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Drilling investigated


#1

Hi,

I have several questions about drilling:

  1. Is it “better” to drill holes in metal that is hard or annealed?

  2. Are there any dangers, such as structural failure, when drilling
    a piece of metal numerous times?

  3. Which method is better when enlarging a drilled hole: drill
    again, using a larger drill bit or using a needle file?

  4. Does the same drill bit behave differently with different metals
    (copper, silver, gold)?

Thank you and keep shining,
Devora


#2

While I won’t claim to know all there is to know about drilling,
I’ll share what I do know…

Is it "better" to drill holes in metal that is hard or annealed?

Generally it’s better to drill annealed metals, I’m assuming you are
asking about the more common jewellery metals.

Are there any dangers, such as structural failure, when drilling a
piece of metal numerous times? 

The closer the holes are together the less metal you have left
holding the holes in place (in this situation it’s best to think of
the holes as the work and the metal as the “air”), there is a point
at which you run out of structural integrity and the piece (the
holes) fall apart.

Which method is better when enlarging a drilled hole: drill again,
using a larger drill bit or using a needle file? 

The best method to enlarge drilled holes (it you want to keep the
holes round that is) is by “step drilling” the holes with
increasingly larger drills until you reach the desired holes
diameter.

Does the same drill bit behave differently with different metals
(copper, silver, gold)?

Short answer; YES, but for small holes (1mm and down) the changes in
behaviour is quite small and can (in most cases) be ignored, but for
some metals e.g. copper you have a very different edge profile than
you would for, for example iron or steel. The body of in
this topic is quite literally huge and can take a lifetime to
assimilate.

Please take this as a rather rudimentary surface treatment of the
topic!

Cheers, Thomas.
Janstrom Designs.


#3
Is it "better" to drill holes in metal that is hard or annealed? 

Its better to use a sharp drill

Are there any dangers, such as structural failure, when drilling a
piece of metal numerous times? 

There’s a variable point beyond which lies heartache.

Which method is better when enlarging a drilled hole: drill again,
using a larger drill bit or using a needle file? 

Depends. On thin sheet with a really large hole I’d suggest drill
again slightly under finished size and follow with a suitable bur.
On thick stock, drill.

Does the same drill bit behave differently with different metals
(copper, silver, gold)? 

Softer metals tend to encourage drifting so a properly done
centerpunch is essential for a well placed, well formed hole.


#4
Is it "better" to drill holes in metal that is hard or annealed? 

Harder metal cuts cleaner than annealed and in the jewelry metals
harder is generally better.

Are there any dangers, such as structural failure, when drilling a
piece of metal numerous times? 

Not unless you remove so much metal that the work loses mechanical
integrity

Which method is better when enlarging a drilled hole: drill again,
using a larger drill bit or using a needle file? 

Depends but usually it is much easier to step drill than file a hole
larger

Does the same drill bit behave differently with different metals
(copper, silver, gold)? 

Yes, in an ideal world you would have different rake and clearance
angles on the drill bit for each metal. But that would require way
too many drill bits so a compromise is used for the cutting angles
and you will see different performance in different metals.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#5
The best method to enlarge drilled holes (it you want to keep the
holes round that is) is by "step drilling" the holes with
increasingly larger drills until you reach the desired holes
diameter. 

All of the thoughts on this thread are true and fine, including the
above. On a more technical level, just FYI - the BEST method to
enlarge holes with precision both in size and concentricity is by
reaming. That can be done either with an official reamer (or broach)
or by using burs at the bench. This just FYI, as most of us can do
fine by using drills most of the time. If you need a perfectly round
hole, though, use a reamer or similar.

http://www.donivanandmaggiora.com


#6
Which method is better when enlarging a drilled hole: drill again,
using a larger drill bit or using a needle file? 

Flame bur, also check out chapter 4 of
"Making the Most of Your Flex-shaft"
http://www.ganoksin.com/item--Orchid-in-Print-Vol-1--flexshaftbook

quite comprehensive on burs and drill bits.

Richard Hart


#7

I have reamers from 0.5mm through to 1" and I have used them all,
although not all on precious metals. I have even made quite a few of
them for one off jobs.

I didn’t mention them because the question really was “just” about
drilling and was quite general in nature, so I chose not to cloud the
issue with terms and that may have been outside the
experience level of the inquirer. I (rightly to my mind) feel that
this should be left to a follow up email (which you have
kindly supplied) so that the is supplied in a logical
progression.

I thank you for supplying the next lesson.

Cheers, Thomas.
Janstrom Designs.


#8
the BEST method to enlarge holes with precision both in size and
concentricity is by reaming. That can be done either with an
official reamer (or broach) or by using burs at the bench. 

Here I go again with my ancient ways, but I suggest that is should
be tried at least once.

Problem with drilling is that drilling is done the best at low
speeds and moderate pressure, almost impossible to achieve with small
diameter drills using flex shaft.

Using reamers is an industrial technique. They are very expensive
and not easily adaptable for jewellery.

Broaches, even cutting variety, are better suited for polishing
inside the hole. They term “cutting” only makes sense from watchmaker
point of view. They do not remove much metal.

The problem was always solved by using jewelers saw with 8.0 blade.
Whatever inaccuracies that may arise out of this approach are
diminishing with practice and easily corrected when bearing is cut.

Leonid Surpin.


#9
The problem was always solved by using jewelers saw with 8.0
blade. Whatever inaccuracies that may arise out of this approach
are diminishing with practice and easily corrected when bearing is
cut. 

After this method a precise ball burr will do the trick. I have the
whole sequential series from 5 mm to.4 mm with a.1mm step difference
for getting holes to the right size (from Fisher). My broach pins are
more rusting away then used; with this precise series no need for
them anymore.

Peter Deckers
New Zealand


#10
I (rightly to my mind) feel that this should be left
to a follow up email (which you have kindly supplied) so that the
is supplied in a logical progression. 

As Thomas points out, the original question was drilling, and the
concept of reaming is the next step beyond that. There’s more info
about drilling than anybody here probably wants to know at various
places: I know http://www.mmsonline.com has a lot, also
http://www.unionbutterfield.com/tech/drills has everything anybody
ever wanted to know about drills and drilling.
http://www.practicalmachinist.com/vb

is a cool place, too. The problem is that your standard twist drill
is a precision tool that rarely gives precision results. There are
forstner bits and bits with carbide inserts and others, but those
are special purpose and usually large size. In order to get a truly
round hole that is to a true size it must be reamed, which is cutting
the hole with teeth - reaming is a process, not really a tool. It can
be done with a reamer or a file- I frequently use round burs. This
whole concept is about precision. You can drill a hole in something
that will do the job just fine. To the casual glance it will look
round, and if that’s enough, it’s enough. If you’re burnish setting
round diamonds, though, you’re going to need more than that.

http://www.donivanandmaggiora.com


#11

Hi Leonid,

Using reamers is an industrial technique. They are very expensive=
and not easily adaptable for jewellery. Broaches, even cutting
variety, are better suited for polishing inside the hole. They term
"cutting" only makes sense from watchmaker point of view. They do
not remove much metal. 

I am a watchmaker and would tend to disagree with both of these
statements. Certainly multi-fluted reamers are industrial and
expensive but a perfectly usable and practical ‘D’ bit reamer can be
made in a few minutes which will open up holes very quickly. Even
quicker if you just want to open up a hole to a known diameter -
rather than making a tapered ‘D’ bit which will open up to any
diameter - is to make a reamer with a sloping face. That is, take a
piece of steel wire the diameter you want the hole to finish up at
and file a long flat on it going from full diameter to maybe 1/4
diameter or whatever size will enter the initial hole. Harden and
temper it and the hole can be opened in no time. A ‘D’ bit, of
course, has the flat filed to exactly half the rod’s diameter for all
of its working length. Watchmaking broaches are made from a steel rod
which is tapered and has 5 flat faces filed along its length equally
spaced around its circumference. They are available commercially in a
wide variety of sizes but can be made quite quickly at home. They
work very well on all soft metals up to, and including, annealed tool
steel and, if used alternately from one side of the hole and then the
other, they will open up a hole very quickly - indeed, the problem is
often in stopping before the hole gets too large!!

Best wishes,
Ian
Ian W. Wright
Sheffield UK


#12
am a watchmaker and would tend to disagree with both of these
statements. Certainly multi-fluted reamers are industrial and
expensive but a perfectly usable and practical 'D' bit reamer can
be made in a few minutes which will open up holes very quickly. 

I am not sure that we disagree on anything, except perhaps on the
best way to enlarge a hole. Given our different fields of endeavor,
it is hardly a surprise.

Leonid Surpin.