GMM wrote:
I need to send a (network, not power!) cable through a door frame.
The plan is to go through the plaster beside the frame (a couple of
inches before an adjoining door), at a bit of an angle to come out on
the edge of the architrave on the other side. The total depth of this
hole will be 200 - 250mm (well, 8 - 10 inches anyway) and most of it
will be through timber.
Soooooo....I was trying to find a drill long enough to get through
that lot. Plenty of masonry jobbies to be had, SDS or not, but
they're not very good on timber. The only things I can find are
extended flat bits (which might be tricky to get going at the angle I
need) and augur bits, which might be fine but really should be in a
brace and a) I haven't got one and b) I couldn't turn a brace in that
position.

Why doesn't anyone sell a standard HSS/spur/multipurpose bit this kind
of length? More importantly, what's the right way to do this?

One way or another, find an engineers supply store and ask for a long
series twist drill, of the dimeter you need. You didn't mention what
diam. hole you want to drill. The smaller the hole, the shorter the
twist drill. A 3/8ths. inch long series drill will be about 12 inches long.

I am not all that clear as to where the start and end of the hole will be.

1. Start of the hole will be a couple of inches away from the woodwork
of a door frame. The end of the hole will be at the edge of the woodwork
of the (same?) door frame.

2. Start of the hole will be a couple of inches away from the woodwork
of a door frame. The end of the hole will come through the woodwork of
the (same?) door frame.

Either way, you will have to start drilling from the end of the hole
described above and come through the plaster about 2 inches away from
the door, to the start of the hole, as described above. I hope you
understand that.

To find out what sort of angle to drill the hole to in respect of the
end to start point. Lay the twist drill on some stiff card that marks
both door edges and the couple of inches away from the door and measure
the angle and if you have one, set a protracter to that angle and use it
as a guide when looking down on it.

HTH

Dave