I've been making these little punches from W-1 for a long time and only recently have problems. The punch is 3/16" square about 5" long. It's used to insert wire and a staple into wood blocks to make brushes. One end gets soldered into a steel holder and the working end gets ground to a 1" x .80" tang. The very tip has a .030" deep groove ground into it to engage the staple crown. To heat treat them, we heat the last 1/2" red hot and dip in water. Wire wheel and polish it, then heat to dark straw then quench again. Now the punches seem to be splitting from the groove on up for a quarter inch or so and blowing the side off. I can use 0-1 but it's very expensive. I'll do that if I can't dial W-1 in. Is there a better heat procedure? The machine that these punches go in is bigger and more powerful, the other machines using W-1 don't have a problem. Any suggestions for steel that I can get in square rod? ...cheaply, of course!
it seems to me that you have a fatigue failure emanating from the notch which acts as a stress raiser.
you could rounding the notch a little more to reduce the stress raiser or I'd make it slightly deeper so that the notch wasnt taking the full force of the press as it pushes the staple.make the sides press the wires as well. they are down below the surface of the wood so a slightly less pressed staple shouldnt cause a problem.
maybe as well heat to light straw on the second quench and allow to air cool may leave the material less brittle. (my aircraft landing springs never get quenched on the temper) Stealth Pilot
I haven't used W-1 in a long time, but for O-1 the oil bath should be about 120 deg F. for less-than-simple shapes.
One reference states that small sizes of W-1 may be fully hardened in an oil bath, also. You may wish to give this a try. Same ref. says the water bath for quenching (brine is preferred!) should be at a temperature between 70 and 90 deg. F.
======================== You might try some drill rod from a different source. W1 is supposed to be a specification and not a suggestions, but not all mills seem to have grasped this yet, or some may be producing to the bottom of the spec (and sometimes falling below it) for economy.
There is square w1 tool steel available, but the price is high. You most likely can mill the drill rod square and still save money.
How big a radius does the corners in the groove have? Can you put a full radius at the bottom?
Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.
John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).
There is no need at all to quench in water after tempering.
Suggest tempering in a toaster oven for an hour and letting air cool. Heating until the surface turns straw colored (500 - 550 deg F) then quenching in water is accomplishing nothing but tempering the surface of the material. The meat of the tool is still going to be hard and brittle which is why it is fracturing on you.
Yeah, the quench-after-temper business seems to be a misunderstanding about what that was for. When you temper the back of a knife blade, for example, but you want to leave the edge hard, you heat the back and watch the colors progress. Quench at just the right time to catch the relative hardnesses you want, back to front.
This really is an inferior way to temper, however, and it's unfortunate that some people seem to think the quenching is a necessary part of tempering in general. For any given hardness, you get the best toughness with a long (one hour or more, for some alloys) temper.
We do temper by watching the color progress. We want the tip hard to resist deforming where it handles the staple but keep the rest of the ground area of the punch tough. The rest of the five inches is untreated. What's the best way to get the different properties we need in different parts of the punch?
To think about it, it seems that it's just this batch or W-1 that I got from McMaster. Most of the other machines use 1/8". Those drive a 20 gauge staple. The problem machine drives a 15 gauge staple...BIG difference. Most brushes that use a 15 ga. staple drive it with a 1/4" or bigger punch. I just can't use that big of tooling. Not only are those 20 ga. machines putting a lot less stress on the punches but I bought 200 feet of the 1/8" W-1 some twenty years ago. Back then it was called "Square Drill Rod". None of the youngsters in the steel service centers even heard that term before.
The reason I use the W-1 is because it DOES go into catastrophic failure. If I use 0-1 the punch will sometimes get a minor chip on the end and sometimes the staple will slide off the tip just a bit as it is being driven into the bottom of a hole in the wood block. This failure isn't always readily apparent. Most of these brushes go into the restaurant trade and loose wire around food is a no-no for some reason.
As far as I know, that's it. That's why the quench-temper method is sometimes used. If you want maximum toughness at the hardest part of the tool, though, you don't get it. You probably know a lot better than most, you're playing a tricky engineering game of trade-off.
That's a very interesting situation. If you haven't done so, you ought to contact Modern Machine Shop or American Machinist and tell an editor there about your application. I think they'd be interested, and you'd get some publicity out of it.
That kind of differential hardening was once a fairly common thing, but I haven't heard about it being used in industry for years. It's interesting that it still has a place. The reason I think someone at Modern or whatever would be interested is that they probably haven't written anything about it for years, either.
Hardening: Preheating is necessary only for intricate sections or large sections where temperature would differ appreciably from surface to center. Heat slowly to 1400 to 1550 F using the upper end of the temperature range for low carbon contents and the lower end of the temperature range for high carbon contents. Using temperatures at the upper end of the temperature range will increase hardenability. Austentize for 10 minutes for small sections and 30 minutes for large sections. Quench in agitated water or brine. A spray directed into a recessed configuration, such as a die cavity, or at the working end of a punch is often used to obtain maximum hardness amd residual compressive stress in a desired area. Approximate quenched hardness, 65 to 68 HRC
Tempering: Temper immediately after hardening, preferably before the tool reaches room temperature; about 120 F is optimum. Allowing quenched tools to stand at room temperature or placing them in a cold furnace will lead to cracking. Therefore, place tools in a warm 200F to
250F furnace immediately after quenching and bring to tempering temperature with the furnace. Except for large pieces, work will heat up at about the same rate as the furnace. Temper at temperatures not lower than 350F and up to about 650F. One hour at temperature is usually adequate; additional soaking time will further lower hardness. A double temper may be required. The low temperatures used in tempering eliminate the need for atmospheric control. Approximate tempered hardness, 50 to 64 HRC.
Looks to me like you would do better getting a little anal about the tempering end of things. A simple toaster oven appears to be good enough for the temper. Although I hear ya about "doing the same as before", we often find that we *think* we are doing things the same but some little part has changed without knowing....heating faster, not holding as long, etc. Also, metals have changed: W-1 that you may have had around for a few years might not be the same W-1 you have now...you never know these days with all the imports. Yea, it probably falls within specs but might be at the upper or lower edge of those specs so may be contributing to the problem.
Forgot to mention: By the graphs in the book, tempering at 400 for an hour will get you about a 60HRC and 500 for an hour will get you to about 57 HRC....not sure if you are shooting for a "real" number or just "whatever seems to work". You might think of investing in one of those small spot-check RC hardness kits...they have a spring loaded punch and a hand held tube microscope to rough check hardness. Mine came from a $
5 lot at auction..not sure what they are had for on the open market. Handy tool for those "gotta have it" times that come up once every couple of years.
Why would Modern Machine Shop want to write about something that has been solved problem for many decades? This isn't a hardening issue as much as it's a selecting the proper material for the job issue. There are far better steels than W1 or O1 available for this particular application. S7 and H13 come to mind. But unfortunately, the OP chooses to be cheap with material at the expense of lost time....
Read the whole thread. It's about differential hardening and leaving a fairly brittle edge, done intentionally for the sake of avoiding an undetectable failure.
Exactly! Material cost is meaningless. I had two 52' trailers full of stuff returned due to bad staple wire. The staple looked fine from the top but it had crumpled under the wire tufts rather than penetrating the wood. That cost me ten grand to repair and ship. And I lost a lot of capital with my customer.
Two more "modern" (which thus involve expensive toys to do them, unfortunately) techniques come to mind, from a differential hardening (as opposed to differential tempering) direction - either heat-treat the tip with a CO2 laser, or heat treat the tip by induction. In either case, the tip area that is to be hard is self-quenched by the bulk of material behind, and the bulk of material behind is never hardened. Then you can temper in a furnace for as long as you like at the temperature that makes for a good tip - the back will still be tough, as it was never heated to harden it. Effectively case-hardening, by limiting the depth to which the metal is heated, rather than by adding carbon to the surface of mild steel.
20-25 years ago this was big news in hardening camshaft lobes, etc. I assume it's still being used in some industries. I see induction-hardened teeth on bandsaws and some handsaws.
Do you have sources for small quantities of S7, H13, etc. in drill rod and rectangular/square format? What are their minimum order quantities? Can these be heat treated by normal shop methods or do you have to send these out? Any URLs?
Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.
John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).
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