Mirror polish possible with leather strops & diamond compound?

Discussion in 'Maintenance, Tinkering & Embellishment' started by Stwida, Feb 12, 2020.

  1. Stwida

    Stwida

    23
    Feb 12, 2020
    So I've got the KME system and I know that they sell different kits you can use for a mirror edge (kangaroo strops + diamond emulsion, lapping films) but I wanted to see if I could make something that worked myself since I'm comfortable fashioning strops and their kits are a bit overpriced, imo.

    Aluminum strips cut to size + cowhide + diamond compound = has potential, no?

    So I made my strops and gathered 1500, 3000, 6000, 14000, and 100000 grit compounds.

    I get a cloudy edge that reflects light, at best. This makes no sense to me based on the grits of compound I have. This is after literally like 6 hours on AUS 8, which is super soft and easy to polish (in theory?!?!).

    I know how to mirror polish. I started all the way at 140 grit, and gradually worked my way up to 1500 on stones. I made sure scratch patterns were aligned. All that jazz.

    But for some reason, as soon as I start using the strops, polishing progress slows by like literally 95%.

    I'm at my witts end and am sick of trying to reinvent the wheel, but for the life of me I cant understand why this setup isnt working.

    I have tried almost literally everything, including but not limited to...

    Restarting the process at 600 grit to realign scratches
    Restarting the process at 140 grit to realign scratches
    Using the rough side of the leather
    Using the soft side of the leather
    Using "too much" compound
    Using "too little" compound
    Using "a normal amount" of compound
    Using compound immediately after applying
    Using compound after letting it dry
    Heating up the compound with a hair dryer
    Adding oil to the compound
    Using a ton of pressure
    Using moderate pressure
    Using barely any pressure
    Spending upwards of a half hour on each progression
    Using parallel strokes
    Using perpendicular strokes
    Using exclusively "away from the edge" strokes for the entire process
    ...and probably more I'm forgetting.

    Every time, as soon as I get off the KME diamond hones after 1500 grit, progress comes to a screeching halt.

    Thoughts?
     
    bucketstove and kreisler like this.
  2. Diemaker

    Diemaker KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    609
    Apr 28, 2017
    Try aluminum oxide or some other softer abrasive, diamond is probably too sharp for that steel. Alox or sic polishing tapes are a great start to polishing, IME.
     
  3. Stwida

    Stwida

    23
    Feb 12, 2020
    Huh........ crazy enough to work. I started on a junk knife for practice.

    Gonna go give it a try on my ZT (cpm s35vn)
     
  4. Stwida

    Stwida

    23
    Feb 12, 2020
    Follow-up: no dice. The edge always ends up very "shiny" (will reflect a phone camera light extremely brightly) but it's just got no fidelity when it comes to objects...
     
    bucketstove and kreisler like this.
  5. kreisler

    kreisler

    592
    May 11, 2012
    kudos for your efforts.
    what micron is your compound
     
  6. Mr.Wizard

    Mr.Wizard

    Feb 28, 2015
    There may be a couple of problems here.
    • Depending on grit system a "1500" stone may not be nearly fine enough to take to a "1500" compound, especially if the compound is used on a soft leather strop. What stone are you using? Have you tried the 1500 compound on as hard a piece of wood as you can find?
    • What do you mean by scratch patterns aligned? You want to change the angle of the scratches by at least 45° between each grit to make sure you are getting out all the scratches from the former step.
     
    kreisler likes this.
  7. bucketstove

    bucketstove

    Sep 23, 2014
    Hi,
    What is cowhide exactly? Have you compressed the leather or is it with as-bought squishyness?
    Also what is cloudy? Is the following image cloudy?

    micro-convexing-from-pasted-mdf.1706583/
    rounded on MDF (wood)
    [​IMG]
    flattened on TIN (metal)
    [​IMG]

    If you want increased flatness you need more rigid substrate
    People who want increased flatness stop on wood, balsa, bass, pine ...

    This is thin cardboard , is this shiny enough?
    bodog post-13861992
    [​IMG]

    bodog: if you call this crap[​IMG]
     
    kreisler and willc like this.
  8. Stwida

    Stwida

    23
    Feb 12, 2020
    This leather, as-is: Tooling Leather 2.0mm Thick Full... https://www.amazon.com/dp/B07PH99KTG?ref=ppx_pop_mob_ap_share

    The 1500 stone is the gold series kme diamond hone. I also move to 1500 compound on the leather after that before moving t the 3000 compound on leather. I didnt know I was supposed to polish on a hard surface - I thought it was the opposite... smoother = better. This could be one of my issues.

    Your scratch pattern comment might be the biggest one. The videos I've watched online have people talking about "making sure your scratch patterns are aligned" and they always move in the same direction. You're saying I should do the exact opposite? This could be a big one.....
     
  9. Stwida

    Stwida

    23
    Feb 12, 2020
    Not sure I understand the question - Isn't grit:microns just a conversion? Or is there something fundamentally different about a supposed "grit" measurement versus a supposed "micron" measurement?
     
  10. 115Italian

    115Italian

    Nov 13, 2015
    Ive hit a mirror polish on 2000 grit ceramic. I always thought you needed to use a ceramic hone prior to stropping. Also did you clean the blade before stropping?
     
  11. Stwida

    Stwida

    23
    Feb 12, 2020
    This leather, as-is: Tooling Leather 2.0mm Thick Full... https://www.amazon.com/dp/B07PH99KTG?ref=ppx_pop_mob_ap_share

    The knife job in thin cardboard impressed me beyond description. It's what I'm going for.

    Upon reviewing other responses, it looks like there may be a few things I've been doing wrong.
    1) The medium (leather)
    2) The scratch pattern - I was under the impression based on my research that I wanted my strokes on every grit to be going in the exact same direction. Rumor has it, I want the complete opposite, in fact.

    When you use that cardboard to polish - do you use any pressure, or just the weight of the knife? Now I'm sitting here wondering if I should glue cardboard to aluminum instead of leather for my custom strops...
     
    bucketstove likes this.
  12. Stwida

    Stwida

    23
    Feb 12, 2020
    I cleaned the blade to an obsessive extent before moving onto each new compound / strop.
    I've never heard of ceramic being required for a mirror polish - maybe some would claim it's necessary for edge sharpness purposes? But I'm the noobie here... :)
     
  13. ToddS

    ToddS Basic Member Basic Member

    379
    Jan 15, 2015
    I agree with the other replies here - you need to add a step between the 1500 grit diamond and the strops. I wouldn't expect it to be possible to polish away the surface damage from 1500 grit diamond with leather strops - they simply can't remove that amount of metal (maybe a powered leather belt or wheel could).

    The 1500 grit diamond surface may look somewhat "shiny" but there is actually a few microns of cold-worked metal that may even have some diamond abrasive embedded. One option is to burnish it smooth and shiny with a ceramic.
     
    Mr.Wizard likes this.
  14. Stwida

    Stwida

    23
    Feb 12, 2020
    Interesting.

    What's funny is, a long time ago when I was just starting all of this and doing freehand whetstone sharpening, I got a REALLY good looking mirror edge on a 6000 grit king stone. I had no clue what I was doing, and wasn't even trying to polish it, but it ended up happening.

    So, what, in theory my grit-levels in my compounds are fine, but the medium that I'm using to put them to work is likely the issue? If I was to stick to the KME guided sharpening system, what do you think is the answer here? Making new strops with some form of wood rather than leather?
     
  15. ToddS

    ToddS Basic Member Basic Member

    379
    Jan 15, 2015
    Polishing is a 3 step process; plane grinding (making the surface flat or setting your bevel), fine grinding, and polishing. You have skipped the second step. A grit in the 5-10 micron range is OK for fine grinding, but it must be on a firm surface so that the grit particles can be forced to penetrate the surface and actually grind away material (albeit slowly). In the final step, we use a softer substrate that can't provide sufficient force to cause a scratch. This is why polishing compound always has the warning to use a "soft cloth."

    https://www.struers.com/en/Knowledge/Grinding-and-polishing#about
     
    Eli Chaps likes this.
  16. Stwida

    Stwida

    23
    Feb 12, 2020
    So, just to make sure I understand... You're suggesting that my main problem is the substrate that I'm attempting to use to apply the compounds (leather, as opposed to something more firm to facilitate abrasiveness)?

    And when you refer to "the final step", that might be a more appropriate time for the leather (or a "soft cloth")?
     
  17. ToddS

    ToddS Basic Member Basic Member

    379
    Jan 15, 2015
    Yes, you need something that actually grinds away metal, but with shallow surface damage, and some burnishing won't hurt either. The final polish can then be done with leather strops.
     
  18. Stwida

    Stwida

    23
    Feb 12, 2020
    Makes sense. Yes, the one thing I immediately noticed and was baffled by was the lack of any visible metal being removed using the compound and strops. I would literally work on a single side of the knife for upwards of half an hour and get just the slightest hints of grey (metal) when cleaning the knife off. Virtually nothing showed up on the strop.

    I will be trying this tonight to see if I get different results. I'm betting I will. My father works in a machine shop and provided me with the compounds 1500, 3000, and 6000. The picture of the work he does using 3000-grit far surpasses anything I've done all the way up to 100000-grit. I knew it had to be something I was missing, rather than the compound itself.
     
  19. Mr.Wizard

    Mr.Wizard

    Feb 28, 2015
    Todd doesn't need me to confirm what he's saying (see his site http://scienceofsharp.com/ and you'll understand) but just to put it another way: an individual abrasive grain only cuts as deeply as it is pressed into the workpiece. Nickel bonded diamond has virtually no give and can produce great pressure and thereby penetration depth. On the other hand abrasive particles will sink all the way into leather, at least when it's new and clean, with only the peaks lightly pressing against the workpiece. This has an equalizing effect on grain size making most compounds act very fine regardless of grade. For this reason coarser diamond compounds are typically used on harder polishing implements such as hardwood sticks or copper plates.

    You can align your strokes at each grit level, but changing directions between grits to "cross out" previous scratches is a standard practice for polishing. Your strokes at the final polishing level can still be aligned to maximize appearance.
     
  20. Stwida

    Stwida

    23
    Feb 12, 2020
    Thank y
    Thank you so much. This is about as straightforward as it gets. Much appreciated.
     

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