Hello,
I recently purchased a Sherburne Caboose Whistle, Pat. 1890212. When hooked up to a compressor, it leaks a great deal around the button shaft. I disassembled most of the whistle, and saw that the air valve is a cone shaped object mounted on the button shaft.
Here is my problem. Is the hex nut surrounding the button shaft, an actual separate hex nut, or is it part of the casting? It would seem to me that it should be an actual hex nut, in order to access the air valve. However, I didn't want to force it for fear of breaking the casting. Any info or suggestions? Thanks!

I pic would be nice so we know of which you speak. But I’ll go out on a limb. Is it a small whistle that goes on a monkey tail? If so the hex castings should unscrew. There may be one at each end of the button shaft. You may need to clean and polish the valve mating surfaces if they’re metal to metal. There may be flat gaskets or o-rings under the hex portions and an o-ring around the button shaft. If o-rings, lightly lube them with a bit of plumbers grease when you replace them. Vaseline doesn’t last as long and might deteriorate the o-rings.

Exploded View

I'd use valve-grinding compound and techniques to grind and lap those surfaces together. Don't just clean and polish them separately and then assemble them.

Do not use automotive valve grinding compound to lap brass valve parts. It is made to grind steel and contains silicon carbide, which is much harder than brass. The carbide particles will embed in the brass and never stop grinding.

At WRM we use garnet abrasive to lap our brass valves. It can be obtained from U.S. Products Company

Wise point. I had forgotten the difference in hardness, and I might add I'd forgotten the tendency of brass to embad small pieces of abrasive.

Thanks for the tips, gentlemen. The pic with the disassembled whistle answered my question. I now know that the hex nut on the button side is in fact a separate piece. I'll have to work on it.
Thanks again for all the replies.

I suspect that those valve parts are somewhere in between "Brass" and "Bronze". There are something like 500 alloys of Brass and Bronze including Silicon Bronze which is almost as hard as some soft steels.

True Brass is way too soft to last very long as a valve seat. Would wear out in a few months / years.

Silicon Carbide is indeed way too hard to use on Brass/Bronze and will embed in the base material.

Garnet is probably a good choice.

Check McMaster Carr for additional options;

https://www.mcmaster.com/lapping-compou ... -on~brass/

(I do not work for or own stock in McMaster Carr).

Lapping old materials with uncertain/unknown properties is a bit of a "crapshoot" and you may have to try a few different lapping compounds until you get a good result.

Cheers, Kevin.

Is this a valve which steals a little air from the brake pipe to blow the whistle? And you turn the whole thing to dump the train?

I'm not sure if the original poster is saying that the main plug cock part is leaking, or the little button valve.
I would certainly start by disassembling and cleaning. There may be an O-ring or other soft seal which keeps air from leakage past tiny button stem. Or it might be a conical metal-to-metal seat.

Regarding lapping cutout and angle cocks in general, I agree use garnet-based lapping compound, such as US Products. I have always had excellent results with this. Stay away from "Clover" type compounds with SiC abrasive. Examine the tapered surface of the plug and the body before cleaning. Shiny spots indicate high spots, areas that are covered in a dirty residue are low.

If the plug and body appear to be badly out of lap, you might start with a 220 grit. Clean everything before you begin. Apply a thin coat of lapping compound to either the body or the plug, push the plug firmly in, and lap with a reciprocating motion, also lifting the plug periodically and pushing it back in. This last part of the motion is very important because it disrupts the lapping particles vertically and prevents them from gouging in and forming a track. After a few dozen of these twist and lift motions, the lapping compound will be broken down. Pull out, clean lightly with a rag, re-apply. When you have a wide, even-colored band which completely encircles the sealing surface of the plug and the corresponding inner surface of the body, and which extends vertically above and below the port opening, then you are done with the first grit. Switch to finer grits and repeat. I use 500 and finally 700 typically for these valves.

Then clean everything very well and wipe down, so no grit is remaining. Coat the plug with a light oil, such as triple valve oil, SAE-10 or 20 spindle oil, or even "3-in-1" oil. Lap using just this oil for a few passes, using firmer pressure than before. Clean again and final lubricate with grease

After assembling, screw a long nipple into one end (use pipe dope) and put an air fitting on the far end of the nipple. Test at a pressure at least equal to the maximum pressure the cock will see in service by dunking it in a pail of water. Bubbles will show if there is leakage through the cock, and/or if there is leakage around the key. If this is cock in the middle of a run vs just a drain cock, after performing this test put a plug in the downstream end and test again with the valve in the open position for key leakage.

The hex is not a nut, but is connected to a sleeve that contains the spring for the push button. The fault that we have found on many of these is the tiny oring at the inner part of the button shaft. This is what seals the air for the whistle. If that oring is split or missing, the air leaks out around the button shaft

Thanks again to all who gave suggestions and advice. I was able to get the whistle working. I was able to clean the push button valve assembly and lowered the air pressure. It still has a slight leak, but the whistle works pretty well. My wife said it scares the cat! HA!
Thanks again!

"Familiarity breeds contempt" was true for me and caboose whistles. I rarely ran across a Sherburne when I started in the hobby, as the common signal on "waycars" in my neck of the woods was a big ball valve with a collection of pipe fittings between the valve and a crude, short whistle made from a piece of pipe. These were common as dirt and uncouth, and I had to get some Sherburnes.

Long story short, all of the Sherburne caboose whistles that passed through my hands came to me as "leakers" to some extent. Some needed lapping badly (as pointed out, all lapping compounds are not the same) and I came to the conclusion that a lot of air must have leaked out of the things without much concern until the caboose fleets disappeared.

None of our cats liked the things either. Come to think about it, our cats didn't care for any of the noisemakers when they were tested, but when stuff was just sitting around they would stick their heads into the mouths of "#25" Supertyfon horn bells and up inside 12" bell brasses. I guess it was simple curiosity... or maybe their purrs resonated just right.

Gham55*
Yes, cats usually get themselves into their own trouble! Ha!