Scrub plane blade radius

[Howard Skillington]

I had been looking at maybe springing for a LV or LN scrub plane when I saw Shannon Rogers’ video in which he suggests converting a cheap plane into a scrub since it is, after all, a rough tool, and saving the budget for another plane whose function requires more precision.

This makes sense to me, so I’m using an old Stanley No. 5 for this project and have spent the money, instead, on a new Wood River jack.

LN and LV both put a 3” radius on the 1-1/2” wide blades of their scrub planes. For his jack-to-scrub conversion, Rogers grinds an 8” radius on that 2” wide blade. (he also moves the frog way back)

Playing with this in AutoCAD I note that a 3” radius on a 1-1/2” blade provides 3/32” of relief from center to corner. That same radius on a 2” wide blade results in almost twice as much: 11/64.” And Rogers’ 8” radius on his 2” wide blade results in just a sixteenth, but it works fine when he demos it at the end of the video.

My question: does anyone’s experience with scrub planes here in the Haven give you a passionate opinion on what the blade radius should be, or is it simply not very critical?

[Tom M King]

3124203124218" is fairly standard for a Jack plane. I'm not sure what the radius is on my Scrub plane, but it's a LOT shorter than the Jack iron radius. Here are a couple of pictures of my Emmert Scrub plane that I bought new in the '70s. We only use it for scrubbing old beams and boards before putting any kind of good cutting edge in them. It'll still throw chips 3 feet in the air even when it's seriously dull like in the second picture. Weathering on the plane is from sweat, and that's not a shadow at the mouth. I expect the reason we don't see antique scrub planes is that they just used smoothers that had worn the mouths too much to be a good smoother any more.

[Nicholas Lawrence]

The distance from the start of the curve (on the side of the blade) to the "longest" part of the cutting edge on mine (a Stanley #40) is about 1/8 of an inch. It cuts well.

[John Vernier]

The thing is, that if you use the tighter radius on a wider blade, you end up with a blade which you really can't use the full width of, because it will cut way too deep for most practical purposes.

I have a couple of scrub planes (a Stanley 40 and an old German wooden horned plane, similar blade width to the Stanley), both with something like a 3" radius. They work well and I use them for aggressive hogging , especially if I'm flattening a piece of rough-split green wood, where I have a lot of thickness to remove from certain areas. I also have a Stanley#5 with a much gentler radius, maybe 1/16" depth of curve to the edge, call it 8" or so but I haven't measured it in a long time, as I freehand sharpen it. I find this a much easier plane for typical flattening of rough sawn dry boards. It cuts a shallower furrow, but wider, and it cuts it very easily. In terms of which plane removes wood faster I'd say it's a wash, but the #5 gives more control towards the goal of flattening a board surface, while the scrub, with its smaller sole and deeper cut, can get away from you, and doesn't lend itself to making a flat surface as easily.

[Howard Skillington]

Thanks for your responses, gentlemen. They all make sense, given the differences in the tools and your uses of them. I think I'll go with 8" for my old jack. If I get to a point where I feel like I'\m ready for a more aggtressive tool I can always grind the radius a bit tighter later on.

[steven c newman]

Happen to have both a jack with the 8" radius, and a #3 sized one with a 3"radius

First off, the jack plane was just a Corsair C-5 jack. $8 at an antique store. Ground an 8" radius on the iron, have sharpened it once since

Secondly, that #3 was a Harbor Freight Windsor #33. It has a nice thick iron, and it has been ground to a 3" radius. It has been resharpened once since. They sell the Windsor #33 for around $10 or so, and you can even use the coupons.

Been using the jack a little bit more, as a few table tops needed some working over
312437
Yep, them scallops. Then go over them at the diagonal with a regular jack plane.
312438
until the scallops go away.

[Howard Skillington]

Just checked out the Harbor Freight site for the Windsor 33 and several people recommend it for scrub conversion. For eight bucks, what the heck...

[Pedro Reyes]

I had been looking at maybe springing for a LV or LN scrub plane when I saw Shannon Rogers’ video in which he suggests converting a cheap plane into a scrub since it is, after all, a rough tool, and saving the budget for another plane whose function requires more precision.

This makes sense to me, so I’m using an old Stanley No. 5 for this project and have spent the money, instead, on a new Wood River jack.

LN and LV both put a 3” radius on the 1-1/2” wide blades of their scrub planes. For his jack-to-scrub conversion, Rogers grinds an 8” radius on that 2” wide blade. (he also moves the frog way back)

Playing with this in AutoCAD I note that a 3” radius on a 1-1/2” blade provides 3/32” of relief from center to corner. That same radius on a 2” wide blade results in almost twice as much: 11/64.” And Rogers’ 8” radius on his 2” wide blade results in just a sixteenth, but it works fine when he demos it at the end of the video.

My question: does anyone’s experience with scrub planes here in the Haven give you a passionate opinion on what the blade radius should be, or is it simply not very critical?

I hate to be the engineer who overthinks sometimes. But often it is not too bad.

I have a 40, but I also wanted to convert an old (cheap) 5-1/4 to a less aggressive scrub/jack in between. I don't have the 40 to go measure with me, but rather than marry a radius, I was approaching it from a projection standpoint. I could share my geekyness and point you to a site where you can calculate projection given a blade width and a radius (or rather calculate a radius given a desired blade projection). More importantly what I would care about is the actual "area" a blade projects, because that is directly related to the amount of wood removed with each successful stroke, and there is a sweet spot somewhere between ease of push and number of strokes.

Assuming better old timers knew best, I would say somewhere between 1/16" and 1/8" projection is good for blades between 1-1/4" and 2" or even 2-1/4".

So your 2" blade projecting 1/16" (instead of 3/32") is likely close to the same projected area (I have not calculated it) so effectively removing the same amount of wood as a scrub (shallower and wider).

Pedro

[Ivan Wolder]

Go to You tube look up Paul Sellers scrub plane and watch his video.I keep going back to him as he shows a very uncomplicated way of doing things that have been proven over time.

[David B. Morris]

...I also have a Stanley#5 with a much gentler radius, maybe 1/16" depth of curve to the edge, call it 8" or so but I haven't measured it in a long time, as I freehand sharpen it. I find this a much easier plane for typical flattening of rough sawn dry boards. It cuts a shallower furrow, but wider, and it cuts it very easily. In terms of which plane removes wood faster I'd say it's a wash, but the #5 gives more control towards the goal of flattening a board surface, while the scrub, with its smaller sole and deeper cut, can get away from you, and doesn't lend itself to making a flat surface as easily.
I agree with this approach. I recently re-purposed an old no. 5 with a 9" radius camber on a new Hock blade. I also filed open the mouth a bit. I find this to be a good compromise between speedy stock removal and control, especially for taking out twist, cup, and the like before moving to a jointer. It's easy to get carried away with scrubbing and create tear-out that will have to be dressed up with a jointer or smoother later. The 9-inch camber provides some insurance against that tendency, but is still fast. For really heavy removal I would reach for my 40 1/2.

[Robert Engel]

Just checked out the Harbor Freight site for the Windsor 33 and several people recommend it for scrub conversion. For eight bucks, what the heck...Stumpy Nubs made one into a scrubber and says it works good.

[Patrick Harper]

I put an 8" radius on my jack, and it works great. As others have pointed out, I think it's more important to get the cutting depth correct. Wider blades will need a larger radius and vise-versa.

[ken hatch]

3124203124218" is fairly standard for a Jack plane. I'm not sure what the radius is on my Scrub plane, but it's a LOT shorter than the Jack iron radius. Here are a couple of pictures of my Emmert Scrub plane that I bought new in the '70s. We only use it for scrubbing old beams and boards before putting any kind of good cutting edge in them. It'll still throw chips 3 feet in the air even when it's seriously dull like in the second picture. Weathering on the plane is from sweat, and that's not a shadow at the mouth. I expect the reason we don't see antique scrub planes is that they just used smoothers that had worn the mouths too much to be a good smoother any more.

Tom,

I have the same scrub plane also acquired back in the 70's, must say mine looks a little better :) not that it makes a difference for a scrub. All the metal plane conversions are great and I expect maybe a little cheaper but....If you have never used a horned wood scrub you are missing one of the true pleasures of wood working. Light, easy to control, glides with ease across any wood, just delightful to use. I just checked Highland"s web site, less than $100 USDs. It would be a bargain at twice the price.

ken

[Tom M King]

Tom,

I have the same scrub plane also acquired back in the 70's, must say mine looks a little better :) not that it makes a difference for a scrub. All the metal plane conversions are great and I expect maybe a little cheaper but....If you have never used a horned wood scrub you are missing one of the true pleasures of wood working. Light, easy to control, glides with ease across any wood, just delightful to use. I just checked Highland"s web site, less than $100 USDs. It would be a bargain at twice the price.

ken

Ken, Yeah, I don't know why anyone would want anything else. It's the lightest plane I own. I have no idea how many square feet it's cleaned up over the years, but it's more than a few. That plane has never gotten wet or been left out anywhere. All the weathering is from sweat, and the wear in front of the blade is from wood shavings. It's been used all day long more than a few days. It's fun and easy to throw shavings several feet in the air as dirty wood reveals what's underneath the dirt.

I can only remember ever using it to flatten one severely warped timber. A Jack will remove wood plenty fast enough for normal work. My Scrub plane is only used for scrubbing. I never knew people used them for anything else.

[Pat Barry]

I hate to be the engineer who overthinks sometimes. But often it is not too bad.

I have a 40, but I also wanted to convert an old (cheap) 5-1/4 to a less aggressive scrub/jack in between. I don't have the 40 to go measure with me, but rather than marry a radius, I was approaching it from a projection standpoint. I could share my geekyness and point you to a site where you can calculate projection given a blade width and a radius (or rather calculate a radius given a desired blade projection). More importantly what I would care about is the actual "area" a blade projects, because that is directly related to the amount of wood removed with each successful stroke, and there is a sweet spot somewhere between ease of push and number of strokes.

Assuming better old timers knew best, I would say somewhere between 1/16" and 1/8" projection is good for blades between 1-1/4" and 2" or even 2-1/4".

So your 2" blade projecting 1/16" (instead of 3/32") is likely close to the same projected area (I have not calculated it) so effectively removing the same amount of wood as a scrub (shallower and wider).

Pedro

You scared the heck out of me with your first comment ""I hate to be the engineer who overthinks sometimes." I read that and thought, oh boy, here comes the science lesson and formula's. But then you got all practical and pragmatic and I could relax a bit. Thanks Pedro, I think you are right on with your approach. By the way, I'm an engineer too and was just kidding about the being scared part. LOL

[Howard Skillington]

Pedro - Glad to have an analytical sort weigh in. Your line of reasoning on this issue is similar to my own; I just haven't collected any empirical data yet.

It is said that there are many paths to enlightenment.

[Jim Koepke]

I just haven't collected any empirical data yet.

My first thought was to not bring my blasphemy into this thread. Then this came to mind:


Just checked out the Harbor Freight site for the Windsor 33 and several people recommend it for scrub conversion. For eight bucks, what the heck...

Thinking with eight bucks on the line, how much empirical data does one need to collect? The bad ebay deal that turned a lemon (beat up #5-1/4) into lemonade (a usable scrub plane) cost me more than eight bucks.

Take a chance and learn from the hard knocks of going to the shop and just doing it.

Scrub plane blade radius? I have no idea. My scrub blade was just held on the platen of my Veritas™ Mk II Power Sharpening System and swung around a bit until it was obvious the blade wasn't straight across. Put it in the plane and it seemed to work fine. If it wasn't doing what was wanted, then it would be reground to correct as needed.

Maybe there is a "perfect" radius to use for each blade. Mine seems to be working fine as it is. Maybe I was just lucky.

If it weren't for good luck, I would have no luck at all. :D

jtk