Closely Set Cap Irons & Compass Planes

[custard]

I'm indebted to DW for raising the subject of closely set cap irons. It's a technique that works and makes a real improvement to the way I work. However, for most tasks I did have working solutions to the problem without closely set cap irons. They were much more laborious, but I could still get the job done.

But there's one application where a closely set cap iron isn't just the best solution, it's the only solution.

Very shallow curves are a standard feature in much of my furniture and that of many other makers. Pretty much every apron or rail will feature a slow curve, often one that can only just be perceived the eye. The shallower the curve the harder they are too make. Using a bobbin sander is much trickier than it looks, often you don't spot the little depression you've sanded in until the piece is assembled and the finish is applied. And a spokeshave will often leave tear out or chatter on heavily figured timbers.

A compass plane should be the perfect solution.

The iron is wide enough to cover the entire thickness of the board in one pass, so you don't need to worry about leaving planing ridges, which means no sanding is needed even for thin film finishes. There's an easy start and finish to the cut with no chatter. The planed surface is superb and also the fairness of the curve is superb.

The problem is that with figured timbers and very shallow curves there's no "downhill" direction for planing, so tear out is generally terrible.

But by combining a closely set cap iron with a compass iron you suddenly get the absolutely ideal solution.

Unfortunately I don't have any projects on the go with shallow concave curves to illustrate the advantages. But here's the compass plane with the sole set flat and used on a block of figured Swiss Pearwood. Big thick shavings and yet a glassy, surface to the timber with zero tear out.

Straight from the plane to the finish with no interim sanding, and so far it's worked on every curve in every timber that I've tried. For me this the "killer app" of the closely set cap iron, in that it permits something that I've never been able to achieve before.

 

[D_W]

I suspect you're not going to get the kind of traffic that other threads (like sharpening threads) because there just aren't many people doing what you're doing with this and the flattening thread, which is using their planes for economic gain and for more than smoothing.

It is these types of things that tell me that the double iron eliminated the single iron on an economic basis, it's just better and all of the forum arguments about sharpness or back bevels or any such things don't really address the differences in practical use.

For something like a compass plane, it suddenly makes the old wooden compass planes a whole lot easier to use, too, and you can do accurate work without leaving marks.

Thanks for posting - we may yet convince more people that you can do a significant amount of work (other than smoothing flat surfaces) with planes!

 

[Paddy Roxburgh]

Do moulding planes with cap irons exist? I've never seen one, but the exact reasons expressed by Custard perhaps they should. Maybe something for you plane makers out there to consider (I appreciate that making the cap iron would be tricky). Tear on a moulding is far more difficult to deal with than on a flat surface.
DW just a quick note as I've heard you say before that most people only use planes to smooth machined surfaces, I can't speak for the rest of the forum or woodworkers in general but personally I could do without planes for finishing machined surfaces as a sanded finish is easily good enough for most of my purposes, however I would really struggle if I did not have planes for shaping and fitting. For example, other than planing to a line I don't really know a way to produce an accurate piece of wood that is 2mm wider at one end than the other. As I work on boats nothing is straight and nothing is square.
Paddy

 

[AndyT]

Do moulding planes with cap irons exist? I've never seen one, but the exact reasons expressed by Custard perhaps they should. Maybe something for you plane makers out there to consider (I appreciate that making the cap iron would be tricky). Tear on a moulding is far more difficult to deal with than on a flat surface.

In general, in the western tradition, No. Apparently some Japanese planes with a profiled sole do have double irons and there was an American planemaker called Tolman who made some - this is a picture from a completed US ebay listing of one of his planes:

Presumably all the other makers realised that they weren't worth the trouble. There are several reasons why.

First off, makers knew to choose straight grained stock for moulded components. Second, for harder to plane woods, there was the option of having your planes at a higher pitch - 50 or 55 degrees or even steeper. Third - mouldings would normally be scraped, sanded or burnished after planing and before finishing. And fourth, for a complex shape, the cap iron would have little or no effect for the portions of the curve that were at a steeper angle to the wood, where the action is more scraping than cutting any way.

 

[Woody2Shoes]

I've been using spokeshaves for a while now for this kind of thing and I feel quite comfortable making concave, and convex, curves with them (esp. the Veritas low angle one).

I recently got a very nice old Record 020 and have fettled it up with a slight camber, corners rounded off and with the cap iron set close to the cutting edge. I must confess I'm finding it harder to get good results than with my spokeshaves! The LA spokeshave is more tolerant of the occasional "uphill grain" situation (usually near the bottom of the hill, so to speak), its blade is wider than the 020's and I find less risk of blade chatter. I wonder if I'm sharpening the 020 blade wrongly (30 primary and 35 secondary)? I would usually try and plane on a slight skew to improve my chances of success, but obviously it's not so easy on a concave curve (the spokeshaves are generally skewable of course).

Any hints/tips? Cheers, W2S

 

[Beau]

Good tip Custard. I experimented with a close set cap iron on my plane but could not see much advantage over using a scraper plane but for curved work that makes a lot of sense. I often reach for the compass plane for one off work and have the inevitable problems with breakout so will give the close set cap iron a go on it.

 

[D_W]

I have an old japanese set of double irons for a moulding plane, and I have a rabbet plane with a double iron, but I don't think for most profiled irons that it would be worth the trouble. They aren't used enough for heavy work as compared to something like a gutter plane.

For planes like beading planes or hollows, if you adjust the iron to match the sole, then you may get out of whack with a cap, and the cap is only going to do anything on a medium light cut if it's within a hundredth of the edge or so. There's too many things going on unless everything is maintained perfectly (which is what I guess the japanese manufacturers of the double iron sets for rounds are expecting).

I just can't see the economic benefit being there for the worker like it is with straight ironed planes and heavy removal curved planes like gutter planes. Especially if you have a selection of good lumber.

 

[Corneel]

I've been using spokeshaves for a while now for this kind of thing and I feel quite comfortable making concave, and convex, curves with them (esp. the Veritas low angle one).

I recently got a very nice old Record 020 and have fettled it up with a slight camber, corners rounded off and with the cap iron set close to the cutting edge. I must confess I'm finding it harder to get good results than with my spokeshaves! The LA spokeshave is more tolerant of the occasional "uphill grain" situation (usually near the bottom of the hill, so to speak), its blade is wider than the 020's and I find less risk of blade chatter. I wonder if I'm sharpening the 020 blade wrongly (30 primary and 35 secondary)? I would usually try and plane on a slight skew to improve my chances of success, but obviously it's not so easy on a concave curve (the spokeshaves are generally skewable of course).

Any hints/tips? Cheers, W2S

I have no experience with compas planes, but when the result of a close set capiron is only so, so, that usually means it should be set even closer.
The grinding and honing angle is not very critical in a bevel down plane, but when planing concave work I could imagine that you are starting to run very low on clearance angle with a 35 degree angle.

 

[Woody2Shoes]

The grinding and honing angle is not very critical in a bevel down plane, but when planing concave work I could imagine that you are starting to run very low on clearance angle with a 35 degree angle.

Thanks, I was wondering about that. The main reason it's a fairly steep angle is because the previous owner (his, pretty unusual, name was stamped on the iron, and it appears that he owned a joinery shop in the midlands in the 1960s - so he probably knew what he was doing) had hand-sharpened it to that sort of angle. Maybe I should regrind down to a 25 primary plus 30 secondary?

Cheers, W2S