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19K views 22 replies 14 participants last post by  TheFridge 
#1 ·
Fabrication and Heat Treatment

For the "Shop Made Tool Swap - 2015: Hand Planes and Spokeshaves", I decided to make two planes (one to keep, one to swap) including the blades. I started with a 1/8" thick 2.5" wide precision ground flat bar of A2 tool steel that I happened to have on hand. After some requests for more information, I decided to start this tutorial blog for making them.

You can buy tool steel pretty cheap from MSC:

O1: http://www.mscdirect.com/browse/tn/Raw-Materials/Flat-Stock/Oil-Hardening-Flat-Stock?navid=12101782
A2: http://www.mscdirect.com/browse/tn/Raw-Materials/Flat-Stock/Air-Hardening-Flat-Stock?navid=12101777

Other sources of tool steel include Online Metals, Jantz, McMaster Carr, and Grainger. Be sure to buy the precision ground variety to avoid flattening hassles later. Blade thickness is up to you… most are between 3/32 and 1/4" for wood-bodied planes, I believe. Tool steel bars come in an "annealed" state, which means it's soft enough to machine. We'll heat treat it later.

These are the two most common steel types for plane blades. O1 is easier to sharpen and can hold a delicate steep (25 deg or less) edge without chipping, but the edge wears quickly so sharpening is needed more often. A2 will hold an edge a fair bit longer than O1, but is harder to sharpen and can have large carbides that tend to fracture on a steep edge… most sources recommend a 30 deg or higher bevel for A2.

I started by cutting the blades out of the A2 stock with an angle grinder and thin metal cut-off wheel:



I just winged it on the blade length… as long as they're tall enough to protrude from the plane body and wedge, they'll be adjustable with a mallet and work fine. I then sanded the rough edges square-ish on a stationary belt sander using a miter gauge.

To grind the bevel, I used my slow-speed 8" bench grinder and freehand ground to the squared edge I made earlier, leaving about a 1/32" edge thickness to prevent thin steel from burning/warping in the kiln:



I dipped the blades in water from time to time to cool them between grinding sessions. The angle is somewhere between 25 and 30 degrees, we'll see if the A2 can hold up to this steeper angle… if not I'll grind it back a little after heat treatment.

I then lapped both sides of the blade flat-ish, as this is much easier in the soft annealed state than after heat treating. I used this grinding jig on my stationary 9" grinding wheel for the bulk of it, then sandpaper on granite for the rest:



This step could probably be avoided if you were careful not to bend/warp the precision-ground stock when angle grinding.

Next up is heat treatment. Most tool steels shouldn't be exposed to oxygen during the hardening, or the carbon atoms will react with it and burn away. This is called "decarburization" and can pit or even ruin tool steel in bad cases. To prevent this I first apply two coats of ATP-641 anti scale coating, a product used commonly for hobby knife making:

http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/heat-treating-accessories/anti-scale-coating-prod23076.aspx



I just paint it on with an acid/glue brush, wait a few hours, then re-coat. This is a thin clay product that prevents oxygen from contacting the steel while heating.

For hardening, I use my Father's digital kiln that's normally for jewelry work (precious metal clay, enamels, etc). It is possible to harden with a torch, but you can't get the "soak" times at the hardening temperatures that the steel alloy's elements need to go into full solution in the steel. A2 and O1 tend to benefit from this soak more than simpler steels like 1095, as they have many small quantities of rare earth elements that take time to distribute.

Here are the hardening steps for each steel type, which I came up with as an average of many separate internet resources (and review from knife form experts for the O1 steps):

O1 Tool Steel:

preheating: 1250 deg F, keep blade in kiln while warming, hold for 10 minutes
hardening: 1475 deg F, hold for 10-15 minutes
quenching: canola oil warmed to 125 deg F, agitate rapidly up and down (NOT side to side), keep going until bubbles stop and piece is hand warm
tempering: 375 deg F, hold for 2 hours minimum, cool with water, repeat for second temper at 375-400 deg F

A2 Tool Steel:

preheating: 1400 deg F, keep blade in kiln while warming, hold for 10 minutes
hardening: 1750 deg F, hold for 10-15 minutes
quenching: cool in still air to 150 F (able to hold in bare hand) before tempering
tempering: 400 deg F for RC 60, hold for 2 hours minimum

For A2, "quenching" just means taking it out of the kiln and leaving it in room-temperature air for a while. This is easier than dunking in preheated oil for O1. I actually do the tempering in a kitchen oven, as the kiln takes forever to cool down after hardening. I generally get lazy tempering and just do 400 deg F for an hour for both steels without bothering with a second cycle.

Here is the kiln and blades after removal:



Notice how the coating pops off during the quench:





After the kitchen oven tempering, you can see the yellow color of the steel below the remaining coating:



This color change indicates tempering hardness, hopefully I got it somewhere around RC60.

Now comes lapping the blades again to remove the coating and make sure they didn't warp during heat treatment. This step took forever and I'm still not completely done:



I'm using a Veritas lapping plate here with grit powder, but it is extremely slow and labor intensive. Wish I had a big coarse diamond stone for this.

Next up I'll work on etching a logo and actually make the wooden plane bodies.
 
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#3 ·
Thanks, it is nice to use the kiln. It is possible to build your own, too. It's just insulated firebrick, a heating element coil, and a PID temperature controller. All three things can be bought online pretty cheap. I might make a big one someday for treating kitchen knives.
 
#4 ·
Excellent stuff. I'm making my own molding planes, including blades, and in a how-to video I bought you can see the bluing of the steel.

Brown Rectangle Communication Device Violet Tints and shades


He just grinded away and never took the steel off until it was done. This is before any heat treating. If the steel had been hardened, that end would have been ruined, so I'm guessing it doesn't matter if you blue the steel like this before hardening?
 

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#5 ·
It generally shouldn't matter if you blue it before heat treating. However, If you get it hot enough to start decarbing the cutting edge, even the heat treatment might not repair it. At least I think so, I don't have all that much metalworking experience, I've just done a lot of googling about knife making.
 
#8 ·
When it comes to heat treatment, prior to hardening, bluing is not an issue, as you have not reach austenite stage yet, so you aren't ruining anything. The problem with bluing a hardened blade is that you basically have tempered it so soft that it won't hold a good edge. However, if you do that, you can anneal the steel, re-harden and re-temper, but it is a labor intensive process. Both bluing and decarbing the edge can be abraded past, it's just a waste of steel. Also, if you don't heat treat the entire piece (sometimes a piece is too large to be practical for heat treating the whole thing), you could go into unhardened steel.
 
#9 ·
Redoak, I do have access to cryogen at work, I might just have to try a cryo treatment. I was under the impression that this was not a huge improvement over straight hardening and tempering, though. I might try the edge first as-is then go the cryo route if it might improve things.
 
#10 ·
Great writeup!
With a background in toolmaking i allways felt that any woodworker should have at least basic understandig of metals. The protective coating you use is new to me. Perhaps since most critical hardening on a larger scale is done here in a bath of molten salt that does not allow for any oxygen to enter.

Keep up the good work. Looking forward to read more!
 
#11 ·
I think it might be a good idea to consider the cryogenic treatment. With A2, you could have up to 20% of it still as retained austenite which has not transformed to martensite. This will limit the hardness that you achieve and could cause brittleness problems.

There are many people who heat treat A2 like you have done and are happy with the results. But it does mean that you do not get the most out of it.
 
#13 ·
Allen-
Thank you for writing out about your blade making. I am grateful for the time and effort you took to explain your process in the step-by-step detail. I've benefited from your description from sourcing the materials to the final lapping. I will save this blog for future reference. Thank you.
chuck
 
#14 ·
After reading up on cryo treatment, I found it it needs to happen before tempering to have any effect. Oh well, maybe next time. I'll test these blades after sharpening and see how well they hold an edge.

Edit: Actually I found a source (Crucible's website) that indicates it may be worth doing a cryo treatment after the first temper then doing another tempering cycle:

"Technically, cryogenic treatments are most effective as an integral part of the original quench, but due to the high risk of cracking, as discussed in the "Quenching" section above, we recommend tempering material normally at least once before performing any cryogenic treatments."
 
#16 ·
Etching a Logo

(Disclaimer: I take no responsibility for anything done with this information, proceed at your own risk.)

I like to etch my logo onto plane blades using toner transfer and salt water electrolysis. This technique is commonly used by knife makers to put a makers mark on their blades, and is pretty simple to do.

I start by making a logo in a program called Inkscape. This makes a "vector" image that can be scaled to whatever size I want without becoming blurry. I then invert the colors and horizontally mirror the image to get something like this:

Black Font Happy Art Darkness


This image needs to be printed using a laser printer (NOT an inkjet printer) onto glossy photo paper. I use "Hammermill Color Laser Gloss Paper, 94 Brightness, 32lb" paper and it seems to work okay, but about any shiny paper will work.

Now I use a clothes iron to transfer the printed image to the steel blade (this is called "toner transfer"). I tape one edge down, make sure things are aligned, then iron away:

Wood Flooring Audio equipment Floor Hardwood


This will liquefy the plastic toner particles and make them stick to the steel. I use the edge of the iron as a burnisher to push the melted toner onto the steel after everything is heated up. After I feel it has been thoroughly heated and burnished, I fill the sink with cold water and put the blade in. After some soaking, I gently scrub off the paper first with my fingers then with a small toothbrush until the bare metal is shining through the non-toner areas:

Brown Book Font Wood Circle


Next I coat the non-image parts of the blade with shellac and then wrap them with blue painters tape to prevent accidental etching of random areas, leaving one small bare metal section to connect a wire to later.

For the etching stage, you'll need a DC voltage supply of some kind. This could be a battery charger or large-capacity "wall wart" dc transformer or a regulated power supply… about any low voltage supply at a few amps capacity will work. Initially I tried connecting the supply directly to the etching, but there was a problem:

Wood Eyewear Cable Circuit component Wire


There is so little resistance while etching that it forms a "short", drawing so much current that it either breaks or shuts off the power supply. So you'll also need a "load" in series with the power supply and your piece being etched to regulate the current being supplied. For a battery charger, put a battery to be charged in series with your etching. For my power supply, I made a "resistive load" by thermally gluing a couple resistors to a big hunk of aluminum so they wouldn't melt under load. Assuming the worst case of no resistance when etching, make sure that:

(power supply voltage [V]) / (load resistance [ohms]) < (power supply max current [amps])

And check that your load resistance can handle the power involved without melting/exploding (thus my large piece of aluminum). The battery charger method makes this easy, as it's specifically designed to handle the battery as its load.

Connect a wire from the negative (black) terminal of your power supply to a hunk of steel that will make your "probe". Wrap some scrap cloth or paper towel around the end of the probe and secure it with a rubber band. Connect a wire from the positive (red) terminal of the power supply to the load, then connect the other side of the load to the blade being etched. You could also have the load on the negative side, it doesn't matter as long as it's in series.

Now mix up some salt water in the kitchen until the salt stops dissolving.

Turn on the power supply, dunk the probe's cloth end into the salt water, then touch the now-wet probe to the area being etched:

Wood Yellow Engineering Metal Art


You should see some tiny bubbles forming in the salt water around the area being etched as you're holding the probe. The steel from the uncovered areas of the blade will detach and plate onto the steel of the probe, leaving an etched recess in the blade. This can take quite a while if you have a smaller power supply… it took about 10 minutes using my 24V supply drawing about 4 amps with my load. Keep going until you can feel the etched recess in the blade using a fingernail. You might have to move the probe around if doing a big etch so all areas get equal coverage. Dunk back in the salt water occasionally if the probe dries out.

After you're finished etching, use sandpaper on a hard surface to remove the toner. I haven't found any other way to remove the toner, it's resilient stuff.

Sometimes the etching leaves weird mottled black coloring in the recesses. To even this out, I coat the etched areas with apple cider vinegar and leave them outside for a while:

Bottle Wood Table Wood stain Banknote


This oxidizes everything the vinegar touches. I then sand the black/rusty stuff off the top, then hit the recesses with a soft buffing wheel to leave the dark oxidization only around the edges.

Here is the completed etch on my swap plane's blade:

Grey Artifact Font Cemetery Art


And another from the previous plane swap, this one came out darker and the head is flipped for some reason:

Sleeve Grey Font T-shirt Logo


Soon I plan on doing this on a brass plate to make a custom branding iron. I did a test with a brass probe and brass piece being etched and it worked well.

Here is a similar set of steps I found online:

http://www.instructables.com/id/How-To-Electro-Etch-a-Solid-Metal-Plaque/?ALLSTEPS
 

Attachments

#17 ·
Etching a Logo

(Disclaimer: I take no responsibility for anything done with this information, proceed at your own risk.)

I like to etch my logo onto plane blades using toner transfer and salt water electrolysis. This technique is commonly used by knife makers to put a makers mark on their blades, and is pretty simple to do.

I start by making a logo in a program called Inkscape. This makes a "vector" image that can be scaled to whatever size I want without becoming blurry. I then invert the colors and horizontally mirror the image to get something like this:

Black Font Happy Art Darkness


This image needs to be printed using a laser printer (NOT an inkjet printer) onto glossy photo paper. I use "Hammermill Color Laser Gloss Paper, 94 Brightness, 32lb" paper and it seems to work okay, but about any shiny paper will work.

Now I use a clothes iron to transfer the printed image to the steel blade (this is called "toner transfer"). I tape one edge down, make sure things are aligned, then iron away:

Wood Flooring Audio equipment Floor Hardwood


This will liquefy the plastic toner particles and make them stick to the steel. I use the edge of the iron as a burnisher to push the melted toner onto the steel after everything is heated up. After I feel it has been thoroughly heated and burnished, I fill the sink with cold water and put the blade in. After some soaking, I gently scrub off the paper first with my fingers then with a small toothbrush until the bare metal is shining through the non-toner areas:

Brown Book Font Wood Circle


Next I coat the non-image parts of the blade with shellac and then wrap them with blue painters tape to prevent accidental etching of random areas, leaving one small bare metal section to connect a wire to later.

For the etching stage, you'll need a DC voltage supply of some kind. This could be a battery charger or large-capacity "wall wart" dc transformer or a regulated power supply… about any low voltage supply at a few amps capacity will work. Initially I tried connecting the supply directly to the etching, but there was a problem:

Wood Eyewear Cable Circuit component Wire


There is so little resistance while etching that it forms a "short", drawing so much current that it either breaks or shuts off the power supply. So you'll also need a "load" in series with the power supply and your piece being etched to regulate the current being supplied. For a battery charger, put a battery to be charged in series with your etching. For my power supply, I made a "resistive load" by thermally gluing a couple resistors to a big hunk of aluminum so they wouldn't melt under load. Assuming the worst case of no resistance when etching, make sure that:

(power supply voltage [V]) / (load resistance [ohms]) < (power supply max current [amps])

And check that your load resistance can handle the power involved without melting/exploding (thus my large piece of aluminum). The battery charger method makes this easy, as it's specifically designed to handle the battery as its load.

Connect a wire from the negative (black) terminal of your power supply to a hunk of steel that will make your "probe". Wrap some scrap cloth or paper towel around the end of the probe and secure it with a rubber band. Connect a wire from the positive (red) terminal of the power supply to the load, then connect the other side of the load to the blade being etched. You could also have the load on the negative side, it doesn't matter as long as it's in series.

Now mix up some salt water in the kitchen until the salt stops dissolving.

Turn on the power supply, dunk the probe's cloth end into the salt water, then touch the now-wet probe to the area being etched:

Wood Yellow Engineering Metal Art


You should see some tiny bubbles forming in the salt water around the area being etched as you're holding the probe. The steel from the uncovered areas of the blade will detach and plate onto the steel of the probe, leaving an etched recess in the blade. This can take quite a while if you have a smaller power supply… it took about 10 minutes using my 24V supply drawing about 4 amps with my load. Keep going until you can feel the etched recess in the blade using a fingernail. You might have to move the probe around if doing a big etch so all areas get equal coverage. Dunk back in the salt water occasionally if the probe dries out.

After you're finished etching, use sandpaper on a hard surface to remove the toner. I haven't found any other way to remove the toner, it's resilient stuff.

Sometimes the etching leaves weird mottled black coloring in the recesses. To even this out, I coat the etched areas with apple cider vinegar and leave them outside for a while:

Bottle Wood Table Wood stain Banknote


This oxidizes everything the vinegar touches. I then sand the black/rusty stuff off the top, then hit the recesses with a soft buffing wheel to leave the dark oxidization only around the edges.

Here is the completed etch on my swap plane's blade:

Grey Artifact Font Cemetery Art


And another from the previous plane swap, this one came out darker and the head is flipped for some reason:

Sleeve Grey Font T-shirt Logo


Soon I plan on doing this on a brass plate to make a custom branding iron. I did a test with a brass probe and brass piece being etched and it worked well.

Here is a similar set of steps I found online:

http://www.instructables.com/id/How-To-Electro-Etch-a-Solid-Metal-Plaque/?ALLSTEPS
Allen,
Cool process. Well done, and thanks for the info.
Roger
 

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