones with the gold color). Use the largest you
can get buy with as the step point on a 1/2" is 1/4", etc. A 1/8" would step up
to 1/4" or so. These are fragile and will shatter if not big enough and too
much pressure applied. The sharp angle on the point though will start drilling
it. First, use a center punch to make a prick where you want the hole. Then use
the center drill to start the hole. After you have went in say 1/8" to 1/4"
with the center drill, change over and use the regular high speed steel bit. If
on a thin sheet, look at the new TiN coated stepped cone
bits. For a cutting oil, and if you cant find any to buy locally, Prestone
(ethylene glycol) will do in a pinch. Mix it with about 1/2 part water. Dip a
small paint brush in it and apply to the turning bit. Keep it soaked so it will
stay cool.
Best,
Will
*********** REPLY SEPARATOR ***********
On 10/30/06 at 9:31 PM Rich & DJ wrote:
>Date: Mon, 30 Oct 2006 16:37:14 -0500
>Several people said step up a little at a time and use oil , all good
>ways. One more thing , make sure the drill bit has a 135 degree grind on
>it , most are 118 degree for alum , and soft steel. If it is 135 it is
>for hard steel and other tough materials .
>
>An old machinist, Rich, kd0zz
>
>
>From: "carl s." <carlseye@tampabay.rr.com>
>Subject: [Amps] drill bits
>To: TARC@hamclub.org
>Cc: amps@contesting.com, mosi <mosi@danmc.org>
>Message-ID: <4546708A.2040704@tampabay.rr.com>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> to all hams who may read this.!!
> Is there one among us who is a master machinist??
> I need someone who can tell me *exactly* what type of drill bit it
>will take to drill thru a steel plate, 3/8 in. thick, Very hard (altho
>hardness is hard to verify) A 1/2 in. Cobalt drill couldn't,touch it.!!!
>
>So , how do I drill that plate ??
> I'll give you any more info I have ( which isn't much)
> Please let me know if you have anything to help.!!!!
> carl / kz5ca
> Mosiarc.!!!!!!!
>
>
>
>
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