Piston duly hardened!

[plumbgun]

Hi all, striving to reduce the inuendi to the minimum, let me just say that within the last hour I have managed to make what seems to be a satisfactory job of case hardening the piston for the Webley MK1 rifle, which was sold without, at the Webley sale some years back. As prommised, here is exactly what I did.

The piston (made of EN1A mild steel) was cleaned, and stood with its piston ring end in steel cup about the size of a tall thin egg cup. Kasenit was packed all around (some had been placed at the bottom first) and a sort of lid was made of aluminium foil, which allowed the rest of the piston to protrude. Apart from the part that was to be carburised, the piston was painted in three coats of tippex . This, remarkably enough, stays on even at high temperatures and prevents scaling due to oxidation. In the meantime a fire had been lit in one of my Victorian grates, using smokeless fuel, and after about an hour, when it was burning clear, the pot and piston were placed as carefully as I could, into a good hot part of the fire. It was then banked up with some more glowing "coals". After about 15 minutes, I could see that the pot was quite a bright red heat (maybe a bit too hot?) and gave the process half an hour longer. The carburised piston thus formed was taken and IMMEDIATLY and PERPENDICULARLY plunged into cold brine. Well! They told me that if I had got it hot enough, it should go bang. They didn't say that it would sound as if the job had cracked, end to end, but that's the sort of sharp crack that it made.

The tippex was removed, the job cleaned, and the hardened case area is a pleasing grey colour. I am not aware of any distortion - it still fits the rifle as it should - and a file won't touch it! Job done! Now I just have to find a way to fit those pesky piston rings.......

Paul M.

[Turnup]

Excellent and informative post - thanks

[kevin42]

Did I not learn in school that to harden steel you had to get it glowing red and then quench it in oil? To soften the same part just let it cool on its own.

Pretty sure that's an easy way to do it or is my memory wrong?

Kevin

[mel h]

Did I not learn in school that to harden steel you had to get it glowing red and then quench it in oil? To soften the same part just let it cool on its own.

Pretty sure that's an easy way to do it or is my memory wrong?

Kevin

Heating and quenchimg will harden High carbon steel but not mild steel. Anealing is the bringing back to a softer state by the process of heating and slow cooling.

Mel.