Why Are Plow Plane Irons So Tapered?

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Forum topic by Ripthorn posted 02-14-2014 04:38 PM 1903 views 0 times favorited 7 replies Add to Favorites Watch
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1459 posts in 3219 days

02-14-2014 04:38 PM

I have this odd hankering to try building a plow plane. Only twist is that I do not have any irons for one, which is not typical of someone looking to build one. I was planning to just make my own out of O1 stock, but would greatly prefer to not taper the irons. Why are they so tapered? Is it mostly so that the iron position doesn’t change through the cut (wedging the iron deeper the harder it’s engaged)? There are so many wedged planes with non-tapered irons that I can’t see why it wouldn’t work with a plow plane. I’ve never even used one, though, so I can’t say for sure. What say ye?

-- Brian T. - Exact science is not an exact science

7 replies so far

View TechTeacher04's profile


394 posts in 1765 days

#1 posted 04-23-2014 06:19 PM

Rhett of Nice Planes uses tapered blades in his planes and states that the wedging action of the taper ensures that the blades stay put during the cut because of the taper.

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Don W

19034 posts in 2801 days

#2 posted 04-23-2014 10:32 PM

Think about the physics. The force upwards tightens the blade, thus holding it in place, but there are many plow planes without tapered irons. Just set the wedge a little harder.

-- - Collecting is an investment in the past, and the future.

View lwllms's profile


555 posts in 3515 days

#3 posted 04-23-2014 10:50 PM

I don’t know of any old wooden plows that were commercially made that don’t have tapered irons. There are metal ones that lack tapered irons. Most people don’t seem to understand there was no standard as to taper and fit to the plane and old plow planes vary widely. Finding irons to fit an old plane is difficult at best. Even irons from the same maker but made in a different run will vary. Most the “sets” of plow irons out there are assembled sets that don’t really match each other.

The amount of taper in these irons isn’t as severe as they appear. The actual taper is what is between the bottom of the groove to the flat face. The rest of the apparent taper houses the groove which fits a mating angled front of the skate. The fit of this groove to the skate is pretty critical. The angles have to match because they give lateral stability to the iron which is needed for heavier cuts usually used with plow planes. These mating angles act similar to a Morris or other taper found in machines.

The depth of the groove, the amount of taper, the distance from the groove to the flat face, the location of the groove, and the width of the blades tang are just some of the variables in old irons. Plow planes are made to fit the set of matching irons, not the other way around as in metal mass produced planes.

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1459 posts in 3219 days

#4 posted 04-23-2014 11:34 PM

Well, then I will likely go with no taper. I understand the physics, I was just wondering if there were any other considerations and if it is feasible to go with no taper, as that would be significantly greater work on my part. This project is on the back burner for a while, but I have some lovely 12/4 black walnut stock just waiting for it.

-- Brian T. - Exact science is not an exact science

View DW833's profile


220 posts in 2116 days

#5 posted 08-09-2014 04:24 AM


Did you make the plow plane? If yes, how did it work out.
I’m thinking of making one. FWW has a good article on making them.
The only blades I found are from LN. $50 for a pair.

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1459 posts in 3219 days

#6 posted 08-09-2014 08:28 PM

Nope, still on the back burner. I am hoping to start this winter. I plan to make my own irons, as I have some metal working equipment.

-- Brian T. - Exact science is not an exact science

View Wally331's profile


350 posts in 2259 days

#7 posted 08-09-2014 09:25 PM

Jim Bode tools has quite a few sets of irons in stock for $55-150. Some matched some not. I’ve been wanting to make a plough for a long time but am waiting on some more funds…

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