How to sharpen and adjust a scrub plane iron
Removing the iron
Metal scrub plane
To remove the iron, turn the lever cap knob, or thumbwheel, anti-clockwise until the lever cap can be removed from behind the clamp bar.
With the lever cap removed, lift the blade up and out through the throat.
Wooden scrub plane
To release the iron, hold the plane up, clear of the workbench, and tap the rear, or heel, of the plane with a small mallet or hammer...
...or, if the plane has strike button, tap the button with the mallet or hammer.
The wedge and the blade should work loose with a few sharp taps.
Sharpening the iron
A hand plane iron usually has two bevels – the primary bevel created when the blade was first sharpened, and a secondary bevel, which can be described as an extra bevel on the existing one, created during subsequent sharpening for use.
The primary bevel is often around 25 degrees on a bevel down iron, with a secondary bevel of 30 degrees, so there is an extra 5 degrees between primary and secondary.
To sharpen the iron, you will need two grades of sharpening stone – 1000 grit and 8000 grit. The 1000 grit stone is relatively rough for initial sharpening. The 8000 grit, being much finer, is used to finish off the sharpening procedure.
Step 1 – Find bevel’s registration point
Placing the bevel of the iron on the 1000 grit stone, find the registration point for the primary bevel.
The registration point is when the bevel edge is felt to be perfectly flat on the stone, with no rocking. To find it, hold the iron on the sharpening stone and rock the blade on its primary bevel.
Step 2 - Tilt iron upwards slightly
When the bevel is flat on the stone, tilt the iron upwards very slightly. This is the position to hold it in for sharpening.
Step 3 – Hold blade
Keep your two forefingers on the blade, and your thumbs behind the top of the blade. Hold your arms in to your sides rigidly.
Step 4 - Move
Now rock your body from side to side, also moving the blade across the stone. Your arms, and therefore the iron, move to the left as your shoulders rock to the right, and vice versa.
Criss-cross the stone to create a series of Xs, going to the furthest point of the stone and back to the nearest point, while keeping your arms stiff against your sides, continually rocking from side to side. This action will sharpen all along the curve of the bevel.
Step 5 – Remove burr
Turn the blade over and, now using the 8000 grit stone, take off the burr by holding the blade flat on the stone and sliding it around.
The burr is a fine roll-over of metal from the secondary bevel to the opposite side of the cutting edge, created by the sharpening action.
It is usually quite visible and you should see particles of it on the sharpening stone after it has been removed.
Step 6 – Repeat on finer stone
Repeat steps 1 to 5 using the 8000 grit stone.
If sharpening your scrub plane iron “freehand” like this seems daunting, there’s an aid you can make yourself.
Use your scrub plane to cut a consistent gouge along the length of a piece of softwood about 150mm (6") long.
Then, in the resulting groove, glue a piece of abrasive such as emery cloth, which you will probably need to cut to size.
You now have a perfect channel in which to slide your iron backwards and forwards to sharpen it.
Start off with a rougher, or lower grade, of abrasive and move on to a higher grade for finishing.
Be sure to remove the burr on a flat surface such as a sharpening stone or an abrasive sheet stuck to glass, not in your newly made guide.
Replacing and adjusting the iron of a metal scrub plane
Step 1 – Bed iron
To put the iron back into the plane, first ensure the lever cap has been removed from behind the clamp bar.
Place the iron onto the bedding points that usually slope at 45 degrees to the sole of the plane.
Step 2 – Bevel up or bevel down?
Ensure the bevel of the iron faces downwards if it's a standard, bevel down scrub plane; if it's a low-angle plane - possibly a low-angle jack with its iron adapted for scrub-planing - the iron must be positioned bevel up. See:for further information about this.
Step 3 – Position lever cap
Replace the lever cap over the iron with the lever cap stops in contact with the clamp bar.
Step 4 – Partially tighten lever cap knob
Partially tighten the lever cap knob, or thumbwheel, by turning it clockwise, but not so tight that the iron can't be moved up and down.
Step 5 – Set depth of iron
Position the iron by hand so that the middle of the cutting edge protrudes from the mouth by between 1.5mm and 3mm (1/16" and 1/8") depending on the hardness of the workpiece. Make the iron protrude less for harder woods and more for softwoods.
The corners of the blade should not project beyond the mouth to help avoid tear-out.
Step 6 – Check lateral position of iron
Also ensure that the iron is properly positioned laterally – that is, that the iron's cutting edge is parallel with the sole.
With the cambered cutting edge of the scrub plane iron, this means the curve should be consistent over the width of the sole.
Step 7 – Adjust by hand or use set screws
Some scrub plane's irons are adjusted by hand only; others are adjusted via set screws – one on each side of the plane's body. Locate the screws if your scrub plane has them.
Step 8 – Sighting
Turn the plane upside down and take a "sighting" along the sole.
Adjust the lateral position of the blade, moving it left or right, by hand or with the set screws, until its curved cutting edge is aligned perfectly across the sole.
Step 9 – Set screw procedure
If using set screws, first back off (slacken) the screw on the side you want the blade to move towards with a flat-bladed screwdriver.
Then tighten the screw on the other side to hold the iron securely. If you go too far, partly reverse the adjustment until it's just right.
Step 10 – Finish tightening knob
Now finish tightening the lever cap knob until the blade is held firmly.
Step 11 - Final adjustment of iron
Any final downward adjustment of the depth of the blade can be done by tapping the top of the blade with a mallet or small hammer. To retract the blade slightly, you will need to slacken off the lever cap knob again and adjust by hand.
Replacing and adjusting the iron of a wooden scrub plane
Step 1 – Slide in iron
Slide the iron into the throat, bevel down, so that it rests perfectly in contact with its angled support. If it rocks, check for any particles of shavings in the throat.
Step 2 – Slide in wedge
Then slide in the wedge over the blade and behind the clamp bar or the stops cut into the body of the plane. Press it down finger tight.
Step 3 – Sight down sole
Place the index finger of your non-dominant hand on the top of the iron, flip the plane over and sight down the sole of the plane looking from the toe. You can then see how far the iron is projecting through the sole.
Aim for a projection of between 1.5mm and 3mm (1/16" and 1/8").
Step 4 – Tighten wedge
Now tighten the wedge by tapping it a little further towards the sole of the plane with the mallet or hammer, so that the iron is held firmly
Step 5 – Retract iron
Sometimes, tapping the wedge can advance the iron further through the mouth. If you need to retract the iron a little because it is projecting too far, tap the rear, or heel, of the plane, then tap the wedge to re-tighten.
Step 6 – Advance iron
To advance the iron further out beyond the mouth, tap the toe of the plane...
...or the top of the iron.
Step 7 – Straighten up iron
If you need to straighten up the iron – that is, make it level across the width of the sole – tap the side of the iron, near the top, with a hammer. Tap it on the left to skew it to the left, and on the right to skew it to the right.
Your wooden scrub plane should now be set up ready for action!