When I need to drill holes at an odd angle (into stone or an immovable object)
I have made a drill guide in hard wood or composite such as worktop laminate. I
clamp the laminate firrmly at the required angle on my drill press and drill a
hole in it. To start a hole at a shallow angle, you can use a centre drill or
countersink at 90 degrees just to break into the surface, then set up the
correct angle. The hole must be a clearance hole for the stone drill. If the
drill has a narrower shank than its tip you could make a through hole big
enough for the shank and a shallow concentric hole just deep enough to take the
tip (I haven't actually done this as I use old metal drills rather than masonry
drills, but I think it would work). I mark the surface with two lines crossing
at the centre of the hole, one being horizontal while in the drill press, so it
is at right angles to the hole. I continue these lines onto the sides of the
laminate so I can see them when it is turned upside down.
I mark the stone with two corresponding lines, crossing where I want the hole,
in-line and at 90 degrees to the hole axis.
Then insert the drill bit in the hole in the laminate, transfer the laminate
to the stone, face down, clamp it so the lines correspond, and attach the drill
chuck to the bit (I'm not sure if you need to support the weight of the drill,
but it would seem sensible). Depending on the accuracy and depth needed, you
may need to drill as far as you can with the laminate in place, then remove the
laminate and use that hole as a guide for the rest of it.
Something I'm planning to do but haven't yet done, to secure a sculpture to its
plinth, is to drill two or more holes at different angles into both. A deep
hole in the dial, shallower in the plinth. Then, stainless steel pins could be
put in the deep holes, the sculpture/dial moved to the correct position, the
pins should drop down into the shallow holes and hold the dial. The only way to
get it off would be to turn the whole thing upside down. To drill the holes,
I'd make two jigs by clamping two pieces of laminate and drilling right through
them at skew angles. Has anyone tried this? Glue would be simpler but too
permanent for the sculpture I have in mind. I used a similar method to hold the
gnomon of the dial I showed at the BSS Exeter conference last year.
Chris
51.4N, 1.3W
----- Original Message -----
From: Alexei Pace
To: Frank King
Cc: sundial@uni-koeln.de
Sent: Monday, June 13, 2011 9:10 AM
Subject: Re: Multignomon Sundial
Good morning,
the only time I need to drill holes at an angle was through wood.
That can be done with a common drill press (ie still having the drill point
vertically downwards), however you angle upwards the material to drill into at
the appropriate angle. Also it has to be secured properly otherwise the drill
bit tends to 'slip' especially at very shallow angles.
Best regards
Alex
On Mon, Jun 13, 2011 at 10:00 AM, Frank King <frank.k...@cl.cam.ac.uk> wrote:
Dear Hannes,
Your problem is turning into a bed of nails...
> ...the dial I had in mind would be vertical
> and facing south-east...
That makes the problem more interesting!
> ... I can see no way, with my limited abilities,
> to get the angles of all those gnomons right.
> Any ideas?
I imagine that all your gnomons are going to be
the same. If you can get ONE right you can get
all the others right! Here are two questions:
What kind of gnomon you would use if you were
making a conventional dial with ONE gnomon?
How would you would attach it to the dial?
You seem to want some kind of rod gnomon. You
can attach that either by drilling a hole or by
making up some kind of mounting.
It is very difficult to drill a hole that isn't
perpendicular to the surface being drilled. It
is probably easier to make some kind of mounting.
You calculate the sub-style height in the usual
way and then design a simple mount. You then
go into mass production.
All the gnomons have to point in the same direction
so you have to have the sub-styles parallel.
There is one interesting constraint that you
DON'T have...
Your hour-lines don't have to radiate from the
same point. You could arrange your sundial on
a tall thin column with the hour-lines running
down, in order, from top to bottom, say from
4h to 14h for a dial that declines south-east.
More interesting still, you could have a
24-sided post with the 6h hour-line on the
side that faces east and the 12h hour line
on the side that faces south and so on.
I have a final piece of advice...
If you really want to drill lots of holes
at awkward angles you are going to need
some kind of jig. I cannot think of a
good way to design this jig but I am sure
there are other list members who can help.
All the best
Frank King
Cambridge, UK
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