Author Topic: DRILLIN the touch HOLE (Read 2723 times)

Articifer Tom · « **Reply #30 on:** December 10, 2005, 07:14:31 PM »

You don't need the vent liner if you have a solid steel tube or bronze , until the vent hole wears out which is very unlikely in peace time. Most liners now are placed to give a uninterrupted path on lined guns.This prevents the hydraulic separation of the liner at the volatile area of the explosion.This is critical on cast iron lined guns where moisture would also be forced in between to corrode.
The accuracy is not affect by this, but by its location . To far back and you pick foil cause misfires to far forward and powder burns front to back.
I think you did fine on your repair Regular internal inspections with a homemade borescope or impressions will keep you safe .
[PS] Now theirs a topic for discussion!!

kappullen · « **Reply #31 on:** December 12, 2005, 04:30:00 PM »

I have heard old timers say in the shipyard during the war, if they broke a big tap off, they would put a c-4 charge over the hole and shatter the tap.

Well you got her done, but maybe some acid in the hole would loosen things up next time.

Some real machine shops have an elox (electrical discharge machine) machine for burning out broken taps and drills.

That $50 to $100 may be money well spent!

Just a couple of more options.

In any case I aim the touch holes to come out in front of that dratted radius.

Kap

Rickk · « **Reply #32 on:** March 06, 2006, 02:28:08 PM »

I want top thank you for making me terrified of drilling a vent hole. I have a Hern mortar barrel, and after reading this thread I rememberd that I have been letting three guys hunt out back for years that own a machine shop with an EDM machine. I cashed in the favor for a vent hole, and it came out really nice.

If you drill straight into the dimple cast into the Hern barrel you will be about .75 from the welded breech. My estimates are that it would take at least a 2 ounce charge to position the powder bag under the hole if drilled straight in.

I elected to have them angle it so that it came out at .40 from the breezh plate. The hole is .20 diameter. With such an angle, it will puncture a bag no matter how small the charge.

To set the EDM machin up, they clamped a bore sized (2.25) rod into the machine and positioned it to point .40 from the end of the rod. They then slid the barrel over the rod and checked to see if it was pointed at the cast in dimple. If it was not, they readjusted and tried again. After a while it both pointed at the dimple and also at the proper part of the 2.25 inch rod.

It worked out perfect.

So, I have to vented barrel, the hardware kit, about 100# of suitable dried white oak that i got from the lumber mill down the street for $40.

I even got a do-it mold and made myself a dozen nice lookin 2.11 inch 2# lead balls just to see what they would look like. ... quite a different experience from casting for my 44 mag - need to make a 3# ladle for the next casting session.

Just gotta find the time to sand, whittle, plane, cut, paint, and finish the concrete powder magazine out back and I'll be in business....

My goal is to be firing blanks by the 4th of July.

Artilleryman · « **Reply #33 on:** March 06, 2006, 03:48:57 PM »

Rickk, I am assuming that your Hern tube is lined, but you did not say anything about lining your vent hole. A couple of posts back there is one from Articifer Tom that is very good advice. If corrison occurs in the vent between the liner and the outer part of the gun tube it becomes a place where a spark can be held that might cause a premature discharge.