[Homeroast] Turning Bottomless Portafilter

Joseph Robertson theotherjo at gmail.com
Sat Aug 28 11:07:09 CDT 2010


I believe it's been done. Again a vice might be nice and I don't mean a
cigarette while using the grinder....my bad. ;^)

On Sat, Aug 28, 2010 at 8:38 AM, dennis true <dennist3 at gmail.com> wrote:

> what about just using a bench grinder.......hehehehhee
>
>
> On Aug 28, 2010, at 2:58 AM, 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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