My arbor has a hole in it???

[45D]

I'm sure there are a few other ways to figure out how thick a spacer (a single is better than a shim stack) needs to be to fix the short arbor problem. I've done a few myself and the fastest / easiest way I've found is to start too thick and reduce until you have the endshake you want. When dealing in thousandths, it's obviously easier to sneak up on it rather than spending a lot of time trying to get close to start with.
The head of a #12 pan head sheet metal screw (belt pistols) or a #14 (for horse pistols) is too thick and can easily and quickly be sanded down to get your specific thickness. If you have a drill motor and a belt sander it only takes a few minutes. Remove the shaft of the screw and you all the material needed to make an excellent spacer. The round head of the pan head makes good contact with the cone shaped end of the drilled arbor hole and is "self centering". I generally get the clearance down to .004"/.005" and then dress the end of the arbor down to get to .0025" - .003". This method can/will increase the wedge slot slightly which is why I always install (in the end of the arbor into the wedge slot) a 1/4 X 28 set screw that has been ground smooth and polished for an adjustable wedge bearing. It not only restores the slot size, it allows you to adjust for any wedge wear as well as wedge placement (how far it inserts) for appearance preference or holstering interference.

As far as the 90° "test" goes, the idea is to have as little clearance as possible between the arbor and the arbor hole. Removing material just to be able to do the test (in my opinion) is more destructive than constructive. The broaching process for the arbor slot upsets material in a manner that causes the twisting of the barrel on the arbor impossible without cleanup. It's more of a "keyed" fit and allows the two assemblies to mate only when aligned (thus the test isn't a reliable method without material removal). You can clean up the arbor to ease removal /installation but there's no real need to go further just for the sake of performing a particular test. A simple small washer in the arbor hole followed by re-assembly is infallible proof of a short arbor . . . with no destruction of the arbor.

Mike

 

[Columbus]

I'm sure there are a few other ways to figure out how thick a spacer (a single is better than a shim stack) needs to be to fix the short arbor problem. I've done a few myself and the fastest / easiest way I've found is to start too thick and reduce until you have the endshake you want. When dealing in thousandths, it's obviously easier to sneak up on it rather than spending a lot of time trying to get close to start with.
The head of a #12 pan head sheet metal screw (belt pistols) or a #14 (for horse pistols) is too thick and can easily and quickly be sanded down to get your specific thickness. If you have a drill motor and a belt sander it only takes a few minutes. Remove the shaft of the screw and you all the material needed to make an excellent spacer. The round head of the pan head makes good contact with the cone shaped end of the drilled arbor hole and is "self centering". I generally get the clearance down to .004"/.005" and then dress the end of the arbor down to get to .0025" - .003". This method can/will increase the wedge slot slightly which is why I always install (in the end of the arbor into the wedge slot) a 1/4 X 28 set screw that has been ground smooth and polished for an adjustable wedge bearing. It not only restores the slot size, it allows you to adjust for any wedge wear as well as wedge placement (how far it inserts) for appearance preference or holstering interference.

As far as the 90° "test" goes, the idea is to have as little clearance as possible between the arbor and the arbor hole. Removing material just to be able to do the test (in my opinion) is more destructive than constructive. The broaching process for the arbor slot upsets material in a manner that causes the twisting of the barrel on the arbor impossible without cleanup. It's more of a "keyed" fit and allows the two assemblies to mate only when aligned (thus the test isn't a reliable method without material removal). You can clean up the arbor to ease removal /installation but there's no real need to go further just for the sake of performing a particular test. A simple small washer in the arbor hole followed by re-assembly is infallible proof of a short arbor . . . with no destruction of the arbor.

Mike

I see this set screw fix mentioned a lot but I can't visualize it, is there any way you could post a picture?

 

[Hiddeninsmoke]

From a mechanical standpoint, the small piece which fell out was probably a thin spacer used to hold the wedge in place. It seems that the basic problem is that at some point the arbor was removed from the frame and, subsequently, was not properly reinstalled.

 

[Bad Karma]

I'm sure there are a few other ways to figure out how thick a spacer (a single is better than a shim stack) needs to be to fix the short arbor problem. I've done a few myself and the fastest / easiest way I've found is to start too thick and reduce until you have the endshake you want. When dealing in thousandths, it's obviously easier to sneak up on it rather than spending a lot of time trying to get close to start with.
The head of a #12 pan head sheet metal screw (belt pistols) or a #14 (for horse pistols) is too thick and can easily and quickly be sanded down to get your specific thickness. If you have a drill motor and a belt sander it only takes a few minutes. Remove the shaft of the screw and you all the material needed to make an excellent spacer. The round head of the pan head makes good contact with the cone shaped end of the drilled arbor hole and is "self centering". I generally get the clearance down to .004"/.005" and then dress the end of the arbor down to get to .0025" - .003". This method can/will increase the wedge slot slightly which is why I always install (in the end of the arbor into the wedge slot) a 1/4 X 28 set screw that has been ground smooth and polished for an adjustable wedge bearing. It not only restores the slot size, it allows you to adjust for any wedge wear as well as wedge placement (how far it inserts) for appearance preference or holstering interference.

As far as the 90° "test" goes, the idea is to have as little clearance as possible between the arbor and the arbor hole. Removing material just to be able to do the test (in my opinion) is more destructive than constructive. The broaching process for the arbor slot upsets material in a manner that causes the twisting of the barrel on the arbor impossible without cleanup. It's more of a "keyed" fit and allows the two assemblies to mate only when aligned (thus the test isn't a reliable method without material removal). You can clean up the arbor to ease removal /installation but there's no real need to go further just for the sake of performing a particular test. A simple small washer in the arbor hole followed by re-assembly is infallible proof of a short arbor . . . with no destruction of the arbor.

Mike

Seems like the pettifogger fix involved a spacer provided by the Dillon company and required a hole drilled into the end of the arbor such as the one in @Columbus revolver.

 

[Columbus]

Are these two holes of any significance? Picture of the front of the arbor and another inside the slot.

 

[vintovka]

Any chance that's a threaded or press fit plug??

 

[Columbus]

After looking some more I don't think it's an arbor issue at all. This picture shows that the contact point in arbor slot is there, this is with everything in place but the cylinder. When the wedge is inserted, it doesn't make any contact in the slot at all, just wiggle around. If the spring wasn't there it would just fall out.

 

[Bad Karma]

After looking some more I don't think it's an arbor issue at all. This picture shows that the contact point in arbor slot is there, this is with everything in place but the cylinder. When the wedge is inserted, it doesn't make any contact in the slot at all, just wiggle around. If the spring wasn't there it would just fall out.

View attachment 109938

Loose and battered wedges and wedge slots were one of the reasons the Army went away from the Colt. Is the hole threaded perhaps? As Mike does for his adjustable wedge bearing?

 

[Rawhide67]

I don't think I've ever seen a hole in the arbor, even as a machining step.

 

[Columbus]

I don't think I've ever seen a hole in the arbor, even as a machining step.

I've owned many and neither have I. But look at what I just found. I kept digging at that hole, couldn't find anything that seemed to fit but pulled out the smallest hex in my screwdriver set and it went a bit farther into the hole and it locked in place, hmmmmm, put a little crescent on it and lookie here! Came right out - looks like someone did the set screw thing - now have to figure it out. If anyone knows how this is supposed to work, please post.

 

[Columbus]

I've owned many and neither have I. But look at what I just found. I kept digging at that hole, couldn't find anything that seemed to fit but pulled out the smallest hex in my screwdriver set and it went a bit farther into the hole and it locked in place, hmmmmm, put a little crescent on it and lookie here! Came right out - looks like someone did the set screw thing - now have to figure it out. If anyone knows how this is supposed to work, please post.

View attachment 109955

I cleaned it up, cleaned the hole in the arbor, put it back in, gave it a little turn just past flush. The wedge is tight, no shake, no rattle, cylinder is tight, woo-hoo! That hole had to be there for a reason...... it was.

 

[Erwan]

Look here why I did it on my Uberti : Barrel to Cylinder Clearance ....
It can be like that on a Pietta too, its more frequent on an Uberti, but that can be with a Pietta...

PS : you'll need a file too...

 

[45D]

Columbus, the Allen screw was there as an attempt at a wedge bearing (at least someone's paying attention!! Lol). Problem is, it isn't really a big enough screw to do the job. You need a 1/4" x 28 screw for that. Now, just because the wedge can be tightened up has absolutely nothing to do with the short arbor. The short arbor means the end of the arbor isn't against the end of the arbor hole. You can now probably drive the wedge in far enough to lock up the cylinder. That's what a correct length arbor won't allow. The arbor dictates the barrel/cylinder clearance . . . but it can't when it's too short.

Mike

 

[Rawhide67]

Well.... There's your set screw. Or counterweight, or whatever. Is that maybe a bubba solution?

 

[Columbus]

Columbus, the Allen screw was there as an attempt at a wedge bearing (at least someone's paying attention!! Lol). Problem is, it isn't really a big enough screw to do the job. You need a 1/4" x 28 screw for that. Now, just because the wedge can be tightened up has absolutely nothing to do with the short arbor. The short arbor means the end of the arbor isn't against the end of the arbor hole. You can now probably drive the wedge in far enough to lock up the cylinder. That's what a correct length arbor won't allow. The arbor dictates the barrel/cylinder clearance . . . but it can't when it's too short.

Mike

1/4" - that's more than half the diameter of the arbor - are you sure?

 

[45D]

Yessir.

It'll look like this. Horse pistol on left, belt on the right. You can see there is plenty of meat for "marrying " the arbor to the barrel assy. This is definitely what you want.

Mike

 

[Columbus]

Yessir.
View attachment 109970

It'll look like this. Horse pistol on left, belt on the right. You can see there is plenty of meat for "marrying " the arbor to the barrel assy. This is definitely what you want.

Mike

And you're using the set screw to reduce the size of the slot or to lengthen the arbor?

 

[45D]

Reduce the size of the slot. My whole explanation of the spacer (above) is for arbor length correction (that's a permanent fix). 2 totally different things but apparently the most misunderstood thing ( not you but a llllllllot of folks want to add the two together!!).

Mike

 

[Columbus]

Reduce the size of the slot. My whole explanation of the spacer (above) is for arbor length correction (that's a permanent fix). 2 totally different things but apparently the most misunderstood thing ( not you but a llllllllot of folks want to add the two together!!).

Mike

In my situation (and I'm a long way from being any kind of gunsmith) I don't see how increasing arbor length would do any good other than have that contact point established. I don't want the barrel assembly moved forward at all. With the cylinder in place and the barrel tight against the frame (where the pins are) everything is just right but the wedge isn't in contact with the forward edge of the arbor slot. If I lengthen the arbor via shims or whatever just until it's bottomed out it might expose a bit of the front of the slot but when I put the wedge in and drive the barrel back to where it's tight I won't have wedge contact any more. I don't see how length correction on the arbor without redoing the slot would help. Somewhere today people were talking about three points of contact for these, arbor bottomed out, purchase for the wedge and tight fit against the frame, takes a bit of work at the factory and apparently it's not getting done. Maybe two out of three has to do it. This gun was built in '93 and I have no idea of when this set screw was put in. If I had a drill press I might attempt the 1/4" but I don't so this will have to do for now. Everything is snug, fit tightly and the cylinder gap is about perfect. Will see how it does on the range. Thanks to all for the suggestions/explanations. What would we do without forums like this?

 

[45D]

Well, fixing the arbor length will keep this from happening . . .

So, it's worth doing, but even more so you'll have the same revolver every time you assemble it.
Somebody here made a comment about barrel harmonics when I had mentioned that the arbor, barrel connection allowed the harmonics of both assemblies to act as one rather than one rattling the other to pieces . . . It's actually fairly high end design but we are so dumbed down "they didn't know what they were doing" back then . . . "they" would run rings around the "smart ones" today lol !!!

So, that's why you need to finish it, it's not hard, I even gave ya step by step . . .
When you drive the wedge in, the barrel assy is being pulled (under great tension) AGAINST the end of the arbor so the "above pictured" CAN'T happen.

Mike