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Thread: Looking for an easier way to flatten the back of plane irons

  1. #1
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    Looking for an easier way to flatten the back of plane irons

    In my hobby of restoring old bench planes, the hardest task for me is flattening the back of plane irons. I currently use an extra coarse DMT diamond hone which works quite well but can be time consuming (I follow this with a Trend 300/100 2-sided diamond hone and then extra-fine sandpaper). However, I have some arthritis in my fingers that makes grinding on the extra coarse hone for any length of time quite painful.

    So, I have considered buying a “Work Sharp 3000” sharpening system for the flattening process, which uses a 6” flat tempered glass lapping plate with PSA sandpaper and runs at 580 rpm. I’m not sure if it would make flattening an iron any faster, but would hopefully be kinder to my fingers.
    But really, I don’t need the other bells and whistles offered by the Work Shop machine – I’m happy using my CBN wheel to cut a hollow-ground bevel followed with several flat stones to cut a secondary bevel – not hard on my fingers. So, I’d like to avoid spending the $200 on the Work Shop machine if there’s another, cheaper way. (I know there’s also a Veritas MK machine out there, but that’s beyond my budget).

    So, here’s one idea and a few questions:
    - I have a benchtop drill press that I can adjust the speed down to 740 RPM. Would it be feasible to chuck one of the Work Shop tempered glass discs to my drill press and use that with the Work Sharp coarse sandpaper discs to flatten plane irons? (The glass disc is 5/8” thick and available as a Wood Sharp accessory for $20 + the cost for sandpaper discs).

    - I’d need to get some kind of mandrel or arbor to adapt the glass disc to use in my drill press (does anyone know the hole size of that disc?). Would that mandrel/arbor need to be anything special to hold the glass disc (e.g., without cracking it and without adding wobble)?

    - I assume my drill press speed of 740 RPM would be ok for flattening plane irons with coarse sandpaper on the glass disc. Am I correct?

    - Is this just a bad idea (if so, why)?

    - Alternatively, is there perhaps a completely different solution for easily flattening plane irons and avoiding painful fingers?

    Thanks in advance for any comments and suggestions!

  2. #2
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    Ya there is another way to use a diamond plate or a corse stone that can be kept flat.
    Hold it like this.
    Im use a piece of hard maple to bear down on plane iron.
    Good Luck
    Attached Images Attached Images
    Aj

  3. #3
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    Alternatively, is there perhaps a completely different solution for easily flattening plane irons and avoiding painful fingers?
    Do you have a belt sander and a vise big enough to hold it upside down?

    Belt Sander Comes in Handy.jpg

    Here a belt sander is being used to work on the bevel of a chisel.

    When flattening the back of a plane iron only the first 1/4" really needs to be worked. Just enough to seat against the chip breaker. One could likely get by with even less than that. My preference for a 1/4" is after this each time the blade is sharpened a bit more of the back gets worked. With less than 1/4" you will have to work more of the back sooner.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  4. #4
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    I restore planes too and on hard to flatten irons I start with 60 or 80 sandpaper glued to a granite tile. I then sand my up back to the coarse diamond stone. I don't skip any grits and use 100, 120, 150, 180, 220, and 320. I usually go to the diamond stones after 320. I also use a block of wood like Andy suggested.

  5. #5
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    Here is another thought that came to mind when rereading and seeing:

    However, I have some arthritis in my fingers that makes grinding on the extra coarse hone for any length of time quite painful.
    For marking corners to be rounded a lot of circle templates have been made:

    Wooden Circles.jpg

    This is only a few of them, they all have knobs or handles.

    One of the small ones works great for applying pressure to a blade being worked without stressing the fingers:

    Working Blade Back Circle Template Press.jpg

    It could be just a scrap of wood or it could be a piece made for the sole purpose of working blades.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #6
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    Ok, that would be easier on my fingers, but how do you prevent the iron secured to the underside of the piece of wood? Maybe hot-melt glue?

  7. #7
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    Quote Originally Posted by James Spangler View Post
    Ok, that would be easier on my fingers, but how do you prevent the iron secured to the underside of the piece of wood? Maybe hot-melt glue?
    It isn't, my hands work in tandem.

    If one wanted to make it more secure the underside could be made with a proud center to sit in the slot on the iron.

    Mine is used on plane blades and chisels but was made primarily as a circle template. It has found an exta use.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  8. #8
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    Let me preface this by saying that now that I’m in my 70s, some things neander are no longer labors of love but simply laborious and cause for discomfort. Similar to Jim’s suggestion, instead of a portable belt sander I use my 6x48 stationary belt/disc sander to flatten the backs of plane irons. If you have one, just make sure the platen is perfectly flat (it probably is) and use a 240 grit belt. Very light hand pressure makes quick work of an odious task and you can then move on to finish up with your stones. I wear leather gloves just in case of a slip, but I’ve never had one. Btw, I have one belt dedicated to this, so as not to contaminate wood with any metal particles.
    Last edited by Stephen Rosenthal; 06-19-2021 at 3:23 PM. Reason: Typo

  9. #9
    David Weaver has a video on his youtube channel showing a simple jig he made to hold the iron. He uses rolls of sandpaper on a long glass sheet . Its seems efficient, easier because of the jig and cheap as he uses regular sand paper and a glass shelf.

  10. #10
    Fine Woodworking had a tip this month to attach a block of wood to the front of the blade with double stick tape. I have some chisels and plane blades that I need to flatten. I shall try it and report back.

  11. #11
    Quote Originally Posted by Eric Rathhaus View Post
    David Weaver has a video on his youtube channel showing a simple jig he made to hold the iron. He uses rolls of sandpaper on a long glass sheet . Its seems efficient, easier because of the jig and cheap as he uses regular sand paper and a glass shelf.
    I have that jig, someplace! When I first started using handtools, David used to hang out here and recommended it to me. It works well for flattening by hand.

    Couple thoughts on the OP's question:
    * I have a Worksharp. It isnt as good for flattening plane irons as I'd hoped, but it works. I added a footswitch so I could position the iron before starting the machine. I use diamond lapidary disks instead of sandpaper.
    * You might be able to do as well on your drill press. I'd be concerned about that glass disk breaking. You might want to attach it to an MDF disk or such.
    * I just checked 2 of my Worksharp glass disks - the hole is 7/16" (may be a tad over).

    * Harbor Fright sells 4x36" stationary belt sander for $79. That might be a better move.

    Fred
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  12. #12
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    Thanks everyone for the comments and suggestions.
    Further investigation on the web uncovered a vendor (Woodcraft) that sells the tempered glass disks for the Work Shop.
    In that description it says "650 maximum RPM."
    So the answer to my main questions is "No, do not run it on your drill press at 740 RPM."

    I will follow-up on some of your suggestions to continue to use the extra course diamond hone with some sort of aid attached to the iron to take the stress off my fingers.

    Regarding the belt sander suggestions, I have an old Ryobi 3x21 portable belt sander that I bought back in the 80's that I love, because the top of it is flat and I can run it upside down clamped between bench dogs. I've tried using it to flatten a plane iron and the iron came out dished a bit in the middle. So I guess the platen is not flat. This thing is out of production and no one sells parts for it any more so I gave up trying to find a replacement platen.

    And thank you Frederick for your comments about using the Work Sharp 3000 to flatten irons. I am still considering that option.

  13. #13
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    Easiest way for me.....to flatten the back of a plane iron.....IF it even needs it, to start with........turn my 6" grinder on....hold the back of the iron to the side of the spinning wheel....1..2..3..4...5...dunk...and check for flat...will check after each...rarely need to go the full 5 seconds.....

  14. #14
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    Using the side of a grinding wheel is a lot like poking at a hornets nest.
    Aj

  15. #15
    I know it might be convenient and I imagine lost of folks have been doing it for ages but Andrew is absolutely on target - wheels are not designed for that kind of use. A wheel failure is likely to be catastrophic to more than just the wheel.

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