One of my most valuable lessons was filing
I’ve had it in mind towrite something - just because I love to
write, because buying files has been covered but not really what to
do with them once you buy them, and who knows? Maybe it will draw
attention away from that other embarrassment.
So, you pick up a piece of metal, you pick up a file and you push
the file against the work a couple of times. What you get from doing
that is a facet. A flat spot filed onto the work. There may be times
when that’s not exactly accurate, but bear with me. The size, shape
and placement of that facet tells you everything you need to know
about what you are doing, so pay attention to it. This is key.
Take a billiard ball or some fairly perfect sphere, and we’ll file a
flat spot on it for some purpose, and here and now I’ll disregard
things about workholding. Youcan draw any line you want through a
sphere - infinitely. From any given point on the surface there is
one and only one line that goes through thecenter, though. We don’t
just want a flat spot, we want one that’s square to the sphere,
which means it’s centered. What does this mean? It means that if you
file perfectly within those parameters your facet will bea perfect
circle, and this is why you need to pay attention to it. If it’s not
square to the sphere, it will be some sort of oval, and that oval
tells you a great deal. The rounded end of the oval will be the high
side, the tapered end will be the low side and in between shows you
the direction between the high and low.
See? File down the high side in the same direction, it will “flatten
out” and gradually you can get your perfect circle. This rather
simple idea applies to any time you are filing a flat onto a sphere
or dome. File a flat onto a domed ringtop and it likely won’t be a
perfect circle but you can use the same methods to analyze your
progress. It SHOULD be at least a regular oval and if it’s not then
you can tell the high from the low and the left from the right. Or
maybe the ring is just crooked, which is different.
Next, take a pipe cut band - just a ring made with a rectangular or
square cross section - and we want to make it a domed band, like 1/2
round wire. You may think that you just start whaling away at it but
that’s how you get lousy work. There’s a system - use and watch your
facets. I’ll assumethat your band is either rolled metal or lathe
turned - a precision band to begin with. Put your ring on the bench
pin so the circle is facing youand file across the upper
corner/edge, making a bevel. You want to leave some edge to the ring
at the hole so it’s not sharp, and the other side of the bevel is a
little arbitrary but you’re looking at about 45 degrees, most
likely. That’s a facet. Do that again and again all around the ring
and what you should have is a bevel all around, removing that corner
edge. What you have now (should) is something that establishes the
edge of the ring, by the hole, all around, and another edge into the
top of the ring that’s also equal and even all around. In reality you
would do theother side of the ring too, of course. Next, do it again
but this time your bevel is on the upper line you just made. Same
thing - a “straight”, arced line on the top and the bottom of your
filing. A clean, defined, regular bevel that bisects the one you did
the first time. At this point your ring is pretty much domed with
great precision and it’s the same work as any other method, it’s
just methodical. Your beveling removed the metal in a regular,
controlled way and watching the faceting makes it so, automatically.
Somewhere in here you just go over all the junctures and make it
truly rounded and there you have it. Done well it should be
indistinguishable from a lathe turned band.
Lastly, we have a flat surface we want to lower by a couple of mm or
whatever. We’ll say it’s hard wax so it’s not such a huge job.
Again, you don’t just whale away at it and hope for the best.
Measure from the bottom (so it’s square, in the end) and scribe a
line all around with dividers. You COULD just file the top down to
that, and sometimes that’s easy enough, but there’s another way. Get
your file and do the same thing as on the ring - file a bevel on the
top edge, almost to the lines but leaving them for reference. Now
you filethe top and watch those facets on the bevels. Big facets on
one side and small on the other means your filing is tilted that
way, and adjust accordingly. In the end you should be able to just
watch everything lower evenly, using your bevels as a visual aid,
until it is flat and straight. Just some generic examples and I hope
this is understandable. I started writing this yesterday and just
couldn’t write it clearly. I hope you all can grasp that there’s a
principle behind this. Use your file markings to guide you for what
comes next, pay attention to those facets.