lapping

[my2cents]

All, I have an old Lunkenhiemer (SP) whistle and the valve wants to leak a little bit. It does not leak mush and really doesn't affect anything I justed to lap the surfaces to stop the weep. I got some 4 micron lapping paste from McMasterr-Carr. I have been trying and have not been successful to eliminate the weep. I put some paste on the valve the put it in the valve body and use a screw driver to twist the valve back and forth to try to lap the surfaces together. I then clean the paste off reassemble and it still weeps when I put it on air.
Am I doing something wrong? I could be using the wrong lapping compound or wrong technique or am I being to impatient. Thank You for all the inputs.

[Mr Ron]

I believe the lapping process requires you to use a figure 8 lapping pattern. A back and forth pattern tends to create channels in the surface. It would be similar to lapping a cylinder to a piston.

[Rwilliams]

Try some extra fine Timesaver lapping compound for soft metals like bronze. Much easier to use a cordless drill to drive the disk body against the seat for faster results. I have found that whistle valve seats and disks do not often play well together when cold. Once heated up on steam, often times the slight leak will vanish when all parts have expanded to an even temperature.

[my2cents]

This is a round tapered stem and seat inside a whistle. A figure 8 for flat surfaces BUT I have been told to be careful because a figure 8 will will not produce a truly flat surfaces because of the irregular forces that are placed on the piece by changing directions in the figure 8 motion. I have been told that larger pieces are easier to lap than small pieces.

[my2cents]

Do you just mix some Timesaver Compound with a little oil?

[Rwilliams]

Timesaver arrives in a metal can not unlike a stand paint can. Inside is a yellow powder the likeness of powdered sugar. Mix a small amount of the yellow powder with a thin oil, apply the oil powder paste to the part surfaces and with a small amount of pressure, continue to rotate the parts until a nice even matching contact surfaces become visible. I often will use black Sharpie to make a few lines on each surface just to act as an indicator of where the seating surface is making full contact. Much cleaner than Prussian blue or layout dye, the Sharpie marks are dry almost instantaneously and do have no effect on the end result desired, just an indicator material to let one know what has happened.

The finer the lapping compound, the finer the oil needed for a good lapping mixture. Often times I use a mix of transmission fluid and WD-40 in a 50:50 ratio for the finest lapping. For coarse grit lapping a heavier oil is needed such as 30 or 40 weight motor oil. The really coarse lapping compounds are almost mixed with a light grease. The finer the lapping compound, the finer the oil should be for best results.

[Howard Gorin]

Steam whistle valves should leak slightly. Without a slight leak the steam line to the whistle will fill with condensate, when you blow the whistle you will produce a shower bath of hot water.

[Bill Shields]

If you insist...toothpaste works well on non ferrous

I am with Howard...a little leak with a drain weep hole if going down hill makes for a more practical whistle.

I never put the whistle valve first off the boiler..always have a shut off for the day when it sticks open and wants to dump your boiler