Uberti 1860 short arbor fix

[ralphlyerly]

I recently purchased an Uberti 1860 .44 open top and it’s overall quality, finish, and action is excellent but for the usual short arbor. In this case, it caused the barrel-cylinder gap to close and action to bind if the wedge was even finger tight. The wedge also bottomed against its retaining screw with thumb pressure.

Larson Pettifogger’s Uberti tuning guide includes a good fix of drilling and tapping the end of the arbor for a set screw but the case hardening was so nice on the arbor that I wanted to try a different solution. A loose washer dropped in the arbor recess works fine but I preferred a more permanent repair.

44D (Mike at Goon’s Gun Works) mentioned putting a fitted steel plug in the arbor recess and this seemed like a good option. I measured the thickness of 2 #10 washers and dropped them into the arbor recess and installed the barrel onto the frame. This created a gap at the joint between the barrel and lower frame because the arbor was now effectively “too long”.

I measured the gap between the barrel and frame using feeler gauges and measured the depth of the arbor recess (with washers removed) using a depth micrometer. The hole bottom is slightly rounded and the center is about 0.016 “ deeper than the edge. I subtracted the gap between lower barrel projection and frame from the thickness of the 2 washers to determine the theoretical thickness of the plug to be installed in the arbor recess. This came out to be about 0.075”.

I just measured the diameter of the arbor recess hole with a set of calipers (not the best way but fine for this purpose) and turned a 1/2” mild steel rod to a diameter about 0.003” smaller than the measured diameter of the hole so that it would be slightly loose and removable. I also tapped a 6-32 hole in the center of the spacer to make installation and removal easy. The last 2 actions were done to be sure that an incorrectly sized plug was not stuck in the arbor hole!

I parted of a spacer about .008 too thick to allow final sizing to fit using sandpaper/emery cloth. The bottom of the spacer protrudes in the center to account for the rounded bottom of the hole, however this isn’t really necessary. The gun was assembled several times sanding the spacer in between and measuring gap between barrel and frame, barrel and cylinder, and wedge fit.

When everything was correct, I measured the thickness of the spacer and considered making a slightly larger diameter spacer of same thickness and shape that would be a press fit in the arbor recess. I ultimately decided to just peen the perimeter of the spacer using an automatic center punch, sand face flat again, degrease parts, and use a small amount of Loctite 640 sleeve retaining compound. The part was then able to be tapped into place with a brass rod and hammer. This was secure but would have allowed the plug to be removed by installing a 6-32 screw in the tapped hole (before the Loctite set) if the final fit was incorrect when the gun was assembled.

My plan involved my small Atlas lathe, however many #8 washers are only a few thousandths larger than the arbor hole. You should be able to fashion a tiny arbor from a screw and a couple of nuts, chuck it in a hand drill or drill press and turn it to proper diameter with emery cloth. You could probably also file the washer to size in a vise. I hope this helps someone.

 

[kh54]

I have neither the tools nor the skill to make anything similar. My solution for all my Ubertis is to use brass washer(s) fixed in place with epoxy. Where one washer was not quite thick enough and two would have been too much I cut a shim or two or three as needed from a soda can then stacked and epoxied them all together.

I admire your fine work and sharing your solution with others!

 

[wiscoaster]

I'm sticking with washers. I just carry a little baggie of spares in my range kit in case they fall out. They do.

But ... if you've got the tools and the skillset, go for it, I suppose.

 

[fishmusic]

I agree with KH45. I don't have access to a lathe but my drill press makes do when I want to alter a washer. I don't have the short arbor issue but did modify a M4 washer to space the trigger/bolt spring so that it lightens the trigger pull.

 

[ralphlyerly]

I used a drill press, file, and emery cloth to turn down many small parts for years before I acquired a lathe.

 

[Smokerr]

I have neither the tools nor the skill to make anything similar. My solution for all my Ubertis is to use brass washer(s) fixed in place with epoxy. Where one washer was not quite thick enough and two would have been too much I cut a shim or two or three as needed from a soda can then stacked and epoxied them all together.
I admire your fine work and sharing your solution with others!

Yea if I get a Colt Walker (the only one I am interested in) the plan would be to check the fit, and do the same.

 

[45D]

Yea if I get a Colt Walker (the only one I am interested in) the plan would be to check the fit, and do the same.

No real need to check, it's short, just figure out your method and fix it.

Mike

 

[Smokerr]

Mike:

Me thinks I need to have some idea of a starting thickness for a shim. Granted I could just put a shim in and see.

But I am also curious and would want to see how bad off it is for a starting point.

None of the issues is intuitive yet, so I like to see.

 

[wiscoaster]

Mike:

Me thinks I need to have some idea of a starting thickness for a shim.

Trial and error worked well for me. No need to get too technical about it.

 

[Smokerr]

I am afraid technical is my default. A lot of years working on stuff that it mattered a lot on. In the end its clear where this goes. But........,

While I found the mfg starting point was usually in the ballpark, it was see what you had, try to understand the principle behind it and then tweak it if need be (some like valve lash there was no question, you set them to mfg spec)

I had some rare stuff that mfg was simply full of it and their stuff did not work at all.

One they gave you a spacing spec, and it did not work at all. Looking at it I thought, hmm, lets try this direction. It worked better and better as I went that way. And it was no where near the spec.

 

[45D]

Mike:

Me thinks I need to have some idea of a starting thickness for a shim. Granted I could just put a shim in and see.

But I am also curious and would want to see how bad off it is for a starting point.

None of the issues is intuitive yet, so I like to see.

I understand what you're saying but in the end, no matter what the "beginning" number is, the end result will be the spacer that "gets the job done". It's funny the methods folks use to get to the same result.
My only suggestion would be start with the head of a #14 pan head sheet metal screw ( #12 for Armys/ Navys) and thin it down till "it works" !!! Can't get much simpler/ quicker than that.

Mike

 

[45D]

I am afraid technical is my default. A lot of years working on stuff that it mattered a lot on. In the end its clear where this goes. But........,

While I found the mfg starting point was usually in the ballpark, it was see what you had, try to understand the principle behind it and then tweak it if need be (some like valve lash there was no question, you set them to mfg spec)

I had some rare stuff that mfg was simply full of it and their stuff did not work at all.

One they gave you a spacing spec, and it did not work at all. Looking at it I thought, hmm, lets try this direction. It worked better and better as I went that way. And it was no where near the spec.

Yup, so taking an unknown spacer thickness and checking the frame/ barrel lug gap ( because the spacer is too thick) will allow a "known" number ( measureed) to close that space down (with wedge in but not in final position of course) 1st step.
That's finding the fulcrum.
-
-
After that, closing down the endshake to your spec will have the element of compression thrown in (wedge). Obviously, thumb pressure won't suffice because it's not enough to end up with a consistent spec. You'll need a good smack with a plastic head machinist hammer. Adjusting the spacer to get your spec will be tedious depending on your number but your wedge slot should stay the same. I, on the other hand, remove material from the end of the arbor (much more control) to get to my .0025" - .003" spec. But, my method opens the width of the wedge slot slightly so the need for a forward bearing for the wedge
becomes necessary ( or I could make a new wedge or buy new wedges). Since I'm not in the wedge making business, an "adjustable" bearing makes things much simpler and gives the end user options.

Mike

 

[Smokerr]

I surely will not argue that, I do want to see the way barrel end interfaces to the frame. In theory that would also give a measurement though I can see it not spot on as its an angle vs a straighter if you shim it some.

I can see the wedge aspect, but it would be one step at a time.

I don't have a drill press so my drilling precision is lacking.

 

[Pete453]

My only suggestion would be start with the head of a #14 pan head sheet metal screw ( #12 for Armys/ Navys) and thin it down till "it works" !!! Can't get much simpler/ quicker than that.

I've done 4 like this, it works like a champ. The bottom of the arbor hole is shaped like the end of a drill bit, so a pan head is self centering. I put them on a snug fitting (Phillips head) screwdriver bit in the cordless and lightly bump them on the running bench grinder. I can knock one out in about 15 minutes and it's good for the life of the revolver.

 

[45D]

I've done 4 like this, it works like a champ. The bottom of the arbor hole is shaped like the end of a drill bit, so a pan head is self centering. I put them on a snug fitting (Phillips head) screwdriver bit in the cordless and lightly bump them on the running bench grinder. I can knock one out in about 15 minutes and it's good for the life of the revolver.

It's definitely an easy way to make an excellent spacer!!!

Mike

 

[prob]

I've done 4 like this, it works like a champ. The bottom of the arbor hole is shaped like the end of a drill bit, so a pan head is self centering. I put them on a snug fitting (Phillips head) screwdriver bit in the cordless and lightly bump them on the running bench grinder. I can knock one out in about 15 minutes and it's good for the life of the revolver.

I couldn’t agree more. The idea to use and take advantage of the self leveling characteristics of the pan head is nothing short of ingenious.

 

[Pete453]

I couldn’t agree more. The idea to use and take advantage of the self leveling characteristics of the pan head is nothing short of ingenious.

It sure is, and I thank Mike for so freely sharing his technique with us. I would have turned a plug to fit. The first one probably wouldn't have been right, I'm sure, it would have taken at least two to get it right. His way nails it first time, every time

 

[M. De Land]

It sure is, and I thank Mike for so freely sharing his technique with us. I would have turned a plug to fit. The first one probably wouldn't have been right, I'm sure, it would have taken at least two to get it right. His way nails it first time, every time

I still lathe turn solid plugs with a hole in the middle for retrieval but Mikes screw head idea works fine and is much easier ,nay essential , if one has no lathe.
I find the correct thickness by first caliper measuring the arbor well perimeter , then using shim stock plugs on an over sized final plug that is gradually shortened to fine tune and driving the wedge in for gap measurements.
The shim stock plugs are when I take to much off the solid plug and need to get back to what is actually needed which means making another final plug. Most times I get it right the first go around but not always.

 

[Secesh]

You would think someone in the loop, importer/manufacturer, would have already discussed this issue and come up with a solution going forward. I do not know since I do not own any of the newer examples.

 

[45D]

You would think someone in the loop, importer/manufacturer, would have already discussed this issue and come up with a solution going forward. I do not know since I do not own any of the newer examples.

Well, Pietta listened and did so a dozen or so years ago. Uberti won't and nobody else did since the start of the reproductions.
Heck, it gives some of us something to do !!! ( along with everything else!!)

Mike