[Homeroast] Turning Bottomless Portafilter

g paris pchforever at gmail.com
Sat Aug 28 08:34:29 CDT 2010


Ray-O:

did you have to bring all tht up??

hahahahaha

On Sat, Aug 28, 2010 at 6:09 AM, Dennis Parham <dparham_is at mac.com> wrote:

> yeah I don't think Id use a hole saw by hand personally if I did it myself,
> maybe on a good drill press and good clamp then take it very slow... also I
> would probably drill out the centers like the guy did on the lathe with
> consecutively larger bits until I went to the hole saw.. Im not a machinist
> but it just seems less parts flying the better... lol
>
> Dennis Parham
>
>
> On Aug 28, 2010, at 8:57 AM, dennis true wrote:
>
> > NO ONE WILL EVER ACCUSE THIS GROUP of under-thinking a problem!!!! I LOVE
> IT
> > I have learned to think about things I didn't know existed before you
> guys are very impressive
> >
> >
> >
> > 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.
> Ray-O  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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