Author Topic: finding center of octagon to round barrel  (Read 1938 times)

Offline yip

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finding center of octagon to round barrel
« on: February 20, 2018, 01:34:28 AM »
 building a fowler and planning on soldering underlugs, whats the best way on finding center of underneath barrel?

Offline Sawfiler

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Re: finding center of octagon to round barrel
« Reply #1 on: February 20, 2018, 01:41:23 AM »
Clamp upside down in a vise and holding a file perfectly horizontal pull towards you. You can site something in the distance to be sure the file is level such as a masonry mortar joint or a cabinet. What you are left with is a perfect line on the bottom dead center of your barrel.
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Offline elk killer

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Re: finding center of octagon to round barrel
« Reply #2 on: February 20, 2018, 02:12:54 AM »
Put the file flat on the bench table or floor, hold the barrel flat and slide it along the file, either way works
only flintlocks remain interesting..

Offline 45-110

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Re: finding center of octagon to round barrel
« Reply #3 on: February 20, 2018, 04:02:55 PM »
here is a little gizmo i frequently use to find center on any thing round when i am not worried about .001" either way. this little tool is a dandy ...............and cheap!
Grizzly H2940 - Round Bar Center Finder

Offline Eric Krewson

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Re: finding center of octagon to round barrel
« Reply #4 on: February 20, 2018, 04:58:39 PM »
I put a three corner file on my table, put the barrel on a flat and drag the barrel across the file, it leaves a light mark that is easily sanded off.

If you look closely you can see the center line. I use a C clamp to hold the lug, solder paste to put it on. After I get it clamped in place it is always just a little off, with the C clamp holding the lug I can tap it a little one way or another to line it up correctly with the center line before I heat it.

« Last Edit: February 20, 2018, 05:03:02 PM by Eric Krewson »

Offline D. Taylor Sapergia

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Re: finding center of octagon to round barrel
« Reply #5 on: February 20, 2018, 10:41:11 PM »
I clamp the barrel in a machinist's vise, using a short level on the flats to make sure it is perfectly square with the world.  Then I place my single cut mill bastard draw filing file on the round barrel, and the level on top of that.  When the file is dead level, I slowly pull the file lengthwise and scratch a line with the file.  It is dead centre on the round section of the barrel.
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Offline longcruise

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Re: finding center of octagon to round barrel
« Reply #6 on: February 20, 2018, 11:13:57 PM »
I've never done this, but here's what I'd do.

Put the barrel in the vise and measure to find exact center of the bottom flat at the breech and just before the transition to round and mark it with a fine tip marker pen.  Clamp a string at the breech end center mark then draw it taut to the muzzle and clamp it so the string intersects The forward mark. That should leave the string marking bottom dead center.

Mike Lee

Offline Bob Roller

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Re: finding center of octagon to round barrel
« Reply #7 on: February 20, 2018, 11:18:55 PM »
I have a top center gauge that combines a level and a center punch.
Goy it from Frank Mittermeier in NYC about 50 years ago and have used
it a lot.

Bob Roller