Converting a #4 to a scrub plane

[Scott Winter]

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.

[Mike Kreinhop]

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.

[ken hatch]

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

[Scott Winter]

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!


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.

[Jim Koepke]

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

[steven c newman]

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.

[Scott Winter]

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!

[Bruce Haugen]

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.

[Patrick Chase]

Sort of nit-picky but...



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.

[Patrick Chase]

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.

[Jim Koepke]

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.


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

[Ron Patrick]

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.

[Bob Glenn]

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.

[Sam Stephens]

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.

[Roy Lindberry]

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.

[Scott Winter]

I ended up grinding down the iron to a 6 1/2" radius last night. Didn't get a chance to finish sharpening the blade since the Sunday night football game was about to start. Other than that all I have to do is file open the mouth slightly, and it'll be all done.

Thanks all for the advice and help!!

[steven c newman]

Ok, here is a shot of the cutter in the Windsor #33 scrub plane..
372875
Plane is about the size of a Stanley #3. Iron is a lot thicker, though...
372876
A shot of it bevel up.....Due to the way the plane adjusts.....bevel does not need to be exactly ground. There is also no chipbreaker used.

When these planes first came out, they were about $9.99+ tax.....now? They run about $15...