I have an interesting question for the folks here today. How does one go about re-grinding the valve seat of a cylinder block? On the locomotive I am currently working on, the valve chest is cast to the cylinder block and is thus not removable. There is also not much room along the long parallel faces (about the thickness of a finger on both sides), so there is not much room for a tool to swing past the edges of the face on two sides. The face is currently worn convex with it resembling a valley. I was not personally the one who made the measurements on either side, but have been told its somewhere around 5-8mm on both sides.

The real interesting part is, how do we go about machining the face back to a flat surface? Short of sending someone in with a chisel, file, and hammer as was done in the past, does anyone have any ideas on how to go about re-machining the surfaces or has had a successful time accomplishing it? The cylinders will stay mounted to the frame and the tanks will be removed before we machine it. We are currently crowd sourcing ideas and trying to figure out what will be the best option to proceed forward with.

After much annoyance trying to edit my photos on mac to work with the site, Ive posted them here on flickr: https://www.flickr.com/photos/75912799@ ... 087240648/

Cool........

I think I would build a jig that mounts to the top of the valve chest through which I could power a grinder installed in a router, such that I could set it slightly lower with each pass until I reach the point at which I have flattened the entire surface. you could start with a coarse grinder until you get close, and then finish with a fine grinder to save time. The addition of a shop vac through the snifter hole will help keep the work clean.

If your valve is balanced, you may find it worthwhile to build up the valve face with silicon bronze or aluminum bronze wire in a MIG welder. This will avoid the loss of the sealing surface for the balancing plates when the valve sits lower in the chest.

I'd also expect that the seating surface of the valve might also need serious attention. You've probably already got that upside down in a mill.......

dave

How far out of flat is it? Is it past the point that lapping will do the job?

What about a metal shaper? It would have to be custom made, but I would think it could be done.

Hey Frisco,

The wear is a convex pattern with the center of the face being lower than the sides (parallel to the frames and not perpendicular to it). Converting the 5-8mm brings it to being around .19685 to .314961. since this was quoted form a member who was trying to recall what the measurement was, I would honestly air on the side of it being 5mm or under. The locomotive was heavily used and suffered neglect to the end of its service life, but I cannot imagine the face would be worn more heavily than .19685 of an inch after seeing that figure!

So to answer the question, yes small amounts of lapping would probably not really solve the problem, as there would be too much time invested with that process to bring it back to flat.

I always hand scrape port surfaces, inexpensive and effective. Use a flat lapping block to Prussian blue the surfaces, and an Anderson carbide tipped scraper to cut. On faces I have run across like yours (really out of flat), use a grinder to knock down the high spots and scrape to final. A couple go arounds of lapping compound for the final finish.

I remember that back around 2006 (before I became a member) that Mid-Continent used an Underwood facing machine to resurface the valve seat on the steam chest of the Western Coal & Coke No. 1. The machine goes back to the early 1900's and will also face the top of the dome. Mid-Continent still has the machine, as far as I know. It only needs an air motor or other electric drive. I will check to see if we still have it and what our policy is about its use.

I had to go way back in the archives of the Mid-Continent Member's Blog to find photos of the machine in question. It was primarily designed to reface the top of the steam dome in preparation for new gaskets, however it was also used to reface the surface of the valve face on the steam chest on slide valves. I am still waiting to hear about the particulars on this machine, but here are two photos of it in action back in September of 2007.

http://midcontinent.org/members/bbs/dow ... .php?id=67
http://midcontinent.org/members/bbs/dow ... .php?id=68

After the valve face was machined flat the sliding part of the valve was lapped in for a steam-tight fit.

Once more into the fray. The machine is an Underwood Rotary Facing Machine. Here is a link to an article in "The Locomotive Dictionary" published in 1916.

http://books.google.com/books?id=6dY-AQ ... ne&f=false

I have conferred with the powers that be at Mid-Continent and, unfortunately, our machine is not available for use off the property. There are probably a few of these machines still out there, so, if anyone has a line on one, please speak up.

The pitting on the faces of the Glenbrook valves was moderate to heavy. The valve faces were reasonably flat and true, just pitted from corrosion. Not having a portable shaper I set up a lapping plate (purchased from McMasterCarr) with an air cylinder and valves. As shown in the photo the plate was pumped back and forth with the air cylinder. I would flip the plate over and reverse the plate regularly. After a while I would lap it against the valve itself and then the valve to the valve face. Lapping three surfaces together prevents the faces from going out of true flat. It took about two weeks of lapping per side. The cylinder wasn't running fast. When ever a shop staff walked by they would add a little more compound. We started with "G" grit and went to "A" grit. The finish was about 85% to 90% clean with no bridging pits from port edge to port edge. I estimate the thickness of material removed was .058" on the left side and .072" on the right. Very simple, inexpensive and fun to watch.

The notion that MCRRM's machine is a seat facer comes from the fact that it was utilized as such by the GCRY during the rebuild of 4960 circa mid 90's. It is in fact a valve facer, the seat facers were/are a bit different in design.

Here are some machines that could work to machine within a recessed valve chest as is pictured in the original post.
http://climaxportable.com/products/cate ... -machines/

Cheers, Jason

They look a whole lot like a router with milling bits in a jig.

dave

My method of preference is to slap the slide valve into a four-jaw and face it on the lathe, then wrap it in coarse emery cloth to level the cylinder valve seat. Lapping compound for the finish, as usual. Sometimes it takes a day unless there is really bad pitting. No skill required for the back and forth part.