turning question

[Jim S]

I am making a muzzleloading fowler and have a barrel that is octagon for about twelve incehs and round the rest of the barrel. My breech plug is 5/8 x 18 and per my calculations requires a 37/64 tap drill. My problem is the bore is off center. When I try to start the hole with a drill, it follows the off-center bore. Any ideas how I can make a 37/64 hole which is centered about 1/2 inch long? I thought about trying to cut an internal hole with a cutter, but tend to start rubbing before the hole develops any depth. Any thoughts would be appreciated.
Thanks,
Jim

[BIGGUNDOCTOR]

If it is that far off center I would do it with a small boring bar. Any type of twist drill will just want to follow the bore. As far as that goes,as long long as I was doing that I might just single point the threads as well. For that shallow of a hole you can use a HSS tool bit blank, and grind a boring bar out of it on a bench grinder. In a pinch I have used endmills as boring bars too.

How off center is it?

Another option would be to put the barrel in a cat's paw to center the bore with the tailstock. A cat's paw is like a 4 jaw chuck that you put on the shaft, and it rides in the steady rest. Or if you have a big enough headstock bore, offset it in a four jaw chuck. I am guessing that it is no more than .030" off center.

[Jim S]

Good idea. I'll make a boring bar out of a lathe bit tomorrow. Part of my problem is my headstock bore is too small. Accordingly, the barrel overhangs the chuck about a foot and the octagon barrel precludes me using a steady rest although I may try same. I can't rell how much offcenter the bore is as I've closed the shop for the night, but I'll check it tomorrow. Thanks for your reply.
Jim

[BIGGUNDOCTOR]

Make a cat's paw for the octagon section. All it is, is a donut with 4 bolts in it that clamp/center the part in it's center. The steady rest rides on the outside of the ring. With this you can turn long odd shaped items. I have seen them made with pipe,bar stock, or any kind of stock found laying around.

[Fe-Wood]

What biggundoc. said... Thats what I would do....

[Jim S]

Thanks guys. I'll make a cats paw.
Jim

[Jim S]

ok I made the cat's paw and cut the bore to the requisite diameter in order to tap the 5/8 x 18 thread. I have cut the thread and now must fit the plug so that it bottoms at both the end of the plug and the tang. This brings me back to file and fit strategies with which I am familiar. Thanks againfor all of your help.
Jim

[BIGGUNDOCTOR]

Glad it worked out for you. Post a pic when it is done.

[Jim S]

Biggundoctor:
That will be a while as I now have a barrel almost fitted for a breech plug, a stock blank which I cut out and a flint lock which needs to be remodelled to fit the size necessary. Then I'll have to forge an iron buttplace and a trigger guard and shape the whole thing. However, if I get it done in my lifetime, I'll attempt to post pictures. Thanks again for your help.
Jim

[BIGGUNDOCTOR]

Awwww, c'mon Jim. Is that all that needs to be done? You can knock that out by the end of next week :D

[Jim S]

Biggundoctor:
I'll try, but don't hold your breath. If it weren't for jobs, wives, and the fact that the last time I forged out a buttplate, it took three tries, I might have a chance. I have a custom flintlock made by Cornell Kemper in the 1970s. Per his son Cornell turned out one muzzleloading rifle per week for years up until his death in the early 2000s
Jim