DIY Induction heater for shrinker endmill holders?

I bought a number of BT40 Lyndex shrink fit endmill holders, but cannot even come close to affording the shrink fit induction heating
system to operate them. I'd like to use the holders, as they are really nice and well balanced.
Soooo.... I was thinking of buying a $100 induction cooker and taking it apart and reworking the coils to go around the endmill portion of the holder.
It doesn't take a whole lot of heat to get the holder to open up enough to take an endmill. I did an experiment where I used an electric range cooktop and heated a 5/8" shrink fit endmill holder up and then inserted a 5/8" carbide endmill. 30 seconds later, it had really gripped it quite hard. Opinions and ideas?
Anybody know if the coils in an induction cooker are flexible and can be reshaped easily?
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rpseguin wrote:

Sayyy you may be on to something there.
http://en.wikipedia.org/wiki/Image:Induction_Cooker.jpg
The red dealie in the center of the (silicone?) pad is probably a temperature sensor allowing closed-loop operation. So you would want to incorporate it into whatever modification you plan.
Be careful to match the impedance of your inductor to that of the spiral - wound unit shown.
--Winston
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I would probly adapt an ac welder..wind up some copper tubing and pump cooling fluid through it.
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What is an "induction cooker" and where can you buy one for $100?
Recently, the guy at the auto repair shop I go to showed me a little induction heater that has a heating coil on the end of screwdriver-like handle. You lay the coil over a siezed-up nut, pull the trigger, the nut turns red and you take it off. Car doesn't catch fire, knuckles aren't bruised, etc.. I have no idea how much the thing cost, but it wouldn't be too hard to find out.
In general, induction heating devices that I have seen aren't all that cheap. So, if you do have access to that $100 device, I'd sure like to know where I could get one.
Pete Stanaitis ---------------
rpseguin wrote:

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http://www.theinductor.com/index.php?m=5&s=0&ds=0&prod 
Scroll down to the MD600
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(Amazon.com product link shortened)09520538&sr=8-5 (Amazon.com product link shortened)
An induction cooker uses induction to heat the pot/frying pan. They are very efficient, compared to electric ranges.
I was just thinking that one of those would make a cheap source for the control electronics and the coils look flexible enough to reshape/ reuse from the one response showing somebody taking one apart.
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rpseguin wrote:
(...)

It'd be much faster and cheaper to weld short vertical tube sections to the cooking surface of a steel frying pan. You could match the ID of the tubes to the OD of your collets plus some headroom. Pack Kaowool in the gaps and Bob's your uncle.
Corrosion control is left as an exercise for the student.
They also make a great gag gift.
--Winston
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While that may be faster to fabricate, it sounds like it would be a lot less efficient in heating the endmill holder quickly. Will the induction properly feed all the way up the tubes and then induction heat the endmill holder through an air gap insulation? Ie, while the tubes may get hot quickly, will the endmill holder get hot fast via induction? Or just slowly via radiation/convection/ conduction?
Looking at this image:
http://en.wikipedia.org/wiki/Image:Induction_Cooker.jpg
I think it is worth a $100 experiment to see about reshaping the coils to be up close to the endmill holder. Take it back to the store: This thing came this way, with all the wires hanging out and it smelled like smoke when I opened the package :-) (just kidding, I would never do that)
Thanks. -Ralph
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wrote:

I haven't followed this thread so excuse me if this has been covered, but I hope you know that the hard part with induction-heated heat-shrink toolholders is not getting the tool in and clamping it, but getting the tool *out*. If you even slightly overheat the holder before you put the tool in, or if your induction heater is just a wee bit slow, you'll never get the tool out. Sophisticated systems, like Bilz's ThermoGrip, involve a *lot* of timing experiments in the course of their development.
All of which is OK if you're planning on making a permanent toolholder/tool assembly. d8-)
-- Ed Huntress
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I believe it. That was one of the things I was wondering about. How do you avoid induction heating of the endmill/tooling? Or, does the "gap"/interface between the tool and the holder decouple it enough to allow differential heating.

Well, I guess I'll try a drill chuck first :-) If all else fails, I've got a permanently mounted drill chuck on a BT40 shank :-)
Thanks. -Ralph
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wrote:

They avoid heating the tool by heating the holder so fast that heat doesn't have a chance to conduct in to the tool shank. If it does, you're a dead duck when you try to get the tool out.
The clamping results in a very tight interference fit, so conduction between the holder and the tool is practically uninterrupted. You don't gain any significant edge from the transition between toolholder and tool insulating the two from each other. The bore of the tooholder is actually cool enough to touch, as is the tool shank, at the instant the holder releases its grip. Power is critical and the timing for applying the removal force is critical. They work in seconds.

Ha! Well, that would solve the problem.
I wrote quite a bit about these gadgets when they were first becoming popular, and they are really great for the appropriate applications. But "appropriate applications" are high-speed milling with some horsepower. Unless you're spinning the tool at something over 10,000 or 15,000 rpm, with, say, 10 or 20 horsepower, their advantages are not very great. Of course, once you've invested in one of the things, it's worth using it for your ordinary tooling and speeds, too, if you're running multiple machining centers and you have a big inventory of tools. I've never heard of anyone using shrink tooling with a drill chuck, but I guess it would be OK if you also had your MC tooled with multicoated or ceramic inserts, running at the max.
Otherwise, the conventional solutions are a lot less trouble and expense.
-- Ed Huntress
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Ed Huntress wrote:
(...)

Thanks, Ed.
I was completely unaware of that.
--Winston
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On Thu, 1 May 2008 20:47:20 -0400, "Ed Huntress"

http://www.ameritherm.com/overview_shrinkfit.php
A lot of good free information available however to get the more detailed technical data you be asked to fill out a form with your contact information.
http://www.cihinduction.com/reheating.htm
Tom
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wrote:

That's good info for making a permanent shrink fit, but the trick with the tooling application is getting the tool out of the holder when you want to change tools. It's difficult.
I should point out that it's easy with carbide tool shanks, but very difficult with steel, because of carbide's lower coefficient of thermal expansion.
-- Ed Huntress
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On Thu, 1 May 2008 23:16:34 -0400, "Ed Huntress"

Not expecting the OP to use that page for his shrink fit, just passing along a source for information.
They have a lot of free information, videos, technical data, theory, application & How To's, including for this OP how to design coils, but he will have to navigate the site to find them all.
Tom
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rpseguin wrote:

Conduction / radiation was the path I was thinking of.
Perhaps that would not work at all. Who knows? :)
Maybe instead, a ceramic holder for the collet bodies to position them above the business area of the inductor? Where did I put those demitasse cups?

:)
--Winston
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Don't know how often you have to do this, but, once you know the temp you want, choose a metal that melts at about that temp., make sure the holder is NOT "fluxed", then dip holder into molten metal, remove from molten metal, then insert endmill.
I don't think you'd have much luck with the unduction cooker. It appears, from what I see, that the pot the sit that would sit on top of it forms part of the magnetic curcuit.
Pete Stanaitis --------------------- rpseguin wrote:

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Tim Williams posts here once in a while, he's done a lot on home brew induction heaters.
http://webpages.charter.net/dawill/tmoranwms/Elec_IndHeat1.html
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