I did consider using silver steel (drill rod) but the sizes available where far from ideal. The steel is also much harder to machine on my little CNC mill. Being a small mill I don't use pumped coolant which also becomes an issue when trying for a good surface finish. Should I have uses silver steel then I would have dropped the temper and would have tried to keep a higher temper at the rocker/valve interface - possible but tricky.
Case Hardening Help!
- Thread starter Mike Ginn
- Start date
Help Support Home Model Engine Machinist Forum:
The advantage of case hardening is that you get a long-wearing part with a tough interior. Hardened & tempered steel would be tough, but may wear faster.
That said, in a model engine hardened & tempered would probably outlast the intended use.
That said, in a model engine hardened & tempered would probably outlast the intended use.
Absolutely - two different processes. Case hardening, by definition, hardens the surface layer to a target depth while leaving the rest of the part unhardened.
One option the OP might consider is induction hardening. Same process, only it uses induction heating, which can localize the area being treated. Instead of minutes to hours, induction heating only takes seconds.
Hi Tim,
I witnessed Induction hardening at a few factories when I was doing an Audit job in Quality... It appeared that many manufacturers of parts didn't have "perfect" control of the process and variable quality as a result... Not what you want when generating a rolling bearing ground surface on a stub axle for cars, etc. You really want the hard surface and ductile core to be "top quality" for durability and reliability. The common approach appeared to be Induction hardening using a controlled current in the induction coil to heat the part, then air blown cooling as the quench. - This was the critical bit of the process, as too slow permitted too much annealing to take place, and a poor depth of hard surface as a result. Oil quenching was too quick = too hard for required core ductility.....
But I am NOT the expert, just mentioning this as a valid process, but needs much care and study to get good results. It is really just a fast and clean heating method, uniform, rather from "the outside-in". The quenching is "everything" to get the variation of hardness.
Any more information from an expert would be welcome?
K2
I witnessed Induction hardening at a few factories when I was doing an Audit job in Quality... It appeared that many manufacturers of parts didn't have "perfect" control of the process and variable quality as a result... Not what you want when generating a rolling bearing ground surface on a stub axle for cars, etc. You really want the hard surface and ductile core to be "top quality" for durability and reliability. The common approach appeared to be Induction hardening using a controlled current in the induction coil to heat the part, then air blown cooling as the quench. - This was the critical bit of the process, as too slow permitted too much annealing to take place, and a poor depth of hard surface as a result. Oil quenching was too quick = too hard for required core ductility.....
But I am NOT the expert, just mentioning this as a valid process, but needs much care and study to get good results. It is really just a fast and clean heating method, uniform, rather from "the outside-in". The quenching is "everything" to get the variation of hardness.
Any more information from an expert would be welcome?
K2
Induction hardenening - hmm. I don't think you can do that with mild steel, which is what Mike's rockers are made of. How would you do it in a home shop anyway?
There are other reson .
1) Cheaper steel
2) Easy to cut.
3) you make part rock hard
Dave
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Induction hardening.... A high frequency high power generator.... onto a coil of heavy copper wire (3mm thick?). Perhaps a weld set would manage?
Or melt?
K2
Or melt?
K2
100model
Well-Known Member
A inverter microwave oven has a 30,000 Hz 1200 watt power supply, while not high power it could heat up small engine parts for case hardening.
Charles - Yes you can. High carbon steel has enough carbon you don't have to add any. With low carbon steel you just need to use a hardening agent such as Kasenit. The only real difference is that instead of using a furnace/kiln to heat the part, you use the induction coil, which by comparison is very fast.
The frequency affects the depth of penetration - higher frequencies have shallower skin penetration depth, while lower frequencies have deeper skin penetration depth
Hmmmm. Sounds interesting.. Must seek out a discarded Microwave oven? - I had a 3kW. muffle furnace, but very slow by comparison, and firing some ceramics one day I let it get a little too hot and the elements burnt-out. Still good with a gas burner poked into the door, but not for sausages! (I later bought a 6kW Kiln for the ceramics, but You could not open the door to get parts when hot! - So no good for metal processing. Ceramics were good though. I sold it a year ago.)
K2
K2
Portable induction heaters are sold in the UK by “Machine Mart“.
Searched on line and there are lots of small induction heaters with cheap electronics.
Nice to know if I ever had an application...
K2
Nice to know if I ever had an application...
K2
Bit over the top.....just heat up with a butane....only a couple of model tappets after all.
Agree Bluejets. But for the fun of "developing tools and processes", many people work out new tools and techniques... This is a new one for me, but I have seen it in factories on Mass production, and it was very accurately repeatable. - on the right job, where a localised zone was hardened. Unlike bench gas blowlamps.
This is something you can buy, and with a stopwatch on the power supply can harden (E.G.) Valve heads without hardening stems, or ends of rockers without hardening the middle, without the mess and post heating cleaning from using Kasenite, or some such toxic chemical. I saw it used to harden the part of a shaft that formed the inner race of a bearing, without losing the ductility of the core of the shaft. like on a crankshaft.
The real difficulty lies in how the part is cooled after heating. I.E. the process I saw had an air jet turned ON to cool the part after the heating coil was turned off. That rapidly cooled the outside, but allowed the core to cool slower. Oil or water-spray quenching had been used previously with results that were too variable (and the oil burned-off so the flames and smoke were a problem for the factory). The "home workshop" would probably opt for heating by gas flame then oil quenching - in an open space!
The problem (and makes your argument a winner!) is that we usually do not have enough components to warrant the cost of such a "technical" tool or process, nor the understanding or instructions to get it right on the "one part for this model".
Enough said?
K2
This is something you can buy, and with a stopwatch on the power supply can harden (E.G.) Valve heads without hardening stems, or ends of rockers without hardening the middle, without the mess and post heating cleaning from using Kasenite, or some such toxic chemical. I saw it used to harden the part of a shaft that formed the inner race of a bearing, without losing the ductility of the core of the shaft. like on a crankshaft.
The real difficulty lies in how the part is cooled after heating. I.E. the process I saw had an air jet turned ON to cool the part after the heating coil was turned off. That rapidly cooled the outside, but allowed the core to cool slower. Oil or water-spray quenching had been used previously with results that were too variable (and the oil burned-off so the flames and smoke were a problem for the factory). The "home workshop" would probably opt for heating by gas flame then oil quenching - in an open space!
The problem (and makes your argument a winner!) is that we usually do not have enough components to warrant the cost of such a "technical" tool or process, nor the understanding or instructions to get it right on the "one part for this model".
Enough said?
K2
Last edited:
100model
Well-Known Member
Not all microwave ovens have this, so look at the door and it will have INVERTER written on it. Panasonic is the main brand that uses an inverter power supply. Sharp uses it as well and I think LG started to use it. You can have great fun experimenting with the inverter to heat up steel.
