oct.-round center lines

[wbgv]

I'm getting ready to install the barrel tendons/sights to an oct.to round barrel..how do I find the true centers  on the top and bottoms ??

[RobertS]

I've never actually done this, but read somewhere that you clamp the barrel in a vise, using a level on one of the octagon flats to be sure that the flat is clamed in the vise on the level.  Then using a flat file with a level on the backside of it, to be sure that it is held level, pull it diagonally down the round portion of the barrel, which should strike a straight line down the top center, or bottom center, if you clamed it upside down. Of course, the line only needs to be long enough to mark the portion of the barrel that you need marked.  Again, I've not actually tried this, and may not have told it exactly correct, but you get the idea. Using the level to index the barrel flat and on the back of the level to strike the line on the rounded part ensures they are in the same plane (theoretically).  I hope this will help, and probably some real gunsmith will chime in soon to set the record straight.

[B.Habermehl]

Real easy, Lay a file down on a flat surface. I use my bench. Lay  the barrel top flat or bottom flat down as needed. Draw the barrel across the file using the bench top as  a guide and a file holder. The resulting file mark will be top dead center or bottom dead center depending weather you had the top flat up or down.  BJH

[California Kid]

BH has it right. The only thing I do different is to use a saw table or other machined surface. A glass table top works real well as its flat. The surface has to be as flat as possible to be accurate.

[billd]

Yep,  just did it, worked great. I used my kitchen counter top. Had to cover the bottom side of the file with masking tape so it wouldn't scratch the formica.  You know, the wife thing..........

[wbgv]

thanks..I was scratchin' my head on that one...simple enough !!

[flintriflesmith]

In the time before formica counters or glass table tops ... A period technique for accomplishing the same thing or maintaining uniform (rather than twisted flats) on a hand made octagon barrel relied on what were called in the period "winding sticks."

Two short, 1 to 1.5 foot or so, wooden strips are used in a manner similar to how Robert described using the file and level. Barrel is clamped in a vise. Stick #1 is balanced on the barrel at the reference point, usually the breech. Stick #2 is then balanced on the barrel at the point you want to check. Step back a bit, bend down, and, looking from muzzle to breech, see if the two sticks are parallel. A 18 inch long stick will easily reveal any twist or wind in the barrel--or determine the top dead center of a round section. Files make handy winding sticks!

Cabinet makers used the exact same technique to work the twist out of boards being hand planed.

Gary

[Kermit]

The longer the winding sticks are, the easier it is to see small variations from the parallelism you are after. I have my grandad's which he made up from maple about 36" long, and inlaid little blocks of ebony near the ends of one. The one with the ebony is the far one. Sighting down over the plain one, it's pretty easy to see if any black is showing at the other end. I still use them when I have to flatten stuff that's too wide for the 18" jointer.