[AT] OT: Cast iron work on a replica cannon

[STEVE ALLEN]

Gentlemen,

I am reporting back on the cannon issue I raised a couple weeks back.

You will remember some of you presented several possible choices for inserts to be used in this application.  I had conversations also with other gun owners.  I spent time on manufacturers' websites.  Based on all of the information gathered, my decision was to approach the situation doing as little change as possible so that, should further repairs become necessary, I can keep the sizes as near original as possible.  

The method I chose as a first step was to go with a Helicoil that made use of the vent plugs/bolts I have been using, 12" - 20.  Going to any other size will necessitate having new bolts drilled for this purpose (remembering that I don't have a drill press capable of such a precise job).

The 1/2" Helicoil requires a 33/64 drill bit, which, given the condition of the worn threads was not much more than smoothing the sides of the hole.  I confess to messing up the first insert. when I knocked off the little tab that the tool uses to put the coil in, I displaced the end of the wire, and threading the plug bolt in resulted in chewing up a few threads on the plug and kinking the wire.  Once we (my son and I) discovered the problem, I simply pulled the distorted coil out and put a new one it.  Before threading the plug into the new insert, I made sure the wire was seated properly.

Proof firing over this past weekend confirms the soundness of the repair:  the insert remains in place, and the vent is well sealed.

Some of you were concerned about the permanence of the Helicoil as a repair in this application.  I am not unmindful of the concern.  The good thing is, if it does prove troublesome in the long run, I appear to have the ability to go up another size in the hole and use a different kind of insert for the same bolt size (1/2" -20).

For now, the repair has taken 8 rounds without any hint of loosening or displacing.  This coming weekend, the gun will be in the field for a battle re-enactment with some two dozen rounds fired.  The next weekend will be another, similar event.  I will be keeping a close eye on the situation.  I am not resting easily, but I am sufficiently confident to take the gun into the field for this extended testing.

I will report again as necessary.

I want to thank everyone again for all the ideas, the suggestions, and the offers of help.  

The "original" Steve Allen