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Author: Subject: Making an induction heater for fastener removal?
Bert
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[*] posted on 3-12-2017 at 09:13
Making an induction heater for fastener removal?


I have a small problem, a drain plug frozen into an Iron gear box. Mechanic tasked with changing gear lube totally stripped the hex drive indentation trying to remove (with an impact wrench!). He then refused to work on it further, and suggested whole gear box be replaced (for an estimated several THOUSAND dollars, if a part could be located. Thanks, buddy!).

I suspect it may also have been cross threaded on installation by a previous mechanic, who then forced it home anyhow.

I need to get it out. Without breaking the gear box, which is not AFAIK available as a new part, and if it were, would cost more than the repair would be worth to obtain and install.

These tools are useful for spot heating a bolt in places a torch would be inadvisable or too imprecise-

shopping.jpg - 54kB

[Edited on 3-12-2017 by Bert]

maxresdefault.jpg - 96kB

But the cheapest version is still kind of expensive. Looking at eBay, Amazon, etc., the components are available and inexpensive...

And after the fastener removal project, the same components could make a small crucible heater for other projects.

Looking at the many online offers of induction heaters as assembled boards without enclosures and associated heating coils. Anyone here done a similar project? (I have seen several posts by members about making and using small induction heaters for smelting).


[Edited on 3-12-2017 by Bert]




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gnitseretni
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[*] posted on 3-12-2017 at 10:32


If possible, weld a short bolt to the drain plug so you can put a wrench on the bolt. That's what I'd try anyway.
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[*] posted on 3-12-2017 at 10:39


Surely it's not the bolt you want to heat, but the casing ?

A blowtorch would be the best bet, even though there is Oil in there.
Protect everything else with plumber's mats (or pyrolysed bread ;) ) and go slow to get as even a heat as possible.

Angle-grind the head on two sides so you can at least use a normal wrench on it.

If it is cross threaded, consider the painful option of drilling it out and re-tapping the hole a size bigger, and a new plug.

Probably less painful than a few $1000 tho.




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unionised
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[*] posted on 3-12-2017 at 10:43


Can you drill and tap a new hole next to the original?
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[*] posted on 3-12-2017 at 10:50


If there is enough 'meat' in the part, that would be an excellent idea.

Now that is a good example of thinking sideways :)




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[*] posted on 3-12-2017 at 11:03


There are screw extraction thread taps which tap a hole in a counter clockwise manner. Drill the hole, tap it, insert a bolt ("left hand threaded") and turn it counter clockwise and it should turn the plug

here is are some taps that can be used
http://www.ebay.com/bhp/left-hand-tap

If the plug isn't recessed, what about just grinding 2 parallel sides flat and using an adjustable wrench to remove it.
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[*] posted on 3-12-2017 at 12:20


Plug is flush to slightly recessed. Intent is to heat the metal AROUND the hole. Chill the plug, probably with a CO2 tank. When loosened by expanding the hole and shrinking the plug thermally, unscrew.

Question of wether the gear box can be cracked or permanently distorted to uselessness by heating unevenly? Unknown.

Drilling a new plug hole is actually something worth looking at, thanks-




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[*] posted on 3-12-2017 at 12:49


A coil induction heater will heat the bit inside the coil, which is why i thought you wanted to heat the bolt.

unionised's idea does sound like the best so far.

If it were me, i;d want the original bolt out and fixed, OCD style.




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[*] posted on 3-12-2017 at 12:57


Screw extractors tend to be made of hardened steel , and are therefore brittle. If an impact wrench wouldn't shift it, then I'd say a screw extractor will snap before achieving anything.

I'd probably go for a gas torch or hot air gun, before trying something exotic like induction heating. The best chiller would be a can of 'freeze spray', which is usually an HFC and chills to -50C. Easily directed onto a small spot.

Last ditch effort: drill it out, with a left-hand spiral drill bit (yes they do exist) - that way if it loosens during drilling it will unscrew.




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[*] posted on 3-12-2017 at 14:48


I use my arc welder with two carbon electrodes to heat up and remove seized bolts, I stick one electrode in the hand piece and one in the ground clamp, they actually make a special hand piece for arc welders to do this but it's just as easy to work with both hands.


arc torch.jpg - 39kB
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[*] posted on 3-12-2017 at 15:54


If I were in your situation, I would grind angles into the head so you can grip it with a pair of vice grips, and heat up the surrounding area with a torch. Get a friend to lean on the handle of the vice grips.
Alternatively, if you need more torque than can be offered by a pair of vice grips, weld a chunk of re-bar or angle iron to it. Sit on that. (If it's in an accessible position)
If all else fails, drill it out and re-tap. Though left handed bits do exist, they're pretty expensive.
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[*] posted on 4-12-2017 at 03:03


I feel your pain, Bert. With the information you've provided, I don't think you'll be able to acheive what you want with an induction heater.

My advice is to drill it out. You can try a bolt extractor (I've used these before http://www.lasertools.co.uk/product/0295 - you'll need a tap wrench for effective use) but if you suspect it's been cross threaded by a previous mechanic the best option is to drill it out and either re-tap it or use a helicoil kit (I've used this kit several times and its a life saver in the garage: https://www.amazon.co.uk/BERGEN-Professional-Quality-Helicoi...).

Sounds like it's going to be a messy job (assuming its still filled with oil - that'll leak when you drill through) but for the sake of saving a grand its probably worth it.
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[*] posted on 4-12-2017 at 03:58


I second the helicoil last resort option - a great invention.



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[*] posted on 4-12-2017 at 09:38


Yeah, I just wanted to buy/build a new toy.

Doing it mechanically, drilling and then using an extractor is sensible.

Also using heat cycling and Kroil repeatedly before even trying to unscrew or drill and extract would be wise. I know the mechanic didn't.



[Edited on 4-12-2017 by Bert]




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cool.gif posted on 4-12-2017 at 18:36


Hex Drive indentation?

Are you suggesting this is an Allen Head, type plug... That has had the sides of the hex hole stripped out?

Drill, if you must. Then, get a Square Extractor of the correct size, and back your plug out. If it doesn't work, you must drill out the whole plug, and tap a new (slightly larger)hole. Don't break off an extractor inside the plug!

The hardened steel of an extractor, is quite difficult to drill through.

Square extractors are less likely to break than reverse thread extractors. Stronger.

Consult a bicycle shop/bicycle machinist. Such an individual might actually be somewhat altruistic.

Last time I faced an unsolvable problem, and needed a custom made part to proceed... A friendly local bike shop made that part for a whomping $15 dollars.



[Edited on 5-12-2017 by zed]

[Edited on 5-12-2017 by zed]

[Edited on 5-12-2017 by zed]

[Edited on 5-12-2017 by zed]
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[*] posted on 4-12-2017 at 19:36


If you are still keen on making an induction heater then http://4hv.org is the place to go for advice.



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[*] posted on 4-12-2017 at 20:57


After the heat cycling and penetrating oil try and undo the sump plug using a small cold chisel or centre punch, I've been able to remove a few bolts sheared off flush by carefully undoing them with a chisel and/or punch, the shock helps get them turning
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[*] posted on 4-12-2017 at 21:11


Quote: Originally posted by NedsHead  
After the heat cycling and penetrating oil try and undo the sump plug using a small cold chisel or centre punch, I've been able to remove a few bolts sheared off flush by carefully undoing them with a chisel and/or punch, the shock helps get them turning


This has never failed for me and I torture myself with this shit regularly.

If you can drill a small, moderately deep hole in your plug that will stop a punch from slipping, it will take an almighty beating.

Gas flame if you have to. Squirts of penetrating fluid on the cool down.

Repeat.......

If the gearbox is actually coming out anyways, it will be even easier to do it on the floor, plenty of space to get at it and no restrictions on swinging away on the punch........


/CJ

[EDIT] - Damn Typo

[Edited on 5-12-2017 by Corrosive Joeseph]




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[*] posted on 5-12-2017 at 01:34


I have bought this https://ebay.com/itm/1000W-50A-ZVS-Induction-Heating-Machine... and it works fine for me.
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