Hand plane performance depends on two adjustments: blade depth and throat opening. These settings determine cutting aggression, surface finish quality, and how well the plane handles difficult grain. Here’s how to set them correctly.
Blade Depth Basics
Blade depth controls shaving thickness. For rough work, set the blade to take 0.003-0.005 inch cuts—you’ll see shavings about as thick as regular paper. For smoothing operations, reduce depth to 0.001-0.002 inches—thin enough to see through when held to a light.
Check blade depth by sighting down the sole from the toe of the plane. The blade should barely protrude past the sole—just a hairline visible when viewed at an angle. If you can clearly see the blade edge extending past the sole, it’s set too deep.
Testing Blade Depth
Make a test pass on scrap wood similar to your project material. Adjust based on results:
- Blade too deep: Plane chatters or digs in, leaving a rough surface. Shavings break into short pieces rather than forming continuous ribbons. The plane requires excessive force to push.
- Blade too shallow: Plane produces dust or discontinuous shavings instead of continuous ribbons. The cutting action feels smooth but ineffective.
- Correct depth: Plane produces continuous, slightly translucent shavings. The surface left behind shows a subtle gloss. Push force is moderate and consistent.
Throat Opening Function
The throat opening is the gap between the front of the blade and the front of the throat. This opening determines how far ahead of the blade the wood fibers can lift before they’re cut. A tight throat prevents tear-out in difficult grain by breaking fibers immediately after they’re cut.
Wide throat openings—1/16 inch or more—work for softwoods and straight grain where tear-out isn’t a concern. The extra clearance prevents shavings from jamming in the throat.
Tight throat openings—0.015-0.030 inch—control difficult grain better. The small gap supports wood fibers right up to the cutting edge, reducing tear-out on reversing grain, knots, and figured wood.
Adjusting Throat Opening
Most bench planes adjust throat opening by loosening two screws in the bed of the plane and sliding the frog forward or backward. Moving the frog forward closes the throat opening; moving it backward opens the throat.
Loosen the frog screws just enough to allow movement—you don’t need to remove them completely. Tap the frog gently with a small hammer or screwdriver handle to shift its position. Retighten the screws and test the opening before reassembling the plane completely.
Matching Settings to Work
For rough dimensioning straight-grained softwoods:
- Throat opening: 1/16 inch or slightly wider
- Blade depth: 0.003-0.005 inch (thicker shavings)
- This aggressive setup removes material quickly without worrying about surface perfection
For smoothing straight-grained hardwoods:
- Throat opening: 0.030-0.045 inch
- Blade depth: 0.001-0.002 inch (tissue-thin shavings)
- This balanced setup produces clean surfaces without excessive effort
For difficult or reversing grain:
- Throat opening: 0.015-0.025 inch (very tight)
- Blade depth: 0.001 inch or less (extremely thin shavings)
- This conservative setup prioritizes tear-out prevention over speed
Blade Sharpness Impact
Sharp blades allow finer depth settings and handle tight throat openings without jamming. A dull blade requires deeper cuts to remove material effectively, which increases tear-out risk and makes tight throat settings impractical.
If your plane suddenly starts producing dust instead of shavings despite correct settings, the blade needs sharpening. Don’t compensate by increasing blade depth—this makes tear-out worse and works the plane harder.
Common Problems
Shavings jamming in throat: Either the throat is too tight for the blade depth you’re using, or the blade needs sharpening. Try slightly wider throat opening first. If jamming continues, sharpen the blade.
Tear-out despite thin shavings: Throat opening is too wide for the grain you’re planing. Close the throat and reduce blade depth further. On extremely difficult grain, try planing at a 45-degree angle to the grain direction (skewing).
Plane digs in at start of stroke: Blade depth is excessive. Retract the blade until the plane enters the cut smoothly without grabbing. This problem appears most often when transitioning from softwood to hardwood without adjusting blade depth.
Maintenance Considerations
Throat opening can change over time as the sole wears from use. Check the sole flatness periodically by placing the plane on a known-flat surface. Light coming through under the sole indicates wear. Resurface the sole on sandpaper adhered to plate glass or a granite surface plate.
The front edge of the throat wears faster than the rest of the sole due to concentrated shaving pressure. This gradually opens the effective throat width even if you haven’t adjusted the frog position. Plan on occasional throat adjustment to compensate for this wear.
Alternative Mouth Sizes
Some planes come with replaceable throat pieces offering different opening sizes. Swapping throat plates is faster than adjusting the frog position. Keep a tight-throat plate for figured woods and a standard-throat plate for normal work.
Block planes typically offer this feature more commonly than bench planes. If you frequently switch between rough work and finish smoothing, a block plane with interchangeable throats saves setup time.
