Cavity size and twisted horns

[Elnathan]

I got a couple of nicely twisted horns that need to be drilled for the spout. Is there a particular trick to figuring out where the cavity ends with horns? I've had good success in the past with just sticking a piece of wire in the inside, marking the length with my thumb, and laying along the outside, but with a compound curve to deal with I'm getting readings that vary a bit more than I'm happy with - hard to tell exactly where I should aim the drill.

They are nice horns, and I'd hate to drill through the side of one of them. How do the pros do it?

[Nate McKenzie]

Instead of wire, I use chair caning material in the same way.  Force it in rather hard and it will take the outside curve and give you a more accurate measurement.

[Gun Butcher]

Outside curve is the way I do it also. I just use wire but I crank on it hard to enough to get it hugging the outside curve.

Ron

[Elnathan]

Oh, I bend the wire to follow the curve of the horn. It just that it isn't quite as accurate as I'd prefer, and I was wondering if there was a radically different method.

[Jerry V Lape]

Sometime a really bright flash light shined inside will give you a shadow where it become solid. 

[Longshot]

Similar to Jerry's suggestion, I've also found that stuffing a short strand of small, clear, Christmas lights into the horn will usually tell you what you need to know.

[Cory Joe Stewart]

The other thing to keep in mind is not just the cavity, but the angle you cut the tip at.  Cut it so that it will assist the drill bit in going towards the cavity.  Once I figured this trick out, I drill through a lot fewer horns.

Cory Joe Stewart

[Tim Crosby]

 Some horns are a Lot easer to drill than others. I try and cut so I have the shortest distance possible to drill. Can you post pix of the horns.

  Tim C.

[Robby]

When I have a particularly nice curve at the muzzle of the horn that I want to keep, i drill in a short distance and burn my way through the rest of the way. The tool is 1/4" diameter Stainless steel, but any steel will work. The curve on the rod can be adjusted to suit the horn. Its a smelly business  and best done when there is a little breeze in the air. It can take many reheating's of the rod so be patient.



Robby

[John Proud]

I use a wire but measure twice. Once on the outside curve and a second time about 180 degrees opposite where you took the first measurement. Both are marked with the result that you get two marks with a space between them. Some times a small space and some times, large. Mark half way between these two and in my experience that is where the solid starts. I usually cut the horn 1 to 1&1/4 inches past that. Rarely have a problem with this method. Maybe 1 in 50 horns. Then I resort to a a drill bit a found years ago. Brad point, 1/4" dia, about 6 inches long with the cutting flute only about 1/4 inch long. Behind the cutting "head" the shaft is reduced to about 3/16 inch. This allows the drill bit to be turned at an angle as you drill the hole.