What are the parts of a metal bench plane?

13th August 2021


	What are the parts of a metal bench plane?


	Shop for Woodworking Hand Planes




			Body
			The cast iron body of the typical bench plane can be anything between 140mm (5½”) and 610mm (24″) long. The shortest are usually smoothing planes, used for putting the final finish on the surface of the wood. The longest are jointer planes, used for straightening, or ‘truing’, long edges and faces of wood. In between are jack and fore planes.

			Bodies are slightly wider than the width of their irons, and bench plane irons vary in width from 30mm (1¼”) to 66mm (2 5/8″).All the other parts are secured to the body directly or indirectly.

			Frog
			The frog is a sliding cast iron iron wedge that holds the plane’s cutting iron at the desired angle for cutting, which in the case of bench planes is usually 45 degrees, although this can vary. The frog is moved backwards and forwards via an adjustment screw to increase or reduce the gap between the cutting edge of the iron and the front of the mouth – in effect, opening and closing the mouth.

			What does machined mean? Most frogs are described as having ‘machined’ seatings. This means that the bottom of the cast iron frog, which seats onto the body of the plane, and the sloping top of the frog, which is the bed for the blade, are very accurately milled by machine after the body has been cast. The accuracy of the milling means both frog and blade will be seated perfectly flat, which avoids ‘chatter’.


			Chatter can result in a series of tiny lateral (across the workpiece) grooves being cut into the wood, rather than the desired smooth result.A thin blade can also contribute to chatter.

			Some bench planes have their body and frog cast as one piece. This is another way of reducing the possibility of chatter. However, if the frog cannot be moved, the position of the blade cannot be adjusted in relation to the leading edge of the mouth to allow for varied thickness of shaving.

			This is why some planes with their body and frog cast as one piece have an adjustable mouth plate at the toe. In effect, the front part of the sole is moved backwards and forwards to adjust the size of the mouth.

			The frog is screwed down into the body through two vertical slots. On many planes, the frog is only adjustable with a screwdriver after the lever cap, chip breaker and iron have been removed to gain access to the two securing screws.

			After the blade assembly has been removed and the two securing screws slackened, the frog is adjusted forwards or backwards from behind, using a screwdriver on the frog adjustment screw.

			However, some planes, such as the Stanley Bed Rock line, have a screw mechanism that allows the frog to be adjusted backwards and forwards without having to remove the iron assembly.But you still need a screwdriver!



			The frog assembly Together, the frog, iron, chip breaker, lever cap, blade depth adjustment control and lateral adjustment lever are called the frog assembly.

			Iron
			Also known as the blade or the cutter, the iron is the all-important part that does the cutting. In a bench plane, it is usually set at an angle of about 45 degrees to the sole, looking at the sole from the side, or cheek, of the plane.

			This angle is called the pitch, or the frog angle. Forty-five degrees is called ‘normal’ or ‘common’ pitch, but some planes have their irons set at different angles. Generally with bench planes, a lower pitch means deeper cutting, while a higher pitch is better for smoothing, particularly when planing hardwoods with alternating grain, known as ‘difficult grain’, such as cherry wood.See What is the perfect pitch for plane irons? for more information about this.

			The cutting end has a bevel – the sharpened edge – which is usually between 25 and 30 degrees to the upper flat surface of the iron, and normally faces downwards towards the workpiece – that is, bevel down.However, there are also low-angle, bevel-up bench planes which have different pitch and bevel angles. For more about these, see What are the parts of a low-angled bench plane? and What are bevel-up and bevel-down planes

			The iron is fastened to the chip breaker with a screw that goes through a long slot in the iron and into a threaded hole in the chip breaker. The screw’s head, which is on the underside of the iron when the plane is assembled, is just wide enough to capture the edges of the long slot as it is screwed into the chip breaker.

			Chip breaker
			This part is a partner to the iron. While the iron shaves thin layers of wood from a workpiece, the chip breaker, located on top of the iron and beneath the lever cap when the plane is assembled, breaks or folds the shaving before it can gain too much leverage and possibly cause a split in the wood. It is the chip breaker that gives the shavings their curly appearance.

			For the chip breaker to work efficiently, there must be a space of between 0.4mm (1/64”) and 3mm (1/8”), between the bottom edge of the chip breaker and the cutting edge of the blade. The actual gap set depends on the kind of planing – generally it’s smaller when smoothing and bigger when reducing the size of wood.

			The iron and the chip breaker move as one piece when the depth of the blade is adjusted, maintaining the same space between the bottom edge of the chip breaker and the iron.

			Lever cap
			The lever cap acts like a clamp, holding the chip breaker and the iron beneath it in position.

			The lever cap is secured by the lever cap screw, which goes through slots in the chip breaker and the iron, and screws into the frog.

			When a cam at the top of the lever cap is turned to its locked position, it presses a steel leaf spring hard against the chip breaker. This action levers the cap against the screw, applying pressure to hold the iron in place.

			During assembly, the lever cap is positioned over the blade with its cam lever in the open, unlocked, position. The cap screw does not have to be removed for the lever cap to be positioned . . .

			. . . The wider part of a keyhole slot in the lever cap allows the head of the screw through, and then the cap is moved downwards so that the narrower part of the keyhole slot goes behind the screw head.

			The cam lever is then pressed down and should find some leverage as it is turned on its pivot all the way to its locked position.If the lever cap is too tight or loose, release the cam again, adjust the screw accordingly and re-lock the cam. There may be some trial and error to get this just right – a balance between the blade being held firmly, but the cam not being too difficult to lock.

			Lateral adjustment lever
			This lever projects upwards in line with the frog’s 45-degree sloping bed.

			It is a simple, pivoted lever which has a small, round plate that fits into the long slot of the iron. When moved with the thumb or forefinger to the left or right, the adjuster alters what is known as the lateral position of the blade – the angle of the cutting edge across the sole of the plane.

			The cutting edge should be set parallel with the width of the sole. If it is found to be slightly skewed, moving the lateral adjustment lever left or right will correct it.

			Depth adjustment wheel
			This is the means of adjusting the projection of the iron, which directly affects the size of the shaving, or chip. Turning it clockwise increases the depth, and turning it anti-clockwise reduces depth.The wheel is threaded onto a pin which screws into the back of the frog.

			The two legs, or the “fork”, of a ‘Y’-shaped lever, called the yoke – which looks like a stubby wishbone – fit into a groove in the narrower front part of the wheel.

			At the other end, the lug of the pivoted yoke is located in a slot in the chip breaker.As the wheel is turned and it moves forwards or backwards along the threaded pin, it moves the yoke with it, which in turn levers the iron up and down via the lug located in the hole in the chip breaker.

			Sole
			The sole is the bottom, or underside, of the bench plane’s body. It needs to be perfectly flat so that the planed edges and faces of workpieces are ‘true’, which means accurate in terms of straightness and angle.

			Toe
			The toe is the front end of the plane’s body and sole. It’s important to press down on the toe, with downwards hand pressure on the knob, to plane a workpiece properly. In many bench planes, the toe is just a continuation of the body and sole of the plane.

			However, the toe part of the sole of some planes can be adjusted backwards and forwards to control the size of the mouth opening. Planes that have adjustable toes have fixed frogs – that is, the body and frog of the plane are cast as a single piece. This has the advantage that it helps reduce the possibility of chatter.

			Heel
			The heel is simply the rear end of the body and sole.

			Mouth
			The bench plane’s mouth is a rectangular slot in the sole which allows the shaving to pass through as the plane is thrust forwards over the workpiece. Some planes have fixed mouths, which means the physical mouth size cannot be adjusted.Others have adjustable mouths (see Toe, above) or adjustable frogs (see Frog, above).

			If you’re making a heavy cut, taking thicker shavings, you want more space in front of the iron for the shavings to pass through. If you’re making a fine cut, taking thin shavings, you need less space in front of the iron. The mouth opening needs to be just marginally larger than the thickness of the shaving.

			Tote
			Also known as the handle or rear handle, the tote is shaped and contoured to fit the dominant hand comfortably. Described as a “pistol grip”, it is screwed to the base with bolts – often one long one right through from the top of the tote to the base of the plane, and a shorter one through the foot of the tote and into the base.

			Knob
			The knob, or front handle, is rounded at the top and curved lower down for a comfortable grip. It is fastened to the body with a single bolt down the middle.

			Wonkee’s note about throats Although it’s not a part as such, some woodworkers refer to the opening which starts at the mouth and widens upwards as the throat. It’s the area through which the shavings pass after they’ve been broken and curled by the chip breaker.