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Portafiller naked conversions

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  • #61
    science-teacher entrusted me with the disrobement of his portafilter. This time before even laying hands on it as it came straight from the fleabay seller to me.
    I had a brainwave on my way home from work on Thursday when I was thinking about my dilemma of holding the portafilter handle in the vice firm enough to work on it but no so firm to leave marks. Since the handle of the 6910 portafilter unscrews I figured I could create something that would screw into the head of the portafilter and also be easy to grip in the vice. After determining the thread was a standard M10x1.5 I grabbed a couple of M10 bolts and an off-cut of wood and created the two jigs here:


    Bloody marvellous I tell you!


    Significantly quicker and easier all around.

    Full process here: Imgur: The most awesome images on the Internet
    Attached Files
    Last edited by level3ninja; 27 August 2017, 08:39 AM.

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    • #62
      Try redoing your attachments as the links are showing as invalid.


      Java "Nice jigs" phile
      Toys! I must have new toys!!!

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      • #63
        Wow the full illustrated process is amazing! Great skills!

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        • #64
          This guy is a wizard!
          PS. your inbox is full
          Last edited by Javaphile; 22 February 2018, 10:46 PM. Reason: Personal info removed

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          • #65
            Is anyone still doing this for a 6910 portafilter? Had one sitting around for ages and have wanted a naked for a long time. Wish i’d seen this post earlier!!

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            • #66
              I like my naked portafilter too. Its not a convert, but came from elektros. Very reasonably priced to suit simonelli, came with a triple basket too, but i havent used that one yet

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              • #67
                Originally posted by crazyhakins View Post
                Is anyone still doing this for a 6910 portafilter? Had one sitting around for ages and have wanted a naked for a long time. Wish i’d seen this post earlier!!
                If it's an older brass one I'll do it, if it's stainless (last 5 or so years?) it's more work than I can undertake for free right now.

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                • #68
                  Howdy pretty new here. I’ve a sunbeam 7000. Just purchased new. Mind if I ask the best way to start a naked conversion on the portafilla?
                  Would it be stainless?
                  do I cut the tubes of first then use hole saw
                  Any tips most grateful
                  cheers Pat��

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                  • #69
                    Originally posted by Patmac View Post
                    Howdy pretty new here. I’ve a sunbeam 7000. Just purchased new. Mind if I ask the best way to start a naked conversion on the portafilla?
                    Would it be stainless?
                    do I cut the tubes of first then use hole saw
                    Any tips most grateful
                    cheers Pat��
                    Hi Pat,

                    It will be stainless for sure. The spouts should twist off. I use the remaining hole as a guide with the pilot bit. Because it's stainless you should be using a tungsten carbide tipped holesaw, but if you have time and a holesaw to burn you can use a bimetal one. The most important thing with stainless is to not let it overheat. You can do this by having a container of water that you put the portafilter and holesaw in periodically to cool them down. I would suggest 10s max of drilling and then at least 20s in the water until it's completely cool again. The hole might take you 3hrs to cut. Your brand new holesaw will be half dead after this.

                    Then you get to the fun bit, opening up the hole. I use a small flapwheel in a drill for that, and I used 5s on, 20-30s cooling in the water. That part took me literally 30hrs. Good luck.

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                    • #70
                      Hi Pat
                      level3ninja is spot on (super write up for anyone wanting a guide with a brass portafilter!) but I’d say save yourself the hours of pain and after you take the spouts off find a local metal work/ machine shop with a lathe that’s happy to do it. They will make a much neater job of if the cut out and it should only need a tiny deburring with a file to taken of the burrs and sharp edge left.
                      Enjoy getting naked.

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                      • #71
                        It's not the heat that makes stainless difficult to cut it's the fact that it work hardens under the tool. You need to undercut the work hardening.

                        Use a drill press, go as slow as possible and use lots of lube (always use lots of lube).

                        Start the drill and press down so hard that it slows down, try to keep this slower speed. If it stalls, back off and start again. If it speeds up, back off and start again.

                        When the tool gets hot, stop for a while and cool it down. Don't dunk the workpiece in water, it's a waste of lube.

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                        • #72
                          Originally posted by Lyrebird View Post
                          It's not the heat that makes stainless difficult to cut it's the fact that it work hardens under the tool. You need to undercut the work hardening.

                          Use a drill press, go as slow as possible and use lots of lube (always use lots of lube).

                          Start the drill and press down so hard that it slows down, try to keep this slower speed. If it stalls, back off and start again. If it speeds up, back off and start again.

                          When the tool gets hot, stop for a while and cool it down. Don't dunk the workpiece in water, it's a waste of lube.
                          I never said it made it difficult to cut. Overheating the stainless seriously weakens it. The difficulty is retaining the patience to get it all done to a good finish while never overheating any part of it. Coolant is more important than lube in this instance.

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                          • #73
                            Originally posted by level3ninja View Post
                            Overheating the stainless seriously weakens it.
                            Yes, if it was hardened originally but that seems unlikely in a portafilter.

                            The grades of stainless commonly used in food processing aren't hardenable by heat treatment. The portafilters appear to be castings so they're not strain hardened either.
                            Last edited by Lyrebird; 1 July 2018, 05:41 PM.

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                            • #74
                              Having done both the earlier 6910s in brass, then stainless and then done one 7000 in stainless, the 7000 is a lot thicker and much harder to do with a holesaw. It also has a ridge that gets in the way. A good lathe is so much easier for the 7000. Be aware that you will still need a lot of cutting fluid to keep the temperature down or the 7000 one will discolour and probably weaken. The 7000 p/f was a bit of a PITA for me, and I have done quite a few p/fs over the years.

                              With hindsight, I would suggest you find a coffee repair guy and find / beg / buy the older brass 6910 p/fs if you have a 7000 (often from free to $20 over here). Another advantage - the stainless takes a lot longer to heat compared to the brass ones. Making it a naked means it never touches the grouphead water, so it takes longer again for the stainless one to heat through. Rough timings from stone cold - about 90 seconds for the SB machines to warm up. One quick preinfusion plus a couple of seconds of "coffeeless shot" and about 15 seconds delay and the brass is ready to fire. The stainless takes a complete single "coffeeless shot" and about 3 (6910 stainless) to 5 minutes (7000 stainless) to get up to temp.

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                              • #75
                                Old thread but thought I'd post anyways. Really wanting to do the naked mod on my portafilter but have a feeling mine is a newer stainless one and have read that it's alot harder to do the mod on! Does anyone know when I can pick up a cheap brass one? I've tried having a look on gumtree and ebay and not too much Luck. Hoping someone knows someone with one or if other sunbeam models fit the 6910 so I can get my hands on one! Cheers

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