Jan 312011
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Generally, the block plane is one of the most reached for planes in most shops. Most block planes are small enough to live in an apron pocket, so it is never more than an arm’s length away. Besides the convenient size, they are extremely flexible in their usages.

Specifically, the 9-1/2 block plane is the regular angle (as opposed to the low angle) block plane with the adjustable mouth. The “regular angle” refers to the angle at which the blade iron sits in the plane body, which is 20 degrees. The “low angle” version of this plane is the 60-1/2 block plane, and its blade iron sits at 12 degrees. The primary difference between the two is the low angle’s ability to trim end grain, like when working on a butcher-block top.  The only other difference is the feel of these planes in your hand. The 9-1/2, with its slightly higher angle lifting the back of the blade and cap iron, can stretch the smallest of hands a bit more than the 60-1/2.

The adjustable mouth on these planes allows you to easily bring the throat in tight when working to remove extremely thin shavings, supporting the wood to prevent tear out. Just as easily, the mouth can be opened up allowing a thicker, less refined shaving fit through, when working to remove material more quickly. If a thicker shaving was attempted, If the throat set too tight, the shaving would jam and you’d have to stop and clear the shaving, before continuing. This would certainly slow down your work.

As you might have already imagined, these block planes have a wide range of functionality. You can easily use it to put a chamfer on tenons and along the long grain surfaces, breaking the edges of any carcass or box, use it as a smoother on small scale work for face, edge or end grain. The block plane can certainly fill in for a wide range of tasks, even though it may not rise to the level of replacing specific purpose made planes. A pinch hitter can always come in handy.

Since the block plane has its iron in a bevel up configuration, you can also buy a spare blade or two that you can use to hone higher angles. This would allow you to just swap out the irons, if you were working on some really figured wood, as the higher bevel angle on the iron is in essence the same as changing to a higher frog angle in the bench planes (which use the iron in a bevel down orientation). Highly figured woods respond better to a higher angle of attack, which (without getting too deep into the science of it) allows the shaving to release without the normal tear out.

Don’t overlook the 9-1/2 adjustable mouth block plane for your shop.  I think you will find it a go-to for a multitude of jobs.

I hope to see some of you at our events across the country.  Feel free to come up and say hello.

Lee Laird has enjoyed woodworking for over 20 years. He is retired from the U.S.P.S. and works for Lie-Nielsen Toolworks as a show staff member, demonstrating tools and training customers.

  2 Responses to “The Plane Facts: The 9-1/2 Adjustable Mouth Block Plane”

  1. I recently purchased a Stanley 9 1/2 block plane on eBay. It was well tuned and excellently sharpened. I noticed however that there is a slight angle (~1mm) side to side on the front adjustable portion of the mouth. Does this need to be squared? The plane works well as is, but obviously the wood compression forward of the blade is slightly different.

    • Jeff,

      Thank you for your inquiry.

      If the trailing edge of the sliding plate is not square to the sides of the plate, then you could theoretically file that line “more square”. If you are not seeing that back end of the sliding plate line up parallel with the front edge of the blade, it could also be the fact the sharpened edge of the iron is not perfectly square or how the blade sits on the frog of the plane has it sitting askance (less than perfectly square with the long axis of the sole of the plane). Of course the blade adjuster of the plane is just for this purpose (letting you make a less than perfectly square end blade project out consistently from the sole to cut an even thickness amount across the width of the blade) – purposefully making the blade be cockeyed, so its less than perfectly square cutting edge then is brought to be “square”, in relation to the sides of the plane body.

      I honestly don’t think the gap that shows as you described will have a visible effect on how the plane cuts. If it were a low-angle block plane and you were trying to optimize the cut for working end grain to get as gossamer shavings as possible, it might make a difference you could notice in using the plane to have the gap be absolutely parallel to the cutting edge of the blade. But I think you’d see cutting results improved just by a more keenly sharpened blade edge (over trying to close that gap) – or upgrading the iron to a Hock blade. A keenly sharp blade is more likely to have your shavings not break off than an edge which is less sharp.

      This could be one of those instances where perfect is the enemy of good. The threaded stud brazed to the plate on those Stanley block planes is a notoriously weak connection. Taking the plate out to file on the back edge to get it more square could have you inadvertently knocking the threaded post loose from the plate. That would be very unfortunate, so go gingerly should you decide to file on the plate.

      Ed Scent
      Highland Woodworking

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