Bacon fat or lard is better. If you use milk then clean everything
nearby as soon as you have finished, milk splashes stain and rust steel
Use a very sharp (or roll-form) tap, and some arrangement to keep the
tap vertical is almost essential - a drill press or the like will do at
a pinch. Without some such arrangement it is very difficult to tap
copper, even a slight misalignment from vertical will cause the tap to
When (dry-) turning or drilling copper I find high speed helps, but
that's a bit impractical when tapping.
As with all tapping, a slightly oversize hole will make life much easier.
As to taps, carbon taps are plenty sharp and hard-wearing enough, but
HSS taps are tougher and break less easily - and toughness counts,
especially if you are hand tapping and aren't using a tapping machine or
drill stand etc. to keep the tap absolutely vertical.
-- Peter Fairbrother
Use a brand new, scary sharp tap. Use cream (I have used the little
coffee creamer packs, not the non-dairy abonations) for tapping fluid.
Animal fats are supposed to work, but I have not tried them. Bacon fat
If you can get at a tapping machine, so much the better. I found that
running the tap fast, helped.
I did a series of 5/16", and 3/8" holes in some buss bars for a large
radio installation grounding assembly. The first two holes destroyed a
couple taps, and the holes. Once we got the tapping machine set up, the
rest of a couple hundred holes, only took a few minutes, and turned out
Try a test hole or two, on a scrap or cut-off.
I'd suggest drilling the holes on the large side of the scale. Not
like you are relying on the threads to hold up any structure, so you can
afford to be pretty generous with the drill size.
No brazing equipment, I'm afraid.
Here's a split-in-half 360 degree panorama
of my workshop:
Normally, my metalwork takes place
on a workmate that sits where the tripod
was to take that shot.
My metal work is very much of the hacksaw,
file, tap-die style.
Actually quite a lot of my metalwork is simply
tool restoration, so wire brushes, steel wool, Solvol
Autosol and wet 'n' dry feature heavily too.
If you just want some "pips" to locate things why not use say 1/8"
copper snap head rivits, no need to form proper heads on the reverse,
just a shallow CSK hole and a punch in the center to spread the end.
Obviously no tapping needed just a hole.
O.K. the job is done.
In my woodwork cum tool restoring shop:
I marked out the position of the holes
(sheet of glass, surface gauge, dividers, fat permanent
marker as substitute for layout blue)
Following my previous difficulties locating
a hole accurately in some soft material
I didn't dot punch; given that I was planning
to use 4BA threads (around 1/8", but a fine thread)
I was using a 3mm drill, as per Zeus chart.
I drilled a 3mm hole in a piece of scrap mild steel,
and clamped the piece of scrap in place, this
faking a drilling bush.
I then used a hand drill (Stanley #803)
to make a substantial start to the hole.
Having "marked" all the holes in this way,
I changed to using a drill stand to get the
(no drill press, I'm afraid) with my Bosch drill. Typical DIY
drill, hammer action, multi speed, reversible jobby.
Having made the thorough holes, it was time
to tap. A second hand Presto carbon steel
4BA taper tap (very long taper) was fixed in a
Millers Falls hand vise
The jaws in this have a vertical 'v' groove,
and the handle can be replaced with a brace adapter.
I held the vise in a very small brace (5 inch sweep).
This arrangement allows very good directional accuracy,
since the assembly is around 16" long from tap to handle.
The only problem is that even a tiny brace can generate
a lot of torque.
I therefore only used this arrangement to start each thread,
around 3-4 turns (in the hallowed 3/4 turn forward,
1/2 turn back method).
The recommended bovine lubrication was used :-)
I then put the tap in a small 'T' holder,
and finished each thread.
The tap was regularly extracted (tedious!) and cleaned
of chips using a small brass brush (actually
a sueded cleaning brush).
Bottom line - I had no trouble, and now have 8 nicely
tapped holes, populated by 8 4BA studs, and the copper
plate sits on my hob nice in a stable and safe fashion.
Thanks to all for your help.
On or around Thu, 15 May 2008 12:10:38 +0100, bugbear
how does it work? I might do one for here. Got one of the ones that
someone recommended, it's better than the ones I had but still plated steel
and will eventually rust just the same, although it seems to work quite
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
I have now; made a soup last night, in a largish
(6-8 pint, I guess) aluminium Tefal pan.
The simmering was gloriously even over the entire
area of the copper, so I guess it's working as designed.
I was slightly disappointed that the simmering
was quite fast; it appears that the cheap
diffuser also sheds some heat somewhere other
than the pan, since (from memory) the simmering
on the aluminium diffuser was slower (but
I was using my hob's smallest burner,
at minimum level.
I suspect that the copper plate
will perform its anticipated task
of avoiding food burning rather well.
Final comment, again from the cooking side.
Since the plate is (fairly) flat, the bottom
of your saucepan needs also be (fairly) flat,
otherwise you won't get the heat from the plate
to the pan.
This is a restriction/requirment which Aga
users are already familiar with, but it
can put the price of the pan up a little.
When I was an apprentice electrical fitter in the '60's I had to make
hundreds of copper contacts and I was told kerosene was the correct
cutting fluid when tapping threads in copper . It worked for me.
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