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View Full Version : OK, I do NOT understand the "Hex driver" article in the current HSM issue



J Tiers
10-25-2013, 10:03 PM
It's the Michael Ward article. he doesn't seem to hang out here anymore, but maybe he will look in...

I mean, I understand wanting nut drivers for model nuts and bolts. No problem there.

What is puzzling me is the process of making them. Or specifically, the forging process described.

There was considerable effort in the article devoted to the form used to shape the hex socket, hardening it (heating and quenching), and drawing it to a good temper. Color charts, temperatures, etc. The point was made that the form should be harder than the part to be formed, so that only the part has its shape changed. Excellent idea, of course.

However, the process seems to include the idea of inserting the hex form in the "blank", and then heating the socket blank to a bright red forging heat with a torch (picture given, red metal shown).

What I don't get, is that the heating to red heat is bound to get the hex form piece rather hot as well..... at least close to red heat, if the part surrounding it is at red heat.

I would have said that is a description of how to draw the temper of the piece, i.e. soften it, lower the hardness, etc. By the time you have it at red heat, you are pretty much annealing it.

There is nothing about using a red-hard material, such as HSS, which I would understand. The most esoteric material mentioned is old allen key stock.

So, why the big deal about hardening?

There must be something I do not understand here.

George Bulliss
10-25-2013, 10:26 PM
One of Mike's goals in his articles is to make them useful to as wide of an audience as possible, giving the readers information they can use, whether or not they actually build the project. This is why he will occasionally divert from the step by step construction notes to discuss home shop procedures in a direction or depth that may not be required for the specific task at hand.

I thought he did a good enough job in conveying the fact that this was a low-precision project that the reader would understand the extra detail for what it was; discussion on various home shop skills that were related to the build.

Of course, I view these articles in an entirely different context than the subscribers and make no claim that my view is correct! I don't have that copy at home yet and am only going on my last read-through, a month or two ago, so this is about as specific as I can get.

J Tiers
10-25-2013, 10:36 PM
I'm not complaining about info on hardening... that's fine. the more the merrier.

I'm just puzzled as to why to BOTHER hardening, when the very first (and only) thing you will do with the thing after you harden it is to anneal it (removing the hardening) before you can ever use the fact that it is (or, more likely "was") hardened.

After all, if one wanted to know how to draw the temper of a small piece of metal, one would likely be told to heat it red hot (and allow to cool slowly). There might be an argument about "dwell time" in hours at red heat per inch of thickness, but these are small parts, far smaller than an inch.

So, I figure that there must be some factor I am not considering that makes it worth the effort to harden the forms before heating them basically red hot.....

dp
10-25-2013, 11:03 PM
I think a lot of the mystery (or confusion?) is in the color of the two operations and I think is why he included the color chart. I liked the article enough to re-read it a couple times. As George says, there is a lot more going on here than making nut drivers. He's provided a pretty fair job of teaching basic blacksmithing. There should be a follow-up video for the new HSM Youtube channel.

Arthur.Marks
10-25-2013, 11:14 PM
What is missing, I expect, is the heating capacity of each piece. The forged part is a thin wall tube. The "die" is a solid form with a bit of excess material. Yes, the forged part also has a larger, solid section, but the thin tube area will absorb heat far faster than the solid rear section can draw it away. So what you have is two different rates of heat absorption based on thickness. It is at least 2:1 for thickness comparison between the die:forged section. Yes, after the whole operation is completed, your die may end up tempered, but during the forging activity it is still hard. ...I think. Certainly no expert here. I am more familiar with a torch when dealing with a comparatively thin section abutting a thick one. It is very easy in that situation to overheat the thin section before the thicker one is even near a significant temperature. Same material, but one needs more input to equal the other. In Photo 20 on pg. 24 this is shown well. See how the part to be forged is already bright red? The die is still clearly black in color--nowhere near red.

lynnl
10-26-2013, 01:03 AM
..... this was a low-precision project .....

Low precision? Really?

I liked the article, but what really jumped out at me was his specifying some of the dimensions (across the flats) to 7 (Seven!) decimal places! :D What is that ...a tenth of an angstrom?
I've always thought Mcgyver to be admirably modest, but that looked like he was showing off. :)

J Harp
10-26-2013, 06:49 AM
How do you keep from thinning the wall of the socket blank too much while forging, and winding up with an oversize opening? That's been the result when I have tried anything like that, I wonder how Michael avoids it.

J Tiers
10-26-2013, 09:52 AM
Yes, I considered that issue of teh thickness, or mass. But to get the whole tube hot, it looked in the picture as if everything were getting red hot.

And, as you know, the metal gets very soft (gray, way past blue on the scale shown) at a temperature which is in no way red hot. I doubt the hardness lasts through the process.

Maybe it's good enough for one shot.......

If he had die-swaged the parts, I suspect he could have totally avoided bothering to harden the hex, since the metal would be forced inward fairly evenly. An un-hardened piece would likely have lasted fine. Thewre is also a chance that the process could be done cold, with an annealed blank, in which case the hardening would be useful.


How do you keep from thinning the wall of the socket blank too much while forging, and winding up with an oversize opening? That's been the result when I have tried anything like that, I wonder how Michael avoids it.

That is the point of the heating.... Mr Ward states that right in the article, saying that he found that cold forging ended up with an oversized part.

And that should be pretty much inherent.... this isn't really a "forging" operation at all, it should really be called "hammer swaging".

If you think for a moment, the chord of a circle (a straight line between two points on the circle) is SHORTER than the length of that portion of the circumference. There is more material than needed. Your problem is to make it go somewhere useful.

You can make it "fold up", which would lead to "points" sticking out at each angle of the hex. That would be with a die holding it on the faces, and letting it form out sideways at the "points", buckling upwards. You can often see something like that in sharply die-bent tubing, the extra material is allowed to move outward or inward.

Remember that a basic law of blacksmithing is that the metal will go "somewhere". If you hit it, you squeeze it out sideways, you normally THIN AND WIDEN the material.

By working hot, and properly manipulating the hammer, Mr Ward was able to cause the material to "upset", or get shorter and thicker along the faces of the hex as it conformed to the shape.

To really do this job right, a pair of half-circle dies would be used to swage down the OD of the part and force it around the hex form. The dies would force the metal to move into the spaces between the original round form and the hex form.

That could be done cold , if the part were suitably annealed first. But a hot work approach is probably better.

J Harp
10-26-2013, 10:20 AM
I suppose it's a matter of practice. I've tried it hot and wound up with it oversize, probably tried to go too far at each step. I'd get two sides closed on the die, then when doing the second, the original faces would pull away at the corners.

By the time I got it into a rough hex, the opening would be too big. Of course I've only tried that a few times, so don't have much to go on.

J Tiers
10-26-2013, 10:26 AM
That's why outside dies would be helpful. They constrain the material and force it to stay closely against the form.

When you hit the top, remember that the "anvil" (whatever it may be) is hitting the bottom.......

Sometimes, if anvil light weight, it is minimally involved, and you are doing most of the work on top, using the mass of the workpiece.

mikem
10-26-2013, 10:28 AM
I read the article right away--I thought it was very interesting, even if it was a week's work to save the cost of a set of nut drivers ($25)

How about heating the tip of the nutdriver red, forcing it over the hex die to form the shape and removing before it shrinks too much?

Jerry-- I enjoy your posts here at the HSM BBS. Hope to meet you again sometime!

Arthur.Marks
10-26-2013, 11:28 AM
Yes, I considered that issue of teh thickness, or mass. But to get the whole tube hot, it looked in the picture as if everything were getting red hot.
Here we disagree. I don't see that in the picture. Besides, it makes no sense. The tube is going to get red hot very fast in comparison to a solid. The blue hue is not actually from the part in photo 20. It is the cone of the torch flame. I see the die as being still blackish grey -- as it is when inserted cold in photo 19.


And, as you know, the metal gets very soft (gray, way past blue on the scale shown) at a temperature which is in no way red hot. I doubt the hardness lasts through the process.
IMO you're overthinking this and ignoring experience. Even a well tempered part will be harder than a fully annealed part of the same material. It is surely incorrect to call only the rapid heating of something above its critical temperature "annealing." Even so, it suffices to say that steel above its critical temperature is rendered soft and more malleable than that below.

Are there other methods to make the socket? Yes. Does that make the method chosen in the article invalid? No. Is the initial heat treatment of the die absolutely necessary? Maybe not. Does it, even so, add a bit of advantage and working time before the die deforms? Arguably so.

I'm no metallurgist, but this is my take given what first-hand experience with a torch I have.

Frank Ford
10-26-2013, 02:11 PM
Haven't tried the technique myself, but it looks quite interesting and worth some experimentation. My first impulse would be to make a simple 120-degree v-block anvil and do the hammering there. That way, I'd be pressing against against three flats of the hex with each blow of the hammer.

J Tiers
10-26-2013, 02:16 PM
IMO you're overthinking this and ignoring experience. Even a well tempered part will be harder than a fully annealed part of the same material.

Not at all.....

This is exactly what I am ASKING...... not "stating".

It very likely IS a case where it works well enough to get it done, which was the basic thought that prompted the question....

I may try it for some other things I need to do, but I think I will do an outside swage die added to the inner form

J Tiers
10-26-2013, 07:19 PM
I read the article right away--I thought it was very interesting, even if it was a week's work to save the cost of a set of nut drivers ($25)

How about heating the tip of the nutdriver red, forcing it over the hex die to form the shape and removing before it shrinks too much?



I bet that would work.... it's basically using what is often called a "hob". Not the gear cutter, but the form which is forced into soft, possibly heated, metal to produce a form.

Some nut drivers appear to be made that way, the ones with a conical surface inside.

Hobs are always hardened (harder than the hobs of Hell, right?), and they work, so that's more evidence of the hardening persisting right through use in hot metal workpieces,.

Counterintuitive, but what works works.

vincemulhollon
10-27-2013, 08:33 AM
My first impulse would be to

Its the surprise of it. So he makes a really nice hardened precision sorta broach, sorta broach as in not an exact clone of the $200 commercial ones but probably good enough 1-time use homemade design, and then drills the future nut driver to the right diameter to broach, I'm thinking ok now the next step is grind/sharpen to perfection and then the zillion ton press but instead he gets out the torch and hammer and I'm like whaaaaa?

I like that article not so much because its right or wrong (if even exists a right or wrong beyond "it worked for him") but because its really interesting to think about.

I know just enough about broaching to be dangerous but basically nothing about blacksmith forging, and most of us here coming from a machining background not blacksmithing it may be that this is just a very small scale of how blacksmiths make pinned hinges or something similar. I think that would be an interesting followup to the story or letter to the editor along the lines of "and I watched a blacksmith make the hinge for a set of pliers which inspired me to ..." or where-ever it is he got this interesting idea. I bet on a small scale this is what blacksmiths do and if not, it would appear to be a perfectly good idea for a blacksmith to try. I bet you could make tight blacksmiths tongs/pliers this way.

J Tiers
10-27-2013, 11:28 AM
I've tried that broaching thing, and it takes a lot more pressure than you think. Maybe less if you get the right grind on the edge. Then you have to pull OUT the broach, which can be hard also.

I like the forging idea.

What Frank Ford is talking about is pretty similar to the half-circle swages. Seems like it should work great also.

duckman
10-27-2013, 06:03 PM
I have a rough idea of what is being said but when I needed a special nut driver I just took an allen bolt that fit, jammed 2 nuts together with a washer in between and used that.

farrviewsouth
10-27-2013, 06:17 PM
Ok, now that is slick!

dian
10-28-2013, 01:33 PM
I have a rough idea of what is being said but when I needed a special nut driver I just took an allen bolt that fit, jammed 2 nuts together with a washer in between and used that.

why the washer?

duckman
10-28-2013, 02:04 PM
Because a lot of times when you jam 2 nuts together they will spin/slip the washer prevents that. Try taking a stud out without a washer and you'll see what I mean. Just got my HSM today some people must be on a priority list.

cameron
10-28-2013, 04:27 PM
The question remains.

Why the washer?

Or rather, why should the washer make any difference?

I'm either to dumb to figure it out, or too lazy and I stopped trying too soon, but I'd appreciate it if someone could explain it to me.

J Tiers
10-28-2013, 08:51 PM
Two nuts directly jammed sometimes actually don't get tight... possibly because there is no "spring" in the setup. Possibly because the friction is too much.

They often seem to just "stop" when they come together. With the washer, there is a "tightening zone".

A washer provides some potential non-flatness for "spring", and since they are often galvanized, some "lube".