The Woodshop Shed

Plane iron angle

Furnished content.
(from WoodNet.net)


This probably belongs in the hand tool forum, but I thought more people would see it if posted here. I recently bought a LV low angle jack plane from a fellow Woodnet member. It's in beautiful condition; everything I could have asked for, except it had an iron with a 30 degangle on it. New LV planes come with a 25 deg angle and that's better for end grain work which was my reason for buying the plane as I want it for use on my shooting board. As I thought about what to do it occurred to me that I have a #4-1/2 LV plane that has a 25 deg iron in it. It was given to me by a friend, but I never use it because the low angle makes it useless for anything except end grain work; the tear out is terrible with normal grain. It'snot made such that it can be used on a shooting board, so it just sat in a drawer unused. Turns out, the blades are interchangeable between the two planes, so I swapped them. The #4-1/2 instantly became a thing of joy to use as a typical bench plane. No more tear out on face grain work, and beautiful, thincurls. It's amazing how a 5 deg difference in angle made such a profound difference in performance. I bought a low angle jack plane, but it's like I got two planes.

The 30 deg blade in the low angle jack plane gives a cutting angle of 42 degrees. Add a 5 deg micro bevel andit's up to 47 degrees, which is actually worse than the 45 deg angle on the #6 Bailey plane I had been using on my shooting board. And the results showed it. It was nearly impossible to get a crisp trim cut on end grain with it. But when I put the 25 deg iron in it, the angle went down to 42 degrees and it was easier to use than the #6 Bailey. That 25 deg iron also had a 5 deg micro bevel on it, so I resharpened it to something around a 1 deg micro bevel, which brings the cutting angle down to 38 degrees. What a difference that made. Now it easily takes off thin shavingson the end of a board cut to 90 degrees without much force to do so. I'm not sure how much further I cango with this logic. For sure I could reduce the grind angle so that the micro bevel is 25 degrees, but I wonder if I could go even lower on the grind angle w/o risking the edge being too weak for the job. If anyone has some insight on this, I'd appreciate hearing about it.

So the takeaway from this is to consider having multiple irons for your low angle plane(s). You're stuck with a bevel down plane to whatever the frog angle is. Most are 45 degrees so that's the cutting angle no matter what angle you sharpen the blade to.But with a bevel up plane, you can swap out the iron for one that better matches the job at hand. The low angle jack plane I bought came with a second blade sharpened to what looks like 45 degrees. That will give a cutting angle of about 56 degrees with a 1 deg micro bevel, and should be excellent for use with really difficult, tear out prone, woods.

Another take away is to be aware that micro bevels make it easier to sharpen an iron but have consequences for how effective it is to use.

John

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