Mujingfang HSS iron

	Mujingfang HSS iron
	Finest abrasives.
	Microbevels front and back.
	Use a jig.

	Copyright (c) 2002-15, Brent Beach

Test Summary

The High Speed Steel irons supplied with the Mujingfang planes are extremely durable. They sharpen to a very sharp edge and wear without edge dropouts commonly found on irons made with A2 and S53 steels. They are more durable than any other iron I have tested, including older production Stanley irons, new production alloy irons (Stanley, Record, ECE), modern laminated irons from Japan (Samurai), A2 irons (Lee Valley, Lie-Nielsen), and the Holtey iron.

The only downside is that they are not, to my knowledge, available in a format suitable for Stanley pattern planes.

The Mujingfang plane

Lee Valley (among others, I understand) is selling a series of planes made in Hong Kong in various styles. The Taiwanese-style comes with High Speed Steel irons (very approximately) 2" wide by 3-1/2" long by 1/8" thick (a little thicker than the catalogue suggests). The irons are held against a metal cross pin by a small metal wedge. While apparently flimsy, the system holds the iron well (after removing the lacquer from the blade, otherwise the iron slips during use unless the wedge is very tight).

This is an interesting looking plane at a good price. After a short trial it was clear that this plane and iron combination could handle a full iron test: it would be able to take 150 consistent shavings less than 0.002" thick along a 4 foot douglas-fir board without chatter.

The design of the plane takes a little getting used to. If you are used to Bailey planes with knobs and totes, there is a learning curve. I found that my ability to estimate a square jointed edge with this plane was poor. With practice, it got better but is not as good as with a taller plane. As well, I push rather than pull planes, so the shape of this plane is less than optimal. There is only a small area behind the iron, so it is difficult to push the plane without holding it around the iron. However, my plane had an extremely fine mouth (a bit unusual given that is it a jack plane) and took the abuse of testing very well - little sole wear after a total of 450 passes down a 4' douglas-fir board.

The Test

The test primarily assesses plane iron durability.

The douglas-fir used in these tests is not subject to tearout, so this test does not determine how the plane handles difficult wood. The test boards are knot free, so the test does not show how the blade handle abuse. I have no objective way of assessing the quality of the resulting surface, so again the results really only measure the quality of the blade.

However, any plane/iron combination that is still taking fine shavings and producing a smooth surface after this test will handle most basic planing operations.

Edge quality is determined using a microscope both before and after use. If you have never seen pictures taken by the QX3 microscope, you should read the short introduction to the QX3 microscope and the pictures it takes.

Factory sharpening

I was so impressed with the initial shavings, I decided to run the test first with the factory sharpening. This is the first iron I have received that is worth testing without honing.

These are pictures of the blade as purchased. I did no sharpening of this blade before these pictures. I took a couple of passes along a piece of fir to check out the plane. The results were so good I stopped and took these pictures. I occasionally sharpen blades with the blade at an angle to the direction of motion to help show a particular sharpening effect. In this case, the angling of the blade was done by the factory. I have no idea why they do it. Perhaps their sharpening stones are narrower than their irons?

The iron comes with a 28 degree primary bevel. The first picture shows the bevel at 10x magnification. There appear to be at least three steps in the factory sharpening. The red line shows scratches from the first grinding (slightly hollow ground?). The orange line shows scratches from a honing that smoothed most of the bevel. The blue circle surrounds a microbevel that is restricted to a narrow band near the edge.

As a reference, the full bevel is actually about 1/4" wide and the microbevel 0.02".

At 200 times magnification, looking just at the microbevel. They appear to have used a very fine stone. The area right near the edge (blue circle) has fewer and finer scratches than the area back from the edge (red circle). The microbevel actually extends back to about the yellow line, but the scratches are only completely removed near the edge.

This is the best factory sharpening I have ever found. The edge is straight across the full width of the iron. At 200 times magnification there are no defects. The bevel near the edge shows almost no visible scratches, which suggests the final honing was done with an abrasive grit size of less than 5 microns.

Right out of the (no-name, white cardboard) box, this iron left a very smooth surface. The plane is easily able to take shavings down to 0.001".

I did my usual test, repeated passes along a 4 foot length of douglas-fir. After 100 passes, the iron shows little wear.

The dark area near the edge, which is about 0.0003" wide, is the wear bevel. This is the smallest wear bevel I have recorded (22 irons from 13 manufacturers at last count) after 100 passes -- about half the size of the next smallest.

This is not a very good picture. My set-up for holding an iron does not work well for short irons. In fact, this picture was so poor I built a new jig just to hold this iron at the microscope. The remaining pictures are better.

Full Sharpening Sequence

Oct 29, 2002 through Nov 11, 2002.

These very precise microbevels are actually produced using a very simple jig set-up. For a full discussion see my JIG.

The new plane iron holder for use with the microscope holds the plane iron with the bevel perpendicular to the line of the microscope barrel. This is good, because more of the bevel is in focus. There is a downside though -- it is more difficult to light the object. With the bevel at 30 degrees, it was easy to reflect light into the microscope (30 degrees from the other side of the perpendicular), but it was hard to get much of the bevel in focus. For now focus wins over lighting. This iron has been sharpened with 15 micron paper at an angle of 32 degrees. I am continuing with the factory grind of 28 degrees for the primary bevel for now. (Continuing the first microbevel 4 degrees higher than the primary bevel.) In order to be able to distinguish the scratches left by the various papers, I angled the iron and sharpening jig to the direction of travel. The line of the 15 micron scratches is shown in red. It appears that there is a slight (0.0005") wire edge, see the yellow circle. The faint lines parallel to the edge are not scratches, they are just smears left when I wiped the blade off. I use baby oil as a cutting fluid and traces are left on the iron (a good thing for the iron, but a nuisance in these pictures).
This picture shows the microbevel left by the 5 micron paper, using the same light as the last picture. In order to distinguish these scratches from the 15 micron scratches I angled the blade the other way to the direction of travel while sharpening. The two yellow lines outline this microbevel. It is at 34 degrees, about 0.005" wide. It looks scratch free in this lighting. The wire edge is gone.
Altering the lighting a little shows three sets of scratches. The 15 micron paper scratches along the red line. The 5 micron paper scratches along the yellow line. Factory scratches along the green line, not yet removed by the 15 micron paper. Again, the lines along the 5 micron bevel are smudges of baby oil. The area where the 5 micron and 15 micron scratches meet, see blue circle, is quite a bit brighter. Having scratches in both directions seems to allow more light reflection.
Finally, the third bevel produced using 0.5 micron paper at 35 degrees, about 0.0017" wide. Scratches produced by this paper are not visible. They are there, but too thin to reflect visible light. A bit like the dog that didn't bark, the absence of 5 micron scratches locates the 0.5 micron bevel. The bumps on the edge could be a little bit of wire edge.
After 50 passes on a 4' piece of douglas-fir, the bevel shows little wear. The slight evidence of wear is the series of faint scratches at the edge. Close examination reveals that the 5 micron bevel is about 0.00015" narrower (2 pixels). This is a very low level of wear given the amount of use, better than any other iron tested to date.
After 100 passes on a 4' piece of douglas-fir, the wear bevel is about 0.0004" wide.
After 150 passes on a 4' piece of douglas-fir, the wear bevel is still about 0.0004" wide.
This is the back side of the iron in the last picture, with the light positioned to show what appears to be a very narrow wear bevel right at the edge (the bright line along the edge). This wear bevel is about 0.00015" wide. Because the light reflects of this wear bevel but not the rest of the back, this wear bevel must be at an angle to the back face. I have not noticed, or not been able to see, this angled portion of the wear bevel on any other iron. I will look for this effect on other irons now.
Again the back of the same iron, with the light moved to show the area behind the edge. Not all the shavings dust has been removed (red circle). The area near the edge (blue circle) is relatively smooth, showing a different type of scratch (spots) that sharpening produces (lines). There is much less wear in this area than is usual. Compare to the wear on the back of the Stanley iron used in the discussion of wire edge below.

Retest

In order to get a test of this iron comparable to my other tests, I reground the primary bevel to 25 degrees.

I then went through the grits, using the same angles for each microbevel that I have used for all my other testing: 29, 31, 32. As with all my other test, I honed the front and back bevels on each grit. Because I use the wood slips for the back bevels as well, the microbevel angles are 3.9, 5.3, and 6.3 degrees. By alternately honing on the front and back, I was able to eliminate the wire edge that appears in the previous test.

Details of this test follow.

The front bevel, 15 micron paper, 29 degree microbevel, 200 X magnification.
The front bevel, 5 micron paper, 31 degree microbevel, 200 X magnification.
The front bevel, 0.5 micron paper, 32 degree microbevel, 200 X magnification.
The front bevel, after 100 passes along 4 foot douglas-fir board. The wear bevel is the slightly darker area, right at the edge. For some reason it shows up darker when partially covered with a semi-transparent red blob.
The front bevel, after 200 passes. Again, it shows up darker when partially covered with a semi-transparent red blob. This wear bevel is about 0.0003" wide. This level of wear is consistent with the earlier test and about half the previous best test result.