I have a Green Mountain .38 cal. octagon barrel that needs to be draw filed to remove the milling marks. Any good hints and/or advice? Mori

Use a narrow file, slightly wider or narrower than the width of the flats, and hold it/work it longitudinally, with the long axis of the file parallel with the bore line. A fine mill file or a fine carborundum or coarse India stone all work well, finish with fine India or soft Arkansas and abrasive cloth WITH A BACKER!

Patience and elbow grease, good luck Mori.
Regards, Joe

Well that's one way but that's not draw filling.

Draw filling is done with a plane old flat file smooth or second cut for finish work.

The thicker and heavier the file the better as it will not flex with downward pressure.
Use to thin a file and you will cut an arc or a convex surface as the file flexes around the barrel

you hold the file perpendicular to the axis of the barrels bore with the tang in your left hand and pull it toward you. This gets the teeth going in the correct direction.

Being exactly perpendicular to the bore in not critical.

What is critical is gentle downward pressure but not rolling the file over the corners. Let the file do the majority of the work but you will still have to put some pressure on it.

And card the file once in a while as any material stuck in the teeth with put a groove in the steel.

You will be surprised how nice a finish you can get with even a course file.

KC you're correct, the procedure I described is not draw-filing. Actually, true draw-filing is done with a specially thick wide-bodied file, usually with no handle or with 2 handles, and the true procedure is almost never seen or done today.

The reason I suggested the procedure the way I did is because I'm familiar with the machined finish left on GM octagon barrels and it doesn't require much metal removal at all to end up with a fine finish.

Actually the main danger is rounding the corners, and IMO the main way to do that in a hurry is to hold a long file crossways as you suggest. IMO it's very difficult, almost impossible, to avoid 'crowning' the flats slightly when using a tool wide enough to be able to rock across the work. One instant of less than 110% full attention can mean disaster, that's why I use narrow tools and take no chances of rocking them. Admittedly it's more work but IMO the product is worth it.
Regards, Joe

Hey if it gets the job done that's all that matters.

And yes you're correct it is very difficult to the unpracticed to keep from rounding corners.

I find draw filing simple, easy and fast. Use a single-cut mill bastard file held perpendicular to the bore. Pull the file towards you with light even preasure; if the file doesn't cut, swap ends and try it again, or you can push it away from you if you prefer; it will only cut in one direction, and that's the only direction you want it in contact with the metal--don't slide it back and forth. Card the file often--this is an imperitive as if the file becomes "pinned" it will leave gauges in the surface. Chalk on the file can help prevent "pinning" and make sure there's no oil on the metal or the file before you begin.

If you don't intend to stone or otherwise polish the barrel's surface after filing (some don't), you might find it of great benefit to stone the file's teeth very lightly before beginning. This serves to knock down the tallest spikey teeth and gives a noticably finer & more scratch-free finish than the same file before stoning. This also works well for lathe files.
Regards, Joe

I don't recall where I found this trick for filing octagon barrels, but I've used it and it works. Mount the barrel on a barrel spinner that you'd use to polish round barrels on a wheel. It'll refuse to let you tilt the file to the flats.

Oh, and John Farner's caution about cleaning the file often can't be emphasized enough. I don't take more than 4-5 strokes on each side of the file before cleaning it. That may be overkill, but it's easier than fixing a big, ugly scratch that will happen if you go too long.

quote:

Chalk on the file can help prevent "pinning"

Aye.

Or bee's wax

Barrel spinner; that's a great idea! Beeswax? I'd have thought that would just gum things up and collect chips? Chaulk your file and the chips just fall away.

I have solved the problem of tilting the file, for me at least. I make a "handle" on both ends of the file using some cloth strips covered in tape. Both handles are very close to the same length and diameter. With "balanced" handles on each end, I can maintain a visual balance on the file as I draw it. Another trick I learned years ago is to start with a clean file and rub chalk into the teeth when starting to work and after each cleaning. The chalk helps minimize getting chips of metal stuck in the file teeth. Both of these ideas were passed to me by an old-school metal worker at the Ford Research Center many years ago.

Chaulk 'em up !

Bees Wax ? ?

I've waxed files with Johnson's paste wax to keep chips from sticking. Never tried bee's wax. The Johnson's didn't work any better than chalk. I apply pressure with my thumb on the center of the file supported by the flat and not on the ends where I pull toward me. Never have a tilt problem that way.

quote:

Originally posted by Toomany Tools:
Barrel spinner; that's a great idea! Beeswax? I'd have thought that would just gum things up and collect chips? Chaulk your file and the chips just fall away.

Wax acts like a cutting oil when it warms up but in a cold shop could retain chips. I've never had a problem though. Never used chalk as I don't have any on hand

We also used bees wax on our disk grinders to prevent aluminum from loading up the disk

Bees wax is not just for bees it's a tool makers universal lube

Never tried it but they used to break it with turpentine or some solvent and use as a cutting oil on the lathe and mill when machining aluminum. That recipe is listed right next to Kerosine and whale oil in my 1950's machinist hand book