HT odd blade and tempering to rc 52? 1084 steel

Fitzhugh

Fitzhugh

Joined
Feb 5, 2013
Messages
194
I received my 2 X 3/16 1084 from Aldo and am going to start cutting some of it up in a few minutes. While I'll start with something more simple while I learn the process, one thing I'd like to make are some joinery floats. They're like single cut files, only with MUCH larger teeth - teeth like you'd find on a handsaw (for wood), only they go all the way across:
homepage_joiners.jpg


Like saws, they need to be hard enough to hold and edge but soft enough to resharpen with a saw file, so they're about rc 50-52.
The charts I've seen say that requires around 600-650F for tempering, hotter than my home oven. Luckily it occurred to me my wife almost certainly has access to a high temp lab oven at work - late night HT raids are obviously in order.

My questions:

Warping - The blade is only toothed on one side. I've read one person say you should not cut them until after HT so they don't warp, but seems most people do. Even the purchased ones are a bit warped.
Would coating in satanite when hardening help? (that's a wild guess) Would the choice of quenchant make a big difference? I recall reading about similar problems when forging files and rasps - something about them being straightened while still hot. I don't get how you can straighten while still hot when they warp when quenched. Or does the warpage happen in the furnace?

Tempering - Looks like I need to get it to 600F. (http://www.cashenblades.com/steel/1084.html) I realized this morning that my wife likely has (after hours sneaky) access to a high temp lab oven at work, if not I won't be able to get to 600F with my home oven. What would you suggest for an inexpensive option? I am more interested in learning and trying things out that getting ideal results, so I don't want to send away for HT.

However, on wikipedia I read that 600F falls in a problematic range:
"Tempering in the range of 260 and 340 °C (500 and 644 °F) causes a decrease in ductility and an increase in brittleness, and is referred to as the "tempered martensite embrittlement" (TME) range. This range is usually avoided. Steel requiring more strength than toughness, such as tools, are usually not tempered above 205 °C (401 °F). Instead, a variation in hardness is usually produced by varying only the tempering time." (http://en.wikipedia.org/wiki/Tempering - see "Quenched Steel" section.)
I've had no luck finding further information and on the TTT diagram both temperature and hardness are on the same dimension - I'm missing something.

Thanks for both your answers here and the great wealth of information shared on the site in general.
 
I'm thinking that HRc 52 is a little soft. The files I've used can cut much harder steel. You should be OK tempering at 400 F. These are wood rasps?

You would quench for @ 5 seconds, long enough to miss the pearlite nose and cool the entire rasp to below @ 900 F. At that point you would pull the rasp from the oil and straighten it. You would want to do that before it started forming martensite. You should be able to let it cool in the air to room temperature (unless you are in a hurry). Quickly and carefully clean the oil off and temper ASAP. If you are going to temper it back to HRc 52 you can give it a snap temper at 300 F to minimize the chances of it breaking or temper at 400 F a couple of times for 1 or 2 hours. If the rasp is to hard to sharpen, you can temper it later at 600 F. From what I have read TME for high carbon steels is less of an issue than it is for the medium carbon steels. You may not gain any toughness when you soften it but you shouldn't loose any either.
Check this out on the web;
Metallurgy of Steel for Bladesmiths & Otherswho Heat Treat and Forge Steel
John D. Verhoeven
Emeritus Professor
Iowa State University
 
That's great info. I have been reading up a lot, enough that I can't always track it all and at times overlook something I've read - like simply tempering it further if needed.

If I find I need to bend them more, or again (if I mess up) I just re-harden and quench, right? Seems I can't just heat it up to bending temp without re-quenching or it will just temper it too soft.

Thanks for the suggested reading. I saw a link for it yesterday but the link was dead. I thought it was just something on a now-dead website and didn't think to actually search for another copy. I'll read it tonight.

You're right, these are for wood. They are supposed to give a smooth finish (not a final finish but much smoother than most rasps), remove stock rather fast, and allow you to get a good, flat (planar) surface. I'm building a workbench that involves a lot of mortise and tenons and these will be much better than chisels. I'll also make a shoulder plane with the 1084, also good for that use.

Thanks!
 
I believe the traditional way of making these was the same way as cutting files (although I might be wrong). So the heat treat process would be similar. You would take the appropriate cold chisel and cut the groves in the metal. You would need to protect the edges with a coating during the heat treatment. You could design these as a push cut or a draw cut. I think in the old days they tempered in molten lead.
 
I haven't seen anything about cutting with cold chisels though I know hand stitched rasps are made with small punches - something else I have to try soon. At least the modern user made floats are filed, but that doesn't seem as viable for production work, you might well be right. Tempering in molten lead - that's something I'll have to read about even though I don't see myself trying it. As a kid I melted lead in one of my mom's cooking pans and got caught - luckily BEFORE she used it for cooking!

I'll see what I can find about HT files. That's a good suggestion since they would suffer similar problems.

Thanks!
 
I haven't seen anything about cutting with cold chisels though I know hand stitched rasps are made with small punches - something else I have to try soon. At least the modern user made floats are filed, but that doesn't seem as viable for production work, you might well be right. Tempering in molten lead - that's something I'll have to read about even though I don't see myself trying it. As a kid I melted lead in one of my mom's cooking pans and got caught - luckily BEFORE she used it for cooking!

I'll see what I can find about HT files. That's a good suggestion since they would suffer similar problems.

Thanks!
 
Please post whatever you discover. You might go over to anvilfire (a blacksmithing forum) to see if anyone there has anymore information.
 
Aw man, another tool I'd never heard of and now must have....

I'd suggest tempering them at 500 or as hot as your oven will get, 50-52 sounds really soft, but 55-56 sounds about right. You could always temper them softer afterwards if that is too hard.
 
Hank-

I have made a few custom handle broaches and a smaller handful push-cut mortise floats out of Aldo's 1084FG. Great steel choice for your situation IMHO.

My work is forged, but those made by stock removal from the 1084 should have very similar performance per given HT.

On a broach, my typical process is to forge the material down to about 110 - 120% finished dimension, grind/file and true all surfaces and set any tapers behind the cutter head. I slow down and take good control of the dimensions and geometry. I file my flats down to about 0.020" oversize, cut the teeth finishing with a 6" 2X Slim saw file. (Tip: Once you learn to sharpen typical abused rip-cut hand saws well, broaches and floats are butt simple.) At this point all surfaces get cleaned up to a 320X to 500X finish and the cutter is inked/torch blued and teeth jointed/re-sharpened to final dimension plus about ~0.010". Now ready for HT.

Hoping we're on the same page, here we come to your questions.

Warp. My take is that since these tools get used hard and have very small cross sections, they receive the most thoughtful HT I can muster. For me this begins with heat control during the forging and most importantly - careful normalization afterwards. At least 3 rounds from past critical on the first down to sub-critical on the last - air cooling to black in between. I also bring these up and let them soak at 1100 to 1250 for 5 - 10 minutes and air cool before finishing (just don't let them hit critical on this one or you will possibly give even simple carbides time enough to pool and gang up on your files/bits later!). After finishing, I apply a very thin satanite wash to help minimize decarb and do the typical austenize at ~1475F for 3 - 5 minutes and point-first end-to-end quench in Parks 50. I rarely get warp out of the quench going about it this way. But if I do, I straighten - hot - out of the first temper cycle or clamp up to bar stock during the second temper cycle. Both work well.

Tempering. My broaches often get used on fossil wooly tooth, ivory and hardwoods and the floats typically on very dry hardwoods. I want "factory" sharp to hold up since these are somewhat difficult for customers to sharpen as well without practice, so I temper them for a good balance between hard and tough. For me, this means about 440 - 450 F in a 2X routine. I have no testing on the final hardness, but would guess 56 - 58Rc. Even at this hardness, they are readily touched up or even jointed/sharpened with fresh mill/saw files (Grobet files anyway). If you have problems with this, a cheap HF diamond needle file can break the "crust" so a regular saw file can get a bite. I am still surprised at how well these hold up over time. More importantly - the folks that use them are too.

Final thought; floats are for planar cutting. The last thing you want them to do is flex in use. Many here may disagree, but IMO heat treating has little to do with flex - overall geometry and cross section are the only useful variables on that. Bottom line is to leave some meat on your float's backside and avoid the frustration of cupped cuts in use.

Suggestion; if you are building joinery floats to deal with multiple large mortises for a bench build, do yourself a favor and borrow, build or buy a heavy mortising chisel. Sharpen it properly, use them both side by side for a day and decide for yourself which is better suited to that job...

Hope some of this helps and good luck.
Andy
 
Thanks for writing up such a helpful reply! I only have a few moments at the computer so I will post a few questions later, but I wanted to thank you for writing up such a helpful response. I picked up the bricks for tbf yesterday morning, torch head arrived in mail by noon. Now I just have to shape some metal and wait for dark.

I'm sorry for the delay, I didn't realize I had to manually subscribe to threads.
 
Somehow I never posted the full reply I wrote after the above. I got sidetracked making my first knife and am now coming back to the float project.

I've got to say Andy Lewis' reply was extremely helpful. I just finished filing the teeth and shaping the profile of the whole thing and came back to re-read Andy's points. I'd filed almost all of them when I started this thread but ran out of steam for filing.

I got some seraset since it is the one thing I found locally, will try that instead of satanite. Otherwise I'm following your suggestions as much as I can. I'm not doing any forging on these, just starting with 3/16 x 2 and using full thickness so they won't flex too much. That's thicker than some professionally sold ones, should work. I'm also doing it all with files - the same 6" 2x slim you mentioned, which I have for sharpening saws. I found it hard to file a perfect straight tooth without any arch or curve but I got very close. I should have started with an edge float - one where the teeth are on the narrow edge like broaches I've seen instead of the wide face like the one I'm starting with.

You're right about floats vs. a good chisel. I can say that without ever using a float! I want them more for small surface work where a small block plane doesn't work so well and for cleaning up the sides of large chiseled mortises and tenon shoulders. The first thing I made from the 1084 stock is a shoulder plane blade so I'll see which works best.

I'll post photos when I finish.
 
Hank-

Sure glad I could help. Will be interesting to see what you come with; please post a pic or two when ready.

I agree on the wisdom of starting with a narrow edge float for filing/sharpening. A lot more forgiving of a bad stroke than a wider-faced tool. Inking the cutter face with dykem or sharpie (or torch just blueing before HT) can really help see where you are hitting. That and thoughtful practice are the best ways I know to get consistently true file strokes. Once you get one of these functionally sharp, stay after it regularly and protect the teeth with a cork or wrap etc. With a little maintenance they will generally cut surprisingly fast for the surface they leave behind.

Also pay attention to the handle-to-cutter geometry on any old ones you come across. Not like the modern ones necessarily and rarely do they have original round handles. Good reasons for both details that aren't obvious until you use one for an hour or so.

Best to you.
 
One thing in your posts that jumps out at me.....2BF.

A two brick forge isn't the right tool for doing a HT on something like this project. I would either wait until you have a better forge or a HT oven, or sen d it to someone who has the right equipment.
I think you would get a better HT with a torch and a rosebud tip than with a 2BF.

Just a thought, but a farriers rasp could easily be re-shaped into floats like these. They are pretty cheap and readily available.
 
Andy, can you describe the handle geometry you mention? Perhaps you mean a flat sided handle so your hand gets feedback of the tools angles and orientation.

Also, about heat treating... you said earlier that you used a light coating of clay to prevent decarb. I guess I'm not clear on why it is more of an issue here than in making a knife blade? Do you have to knock the clay off in the moments before quenching or do you quench with the clay? Did you coat all surfaces or just the toothed side? I'd love to see photos if you have them!

Most of the teeth turned out well. A couple have larger spacing because I didn't pay proper attention when filing and had to clean up a bit. They're all the same height, though, and that matters most. After roughing them in with the piece in a vise and filing standing up I found it much much easier to get a nice straight tooth when sitting down and all contorted over the tool with a light very close. I managed to get all the slightly arched surfaces straight this way. NOT good for us with neck problems!

Stacy, thanks. I've had no problem so far getting a similar size piece hot enough to HT with the 2BF. That said, you are so right... I've only made a few tools and finished one forged knife and already want a real forge! I'm going to give it a shot though. I'd rather mess it up and learn from it than send off for a heat treatment. Or so I say now - ask me when I screw up something after all that time filing! In almost everything I make it is the process more than the result that I enjoy and while I don't disparage those who use purchased blanks or pay for HT I'd rather end up with the uglier and poorer functioning tool I'm likely to get from doing it all myself. It's just more fun :)

I've also seen auto body files that have very similar tooth patterns already cut. They might be finer teeth, only seen photos. I'll call my sis and ask her for any old rasps. How did I not think of that before? She trains horses. Her latest was a rescued feral from the desert that she kept for months, "broke" (seems wrong word for her method) and turned into a fantastic horse for the rescue program to find a home for. Hope her husband hasn't claimed all that steel for himself yet...
 
Stacy, since reading your above response about torch vs 2bf I've seen other posts in which you suggested something similar. Do you recommend a torch with rosebud tip when the forge can't get hot enough, or is it a matter of even heating or controlling the heat? I think I'm missing something.

Andy, do you coat all your blades to prevent decarb or is there something about these that makes it more important or more of a problem?

I'm kinda tempted to try Bogg's Tool's file sharpening service on this at some point. I don't think it is going to be necessary but I've read great things about their results and they are not expensive. It seems odd to use a file-sharp edge (or a bunch of them) instead of a stoned and honed-sharp edge. But hey, that's what everyone does and in this case, everyone really does know more than I!

Edit: Float's in the oven now tempering, came out of quench perfectly straight :) Will post photos when it's out. I used a very light coating of ceraset and it hardened nicely - or so my quick file test suggests - and came out nice and clean. I'm SO relieved I don't have to fight it back to straight. Hope it stays that way in the tempering.
 
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Hey Hank. Apologies for the slow response. I was out of pocket over the weekend.

So, yep. That's exactly what I meant on the handle shape and geometry. The first push float I made worked OK but since seeing a similar antique, I held the HT'd cutter under water in a 5 gal bucket and heat bent the shank up about 15 degress. In the process I destroyed the dowel-based handle and my replacement was similar to the antique. Tall rectangle, tapered in x and y toward the nose, heavily chamfered to almost an octagon. It performed much better after those mods. I was just generally saying that it's smart to pay attention to the time-tested details of any hard-use hand tool.

On the clay coat before HT; I meant a very thin wash. As in just a few thousanths. I have found that even when it is thin enough after drying to see faint reflections in 220X polished steel underneath, it is adequate to reduce the surface decarb/mottling/weirdness associated with heating steel past critical for HT. I do preHT shaping and finish work as if it's ready to go out the door. Preserve as much of that as possible by the Satanite wash and end up with minimal clean up after HT. I usually put a wash on any surfaces that will be polished in the finished item.

The reason preserving the pre-HT surface dimensions is more useful with these tools relative to a knife blade is that, with the tooling most of us have available, these are most easily toleranced to within a few thousanths before hardening and you obviously want to preserve that afterwards. That kind of dimensional accuracy is pointless on the business end of most fixed-blade knives. (Please forgive me all of you folder makers - and Nick -I feel your pain.)

Applying the refractory wash is straight forward. Finish to 220 or 320X, clean the tool steel with dish detergent, hot water and a tooth brush (several rounds). Mix about a teaspoon of dry clay into ~16oz of deionized or distilled water. (Minerals in the water here do weird things.) The clay that stays suspended after standing a minute or two is relatively fine. Just dip the warm clean tool in the suspension and dry over heat. You may have to play around with the dilution because how much sticks to the steel is influenced by surface condition, temps, etc. Most of this wash will pop off the hardened part sections at quench IME. I typically start back at 220 post-HT to scour off the surface steel and polish up through the grits.

Hope this helps.
 
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