colt banner

Author Topic: Uberti short arbor  (Read 111 times)

Offline ssb73q

  • Hero Member
  • *****
  • Posts: 2990
  • Gunsmoke junkie
    • View Profile
Uberti short arbor
« on: June 18, 2019, 09:30:44 AM »
Hi, all recent BP revolvers made by Uberti have a short arbor. All recent Pietta BP revolvers (other than the Paterson) have a correct length arbor. One may ask why a correct length arbor is important? Take a new Uberti revolver and begin hammering in the wedge. Notice that the cylinder to barrel gap changes as the wedge is hammered in. Hammer enough and the gap disappears to where the cylinder is prevented from rotating. If one is interested in reproducible accuracy, the revolver gap must be held fixed. Remove the barrel and reinstall it and you have a new poi compared to the poi before. Also, the gap can change while shooting.

If you are serious about reproducible accuracy, the Uberti short arbor issue must be fixed. One way to do this is send your revolver to Goon's. There are a number of other paths to resolve the short arbor. Some drill a hole in the end of the arbor and insert a Dillon Precision index button. The button is then filed down to produce the desired gap. In the past I have solved this issue by JB Weld a brass button to the end of the arbor and filing down the button to produce the correct gap. A weakness to my past system is that is easy to over file the button. Then one must start over. Another issue is that if I want to increase the gap, I need to start over with a longer button. Of course there are probably another dozen methods to repair a short arbor.

I have recently taken another path. The short arbor end is drilled and tapped to insert a 10-32 set screw. The set screw is turned in to produce the desired gap. The set screw has a blob of nylon on the threads that keeps the screw locked in position. An advantage of the set screw is that the gap can be easily changed if ever desired. One gap for BP and another for smokeless with conversion cylinders. If happy with the gap set, adding a drop of loctite ensures it doesn't move with time. Over the last day I have replaced nine of my epoxy on brass buttons with set screws. I still have another seven Uberti revolvers to do. The photos below is a Uberti 1862 with arbor lengthening set screw attached.

Regards,
Richard
There’s nothing better in the morning than the smell of bacon and black powder smoke!

Offline ShotgunDave

  • Hero Member
  • *****
  • Posts: 680
  • Black Powder Syndicate
    • View Profile
Re: Uberti short arbor
« Reply #1 on: June 18, 2019, 10:32:28 AM »
I do something similar to the brass button method. I use a slice of a steel rod, and solder it to the end of the arbor. Then dress it down with a file for perfect fit.



I know Mike (45 Dragoon) does it the opposite. He puts the button down in the barrel recess and JB Welds it in place.

I like your method, but I can't get past that there is reduced surface area on the mating surfaces, because the set screw is smaller in diameter. I also don't like that the threads of the set screw are eventually going to take a beating, making it hard to get the screw out and possibly damaging the arbor threads. That would make it hard to repair the threads for a new set screw.

I'm positive I'm overthinking it, but it's just easier for me to solder on the button and dress it down. If I ever need to remove it, I just warm the arbor with the torch and it falls off.
"Never trust quotes from the internet"
-Abe Lincoln

Offline ssb73q

  • Hero Member
  • *****
  • Posts: 2990
  • Gunsmoke junkie
    • View Profile
Re: Uberti short arbor
« Reply #2 on: June 23, 2019, 08:12:58 AM »
Hi Dave, a lot of shooting isn't showing any problems using the 10-32 set screw arbor lengthening method. No set screw adjustments have been needed. The force on shooting is to reduce the set screw loading from the wedge being hammered in. The gas pressure on shooting is trying to pull the barrel away from the frame, reducing the loading on the set screw.

The only potential future issue using the set screw is that the area of the arbor end metal has been decreased. Will that prematurely cause the end of the arbor to fail in time? Don't know, but I am monitoring gap to see if there is any change with shooting. None noticed yet.

Fundamentally, I dislike doing any modification to original design. The correct cure for short arbor Uberti's is a correct length arbor. Pietta can get it right. Why can't Uberti?

Regards,
Richard
« Last Edit: June 23, 2019, 08:17:59 AM by ssb73q »
There’s nothing better in the morning than the smell of bacon and black powder smoke!