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Induction heater / forge

#1
Hey Guys,

I was chatting with KEB about small boring bars. I had to borrow some that he made up for the engine I am repairing. This shows that I need some too and I think the best way is to just make some myself which brings me to this post.

The ones I borrowed from him are ground down from a single piece of HSS. This is a crazy amount of grinding.
He wants to start using tool steel because it is easier to reduce down in a lathe but would then have to heat treat.

So I am now thinking about building a small induction heater / forge to easily and uniformly heat any of these custom tools.

Anyone on here done that yet?

I think all thats needed is a power supply, an oscillator and some copper tubing.

"Come at me bro" - The Douche
 

Tom Kitta

Active Member
#2
I just bough a kiln - they also come for sale from schools at KMS for like $200 or $300. Seems cheaper just to buy one and even fix as needed vs. having to build one from scratch.

Induction heaters (home made spiral - popular from China) on the other hand - with a little spiral and controller are cheap - they will heat the round bar quickly but don't have much in the way of temperature / time control.
 

Tom O

Active Member
#3
Back in school shop class (68) ? We whacked a rightangle into some 3/8 round steel bar then ground it to shape and tempered it with a torch! It worked fine.
 

Tom Kitta

Active Member
#4
For small things - such as 3/8 round bar that don't need too much precision in how hard they get a torch works great. For say 1.5" bar you would run into core heating issues - i.e. outside sure would be hot but the inside sort of ... on the colder side. Also it is not very prices to tell exact temp from colour.

Also tampering requires time and temperature settings that are somewhat precise - through you could get away with say old toast oven (temps are that low) for some work.

Torch works for say home made screw driver - its small and doesn't need some precise hardness.
 
#5
Induction heaters (home made spiral - popular from China) on the other hand - with a little spiral and controller are cheap - they will heat the round bar quickly but don't have much in the way of temperature / time control.
How cheap is cheap and where does one get them? A thermocouple and PID could solve the temp control problem.

Been messing with this arrangement.

CCForge.JPG

With out much success.
 

Tom Kitta

Active Member
#6
For a little forge the setup on the picture is not that hard to achieve - even through second hand large forges can be had for cheap. For metal hardening or case hardening the main obstacle is time in addition to temperature control - sure a thrmocuple can tell you its now 1500F but how are you going to keep it at that temp for hours? Sure you can make a controller - but now you essentially build a klin.

If you want to build a klin for practice - then its fine - or as a project - go for it. I just doubt you can build something you can get for $200 for ... $200.
 
#8
YYC, if you switch to MAP gas you will have better success.
Have used MAP, and Ya, it gets things hotter faster. The problem I have is that I never see cherry red. I get dull red and then poof... orange. So, I miss the critical temperature. That and not really knowing what I'm doing. I unknowingly tried heat treating a piece of stainless one time Daaaaa.
 
Last edited:

Dabbler

Well-Known Member
#9
Soooo... I was introduced to propane/oxy a few months ago. You can kit up for it for a little less than oxy/acetlyene, and get bright orange with it. With MAP you can get to meduim red without oxygen, and will get you to Rockwell 40 with 4140. To het hotter with anything you have to have oxygen, or a blower. My friend's heat treat furnace runs off of household natural gas with a blower, and gets to about 2100F - bright yellow. It will treat almost all of the normal tool steels, but not the exotics.
 
#10
I just bough a kiln - they also come for sale from schools at KMS for like $200 or $300. Seems cheaper just to buy one and even fix as needed vs. having to build one from scratch.

Induction heaters (home made spiral - popular from China) on the other hand - with a little spiral and controller are cheap - they will heat the round bar quickly but don't have much in the way of temperature / time control.
oh, do you have a link?
I searched "Kiln" and it didnt come up with anything.
Yeah, on the high side of things I could build a 2000w unit for just under 300$. So A kiln for the same price could be better.

doesnt seem like anyone else has played around much with induction though. Still might be a fun project.
 

kevin.decelles

Active Member
Premium Member
#11
I built my kiln back in 2001 following the Gingery book "lil Bertha A Compact Electric Resistance Furnace" Link to Amazon

It uses fire brick, some refractory and a electric heating element. For the element I sourced it out of BudgetCastingSupply.com Link to BCS which is a pretty good no-bullshit outfit out of California. I've picked up crucibles there, as well as 200 lbs of Petrobond sand many moons ago.

All in I probably spent $120 (2001 dollars) building it -- still going strong today as it's the unit I use in winters to melt aluminum. My next project will likely be to add a controller and thermocouples to it as Tom said in order to maintain temp, but I've had really good results annealing metal with it just by using color/common-sense as a guide.

I learned plenty doing it, but had I the chance to buy a used Kiln I'd buy the kiln. If you crack the nut on induction, let me know as I'd love to pirate your design.
 
#12
I built my kiln back in 2001 following the Gingery book "lil Bertha A Compact Electric Resistance Furnace" Link to Amazon

It uses fire brick, some refractory and a electric heating element. For the element I sourced it out of BudgetCastingSupply.com Link to BCS which is a pretty good no-bullshit outfit out of California. I've picked up crucibles there, as well as 200 lbs of Petrobond sand many moons ago.

All in I probably spent $120 (2001 dollars) building it -- still going strong today as it's the unit I use in winters to melt aluminum. My next project will likely be to add a controller and thermocouples to it as Tom said in order to maintain temp, but I've had really good results annealing metal with it just by using color/common-sense as a guide.

I learned plenty doing it, but had I the chance to buy a used Kiln I'd buy the kiln. If you crack the nut on induction, let me know as I'd love to pirate your design.
Thanks Kevin,

"Necessity is the mother of invention"

The guy I was looking into this project with decided it was just easier for him to use MAP and a couple firebricks to accomplish what he needs so I think this project is going to get dropped until I have the need again.

But for SURE if I build anything like it I will document it and post it here. (I will document better then the last project)