What is a jack plane?
The term “Jack Plane” commonly refers to the bench planes No.5, 5-¼, and 5½. The Jack plane is longer than a smoothing plane and shorter than a jointer plane. Another, older term for jack planes is the fore plane because it is used “before” the other planes. The jack plane was originally used as a first plane for preparing and sizing the rough surface prior to using a jointer and smoothing plane.
For its original use, the blade/iron is heavily cambered and the mouth/throat is wide open which allows cutting of the thick shavings effortlessly. In rough cutting with a cambered blade, the cap iron/chip breaker doesn’t have the same use as in other bench planes, and it is commonly placed farther away from the blade edge.
The name Jack comes from the saying “jack of all trades” as the versatility of jack planes allows them to perform some of the work of scrub, smoothing, and jointer planes, especially on smaller pieces of work.
What are Jack planes used for?
A jack plane can be used for:
- General sizing of timber
- Jointing and straightening surface
- Smoothing and polishing the surface
- Shooting with the shooting board
The jack plane is the true “Swiss army knife” among the bench planes, as the Fine Woodworking-magazine states in its article title: “Jack of all planes”. The well-functioning jack plane is suitable for many completely different duties by only setting up the plane differently.
By altering the blade shape, mouth size and cap-iron/chip breaker placement, the same jack plane can hog wood, joint it, and finally smooth it for finishing. Often the Jack plane is the first plane recommended for beginners due to its high level of versatility. Let’s take a closer look at the various ways of use of the Jack plane:
Roughing and sizing – the original function of the Jack plane
The original use for the jack plane is the fast and efficient dressing of the timber to size. For this function the blade/cutting iron is cambered to 8-14″ radius, the mouth of the plane is wide open and cap-iron/chip breaker is moved far from the edge. This provides efficient cutting action and chip removal. The tighter the radii of camber, the more aggressive the cutting action and the deeper cut you can take.
Jack plane vs scrub plane – what is the difference?
When comparing the two planes to each other, size wise the scrub plane is narrower and shorter, the blade is narrower and shaped with tighter radii. The mouth of the scrub plane is also bigger than jacks and the scrub plane is a so-called single-iron plane without cap-iron/chip breaker. It is also lighter than the common jack plane. It must also be noted that the scrub and the jack planes are products of two different woodworking cultures who developed different tools for the same job.
Smoothing – jack plane for smoothing
The length of the jack plane is longer than common smoothing plane but only 2-4″ or so. This makes the smoothing function possible. Smoothing is the most demanding task that can be done with any bench plane, particularly this comes out with longer planes such as jack plane. The sole of the plane must be perfectly flat, the blade/iron and the cap-iron/chip breaker have to be suitably shaped and fit together, and the double-iron, the frog, and the body must be perfectly mated together without slightest of play.
For the smoothing, the blade of the jack plane should be ground and honed like a typical smoothing plane blade, with a very slight camber where the corners are eased ever so slightly that they stay just below the sole when the desired thickness of the shaving has been achieved. The cap-iron should be set very close to the edge to prevent the tear out.
The blade of the bevel-up plane can be also cambered for the smoothing function. There is no cap-iron in bevel-up planes and the means of reducing or preventing the tear-out are the adjustment of the mouth and the bevel angle of the blade. Higher the cutting angle, the lower the tendency for tear-out.
Jack plane vs smoothing plane?
When comparing the jack plane to the dedicated smoothing plane/smoother there are couple things to note.
The longer sole of the jack plane causes it to span over the valleys and to level up the peaks and not to follow along with the surface as accurately as shorter smoother. This makes the smoothing work with jack plane slower and when the jack plane is also heavier than the dedicated smoother then the smoothing work with jack plane is generally more tiring.
Read more about smoothing planes from my recent article: Best smoothing plane -which smoother to get?
Jointing – jack plane for jointing and trying
The length of the jack plane (about 14”) makes it suitable for jointing shorter pieces of timber. Rule of thumb states that the length of the plane should be at least half of the length of the piece to be jointed, so according to it, the maximum length of the piece that you can easily joint with jack plane is 28”.
Jack plane vs jointer plane
Compared to dedicated jointer the common No.5 jack plane is still relatively short. When the really straight surfaces are needed then nothing really compares to 22” long No.7, or really long 24” no.8 jointer planes. On the other hand, the dedicated jointers are big and heavy planes to move and operate which makes them fatiguing to use for long periods. In case the piece to be planed is short enough then it is sensible to use shorter jack plane for jointing.
Shooting – The jack plane is ideal for the shooting board
Shooting boards are so useful jigs that they should be used in every workshop. The jack planes work great with shooting boards. Especially the low-angle bevel-up jack planes are appropriate for shooting board use because of their adequate mass and low bedding angle (usually 12°) which with the normal blade bevel angle of 25° creates overall cutting angle of 37°. The low cutting angle works best when cutting the end grain. The mass of the plane provides inertia that helps to propel the plane through the tricky cuts easily. When using shooting board for long grain shooting, the blade can be replaced with another higher bevel angle one which provides tear-out free cuts even in curly or otherwise tricky woods.
Jack plane, bevel-up or down?
There have been lots of hype and praise recently around the woodworker circles about the excellence, the versatility, and the ease of use of the low-angle bevel-up planes, and all the praise have not been unfounded. But is the bevel-up geometry really suitable for a jack plane use?
My personal opinion is mixed. If the low angle jack plane is to be used as a roughing “scrub” plane, then the cutting geometry of the plane is against it. A common plane blade with 45° blade bed angle can be shaped with quite tight radii easily, but if one is to shape the bevel-up blade with the camber that is similar from the woods point of view, the radius should be extremely tight.
A common camber for a jack plane blade is around 14″, to get similar working camber to low-angle jack, the radius of the camber should be only 4.2″. And if one wants even more aggressive camber then the resulting radius for the bevel-up plane is ridiculous. I made the following image to illustrate the difference between the cambers:
Smoothing and jointing tasks are well-suited for the bevel-up jack plane. The cambering requirement for smoothing is so small that the blade is easily shaped to slight curvature. The stable blade support, thick blade, low center of mass and easy and accurate adjustment of the blade position are the strengths of the bevel-up plane and they ensure that the tool is a joy to use.
Interesting read about cambering the bevel-up planes and the camber radius calculator can be found at http://www3.telus.net/BrentBeach/Sharpen/camber.html
Choosing the right Jack plane size
Jack planes come in a couple of sizes. Most common sizes are from the smallest to largest: No 5-¼ junior jack, No.5, and No.5 ½. Some woodworkers state also No.4 bench plane also as a jack plane in case it is set-up as a jack plane, with a heavily cambered blade and open mouth. But to simplify I refer No.5 series only as a jack plane.
- The no.5 standard jack plane is the world most common plane size, found almost in every shop and homeowners toolbag alike. It is 14” long with a 2” wide iron. It is a good compromise between the length and width and it works well with an easy as well as hard to plane woods. Its versatility and ease speak for themselves. No.5 is a good plane to learn basic planing techniques and plane set-up. Vintage Bailey No.5 is one of the cheapest planes around and I recommend them for rougher use.
- No 5-¼ “Junior Jack” is smaller Jack originally designed for use in schools. It is 2” shorter in 12” long and only 2” longer than No.4. The Bailey pattern junior jack blade is only 1¾” wide which makes it useful for jointing narrow edges and smoothing harder woods. The modern Veritas version of the plane comes with ¼” wider blade, making it same width as No.5.
- No 5½ is wider and heavier Jack plane for rougher work. It is more tiring to use due to heavier mass, especially with harder and trickier woods. It is the same size as old English Panel plane used for smoothing large panels and can be set up as one.
Read my guide about choosing the best jack plane : How to choose the best jack plane?