Buttoning up the open tops

This refers to the addition of a button on the nose of the cylinder and barrel mount arbor on the Colt open top style revolvers. As some or most of you may know a few of the brands seem to take pride in missing the boat on how the arbor is supposed to fit on these guns. And that leaves it up to us to correct this oversight to make it easier to reliably and accurately strip the guns and re-assemble them.

I've done a few before for myself and just muddled through since it seemed like I would not be doing this on a regular basis. But in a weak moment I offered to do a couple of Uberti 1871 conversions for a fellow cowboy shooter. And today was the day I did the work.

I was looking at doing a couple of them and figured that since I'd done a few already and likely would do a few more over the coming years that it was time to get properly set up for this sort of job. So a couple of hours later I'd come up with the goodies in the first picture.

What you're seeing is a special small C clamp that uses an 8-32 screw to clamp the buttons in place for soldering. The taller cylinder has a stepped hole in the top to hold the buttons for the size of the arbor on this gun. This is used to seat the buttons and hold them while filing down the nose to adjust the barrel gap. I'll see how well this works for future sizes. I might have to do up something a trifle more adjustable or just make them up and label the sizes. the bit of angle holds the button in alignment while I clamp it. The coin like thing with the cross hatching is the button about to be soldered to the nose of the arbor in the picture. The cross hatching was filed in shallowly with a triangle file to aid in getting the solder to flow more readily. This is shown in a close up of the back side of the button in the second picture. The button stock is turned in the lathe and sized to match the arbor then the nose shaped and the back side parted off.

The next picture shows how the angle and clamp are used. And the last one is setup and just about to reach for the propane torch.

The solder used is a soft basic old 60-40 electronics solder. But I use a really good separate flux that I know works well with steel and does a bang up job with copper.....unlike most of the useless stuff sold in the plumbing sections at the hardware stores these days I might add.

The button is shaped with a flat point truncated cone shape where the flat nose is about 1/8" diameter and the angle of the cone is a little sharper than the point of a twist drill. So the contact point of the button is the circumference of the flat nose. The button is cut off a touch long and the flat point filed further down and bigger in diameter until the "dry fit" of the button in the gun results in the cylinder gap being correct. The wedge is deliberately driven in slightly harder than normal to ensure that the button is in contact and it's not simply sprung. You can pretty clearly see this shape in the third picture with the clamping screw sitting against the flat nose of this button.

When the button fit is correct I solder it on as seen in the pictures. Afterwards any solder is dressed off with a dull file. Why dull you ask? That's because the arbor is heat treated and I don't want to ruin yet ANOTHER file finding out just HOW hard it is. And we're only cutting off any blobs of solder after all.

In the case of both of these guns the wedges proved to be a few thou too wide after the button work. So those were lightly ground off and re-blued to seat to the correct depth. The final gap being set close to .006. One came in at a "tight" .006 and the other a perfect .005.

Hope this helps someone out.

When the guns are set up so the wedge is a locking device and not a gap setting adjustment device the guns are a lot easier to work with. And I can't help but think that they'll last longer too by removing the spring inherent in the improper fit.

By the way, if you don't have a lathe you can fake it with a hand drill and a thick washer. Use a small counter sunk head screw and nut to pinch the washer. The counter sunk head will hold it centered. Then use a file to dress down the diameter until it is just fits into the arbor hole in the barrel. Careful work will ensure it's "round enough". Then test fit it and if it's out mount it up on the screw again and turn an angled shoulder. Then dry fit again.

Keep going until the cylinder gap is spot on with the wedge bumped firmly into place.

Because it's very near the proper size you can use this same bit of angle iron trick to line it up and even clamp it in place with some wire and leave it there while soldering. Just at the end when the solder is still liquid be sure to use something to firmly push the washer against the end of the arbor for a nice thin joint. After it's cool file away any lumps of solder and any steel from the washer that sticks out past the diameter of the arbor.

That's certainly a method that would work.

The arbors on these two guns tended to make the file used to dress down the solder joint and any few thou of overhanging steel skid off their hardened surface though. I'm not sure how successful drilling the arbors IN THIS CASE would be. On my cap and ball guns the arbors were not hardened though. Or at least not to the extent of these guns.

For drilling a suitable washer of the same outer size as the arbor then whatever drill fits the hole would work well to spot the end in a centrallized manner.

That's if you want to use a Dillon button. But it's a lot more work and doesn't ensure the central positioning unless care is taken with the hole.

Jbar, the only thing I'll add to your otherwise great post is to clear up that for the centering drill marking you want to extend the quill first then grip the arbor or clamp the frame in the drill vise. That way the quill retracts and gives room for the centering drill without the need to lower the table and lose the "registration" of the arbor with the quill center line. I'm sure you meant that to be clear but perhaps it needs mentioning for a few of the folks.

But yeah, that's a NICE way to do a neatly centered pilot hole in the arbor if the drill and Dillon pin method is used.

In a perfect world I like the idea of the two flat surfaces. The idea of the truncated cone with flat nose providing a ring of contact is not bad. But it's certainly a second best to the idea of flat to flat with the greater contact area.

One thing for sure though. Regardless of if it's Mike's method with a shim glued into the end of the barrel's stub bore or a shim soldered to the end of the arbor. Being attached securely hands down beats an unattached "drop in place" shim which flies out and runs for freedom every time the gun is taken apart.

When I get some time in a day or two I'm going to play around with options for making and adjusting buttons for the solder method that doesn't require a metal lathe or drill press to produce.

It's nice for me with the shop at my fingertips but I'm sure there's lots of you without such equipment that would like to fix your own guns if it can be done fairly simply but accurately with simple tools.

I'd thought about the screw as well but I agree with Mike on the lack of seating area with a set screw nose.

If the arbor was shorted a touch, about 1/32" or 1.5mm would do it, then a round head screw could have the head turned to match the shape of the bottom angle of the hole. I'd likely still want to rely on shim washers and a snug tightening job instead of just the threading. But that would be a nice option. And it's not hard to turn a big batch of shim washers from shim stock.

This would work nicely if the arbor is only case hardened. Otherwise threading tough heat treated steel is something that requires delicacy and good quality taps. But at least the case hardening would be removed when the nose of the arbor is initially shortened by that first 1/64 to 1/32 inch to make room for the head of the screw.

The nose buttons I've made up are also just a ring of contact due to how I size them down to fit. But knowing that this ring will be peened down a little over the first little while I deliberately left the cylinder gap at a slightly generous .007'ish so that when the button's contact edge peens down a couple or three thou it'll still be a good fit. And if it never does peen down that's OK too.

Yeah, it seems a little generous. But since I have not done a lot of these I wanted to start a touch more open so if the ring of contact around the truncated cone button peens to match the actual angle of the end of the hole in the barrel that it's got a few thou to move back.

I'm going to mention to the guy that if it doesn't close down a little over the next couple of hundred rounds that we could dress the end of the button down a touch to close up the gap a hair. But without a lot of experience on this sort of thing I wanted to err on the side of having to remove more later instead of figuring out how to add some back.

The metal working I'm good with. It's the issue of learning the gunsmithing specific tricks that I'm having a great time learning. But since this is for someone else instead of me I'm trying to be a trifle conservative this time.