LumberJocks

Tip: Closing the Mouth on a Fixed-mouth Block Plane

  • Advertise with us

« back to Hand Tools forum

Forum topic by drsurfrat posted 09-19-2020 03:24 PM 532 views 0 times favorited 12 replies Add to Favorites Watch
View drsurfrat's profile

drsurfrat

164 posts in 73 days


09-19-2020 03:24 PM

Topic tags/keywords: plane block plane mouth grinding sharpening fix cheap

Sorry to start another topic, but I couldn’t find any existing thread that this would fit into.

I found a way to close the mouth gap on cheap fixed mouth block planes like the Stanley 110 and numerous similar planes. I have been looking into this for quite a while, and I don’t think anyone else has put this out there.

I discovered this geometry when i was trying to correct a block pane with the wrong side of the blade beveled. As I was regrinding the bevel up, I got lazy and left some of the wrong bevel on the bottom (shown in red).

It turns out that as long as the bottom bevel still clears the wood, it will cut. It would seem that this would actually be better for edge toughness, since the angle of attack (top bevel, shown in blue) is the same, but the total angle of the grind is increased.

I can’t think of any drawbacks. It isn’t any harder to sharpen, It actually works in practice.

Benefits:
  1. Turn a $2 garage sale plane into a real user.
  2. Narrow the mouth on a fixed-mouth plane.
  3. The overall bevel doesn’t have to change, but the underside is thicker for less flex/chatter.
  4. It is a faster way to recover pitted blades, especially when the pits are on the flat, polished side.
  5. It might even be very good for figured wood if you grind the real, top bevel steeper. I haven’t tried that yet.

And at $2 apiece, you could keep a dedicated set.

-- Mike (near Boston) ... Laziness is the mother of invention, necessity is the mother of exhaustion - me


12 replies so far

View Loren's profile

Loren

10720 posts in 4534 days


#1 posted 09-19-2020 03:28 PM

The relief angle on the bottom needs to be at least 12 degrees I think. That’s why low angle block planes are 12 degrees, it’s as low as one can go and still cut like a plane.

View drsurfrat's profile

drsurfrat

164 posts in 73 days


#2 posted 09-19-2020 03:40 PM

Relief angle, good descriptive word. thank you

Low angle blocks already have an adjustable mouth, so no need to do this.
In this case it’s for those cheapies with 38-45 degree bed angle. I think (?) the relief angle undercut on the cheap blade could be as low as 1 degree, almost parallel to the plane sole, just so it clears the wood. I the the 12 degree low angle is just so that there is (barely) enough meat in the casting to hold the blade without cracking.

-- Mike (near Boston) ... Laziness is the mother of invention, necessity is the mother of exhaustion - me

View Loren's profile

Loren

10720 posts in 4534 days


#3 posted 09-19-2020 04:57 PM

^^^ yeah, that’s it. The top bevel of 25 degrees may be the sticking point. I read some stuff about this years ago and the details got foggy.

What you’re doing is sometimes called double bevel sharpening and it’s used to make the plane cut with more of a scraping cut by making the overall bevel more obtuse. It’s useful for figured woods prone to tear out, not so much end grain where an acute sharpening angle helps. Brian Burns developed a system for sharpening these bevels and as I recall in his booklet he wrote that going lower than 12 degrees on the back was counterproductive, but I could be mistaken in that recollection.

View drsurfrat's profile

drsurfrat

164 posts in 73 days


#4 posted 09-19-2020 06:32 PM

I knew I could’t have been the first to think of it. I just watched the video. He does polish the back of the block plane blade at 8 degrees, but only a microbevel on 8000 grit. I meant to use a grinder and remove a significant amount from the backside to close the mouth of the plane.

Loren, Thank you for the reference and conversation.

-- Mike (near Boston) ... Laziness is the mother of invention, necessity is the mother of exhaustion - me

View AMZ's profile

AMZ

192 posts in 275 days


#5 posted 09-19-2020 06:49 PM

Shim the bed to move the blade a bit further out.

View Bstrom's profile

Bstrom

138 posts in 59 days


#6 posted 09-19-2020 07:19 PM



Shim the bed to move the blade a bit further out.

- AMZ
</blockquote
That does seem to be the simplest solution..Assuming the adjustment still work

-- Bstrom

View AMZ's profile

AMZ

192 posts in 275 days


#7 posted 09-20-2020 10:38 AM


Shim the bed to move the blade a bit further out.

- AMZ

I’ve done it, and the adjuster still works. Maybe a dozen years ago ( or more ), I read an article by, I think, Brian Boggs, on how to supercharge a spokeshave, and to tighten up the mouth, he applied a bit of epoxy, covered with greased cardstock and then clamping in the blade. After the epoxy setup, he removed the cardstock, leaving a much tighter mouth.

I’ve used metal shimstock and it does not need epoxied. But in the end, a super sharp blade trumps a tight mouth everyday.

View HorizontalMike's profile

HorizontalMike

7898 posts in 3800 days


#8 posted 09-20-2020 10:53 AM

Just for the sake of suggestion… How about using aluminum furnace tape as you “shim” media? Easy to apply, easy to remove… Just my $0.02 worth.

-- HorizontalMike -- "Woodpeckers understand..."

View Derek Cohen's profile

Derek Cohen

507 posts in 4854 days


#9 posted 09-20-2020 01:15 PM

Here is what you do: epoxy brass shim on the bed in front of the mouth. This will lift the blade and close the mouth. Add more shim until it is closed as you wish.

This LN #103 had a mouth a little too large. Note that the bed angle was originally 20 degrees. Now it is 19 degrees …

Regards from Perth

Derek

-- Buildiing furniture, and reviewing and building tools at http://www.inthewoodshop.com

View drsurfrat's profile

drsurfrat

164 posts in 73 days


#10 posted 09-20-2020 01:21 PM



... But in the end, a super sharp blade trumps a tight mouth everyday.

- AMZ

Amen Brother

-- Mike (near Boston) ... Laziness is the mother of invention, necessity is the mother of exhaustion - me

View AMZ's profile

AMZ

192 posts in 275 days


#11 posted 09-20-2020 06:54 PM



Just for the sake of suggestion… How about using aluminum furnace tape as you “shim” media? Easy to apply, easy to remove… Just my $0.02 worth.

- HorizontalMike

Why not! It should work!

View bandit571's profile

bandit571

26741 posts in 3569 days


#12 posted 09-20-2020 10:14 PM

Looking more like a solution in search of a “problem”....

-- A Planer? I'M the planer, this is what I use

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com