[Homeroast] Turning Bottomless Portafilter

Demian Ebert coffehound at gmail.com
Sat Aug 28 13:16:27 CDT 2010


Then I guess I was just plain ol'lucky. Better quit while I'm ahead.
Besides its not like my existing PF will need to be replaced anytime
soon.

Demian

On 8/28/10, Rich <rich-mail at octoxol.com> wrote:
> A 2" metal cutting hole saw in a drill press is capable of snatching
> something like a portafilter out of a press vice that is clamped to the
> table and flinging it a very long way at a very high velocity.
> Accidents with hand tools require stitches while accidents with  machine
> tools can require artificial limbs or morticians.  You can be learning
> the difference between a professional and amateur in nanoseconds.
>
> Demian Ebert wrote:
>> Well all I can say in response to that metal working lesson is I guess
>> I'm lucky. Although a certain amount of care and planning went in to
>> the exercise. Having succeeded once I'd try again and I probably
>> wouldn't learn until I broke something or was bleeding.
>>
>> I did see some really nice metal-specific hole saws on the Otis
>> service cart the other day. They've been reworking the elevators in
>> our building for months. The guy said they worked like a charm.
>> Perhaps the wood model could be upgraded if I had to do it again.
>>
>> Demian
>>
>> Got hole saw?  :)
>>
>>
>> On 8/28/10, 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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