Scott flame licker build

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madjackghengis:
Hi John, and greeting to all reading, I put my emphasis on lapping because I use that as the means of fitting solid, closed end connecting rods with pressed in hard bearing races that Rockwell about a C-63-65 out of 10100 Torrington bearing steel, and lap for oversided rollers which come in increments of two tenths over, up to a thousandth, and then in one, two and three thousands oversized, before one needs to press out the races and put new, undersized races in. The lapping is done with an expanding cast iron mandrel, and I've made replacement mandrels for rods, for the pinion side race on the primary engines I rebuild, having worn out the original lap heads. Using the same compound on say delrin first, using the long lap and short lap method, on a cylinder, it can be brought to an almost mirror finish, which is achievable with finer lapping compound and finally rouge as you suggest. Having fitted rods for many decades to existing crankpins, using bore guages, and finding the quality of finish being in the micron range, I have come to expect such a finish after lapping, and found one can get pretty large without going to rings, and getting full compression, particularly if you have a tool post grinder for finishing the piston, as that eliminates all but the final lap on it. I like less than half a thousandth up to an inch, with steel or cast iron in cast iron cylinders. I find it hard not to lap to such standards on anything open to it, having done it so many years on the machines I've routinely been rebuilding and having both the full equipment and experience. I too dispose of the delrin only after it has been cut down to the point there's nothing small enough to lap with it anymore, but being cheap to buy in a stick makes it handy, and it cuts very accurates, and holds on size unchanging with temperatures in the normal range. It also is the only real method of using glass cylinders with any expectation of accuracy and close fitting pistons, and allows fitting less than a tenth of a thousandth with graphite pistons if a lathe will hold that for the short length of the piston, which most lathes will. Excuse me if I took over your post for a minute, John. cheers, jack

Brass_Machine:
John,

The piston and cylinder look fantastic. They look silky smooth.

John\Jack would love to see a thread about lapping cylinders and the techniques.

Eric

Bogstandard:
Nick,

I'm not criticising anyone about their methods at all, and as you know, I wouldn't do that unless it was unsafe to show. I am just showing the standards I always try to achieve, it is a personal thing on my part.
People can emulate or not, that is their decision. But until they are shown or told the choices, some of them most probably don't realise there are any choices to make.

Actually Eric, photos, especially with flash, usually show surface finishes worse than they really are. This pair are actually a lot better in real life than what is shown here.
If I wasn't so fussy about any work that I do, they would most probably run plenty good enough as they are.

With regards to showing lapping etc. The US lads have a definite advantage over me in that department. They have retail access to very cheap soft laps, whereas in the UK, although most probably available, they will be neither as cheap or accessible as the US ones are.

So I personally have to use old and trusted methods for achieving what is required.

John

saw:
This is so very nice. :clap:

NickG:
John,

I agree, and it shows in your finished work which is 2nd to none. Good point, I didn't realise there was a choice and I have probably made many a cylinder and piston worse by trying to lap it the wrong way. It sounds like your lapping method and otheres discussed in this post are robust, tried and tested ones though so I will be trying it again at some point. :thumbup:

Nick

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