Bigger Convex Curve than #18 Hollow Moulding Plane - How to?

[Paul Carson]

Hello,


I'm interested in trying to reproduce some picture frame moulding which incorporates a wide (2.5 - 3 inches / 60-80mm) shallow convex curve. I'm awaiting the arrival of the largest hollow plane #18, which I believe, produces a 1.5 inch wide convex curve but this is about half the size I require. And I haven't seen any individual moulding planes with this profile.


Can anyone recommend a hand tool process to produce this kind of curve on moulding?


Is there a reason that hollow and rounds stop at this width?


Many thanks, Paul

[Zach Dillinger]

Here's how I would do it. First, lay out the curve on the end grain of the wood, then plow grooves of various depths in various locations so that the bottoms of the grooves come to or very near the curved line. Split off the waste between the grooves with a chisel, then carefully finish plane the curve using a regular bench plane, finishing with a curved scraper if needed. If the sides of the curved piece are tight to another piece, you might need to use an open sided plane to finish the work in order to cut right up to the edge.

Failing that, if you are in a tool making mood, you can always make or modify an existing plane to imbue the sole with the proper radius.

[Warren Mickley]

Making a moulding plane three inches wide would not work well because the shaving has to get all the way out the side of the plane. I would rough the moulding out with a jack plane. Use a marking gauge on each edge so you know how deep you are going, but do the rest by eye. You are not talking about very much depth here so it should not take very many passes. Then smooth things out with a smoothing plane. When using the smoothing plane, concentrate on just altering the angle very slightly from pass to pass, rather than trying to eliminate a particular ridge left by the jack plane.

If you were doing a lot of this moulding, you could alter a wooden smoothing plane to have a slight concavity on the sole and on the iron. This takes a lot of work and skill to get going, although in the long run it would yield the nicest surface with the least effort.

A hollow plane that is 1.5 inches wide does not just produce a 1.5 inch wide moulding. It produces a moulding that has a radius of about 1.5 inches, but this moulding could be a half inch wide or three inches wide, whatever you want. And actually if you had a 1.5 inch hollow plane, you could alter it to cut a much bigger radius. I doubt you are making enough moulding to justify the trouble.

[James Waldron]

If I had a lot of this work to do, I'd consider making a round bottom "Krenov" style moulding plane, with the shaving escaping out the top. In my view, a traditional style moulding plane would be a prohibitively lengthy and difficult investment for a single use tool. The glued-up plane works as well as a traditional style construction.

For a lesser effort, I'd go my 10-1/4 (because it cuts all the way to the edge of the plane) to rough out the cove (possibly with saw kerfs for a deep cove), refine a bit with a narrower rabbet (rebate) plane, and then maybe go at the refinement with a No. 18 or a suitable gouge on the high spots, and finally finish the surface with a curved scraper.

For the "tailed species" such a cove is made with an angled cut across the blade of the table saw. Busy set-up and requires multiple small bites to avoid damage to the blade messy surface on the work. Lots of noise and saw dust involved. A somewhat dangerous practice even by table saw standards. Requires removing all safety protections. I've done it; don't like it at all. Not likely to ever do it again.

[brian zawatsky]

+1 on using a jack and/or smoother to rough out the curve. If you have a cheap old $2 flea market handsaw laying around you could always sacrifice it to cut out a card scraper and grind it to match the radius that you are trying to reproduce. I’ve done this before and it works very well for final fairing of the curve, but you have to get close to the proper shape using the planes first.

[chris carter]

Is there any reason you can’t just eyeball it with the 18? I should think that you could get so close that the ripples would be hard to see by eye and they’d be small enough that a few passes with a card scraper would be all that’s needed to get it perfect.

I don’t have a ton of molding experience, but when I’ve done it I never actually made my curves match the profile of the planes I own. I just did what looked good to my eye and then grabbed what was close, erring on undersizing for the rounds and oversizing for the hollows (or maybe I have that backwards).

[steven c newman]

If I remember correctly...a conVEX curve is like the state of Ohio....low on the edges, high in the middle? If so...just hand plane the curve....and clean up with a scraper. Draw the profile on the ends, plane away what is above the line....or, get a handrail plane.

[Mike Lemon]

Core box plane? But a one off plane like others mentioned would probably be easier.

[steven c newman]

IF he was doing a concave molding......as in a cove.

[Jim Koepke]

As others have mentioned doing this with a regular bench plane with the aid of a rabbet plane might be the easiest way if you do not plan on doing this for the rest of your life.

A starting point may be to make a gauge from a thin piece of wood or plywood to check your work. It likely would be too difficult to make a scraper with an arch cut into for use as a gauge and to do a little clean up if needed.

A #18 plane, theoretically, has a radius of 18/16" or 1-1/8". This would make a 2-1/4" diameter circle. If you have a large round sole plane the radius could be modified to make a shape more to your liking.

Remembering the difference between concave and convex is easy with a little helper. Concave goes in like a cave. Convex rises like a hill there to vex me when walking.

jtk

[Tom M King]

Before I started accumulating molding planes, I'd use the table saw, and shoulder plane. Use the piece you're matching to place over the table saw blade to set the fence position, and height of blade not quite touching the piece. Take that cut. Move barely one blade width over, and repeat. Once as much of that is done as possible, the shoulder plane can even out the ridges. Scraper and/or sanding sponges finish. Lacking the table saw, the same idea can be accomplished quite a number of ways.

It's just a lot more fun with molding planes.

I wouldn't bother to make, or modify a plane for one piece of molding.

[Jim Koepke]

Before I started accumulating molding planes, I'd use the table saw, and shoulder plane. Use the piece you're matching to place over the table saw blade to set the fence position, and height of blade not quite touching the piece. Take that cut. Move barely one blade width over, and repeat. Once as much of that is done as possible, the shoulder plane can even out the ridges. Scraper and/or sanding sponges finish. Lacking the table saw, the same idea can be accomplished quite a number of ways.

It's just a lot more fun with molding planes.

I wouldn't bother to make, or modify a plane for one piece of molding.

This seems like a lot of work.

The plane could be used to put a light curve on a lot of pieces in the future.

jtk

[Tom M King]

I needed it that day, and that was probably at least 35 years ago, before I was as well equipped as I am now. I don't remember how long it took, but do remember finishing that job that day. It couldn't have taken that long. Years later, my picture was in a small town newspaper making a short piece of large bed molding, on sawhorses on the sidewalk in front of the house it was going on, to replace a rotted out gable cornice molding, with hollow and round planes. For one piece of molding, any way to get it done, with what you have at hand, is the way to do it.

[Mike Lemon]

I'd use the table saw...Take that cut. Move barely one blade width over, and repeat.

That sounds like a pain. Why didn't you just run the piece through at an angle to cut the cove in just a few pass? Just curious.

[Jim Koepke]

That sounds like a pain. Why didn't you just run the piece through at an angle to cut the cove in just a few pass? Just curious.

Because he wasn't cutting a cove. He was cutting a rather large bead, even though it was shallow, it was a raised form.

Basically make the center cut, move the fence a kerf width, slightly raise the blade, then make two cuts, swinging the piece end for end between cuts with the same setting. repeat until done.

jtk

[Stewie Simpson]

Paul; view the attached video; https://www.youtube.com/watch?v=ijUDrOsHW54

[Tom M King]

That sounds like a pain. Why didn't you just run the piece through at an angle to cut the cove in just a few pass? Just curious.

I thought we were talking about a convex shape. It was for a short, missing piece on a mantle. It had a couple of quirks, but they weren't very deep. There wasn't much of a cove. It was on a strange, early 19th Century mantle. I don't know what the part of the frame looks like that this thread started about, but the question was about a convex shape. I never heard a question about a cove. It would take a LONG time to cut a cove with any hollow plane.

[Tom M King]

It seems like some people are confusing the difference between a hollow plane, and a round plane, not to mention convex, and concave.

Here is a picture of a Hollow plane. The sole of a round plane curves the other way.
https://cdn.shopify.com/s/files/1/0978/7942/products/372036_1900x.jpg?v=1497016328

[Mike Lemon]

I think the original question is throwing people (it is me). It says convex but reads like concave is meant. Convex is easy- grab any plane and go. I don't even try and I get convex when I plane.

[Jim Koepke]

I'm awaiting the arrival of the largest hollow plane #18, which I believe, produces a 1.5 inch wide convex curve [edited] Is there a reason that hollow and rounds stop at this width?

They do become harder to push the bigger they get.

My understanding is the numbering system for hollows & rounds would have the #18 being 1-1/8". A 1-1/2" plane would be a #24 which is also the largest hollow plane in my accumulation. It doesn't have an accompanying round. Hollows and rounds are a 1/6 section of a circle. By working sections side by side you may be able to create the profile you are trying to match.

It will be easy to see if the plane will match the profile. Retract the blade and set the plane on the molding. If the plane sole contacts fully, it should be fairly easy. If the sole meets in the center but not the edges, it is still doable. If the edges touch but the center doesn't, oh well.

jtk

[Keith Mathewson]

It takes a little time but you can hit a larger curve.

[Matt Bickford]

Hollows and rounds don't stop at 1.5" radius. Larger sizes are not as common but they are out there. There's a good chance that the 18 you have coming creates a larger arc, in fact.(note: the physical size of the plane tends to remain the same with these larger radii. They just create less than 60 degrees of an arc.)

If you really want to use this method then make the round of the planes you have coming to the profile you want and then use it to change the hollow.

I have made a hollow/round pair that cuts an 8" radius, for instance.

[Paul Carson]

Really informative and helpful. I think I'll wait and see how well the #18 on the way conforms to the curve I need to make, and assess what kind of adjustment would be necessary as Matt has suggested.

If the adjustment is too drastic I may try bench planes + a curved scraper, and if I end up having to make much more of the same profile then I'll look at the possibility of converting a wooden jack or similar.

Thanks again