Looking for what other museums & railways are using for grease on angle cocks and similar tapered plug cocks.

The design of the tapered plug cock requires a fairly viscous grease to prevent the two bronze/brass tapers from siezing up. Think of it like a morse taper drive. The spring is always pressing the plug in the direction that would tend to wedge it. Obviously there can't be an air gap between the plug and the body, otherwise it would just leak all the time. The grease fills up that space.

I can tell you what I found does not work: AAR brake cylinder grease, nor EP-2 bearing grease. Both of these work for a short time, and then the grease extrudes out, the handle gets very hard to turn, and/or the valve starts leaking.

I should add that my standard process for lapping these plug cocks, all the way from 1/4" drain cocks to large angle cocks, is:

Disassemble and clean.

Relieve burrs and sharp edges on the ports in the plug and the body. These tend to break off and gouge the surface when the handle is turned.

Lap with 320 grit garnet mixed in a light grease base. United States Products will sell small quantities of this lapping compound. I attach a threaded fixture to the threaded hole typically found on the wide end of the plug (opposite the handle end) and lap with a oscillating rotary motion along with periodically pulling the plug up. This reduces the tendency to "dig in"

After obtaining a uniform surface color and "frosted" appearance across the entire plug and the interior tapered mating surface in the body, clean out the 320 grit compound, repeat with 600 grit. When done, the plug will look dull and smooth, and will feel smooth to the touch.

Clean out all abrasive residue with solvent, blow dry.

Spread grease on the plug, insert the plug, and swirl back and forth, up and down, until the grease is evenly distributed.

Reassemble with the spring and cap. Rotate the key through several 360 degree cycles in both directions.

I test these by placing a known-good ball valve at one end, and an air fitting at the other end. The lapped plug cock is tested for leakage out of the body (around the narrow end of the key) with the ball valve closed and the plug cock in both open and closed positions. Then with the ball valve open, tested for leakage at the opening with the plug cock in the closed position.



Recently I've experimented with Molykote 111, which has an NLGI rating of between 3 and 4. It is somehat costly. Results have been encouraging. It is very tacky and resists wash-out. This is a silicone grease.

I have yet to order BASO Y70AA, a product that is specifically designed for natural gas plug cocks. It is obscenely expensive. It seems to be a moly based grease with zinc additive. I can't find any data on its NLGI rating.

Another possible candidate is Lubriplate 130A, a Calcium Sulfonate grease with zinc described as between a 2 and 3 BLGI.

Thoughts and experiences?

From the Railway Pipe Fitter's Handbook, Simmons-Boardman, 1925. You may want to scale the recipe down a little...

I'd look into a high pressure moly based lube. Something like Never-seez black moly. Moly kind of sticks into the metal and resists pressure very well.

I also wonder if this was one of the places where you were just expected to clean and lube often....

I'd recommend a two-step process. Assumie that the two surfaces are correctly lapped together, and thoroughly cleaned including any fine grit remaining embedded in the surfaces.

First use one of the products that produces a 'barrier layer' on the metal surface -- "friction modifiers", molybdenum disulfide, anti-seize/break-in lube. Allow this to 'bond' to the metal, then wipe off any excess.

Then use a suitable pressure lubricant between the surfaces. Remember that this is a static contact, not a hydrodynamic or "EP" in the normal sense of rotary contact. With the surfaces free of significant asperity and treated, this might even be something like green bicycle grease. I think I'd use something like Molycote 'high-vacuum' grease, which is mentioned as effective in plug valves. It is silicone-oil-based with silica thickener, but can be effectively thinned to suitable consistency by a number of solvents.

Surely there are enough tribology nerds here to work out the best options from first principles...

Look into Timesaver, a non charging lapping compound. Timesaver will cut then break down.
Most lapping compounds will charge the softer material and continue to cut the harder material.

I'm all for reconditioning old parts when practical, or sometimes just for the experience. After all, we are about Railway Preservation.

But what is the justification for reconditioning old plug-style angle cocks or cut-out cocks when new angle cocks can be had for around $75.00? Is it worth your time and effort?

A product you might want to consider is Relton Stick-Kut. It is a soft wax that is thicker than grease. It is used to lubricate band saw blades. https://www.relton.com/stick-kut

Another product would be anti-seize that you have worked powered graphite into to thicken it up. Loctite makes marine anti-seize that is really thick.

I've heard that Moly corrodes copper alloys.

Tom Hamilton

I wouldn't over complicate anything here - it's an angle cock. Vaseline and graphite worked for years. The General Foreman of the Central RR of New Jersey thinks the bees wax, valve oil and graphite mix is better. Graphite is the key ingredient. What the graphite is mixed with just holds it in position on the surfaces to be lubricated and it would be nice if it's not acidic. Or, just put a little M-914 brake cylinder lube on it. You should have some from doing COTS. If not, I'm sure Multi Service would be happy to sell you a 5-gallon bucket. Railroad tools will sell you a single 14oz tube. https://rrtools.com/product/grease-brak ... -Y0lrYrEFZ

Who is selling new angle cocks for $75? I see reconditioned ones for about twice that.

And yes, the point is preservation. I guess it is the same argument as converting lighting to LED.

In this case, the two materials are the same. Garnet does not embed in brass/bronze.

The question wasn't really about what might work, but what does work, in the experience of people who are actually doing this. But perhaps the answer is nobody cares, because the old plug cocks are just being thrown out and replaced by ball valves.

Hi Jeff, At WRM we use brake cylinder grease on tapered plug cocks. We do not experience weather as cold as you do, so that might make our experience different. I can see adding some fine graphite, but so far we have not. At WRM we remove ball valves, when found, and reinstall plug cocks. Several years ago we made up several sets of different size male and female iron laps to service cocks. I think the biggest problem is moving the plug inboard if very much lapping is required. On a few cocks we have had to make new plugs. If I recall correctly, one of those was a double cock. These were machining jobs, the cocks were not cast. It was a labor intensive effort. As I recall we used 360 brass.

Thank you David, I'm glad to see there is at least one other conventional plug cock advocate in the rypn world!

I've contemplated if it is worth it to make up male/female lap sets for this work.

Down the road from you, at OERM, there is an actual cock lapping machine. I have never seen it in operation. But I think it does the "turn, turn reverse, lift" motion of the plug (key) itself inside the valve, and doesn't employ cast iron laps.

My experience with the "lap the plug against its own body" approach is that I get a uniform surface appearance on both the plug and the body. As opposed to the ill-advised method of trying to lap slide valves to their own seats directly, where the result will be visible ridges and valleys. I suspect the difference is that since the motion is rotary, eventually a given point on the surface of the plug will be exposed to a continuous band on the body, and vice-versa.

I have found that a critical step is using a deburring tool on all port edges. Otherwise, the burrs turn into little thin brass shavings that tend to break loose and scar a groove in the mating surface. And also to lift the plug out periodically and to avoid too much pressure, which tends to eject the lapping compound and create metal-to-metal contact.

AAR M-914 brake cylinder grease has been not that effective for us. It seems to work well for a short time, and then get displaced. This happens even on the test bench. But we're generally using a "cold weather" formulation of that grease so perhaps it is not viscous enough.

Someone mentioned using never-seize. Never seize is NOT a lubricant but more like a very fine grinding compound. As such it will accelerate wear on moving parts like angle cocks. Because of this, the FRA is death on using never seize on air brake components. Whenever it finds never-seize on air brake assembly bolts during an inspection, it will demand the removal of the affected item for an internal inspection to see whether the stuff has gotten into the moving parts..

The Never-Seez that I specified is specifically a lubricant used in high load slow speed applications, including roller bearing assemblies and things like screw jacks, etc. It is NOT an abrasive by any means. If you do some research, you'll find Never-Seez is a brand with dozens of products for many situations, not just the one thing you see on the shelf at Autozone.

I have located a WABCO repair specification document. I'll try to scan it and upload it here.

It mentions that the key and body should be lubricated with "#4 zinc-based grease, commodity #263"

Whatever that was! It's not clear if #4 is the NLGI grade.

This spec was revised in 1967 and makes reference to keys with O-rings. The O-rings were supposed to be lubricated with a "#2 silcone-based grease"

Also, the WABCO parts catalogs show that "repair-sized" keys were available, as were reamer tools to ream out gouges in the body and open it up to the next standard size. Keys should sit no more than 3/64 below the large end of the body taper, and should never sit above it.

We've obtained many "new old stock" parts from different transit companies. but I don't recall ever seeing this treasure trove of replacement keys.