Following on from a previous thread, I have a couple of small components,
a couple of "tappets" (EN1 bar turned to 10mm diameter then bored 9mm
diameter, 9mm deep leaving a 1mm thick top and 0.5mm sides) I need case
hardened and the corresponding cams which are machined from a piece of EN8
(we spoke about that earlier).
First test piece was a spare tappet, I put it in a small tin full of the
Eternite, put the lid on and brought the whole lot upto big propane torch
orange for 10 minutes, left it for 30 minutes as per instructions, at
which point you are supposed to quench, but by that time the tappet was
barely warm. I couldn't detect any hardening.
Tried again tonight, but this time got the tappet hot and dipped it into the
Eternite, left for thirty minutes. This time, still barely warm so not a
lot of point in the quench. However, the tappet was covered pretty evenly
in a black scale, but not hard.
Thinking about it, heating to 900C, holding it for a while and cooling
slowly is called annealing isn't it? How long does the component need to be
held at temperature to absorb the carbon?
Tried the EN8 cam, covered in black scale, but no evidence of hardening
and after 30 minutes, little point in quenching something that is already
a) What I am missing here?
b) Whats the best treatment for getting the scale of and the component
c) Did I really pay £20 for a bag of charcoal and is someone having a laugh?
(10Kg bags were 20pence at Sainsburys last Christmas)?
15 years ago