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Thread: Converting a #4 to a scrub plane

  1. #1
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    Converting a #4 to a scrub plane

    Hey all,

    I've been thinking about what to do with my inferior #4 smoothing plane I got for about $20 off Amazon. I was thinking about converting it to a scrub plane instead. I was curious at how much of a camber I should put on the blade? I've read anywhere from an aggressive 3" all the way to 8". I'm not sure how aggressive I should go with only a 9" base. I'm going to be using it on rough sawn timber.

  2. #2
    I remember seeing a Paul Sellers video where he converted a Stanley #4 smoothing plane to a scrub plane. He used a 7-inch radius for the camber, knocked the corners of the chip breaker off, and slightly enlarged the mouth of the plane with a file.

  3. #3
    Scott,

    A purpose build scrub's iron is very narrow and has a very aggressive camber.check out the ECE scrub plane. A number 3 would make a better scrub but the 4 can work.

    A better option is a nice wood stock scrub, they are very cheap and last a long time. Mine is going on 40 years.

    Bottom line a converted plane is a kluge, they will work but....
    .
    ken

  4. #4
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    Quote Originally Posted by Mike Kreinhop View Post
    I remember seeing a Paul Sellers video where he converted a Stanley #4 smoothing plane to a scrub plane. He used a 7-inch radius for the camber, knocked the corners of the chip breaker off, and slightly enlarged the mouth of the plane with a file.
    I'll have to see if I can dig this up. Thanks!

    Quote Originally Posted by ken hatch View Post
    Scott,

    A purpose build scrub's iron is very narrow and has a very aggressive camber.check out the ECE scrub plane. A number 3 would make a better scrub but the 4 can work.

    A better option is a nice wood stock scrub, they are very cheap and last a long time. Mine is going on 40 years.

    Bottom line a converted plane is a kluge, they will work but....
    .
    ken
    I appreciate the advice Ken. Main reason I am doing it with this #4 is because it is very bad at its designed job, so I wanted to at least make it somewhat useful.

  5. #5
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    Unless the plane has adjustment issues, there shouldn't be a need to modify the chip breaker. The chip breaker on a scrub plane is only connecting the blade to the adjustment mechanism. The #40 scrub plane doesn't have a chip breaker.

    Just about any bench plane could serve as a scrub plane. One aspect of the scrub plane is its lightness so it can be directed at smaller targets to knock down a twisted corner or stand up edge.

    It might help to consider the kinds of surfaces to be worked with a scrub plane to determine the radius of camber. A bigger radius if you are working with stock needing light removal or hard woods. A smaller radius would be for heavier removal and softer woods.

    Turning a lemon #4 into a scrub plane is about the same as my #5-1/4 piece of a bad deal on ebay turned to scrub.

    Yeap, bad deals happen, sometimes they can be salvaged.

    jtk
    Last edited by Jim Koepke; 12-03-2017 at 2:16 AM. Reason: wrong plane #
    "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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    I have a "Corsair C-5" by Great Neck Tool Co........Just a cheap jack plane...however, it has had a 8" radius camber added to it's 2" wide iron. Corners of the chipbreaker are right at the corners of the iron. I think I might have resharpened it once or twice in 3 years...

    Works very nice as a scrub plane.

    The Windsor #33 from Harbor freight is a #3 size non-chipbreaker plane....grind a 3" radius to the iron, and call it good. I use mine where a smaller scrub plane works better than a jack plane.

  7. #7
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    Quote Originally Posted by steven c newman View Post
    I have a "Corsair C-5" by Great Neck Tool Co........Just a cheap jack plane...however, it has had a 8" radius camber added to it's 2" wide iron. Corners of the chipbreaker are right at the corners of the iron. I think I might have resharpened it once or twice in 3 years...

    Works very nice as a scrub plane.

    The Windsor #33 from Harbor freight is a #3 size non-chipbreaker plane....grind a 3" radius to the iron, and call it good. I use mine where a smaller scrub plane works better than a jack plane.
    I have the C4 Great Neck plane that is going to be the one I am converting to a scrub plane. I am actually headed to Harbor Freight today, so I may look to see their #3 and make that a smaller scrub plane as well. I was actually going to get a cheapy bench grinder to do the deed, so I'm glad you mentioned their plane as an option as well!

  8. #8
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    What serves as a scrub for me is a dogmeat #5. I just radiused the iron until it worked for me. I have no idea what the radius is, and suggest that you not get hung up with something exact. It's for hogging wood that's not supposed to be there, not for machine precision. Remember, you need to be able to push it. Too great a camber and you'll be taking a deep cut that's hard to sustain.

  9. #9
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    Sort of nit-picky but...

    Quote Originally Posted by Jim Koepke View Post
    Turning a lemon #4 into a scrub plane is about the same as my #5-1/4 piece of a bad deal on ebay turned to scrub.
    The 5-1/4 (though not LV's rather different "5-1/4W") has a 1.75" iron, so it would use a ~25% smaller camber radius than a #4 to achieve any given cut depth.

  10. #10
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    Quote Originally Posted by Scott Winter View Post
    Hey all,

    I've been thinking about what to do with my inferior #4 smoothing plane I got for about $20 off Amazon. I was thinking about converting it to a scrub plane instead. I was curious at how much of a camber I should put on the blade? I've read anywhere from an aggressive 3" all the way to 8". I'm not sure how aggressive I should go with only a 9" base. I'm going to be using it on rough sawn timber.
    I'd do about 6" camber radius on a #4.

    For the range of widths/radii we're talking about, cut depth at full extension (the extension such that the corners are level with sole) is roughly proportional to blade_width^2/camber_radius. Scrub planes are indeed typically configured with 3" camber radii, but their irons are at most 1.5" wide so the resulting cut is about 1/16" deep in the center. If you put that same 3" radius on a #4's 2" wide iron then it will take a ~1/8" deep cut at full extension. That's not going to be manageable in anything much harder than Balsa.

    In contrast a 6" radius on a 2" iron yields a 1/16" cut at full extension, which is pretty reasonable IMO.

    Of course you can also use a smaller radius and simply take narrower cuts by never extending the iron all the way.

  11. #11
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    Quote Originally Posted by Patrick Chase View Post
    I'd do about 6" camber radius on a #4.

    For the range of widths/radii we're talking about, cut depth at full extension (the extension such that the corners are level with sole) is roughly proportional to blade_width^2/camber_radius. Scrub planes are indeed typically configured with 3" camber radii, but their irons are at most 1.5" wide so the resulting cut is about 1/16" deep in the center. If you put that same 3" radius on a #4's 2" wide iron then it will take a ~1/8" deep cut at full extension. That's not going to be manageable in anything much harder than Balsa.

    In contrast a 6" radius on a 2" iron yields a 1/16" cut at full extension, which is pretty reasonable IMO.

    Of course you can also use a smaller radius and simply take narrower cuts by never extending the iron all the way.
    When using my scrub plane, it is seldom if ever set to take a full width shaving.

    Quote Originally Posted by Patrick Chase View Post
    Sort of nit-picky but...

    Originally Posted by Jim Koepke
    Turning a lemon #4 into a scrub plane is about the same as my #5-1/4 piece of a bad deal on ebay turned to scrub.
    The 5-1/4 (though not LV's rather different "5-1/4W") has a 1.75" iron, so it would use a ~25% smaller camber radius than a #4 to achieve any given cut depth.
    My point is Scott has a plane that didn't meet the expectations he wanted in a bench plane. My bum ebay deal of a #5-1/4 also fell short of my expectations for a bench plane. Two lemons turned in to two servings of lemonade.

    The radius on my scrub is neither known to me nor does it matter to me. It is always easy to change it if it isn't working. It was cambered to a radius that "felt right" at the time. In use my shavings are an inch wide at most.

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

  12. #12
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    I converted a 1970's stanley no. 5 (wasn't good for much else) ala CS and used an 8" camber, works great. Have thought about doing this with a no. 4, and, since it is the same sized blade, the 8" camber should work just as well.

  13. #13
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    I did the same with a number 4 that I couldn't make work for anything else. It works great. Don't sweat the numbers, just grind, hone and use it. It will work out just fine.
    Life's too short to use old sandpaper.

  14. #14
    My preference is for an aggressive cut with a scrub -I used a dinner plate to draw the radius so it's probably ~5". Definitely not taking a full-width shaving with this, but that's not the point. the point is to quickly and aggressively eliminate the high spots. Mine is a converted #4 that already had a wide mouth. Smaller plane is preferred usually b/c it's less weight. I wouldn't worry much about the cap iron. Chatter shouldn't be a problem. Most of the scrub work is done cross-grain anyways.

  15. #15
    My fore plane is a Stanley number five with a 6" radius on the iron. No other modifications were necessary, and it works very well for my purposes.

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