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Drill bits


#1

I’m just wondering what kind of drill bits the professional jewelers
use when drilling gold/silver/copper/etc. I’ve been using highspeed
exclusively for a while I’m wondering if there’s a better way. I’ve
tried carbide a while back but I found that to be very unreliable
because the tiny ones break too easily… any suggestions?

@Tato_Mann


#2

I am drilling multiple small holes in steel (approx. 12 gauge) and
find that the drill bits that I am using only last for 3 or 4 holes.
Any suggestions? I have purchased bits from my local hardware
store and from my jewelry supply store. Neither works for very
long. Suggestions? thanks Lori Swartz


#3

G’day Lori; Use only ‘high speed steel’ (HSS) drill bits. Keep the
drill chuck tightened firmly. Do not use a very high speed with the
drill press. Don’t use a whole lot of pressure; let the drill do
the work. Use a lubricant but not oil. Water is fine - engineers
use spit! Which is excellent, but CRC or WD 40 works well too. Talk
an old-timer machinist into giving you a lesson on how to sharpen
twist drills properly. You can’t tell people how to sharpen drills;
you have to show them and make them repeat the lesson in front of
you! Not complicated but a bit tricky till you know how - like
everything else.

Cheers for now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ


#4

Hi lori, in answer to your drill problem;

  1. Buy a center drill of the correct size from MSC or some other
    machine tool catalog(use german or swiss or top quality u.s. bits)
    and start your hole with this drill ,just start the hole do not go
    through

  2. Always make a situation where you clamp your material, and do it
    on a drill press

3 Always use a lubricant also sold in tool supplies rpm not too
fast, not too slow ,drill speeds come in machine shop reference
books, or pamphlets there is a simple formula

  1. Carbide drills last longer but require extreme care when coming
    down on the work and lube, and center drilling first ,faster rpm

5 Watch what is happening with an optivisor

  1. Learn to recreate your drill point with a sharpening wheel(always
    with an optivisor on) on a tool room grinder($30, sears) the exact
    angle that it was ,about 118 degrees inclusive ,don’t turn it blue
    practice on large ones(drills)

  2. Have backing under your piece and set your depth so that you just
    come through, no more ,and easy does it

  3. Get the machinist’s handbook contact starrett, morse, etc and get
    their handouts on drill speed tool sharpening, etc.

                                                     dp

#5

Hello Lori;

Assuming you are using a product called “mild steel” which is a low
carbon steel, the problem you are having may be due to the presence
of “mill scale” on the steel. This is thin gray oxide layer that is
quite hard and will dull your drill bits. You need to remove it
either by etching or abraision. You can sand-blast or what I find is
easier is to coat the steel with a layer of a product called “Navel
Jelly” (that’s navel as in Navy, not belly-button). It’s really a
jellied form of muriciatic acid. Leave it on for an hour or so, then
rinse thouroughly with water. When you are drilling, make sure you
keep a light oil on the spot you are drilling. Machine oil works
fine. I prefer a little “motor honey” from the auto parts store
thinned down with turpentine. If you aren’t using oil, your drill
bits are going to overheat and that will ruin the temper and they’ll
dull. Your other option is carbide drill bits, which are quite
expensive, but will cut through just about anything, mill scale or
other, but run them fairly fast, as they chip easily.

David L. Huffman


#6

best bet might be to use either a titanium coated or a carbide drill
bit, either will last longer for your application although both are
more expensive


#7

Lori, I purchased a set of 115 Titanium drill bits, in a nice metal
flip-up box, from Harbor Freight for $39.95. These are very sharp,
run cooler so they don’t expand, and can be resharpened. The sizes
run from .0625" to .5". I keep the smaller ones at my bench and the
larger ones in my woodshop. By the way, you can resharpen most drill
bits on your India stone by hand - run the 2 very bottom cutting
edges on the stone a few times, keeping the original bevel - you can
then use them virtually forever or until the temper is gone.

Jim Marotti
Lancaster, TN


#8

Dear Lori, Are you running the bits with a cutting oil? This is
available at any hardware store. Cutting oil and slow speed.
Sam Patania, Tucson


#9

Hi Lori,

I am drilling multiple small holes in steel (approx. 12 gauge) and
find that the drill bits that I am using only last for 3 or 4 holes.

You didn’t say how small, it’s all relative. I recently had to drill
some #55 holes (.052") in 1/4" hot rolled steel. I used high speed
steel bits purchase from an industrial supply. I was able to get 12
holes from each bit. However, in the interest of not generating lots
of scrap due to broken drill bits stuck in the work, I limited the
drilling to 10 holes each.

The trick to not breaking small drill bits is holding the workpiece
solid & having a very good drill press. There should be no lateral
movement between the workpiece & drill bit while the drill is
running. The other things to consider are drill speed (I used about
2500 rpm), bit lubrication (I used Tapmatic Cutting fluid) &
pressure on the bit. That’s hard to quantify for a manual
operation. Don’t press so hard the bit bows & breaks, but hard
enough to keep the point cutting. This usually takes a little
experience (broken bits) to develope.

If I were you, I’d practice on some scrap until I felt comfortable,
then move over to the workpiece.

Dave


#10
    I am drilling multiple small holes in steel (approx. 12 gauge)
and find that the drill bits that I am using only last for 3 or 4
holes. 

hi, Lori

A few questions first: What kind of steel? What size drill bits? Are
the bits breaking or getting dull? In general: If you use a good
cutting oil and slow the speed of the drill down, the bits should
last better. Don’t use motor oil, or 3 in 1 or other lubricating
oil. You need a cutting oil or tapping fluid. Tapmatic is one brand.
I think Home Depot will have it. Depending on the answers to the
above questions, I may be able to give you additional
Deb


#11

Hello Lori, I think your drill bits are made of carbon steel. This
material gets soft at 300 degrees Celsius. When you buy at your
hardware store HSS (High speed steel) drills, you will see they last
5-10x longer. HSS gets soft and blunt above 550 degrees Celsius. Also
good cooling will help. So use, water, or better a drilling oil
solution.

Martin Niemeijer


#12

Hello Lori, Re your question:

    I am drilling multiple small holes in steel (approx. 12 gauge)
and find that the drill bits that I am using only last for 3 or 4
holes. Any suggestions? 

Your drill bit needs to be appropriate for the metal - is the steel
hardened by chance? Also, lubrication is important, especially as
speed increases. I’ve found that a drop of oil (wintergreen smells
good) on the spot where the hole is to be drilled helps. The oil
works down the hole as it’s drilled. Hope this helps, Judy in Kansas

Judy M. Willingham, R.S.
Biological and Agricultural Engineering
237 Seaton Hall
Kansas State University
Manhattan KS 66506
(785) 532-2936