[Homeroast] hacking a silvia portafilter

raymanowen at gmail.com raymanowen at gmail.com
Mon Sep 13 02:50:07 CDT 2010


The following has a lot to say about the hardening of brass: <
http://www.artmetal.com/blog/tantoinette/2008/11/heat_harden_brass>

Not to bore anyone with car stuff, but manual transmissions used to employ
brass rings to assist in synchronizing the sliding spur gears when shifting.
An easy project for an advanced high school metal shop or commercial metal
fabricator would be to investment cast a popular-size brass porta filter
handle with a deeper, slightly repositioned “boss” for the handle screw
threads and no bottom.

On the other hand, the hack job of great dexterity and little foresight will
create lines of increased stress and strain near the threaded base of the
handle itself. The stress risers will cause the brass to “work harden” with
every lock/ unlock operation.

If the barista is a little heavy handed, the hardening will progress to the
point where the piece is brittle and will act more like an egg shell than
Marine grade brass.

(If the specific heat of brass is supposed to stabilize the temperature of
water, it's already a bust.) The specific heat of water is higher than brass
and there is virtually no contact or heat exchange, even with a normal p/f.
None at all in the tricked-out bottomless ones.

Cheers, Mabuhay, Lloniannau i diod da o goffi! -RayO, aka Opa!

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