[Homeroast] Turning Bottomless Portafilter

Joseph Robertson theotherjo at gmail.com
Sat Aug 28 09:17:29 CDT 2010


RayO,
At least we not talkin bout the proper use of a musket. ;^)
JoeR

On Sat, Aug 28, 2010 at 1:55 AM, <raymanowen at gmail.com> wrote:

> Be safe -ro
>
> On Sat, Aug 28, 2010 at 1:47 AM, Joseph Robertson <theotherjo at gmail.com
> >wrote:
>
> > Well RayO,
> > I did enjoy reading this one. Although if I hadn't worn a  welders hat
> > studied metallurgy in college and a worked as machinist in a former life
> I
> > probably would have not responded to this post. I do believe I could cut
> my
> > next portafilter in the time it took you to write this last post of
> yours.
> > In fact I'm temped to give it a try. If I do I will post the results in
> > this
> > thread. Even from the hospital if I have to.
> > I have eaten a lot of crow and hat in my day but I think not this time.
> > JoeR
> >
> > On Fri, Aug 27, 2010 at 11:58 PM, <raymanowen at gmail.com> wrote:
> >
> > >   1. "...use a hand drill / Vise to hold it and a hole saw to cut mine
> > >   out.
> > >   2. From now on I will do my own.
> > >                             [When you see something done by someone
> > >   experienced in doing it, the process always looks easy. Something
> looks
> > >   simple like changing the engine or automatic transmission oil and
> > filter
> > >   when someone else does it-  or a flat tire? Looks easy when you see
> it
> > > done.
> > >    Show of hands- How many people actually do their own maintenance on
> a
> > >   regular basis?]
> > >   3. The chrome coating is real thin. the core is bronze I think.
> > [Bronze-
> > >   like the Temple bells in Thailand? Stupid Marketing always says
> "Heavy
> > >   brass" or "Marine grade brass"] Their specific heat is lower than
> that
> > of
> > >   the water they don't touch...
> > >   4. Very easy to cut with a hole saw."
> > >
> > > Maybe Not-
> > > Did you see the machinist using a Hole Saw or claw hammer?  He did Not.
> > > In order to do the machine work with precision, conserve tools and the
> > > porta
> > > filter handle itself, the cutting tools and workpiece were firmly
> mounted
> > > on
> > > the lathe.
> > >
> > > If your friend did not fracture the porta filter handle between the two
> > > jaws
> > > of the bench vise; did not break the pilot hole drill bit when the hole
> > > saw seized in the work piece, crack his wrist, yank the pf out of the
> > vise
> > > as it broke and busted the drill motor when it hit the floor, he's
> either
> > a
> > > Magician or extremely lucky.
> > >
> > > Luck and Magic may be entertaining, but have no place in a machine shop
> > or
> > > on the highway. (When you feel inclined to buzz it over 100, are all
> the
> > > lug
> > > nuts torqued, tire pressures and engine oil just right? Do you Know so
> or
> > > just Hope so?)
> > >
> > > Cutting out the entire bottom of a portafilter might seem easy with a
> > large
> > > hole saw, bench vise and hand drill, but it's not the all-pro move. It
> > will
> > > probably cost you some painful surgery, a hole saw, a hand drill, a
> porta
> > > filter and some CSA points.
> > >
> > > At Colo School of Mines Earth Mechanics Research Institute, I used a
> > > 500-ton
> > > press and 12,000 psi triaxial pressure to test and chart record the
> > failure
> > > point of 2" OD X 4"L oil shale cores, up to 480° C, (Love PID
> controller,
> > > type K s/s sheathed grounded junction thermocouples) and my strain gage
> > > load
> > > cell.
> > >
> > > According to an ME/ Chem E friend, "Some of the stronger bronzes need
> > full
> > > hydrodynamic (pressure) lubrication, or they gall and seize. (That's
> what
> > > grabs and breaks the hole saw, your wrist, and yanks the pf out of the
> > vise
> > > if you had a good grip on the drill)
> > >
> > > The heavily leaded bronzes survive much better when lubrication is
> > > marginal,
> > > if speeds are Slow Enough. Ever seen a slow hand drill? Hammer
> Mechanics
> > > usually run full-speed.
> > >
> > > The opposing material and finish can make a big difference in the wear
> > rate
> > > and tendency to seize and gall. (Break your wrist)
> > >
> > > Poor geometry usually can not be compensated for with "better" as-cast
> or
> > > annealed materials." The tabs of 58mm pf handles each have to withstand
> > > almost 300 pounds in shear at 9 bar pressure. Things could go rong in a
> > > hurry if the shot stalls and the OPV doesn't bypass and relieve the
> pump
> > > pressure, like my former Crapesso.
> > >
> > > Don't even think of using type J thermocouples around moisture- the
> > couple
> > > is Iron/ Constantan. Guess which one corrodes like Hell and destroys
> the
> > > junction?  Type K couple is Chrome-Nickel/ Aluminum-Nickel or Chromel/
> > > Alumel.(Was © Omega) The Chromel is a laboratory-grade Nichrome- the
> > heater
> > > wire in toasters- and can withstand ≤ 3000° F.  Alumel is a little
> lower
> > > and
> > > type K is a stable Seebeck couple at 2700° F.
> > >
> > > Cheers, Mabuhay -RayO, aka Opa!
> > >
> > > Do what you always did, get what you always got- If you get back
> without
> > an
> > > ambulance ride or tow truck, maintenance was OK.
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> >
> >
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