[Homeroast] Turning Bottomless Portafilter

Dennis Parham dparham_is at mac.com
Sat Aug 28 08:09:36 CDT 2010


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.
>>  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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