Question about Arbors

Thumb Buster · November 14, 2015, 12:34:38 PM

I've always had a mind to ask this question about arbors but then fail to do so. $:-\$ On top of the arbors on all my cap guns and right where the cylinder face is there's a notch cut into the arbor. No burrs appear to be visible on the inside of the cylinder itself. I attribute this to my loading 'on-the-gun' as this seems to be the logical spot the cylinder would lean, if any, during the ramming of the ball. There seems to be no substantial wobble on the cylinders and that is what puzzles me. This does not effect the shooting or add fouling at all. Is this normal for a 'on-the-gun' loader or something else? Is this a major concern that can lead to a failure on down the road?

Lefty Dude · November 14, 2015, 12:44:32 PM

Normal, it is gas cutting of the BP fire. It gets rather hot at that location.

Thumb Buster · November 14, 2015, 12:48:22 PM

Thanks for the reply LD. Didn't consider that.

Noz · November 14, 2015, 04:53:38 PM

Lefty is correct.

Coffinmaker · November 15, 2015, 01:48:09 PM

NOT!!! Nanny Nanny POO POO!!
Znot flame cutting. That little "notch" if you will, is there from the factory and is deliberately cut in the Arbor. The flame or gas blow-by if you will, is either hot enough nor high velocity enough to produce that notch. If it were, it would eventually cut the Arbor completely in half.

What is it for??? I honestly don't have a clue. Maybe the engineers who built the things should hazard a WAG (Military acronym for "Wild A$$ Guess). It will, however, hold a large amount of sponge (carbon fouling) fight in front of the cylinder. It does not prevent the sponge from creeping up the Arbor under the cylinder at all. Nor does it prevent the sponge from deflecting into the Arbor bore in the barrel lug.
It is, however, inconsequential. SO:

THUMB BUSTER, When your loading "on the gun" the cylinder doesn't lean. Unless the cylinder and Arbor are badly worn. It is .... Normal (a setting on a clothes dryer) and is of no concern. Other than making you go Hum.... when you look at it, it is of no concern at all.

Coffinmaker

Johnson Barr · November 15, 2015, 02:05:46 PM

I find that groove to be a Pietta standard. Probably has more to do with the 'Gorilla' that hammers the barrel wedge into a bind between arbor, barrel and cylinder. But that's my thought after having corrected barrel to frame, frame to arbor alignment issues with 'hammered in' wedges.

Thumb Buster · November 15, 2015, 02:23:55 PM

Coffinmaker, my speculation on the cylinder leaning didn't seem feasible to me but I had to ask, and I sure as heck never thought to look for that notch when I first got the revolvers. Now I will. Whatever the reason for its existence is you and the others have answered my main question. (Experience has told me just the use of the word 'engineer' is sometimes enough explanation for anything.) T'aint nuthin' to bother 'bout...and that was my main concern. Thank y' all. As for that gorilla...I've run into his handiwork also.

Noz · November 15, 2015, 04:05:12 PM

Flame cutting is a reality. I saw this on my 41 mags in my previous life.

hellgate · November 15, 2015, 04:20:11 PM

The more a gun is shot the deeper and slightly wider the notch gets but the rate of enlargement slows as the shooting continues. I use the size of the gas cutting to tell me just how much the gun has been shot by the previous owner. No notch: barely shot if at all. There isn't one on a new gun. I've never had the gas cutting get deep enough to become significant; it's just an indicator or usage. If you look at a Remington you will see a little cutting on the top strap as well as the cylinder pin.

Lefty Dude · November 15, 2015, 06:46:30 PM

Funny thing, all my new pietta's do not show the fire ring. Only after they have been shot several times will the cutting appear. The new arbors are as clean as a can be on the cylinder face end.

Coffinmaker · November 15, 2015, 07:34:16 PM

Awright Awready!!
I just hadda know. 'Cause I admit, I haven't paid much attention to it. Didn't matter. So:..............
I went down and pulled every Cap Gun I own out of the safe. Inspected every Arbor. From my "Just Barely Shot" right thru my "Go-To"
guns that get shot most every weekend. They all have that little "mark" on the Arbor right where the front edge of the cylinder hits. On 'MY' guns, it starts as a tiny little shiny spot. Then, as the amount of shooting increases, the little spot gets darker, a little thicker and a little wider and darker. With the unbelievably accurate "Thumbnail Test," I only find a little roughness. No Groove. No doubt the roughness and color change is a result of firing. I did not find any actual "depth."

Noz,
Agreed. I had many guns come into the shop for various work and some of them showed a amazing amount of flame cutting in the Top Strap. All were "high pressure" guns. 41 Mag, 44 Mag and surprisingly, a lot of Ruger 45 Colt guns that were reloaded to 44 Mag and Beyond pressure. No dispute, Flame Cutting is a reality.

Although. Our Cap Guns do not have gas rings that rotate to disperse the effects of gun gas behind the bullet. The Arbor is rigid and can't move out of the way. Yet, I personally haven not seen evidence of actual "cutting." Discolored yes but not cut. those that have a lot more years on their Cap Guns than I do, may have a better handle. It is still a non-issue.

Coffinmaker

Lefty Dude · November 15, 2015, 07:44:01 PM

Now that we have that issue put to bed, Lets do what cowboy shooters do best. Lets all go SHOOT !

will52100 · November 16, 2015, 04:43:49 AM

First time I noticed flame cutting was on a Uberti Walker. I had two guns, one was giving me fits. The one that was giving me issues wouldn't go a full cylinder full without binding, no mater what I did. On the walkers arbor there is a step down rite in front of the cylinder. The one that was giving me fits I noticed a shallow notch forming. Turns out the step down on that walker was a little further forward past the cylinder than the one that worked fine. The flame cutting showed the path of the gas. A little work with needle files and it'd run with the other one without binding up. This was with full 60 grain charges of 3F black powder.

I've seen notches on just about everyone of my cap gun's arbors, less on newer, more on older. I've seen less cutting on my 2nd gen colt, but then it hasn't been shot as much and may have better case hardening than the clones.

Cutting does occur, just depends on the powder charge, amount it's been shot and how tight the cylinder gap is. I have found that after a while it doesn't seem to get any worse. A slow burning powder will flame cut more than a fast powder, you con't get much slower than black powder for burn rates. Not to mention black powder has a lot of solids in it that are abrasive and not consumed by the flame.

Flint · November 17, 2015, 04:12:02 PM

To add to this overdone debate, look for flame cutting in the top strap of full framed guns, Remington, Ruger, Colt SAA etc.... it's there. Many revolvers are factory cut in the top strap to relieve the flame cutting by giving the cylinder gap flash more space to dissipate.

will52100 · November 20, 2015, 11:09:34 PM

Didn't know that about some having a relief cut, makes sense though.