View Full Version : Lapping??
09-06-2003, 11:43 PM
I am in the process of machining a model steam engine. With my limited experience (fine machining/grinding I'm not so familiar with). . . My question: If a can machine/finish with .001 feed cut is lapping an advantage or necessary for bushings or cylinder/piston? Look forward to your feedback.
09-07-2003, 12:33 AM
I think what you are interested in is honing and yes this is needed for lay (surface condition)control. For your bushing and cylinder wall surfaces you would want a cross-hatched surface for uniform oiling and dirt removal during operation of the machine. A fine hone stone should do the trick. Have fun and work safely.
09-07-2003, 02:32 PM
For a Cast Iron Steam cylinder, all you will need is to finish the bore with a freshly sharpened and honed boring tool with a very slight radiused nose. Use a very fine depth of cut and very fine feed. You won't have to do anything else to it as a steam cylinder, in service, gets a "water sheen" that is almost a glass-like surface.
09-30-2003, 02:45 PM
I have never made a steam engine or any other kind for that matter, but have heard about the "water sheen" before. I'm curious. Can you share more about it? Can it be done on any part? How? How long does it take?
10-06-2003, 02:13 AM
I know zero about what I am talking about but one would think that the evaporating water would deposit minerals on the surface. Since they tend to be soft ones, they would fill the pores of the metal like a wood finish until you got a glassy surface.
It at least SOUNDS good...
10-06-2003, 11:57 AM
We use cast iron frying pans at home. They need to be "seasoned" before using the first time. Smear with vegetable oil and heat in oven to about 400°. Let cool then use. With repeated use the cast iron turns black and gets a smooth finish that doesn't stick to most foods or wash off with ordinary dish soap. Anything with tomatoes will begin attacking the finish if not washed off promptly, indeed certain chili formulations may render the skillet in need of re-seasoning. One person told me not to wash a seasoned skillet, but I wash them anyway. Dish soap and Scotch-brite, a hot rinse and dry immediately - no rust.
Perhaps the black sheen on the skillet is similar to a water sheen.
10-08-2003, 01:20 PM
[This message has been edited by pgmrdan (edited 11-16-2003).]
10-11-2003, 08:19 AM
Paul, what I was talking about is, in my opinion, just a natural happening as per "pgmrdan's" message. I do not think that it is a "process" that can be applied to other parts. I built my first engine, a Stuart 10-V, back in 1972 or 73, and just used the "freshly honed boring tool" as directed for the final cut, and after running it for a while, the inside of the cylinder looked like glass.