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making plane irons for wood planes

Lanso

Cast Iron
Joined
Mar 16, 2013
Location
Cerritos, CA
Richard Newman posed the following:

Stephen, I don't want to hijack GregSY's thread but I'm real interested in discussing making plane irons. We should start a new post about it, can you use your moderator magic to do that with the above post's?

Lanso asked:

How do you like the HSS tip you welded on? I made 2 or 3 HSS blades years ago and they have held an edge better than anything else I’ve tried.

Discussion continued as below.
Feel free to jump in.
 
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Lanso, agree completely.

CPM M4 is my favorite cutter material for the metal planer, and for woodworking plane irons as well! It seems to hold an edge about twice as long as OEM Stanleys, and gets sharper and lasts "much longer" than A2. Plus it is tougher than the D2 iron i made long ago. What's not to like, as they say?

smt
 
Stephen and Lanso, do you butt weld the tool steel to a mild steel body?

Year ago I bought a planer knife with a m-42 laminated edge from Bimex, cut off a piece, silver soldered the M-42 side to a piece of low carbon, and then cut off the rest of the planer knife stock, In effect transferring the thin piece of M-42 to my steel blank. I didn't get a perfect braze, but the iron worked ok, but really not any better than a Hock iron. Could have easily been my technique tho...
 
Richard- true fusion butt weld.
Bevel edge both parts, then weld

I initially tried TIG'ing them with stainless rod. I was not able to keep them straight (bent like a hocky stick when first side was welded). Then flipping over to do the other side would crack the weld on the first side.

So after some experimentation, I used Acetylene torch, and arc weld rods.

The shanks are A36/structural steel 'cause it is cheap and on hand. The bits are sawed out of CPM M4 annealed/normalized. But once welded, the HAZ is hard and brittle, so they have to go in the pre-set furnace in a foil bag "immediately". With the Oxy - Acetylene process I was able to play heat on the HAZ as necessary throughout the welding process to yield a tougher weld and could get a half dozen or so blanks made before sealing them up in foil for a 24hr anneal cycle.

After they were annealed, they set around until I need one or 2. Then they are rough sized and cleaned up for width, and ground to be somewhat flat. After HT for hardness, they are machined for what ever plane they will fit (center slot, e.g.), stamped, and finish ground.

I don't use bronze or silver solder because it won't survive heat treating. I am (or was) somewhat leery of using pre-hard blanks, and then degrading a large HAZ with the heat necessary to hard solder. The welded construction also gives a wider range of options for making blanks with hardened bits, that can be processed later as far as all the machining on the soft shanks.

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smt
 
Stephen, I don't want to hijack GregSY's thread but I'm real interested in discussing making plane irons. We should start a new post about it, can you use your moderator magic to do that with the above post's?
 
The question has come up:

Stephen, I don't want to hijack GregSY's thread but I'm real interested in discussing making plane irons. We should start a new post about it, can you use your moderator magic to do that with the above post's?

My "mod'magic" is not highly accomplished, so I did not (yet) remove these from Gregsy's post in fear of obliterating all of it. maybe later.

But, go for it - discuss making plane irons!

I'll cut and paste my post in a bit.

smt
 
Thanks for creating the new thread Stephen

So, my question: what is the advantage of welding up a composite iron rather than just making it completely from hss flat stock (other than material economy) Sounds like the welding, annealing, normalizing is a PIA, wouldn't one save more in time than the extra hss steel would cost? Just start with unhardened stock, machine, heat treat, grind to final thickness?

How critical is the heat treat for the CPM M4? I wouldn't attempt it, but can I assume a heat treating outfit would know how to get it right? Is it something really exotic?
 
I wonder how an edge made of Tantung, Crobalt or Blackalloy would work? I assume the stuff can be brazed, not sure about welding. If you could get it sharp, it would be very difficult to dull it.
 
Good question Conrad, I've had the same thought. I'ts pretty pricey stuff, but I've gotten it cheap on ebay

I've used it to make hand turning tools for the wood lathe - silver brazing a small piece into a rabbet on a mild steel shank. They work great for scraping ebony, get sharp and hold up really well. It's used for shaper tooling for solid wood for the same reasons.

I should try a butt braze and see if it's strong enuf to survive as a plane iron. Making a laminated iron would be tricky, thin wafers are not available. Would have to braze on a thicker piece and grind most of it off, but I've been told that Tantung is hardest close to the surface of the blank due to chilling quickly after casting. I use parting tool blanks, maybe they are thin enuf to be hard thru and thru. The best part for me of using Tantung is no need to do any heat treating.
 
Here's the old Crucible comparator.

https://www.crucible.com/eselector/general/generalpart6a.html

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CPM M4 is more than twice as wear resistant as D2 while being 50% tougher.

IME (limited to a couple blades) D2 is too subject to chipping thin edges. (not tough enough) I have been satisfied that CPM M4 at Rc62 is tough enough and have not experienced "chippyness". For me that excluded CPM10V which has insane wear resistance, but only D2 toughness.

Going the other direction, CPM 3V is tougher than necessary at the expense of wear resistance, which is less than CPM M4

CPM 9V could be worth experimenting with - 50% more wear resistance than CPM M4 & almost double the toughness. Except those values are at RC 54.

People tend to think of "hardness" as the only quality of a knife edge, but it really has a very minor role in the attributes we actually need from that edge. An edge has to be hard enough that it does not bend when thinned to the geometry and applied to the work we want to do with it. Hardness is essentially a proxy for strength. (not directly wear resistance).

It is important for most practical woodworking tools that they be relatively easy to grind and especially to hone. I consider M2 relatively easy to grind. CPM M4 has the same grindability value. The value for straight M4 is aproximately 3.5 times lower.

https://www.crucible.com/eselector/general/generalpart5a.html

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I chose (or impecuniousness forced :) ) me to not look at cutting materials that were less tough than D2. I would rather hone an iron that gets dull from wear, than one that is delicate and chips in difficult wood. But i would be happy to be funded to explore further. :D

I have several closely hoarded strips of tantung and it is my go-to material for tipping woodworking machine cutters. I have not gotten around to trying it as a plane iron. It might cover most of the bases, if you can make a thin edge without it chipping.

Richard, I prefer the soft shank welded to hard consumable edge. I "feel" (no experiments) that it adds a little to vibration damping. But the big factor is the convenience it provides to make hardened, un-machined blanks; which can be later machined to suit the plane they are needed for. There is a lot of value and economic efficiency in that model for a niche maker.

If this were resolved on a "production" basis, the savings over all HSS blanks is also significant. I was buying such small quantities (direct from Crucible) that I kind of doubt there was much price consideration, but if memory serves (it often doesn't :) ) the price for an approximately 2-1/4" wide x 1' long bar of 3/16" (the thinnest rolled plate available at the time) was around $90 - $120. I bought several bars at different times within approximately that range.

So the material would have cost about $80 for a 2-3/8" wide plane iron.
Or it could be cut either direction and yield bits for irons from 1/2" wide through a #8 jointer with 2-5/8" wide iron, and get maybe as many as a dozen bits. In my metric, A36 is practically free. So basic steel materials before welding gasses and filler rod was either approximately $80 per solid jack plane size blade, or approximately $10 per welded up version. And again, I have a faint feeling the welded up is "better".

Lately I tend to buy specialty steels from Hudson. Their prices on CPM M4 look good, but they don't list any thinner than 1/2" thick online. I'll try to remember to call them tomorrow and order some if they stock it thinner.

smt
 
Lanso, agree completely.

CPM M4 is my favorite cutter material for the metal planer, and for woodworking plane irons as well! It seems to hold an edge about twice as long as OEM Stanleys, and gets sharper and lasts "much longer" than A2. Plus it is tougher than the D2 iron i made long ago. What's not to like, as they say?

smt

Stephen, how do you sharpen it ? Reason I'm asking is that it should do way better than twice the OEM Stanley.
 
I would be happy to make a welded iron, but my welding skills are almost non-existent and I don't have a heat treat oven. Much as I'd like to acquire both, I have other cats to skin, so...

AS to the hardness/toughness metrics for judging alloys, I wonder if there isn't more going on at the edge. I remember scientific studies done to determine how carbide saw teeth dull. It was determined that a chemical reaction between stuff in the wood or mdf and the carbide binder promoted by heat and pressure at the edge was the mechanism, not chipping or abrasion. Tool steels are much a different animal, but who knows?
 
I would be happy to make a welded iron, but my welding skills are almost non-existent and I don't have a heat treat oven. Much as I'd like to acquire both, I have other cats to skin, so...

AS to the hardness/toughness metrics for judging alloys, I wonder if there isn't more going on at the edge. I remember scientific studies done to determine how carbide saw teeth dull. It was determined that a chemical reaction between stuff in the wood or mdf and the carbide binder promoted by heat and pressure at the edge was the mechanism, not chipping or abrasion. Tool steels are much a different animal, but who knows?

Given that a properly sharpened plane iron will cut your arm hairs half height effortlessly, I would bet there is much more going there than simple abrasion/toughness etc.
 
How critical is the heat treat for the CPM M4? I wouldn't attempt it, but can I assume a heat treating outfit would know how to get it right? Is it something really exotic?

-For stamping die tooling made with any of the PM steels the results were much less than optimal when we did this in-house. Dies and punches that were sent out had much better results. Not just any HT house can do this, you have to ask what equipment they have or check with stamping die houses for success with PM. It's not exotic material any more, unlike it was 25 years ago, but not every HT'er is really able to do this. I always wanted to try the M4 variety on a plane blade, thanks for this thread.
 
I'm getting tempted to try a Tantung iron. So, the question is how thick should it be for a Stanley bench plane? The laminated irons for infill planes and old wooden planes are way thicker than the Stanley production irons, and I've always wondered if that is a factor in their performance? My understanding is that the thin Stanley irons were designed for easier and more economical production rather than cutting ability. I also seem to remember that some of the earlier ones were laminated also, but still thin.
 
I think the surface hardness vs. center thing is less of an issue with modern cast alloys (Tantung G). First thought is could you take a fairly inexpensive lathe tool, say 3/8 x 3/8 and EDM a few slices out of it? The cost per blade would then be maybe $15 or so for the material. Other thought is I know they have plasma sprayed the stuff. Could a thick enough layer be put on a blade to survive multiple sharpenings?

I've got a couple Hock blades in my Stanleys and really like 'em.
 
I'm getting tempted to try a Tantung iron. So, the question is how thick should it be for a Stanley bench plane? The laminated irons for infill planes and old wooden planes are way thicker than the Stanley production irons, and I've always wondered if that is a factor in their performance? My understanding is that the thin Stanley irons were designed for easier and more economical production rather than cutting ability. I also seem to remember that some of the earlier ones were laminated also, but still thin.

Thickness is a big factor in performance. The thicker the blade, the less it vibrates, the stabler it is in the cut. This can be mitigated to some extend by gluing a piece of paper under the blade, wetting it slightly and then allow the blade to bed in it. Makes a big difference. Also, a thicker blade can be lapped both sides i.e. cutting edge is "inner steel". You don't get a decent sharpness with one side of outside steel.
 








 
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