McIntosh C20 - can and should I bring it back from the dead?

Discussion in 'McIntosh Audio' started by neevo, Aug 7, 2018.

  1. neevo

    neevo Super Member

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    1,524
    Location:
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    Picking up the chassis and various other bits I’ve had plated on Wednesday. Everyone cross their fingers it’s turned out ok.

    Can’t be worse than what it started as mind you.
     
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  2. neevo

    neevo Super Member

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    1,524
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    I picked up the chassis today... it currently sitting on my bench all wrapped up and ready to unpack (like Christmas).

    Whats the verdict... I'm very happy :)

    The finish is exactly what I hoped for on the chassis, its not shiny although a little shinier than OEM, but apparently Sam the chrome said it will dull down further if its not polished, so I imagine it will settle in to a finish that is pretty bloody close to factory. Either way I am very excited.

    Hope to get it unwrapped asap and put it back together with some of the painted parts so everyone can get a view of what it will look like done.
     
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  3. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    So here we go. Like unwrapping Christmas presents...

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    It took me a while to unwrap all the tiny parts from the wire they were plated on:

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    It’s hard to gauge what the end result will be like in parts so I quickly put the chassis together:

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    It’s not flawless but I really like the fact all the issues haven’t been wiped away. I now have a gorgeous shiny and clean chassis I can be proud of.

    All I need to work out now is a way to set my semi hollow rivets so I can put everything back together. I’ve purchased some 6mm long ones in the hope the additional length will press better as the 3mm ones just squashed.

    Before:

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    After:

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    Last edited: Jan 23, 2019
  4. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    I really think this could work!!!

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  5. mvandyke

    mvandyke Active Member

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    127
    Location:
    Bend, OR
    Looks great. I love the effort that you've put into this restoration!
     
  6. jkaley

    jkaley AK Subscriber Subscriber

    Messages:
    91
    You Sir, have lost your mind; and I hope you never find it :)
     

     

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  7. neevo

    neevo Super Member

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    1,524
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    Thanks, appreciate the comments. I’m keen to get it going again ASAP but still have some items I need to do obviously.

    Next up I need to make the end panels; which means I need to make some T-Nuts for my new mill too. It’s never simple. But hope to be milling those this weekend.

    Then I need a solution on setting these semi hollow rivets. I’ve tried everything but nothing is really working and I need the ability to set them deep in the machine for the tube sockets.

    I’ll show some test pics soon as I’ve bought some longer ones that I hope will work better. My current options are the air hammer setup I bought plus maybe using those parts in my drill press and seeing if I can set them that way.
     
    Last edited: Jan 23, 2019
  8. neevo

    neevo Super Member

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    1,524
    Location:
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    Well I really cannot figure out a way of getting these rivets set and I have my heart set on the semi hollow ones to properly match the original look. Up until this point I had been using these 3mm long rivets (I have both Stainless and Zinc Plated):

    25E318F0-77B0-4B9C-97FD-5994EABE0472.jpeg

    But as you can see they are not pressing nicely with any of the methods I've tried so far (hitting them with a hammer and air gun):

    9B41275B-AF8A-4764-BA4C-4405115F8EF9.jpeg

    Here is the gun ready to try some 7mm long rivets as I hoped maybe the others were too short:

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    Here they are set. The red is the 7mm which I quickly abandoned because it seemed way too long and was splitting terribly:

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    So I am still back at square one :(

    I have one last thing to try and that is setting up the parts in my mill and seeing if I can use it as a pseudo press. If that doesn't work I feel I might have to either find the proper tool, find someone locally to do it for me or potentially (and least desirable) use another method like hollow rivets or bolts.
     
  9. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
    Sydney, Australia
    Tried the mill as a press. It has the stability:

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    First try wasn’t very good as there were burs on the sheet metal:

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    Second attempt was better but I can’t get the leverage to properly compress the rivets:

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    This one is still quite loose and not good enough to use. I'm also worried I might break the mill by yanking on the handle so much.
     
    Last edited: Jan 29, 2019
  10. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
    Sydney, Australia
    Used the mill for the first time in anger today. Whilst I’m missing a piece of the mill to control the fine z axis (up/down) I thought I’d try and get the panel outside dimensions by marking up the outside and eyeballing it.

    I did most of the work with a 50mm carbide face mill and it rips through the Alu like butter. I need to tram the head in a bit better (have to shim the column) as I’m not getting a crosshatch pattern in the parts, just 1 side of the cutter, but the finish is ultra smooth and I cannot feel the cuts with my nail. Running the cutter at max RPM (1400 RPM) it gets it down to dimension very quick. I then finish pass by climb milling to get the best finish.

    Ready to rip:

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    I then used an 8mm end mill to face off the ends down to 130mm overall length.

    So I have my parts done:

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    Annoyingly there are some knicks in the Alu (I suspect inclusions from manufacturing as they weren’t put in there by me):

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    So I have both parts in the mill now and will run the face mill over both together to bring them down and remove these divots. Luckily I have enough meat on them to reduce them a bit and still be around 13mm.

    Tomorrow I’m going to set about pocket milling them to get the final shape. When I did this on my lathe I put them both in the vice and milled out the middle, any machinists with some ideas on how best to do the back side milling?

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    Last edited: Feb 1, 2019
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  11. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    This is how I milled out the back/middle section last time. I’m sure this is not ideal as given the amount being milled out there’s not much meat holding the parts.

    upload_2019-2-2_16-24-8.jpeg

    My vice is much bigger this time. Do those with milling experience have any advice? I think my options are:

    1. Do what I did above and go slow
    2. Mill out the backs on each individually and leave them only with pockets. Then find a way to clamp them to the milling table (I don’t have any clamps yet, just the vice) and break the sides open.
     
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  12. MACKIE1975

    MACKIE1975 Well-Known Member

    Messages:
    825
    Just came up on the auction site

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  13. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    There’s always a few on there. Crazy prices though.
     
  14. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    A couple of hours on the mill this morning and I’ve managed to knock out the end panels. I’ve yet to drill the holes for the mounting posts but I’m waiting on my keyless chuck for the mill so I can do it on that instead of my drill press.

    First up I milled out the centre section. I didn’t go as deep as last time as I tested the old end panels on the preamp and realised I only needed 10mm depth.

    Went slow to ensure I didn’t pull the parts out of the vice:

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    It makes a real mess so I’m glad I made the Perspex chip guard. Next up I grabbed an 8mm end mill and set about milling the stepped down end sections. These only need to be 2mm low and took no time to do:

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    Here they are in their primary stages:

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    Here is one against the old one I made. A real step up in quality and accuracy:

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    It was then I realised I had some of the rounded corners still present on the front. Not an issue as I had a load of material to play with on the depth, so I put the parts back in the mill and took a skim cut of the fronts. I also took a 4mm end mill and cut the corners of the step down section so the radius was right and didn’t foul the glass.

    All done and ready for drilling the mounting holes and then polishing:

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  15. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    End panels are marked up and mounted in the vice:

    6FDA56CF-3ACA-468C-9A69-CB256FDECEAA.jpeg

    Need to be patient and wait for my keyless chuck to arrive before I drill them. I’ll likely drill them out to 5mm and then figure out a way to mount them.

    I’m thinking I will use a plastic, nylon, delrin insert in the hole and press that in with an undersized hole in it that will tightly grip the metal rod/post on the upper and lower rails.
     
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  16. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    My drill chuck arrived for my mill (it’s amazing how cheap you can get these things these days) and I set about drilling my mount holes. I’ve gone 5mm and 8mm deep with a plan to inset some plastic to receive the posts on the upper and lower rails. I have Acetal, Nylatron and Delrin I can use so plenty of options to try.

    Here it is being drilled:

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    So I have 2 end panels:

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    I need to finish them. So I grabbed my sanding block from when I did the front panel:

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    But decided against it as I wanted to wet sand with a constant stream of water. So instead I mounted some 600 grit on a piece on pine and run cold water over it in the kitchen sink:

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    Given the issues I had last time I started with 600 grit to make sure I didn’t round off the edges. I was amazed that the 600 grit didn’t take long to get rid of the milling marks, a testament to how well my newly acquired mill is working.

    Sanded 600, 800 and 1200 grit:

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    Next up I whacked some tunes on in the garage and set about polishing the end panels. Started with a rough wheel and black compound and then moved on to brown. Getting the pieces nice and hot and really working the wheel on them. I might have done a little too good a job on them as the top and bottom rails are not quite as polished, so I might have to give them another hit:

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    Test fit:

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    Loving the look!

    So all my Alu parts are now ready for anodising and I’ll get them over there ASAP. Once they’re done I’ll be ready to try and find someone to print my lettering.
     
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  17. quartersaw

    quartersaw Well-Known Member

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    959
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    Fantastic!
    What could be more satisfying than such fine craftsmanship?
     
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  18. jkaley

    jkaley AK Subscriber Subscriber

    Messages:
    91
    When we went to the moon, there were countless other things that we learned along the way. You're on a similar journey. In the end, you'll have a nice C20, but the knowledge you've gained (and shared) is the real reward. Thanks for posting all of this!
     
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  19. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
    Sydney, Australia
    Yeah I completely agree with you both. There’s something very satisfying with taking raw stock and turning it into something. Plus I love the whole process even though I sometimes get sidetracked.

    My latest sidetrack idea is to make a shop press to set my rivets. I have an old bottle jack here and think I’ll visit a scrap yard to try and find some steel to make a frame.

    I’ll make some setters and dies out of the ones I bought. Fingers crossed it works!
     
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  20. neevo

    neevo Super Member

    Messages:
    1,524
    Location:
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    Project shop press begins.
     
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