Lapping a model engine cylinder with diamond paste
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- Опубликовано: 17 окт 2024
- Lapping a steel cylinder with diamond paste.
According a fine article by Ken Croft that can be found here:
www.adriansmod...
Brass and bakelite tools were used with Hyprez 8-FS-40 diamond compound.
Another excellent job from you Olli...but why don't you posting this to our Emco group...?
Is this cylinder for the DJS15 engine? It looks beautifully machined. Fantastic finish. I have a couple of Rossi Mk2s with steel liners that I'd like to lap and make new pistons for. I'll do it the same way as you have here.
How did you check for roundness with a bore comparator? Bores can be bi lobed, tri lobed etc. which bi lobe or tri lobe measuring instruments will not detect if the bore has a constant dia., but is lobed.
Nice work Olli, but although I like to keep my hands clean I would never under any circumstances wear a glove of any kind to hold a rotating item in a lathe. There have been many cases where the glove has been picked-up by the rotating item and the consequences have been dire, any where from simply skin being ripped of the hand to... well, just think about it. PLEASE DON'T DO IT.
What grade steel ?
Superb Job !
never, ever, use diamond paste in your machine shop, because, as they say, a diamond is forever, it will not break down, it will wear down your tools. This produces a mirror finish which isn't necessary for model engines, especially those with rings, it hampers oil retention.
One does not produce a mirror finish in any cylinder regardless of if it is a model or a full-size engine and it needs to be cross hatched ringed or not, oil retention comes from the cross hatching.
Y'all clearly never actually designed a piston seal.
Diamond paste is ok as long as you keep it clear of slide-ways and as long as you are fastidious about cleaning the part you have used it on, in Olli's case I would use an ultrasonic bath to get rid of any trace of diamond in the bore. As for the old wive's tale about the criss-cross pattern produced by a typical Delapena or Sunnen honing machine, yes, I know of Rolls Royce solving valve guide problems by breaking the mirror finish with a cross hatched pattern, but that does not apply to our little engines. Low level commercial model aircraft or model car engines have a cross hatched pattern because it is "good enough" and to do better costs money. But if you get the chance to examine a current 2.5cc high performance engine that runs upwards of 30,000rpm or a tether car 1.5cc engine that approaches 40,000rpm, you will see that they all have a mirror finish to the cylinder bore. Do you really think the guys who make these engines have missed a trick?