# Magnetic Chuck



## 34by151 (Jun 19, 2021)

Made two magnetetic chucks over the weekend

Pics was taken before face milling the surface
They are made from the transfromers from 4 old microwave ovens

To Make the magnets strip the transfromers from the microwave oven
Cut off the base so you are left with the primary and seconday coils on the core
Remove the coils from the core and disgard the seconday (thinner wire) coils
Fabricate a box and weld in the cores. 
Make sure the primary coil will be below the lip of the box
Reinstall the primary coil and solder then to a cable
Fill the box with epoxy
Once dry surface the top

As I used 2 coils for each unit, I wired both coils in series but used 3 wires (4mm mains cable)
The center connetion is the green wire, blue and brown to ends of the coils
This way I can connect then to the power supply in series or paralel

For the power supply im using a 48v/30amp switch mode power supply on each unit

I made one with a pipe in the middle for drilling though this one is used in the mill. The other is mounted in a workbench flush with the surface.
I use this holding parts that I have cut on the cnc plasma. Makes it easy to get though dross removal very quickly. I use a twistknot wire bush on the angle grinder for this

As soon as I collect some more old microwaves the plan is to make an second one for the mill and one for the gearhead drillpress


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## Eddyde (Jun 19, 2021)

Wow that's a cool project, Please post more pictures!


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## 34by151 (Jun 19, 2021)

Ill grab some of them in use tomorrow


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## markba633csi (Jun 19, 2021)

You must have a surplus of old style microwave ovens down there-  here in the states most of them now are inverter style without the large transformer  
Great project, can't beat the price!
-Mark


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## 34by151 (Jun 19, 2021)

markba633csi said:


> You must have a surplus of old style microwave ovens down there-  here in the states most of them now are inverter style without the large transformer
> Great project, can't beat the price!
> -Mark


The only thing that cost was the epoxy resin $100 bucks the transformers were free and the steel was scrap around the workshop


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## 34by151 (Jun 19, 2021)

Oh yeah cut the ends of some computer power cords (have a box full in the shop) for the wiring.
The PSU's were also supluss. They came out of my CNC Plasma when I upgraded the servo's from 48vdc to 90vac
But they are only about $30 each new anyway


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## vocatexas (Jun 19, 2021)

There's a You Tube channel called Make it Extreme that did that a couple of years ago. I keep meaning to do the same myself. I'll have to add this to my 'list of things to do'. Thanks for the write-up!


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## Winegrower (Jun 20, 2021)

I would like to know how effective these mag chucks are on a mill.   It would seem that the milling forces would exceed the capability of the chuck.    But if it worked, wow, that would be a terrific tool.     Anybody??


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## Eddyde (Jun 20, 2021)

Winegrower said:


> I would like to know how effective these mag chucks are on a mill.   It would seem that the milling forces would exceed the capability of the chuck.    But if it worked, wow, that would be a terrific tool.     Anybody??


I suppose it would depend on the operation and if the work was up against a stop. I think it would be very handy for working on sheetmetal where clamping in a vise isn't possible.


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## 34by151 (Jun 20, 2021)

Winegrower said:


> I would like to know how effective these mag chucks are on a mill.   It would seem that the milling forces would exceed the capability of the chuck.    But if it worked, wow, that would be a terrific tool.     Anybody??


How well it works depends on voltage
Im using 48v which seems to work well

I have not found anything that makes a part move on my mill

I was taking 2mm off the face of a 350 grade steel part using an 8 tooth 150mm face mill with no isssues at all
I find its great for parts the are odd shaped and not easy to clamp in my vice
It also makes it quick and esay for driling. I bring the quill don to the hole then turn on the vice. IE align the part to the quill rather than the other way around, much quicker


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## 34by151 (Jun 20, 2021)

I was grinding a toothbar the other day. 

Pic of one installed on my Kubota BX23s Tractor 



I grind the cutting edge with a 9in grinder first as a roughing cycle then finish off the edges in the mill.
Its a lot quicker than doing it all on the mill

The bar is 1240 long 350 grade steel 10mm thick

When grinding I hold it using one of the clamps on the bench
When milling I do the same one magnet unit on the mill but move the part. 
Ive also done it with both magnets one on each end
Nothing moves

In saying that while grinding with the 9in when the grinder is clost to the maget, say 100mm away, the pull on the grinder is easily felt.
Does not seem to have any efect on the motor operation though 

This is the main reason for collecting more microwaves to make more magnets. Id like 2-3 dedicated for the mill, one for the gearhead drill press and 1-2 for the bench. 

Made the first ones to really find out how well they work. They work so well and make life so easy need to make more to stop having to shift them around. I did a test one one of them using a 12v car battery for power. Clamped it to a 2400x1200x12mm sheet of steel laying flat on the floor. Picked it up using the forks. No issue at all aprox weight 280kg. Second test moved the camp to the side and picked it up moving the sheet from horozontal to vertical, no issues or slip. That was with 12v, im using 48v on them now which is a massive increase in clamping power

In saying all that I still use my vices and indexer on the mill. Its just giving me more options but I must admit i use the vice a lot less

My drill press is a 1.5hp gear head unit. MT4 spindle 3 axis power feeds and coolant. Really a mini mill.
I rearly use the vice on it nowdays

On the bench the magnet is the goto for parts holding, rarly use calmps or a vice

Where it wint work is the welding bench. Not good to have the welding current pass though the magnet and they are too powerful anyway and would bend your welding arc


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## Flyinfool (Jun 20, 2021)

Hmmmmmm.....
I wonder how the molten puddle of steel would react to the magnet. Or is it that the steel is no longer magnetic above some certain temp?


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## 34by151 (Jun 20, 2021)

Havent tyied it

Dont wnat the current to go through the magent coils. Im often using 400A 3 phase welder worried it could burn out the coil or destry the psu.
As for the arc it will definatly bend the arc. It pulls my 9in grinder as i use it!!

If you try it would sugest turning up the shelding gas as the gas wont be affected by the bend in the arc and you may have weld exposed to perosity


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## Shotgun (Jun 24, 2021)

I'm not seeing how the current would pass through the magnet coils.  They should be insulated already.

Also, and electromagnet's strength is a function of current. . .not voltage.  The 12V battery could have been pushing 200A, whereas I have a big 48V supply that is limited to 30A.

What happens to the chips as you're using one of those on the mill?  I would think that it would make cleanup easy, but do the chips stick in the cutter?


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## 34by151 (Jun 24, 2021)

When you cut the transformer and remove the coils you need to cut the terminals off.
When building the magnet I just trimmed the wires to length and stripped the insulation (scrape it off) then soldered my lead on

I doubt the battery I used could supply 200a. It's a dead one that wont hold a charge, wont start a car
I just use it as a capacitor on an old unregulated battery charger. This provided the power supply for my 12v diesel pump. This draws from a 44gal drum. 

Re chips it really depends on what your doing and how tall/wide it is
If the chips fall on the magnet they will stick but dont pose an issue. If they buildup close to the job your toll will move them anyway.
I havenot seen any issue with the cutters operating any different to normal

PS I havent maeasured the current I do run the 2 coild in paralell on the psu when cutting. I rin them in series or paralell on the bench depending on what im doing.

I need to move some 12mm sheets next week these weigh about 500kg. They are stored in the old vertical rack. So I need to puck them up and move them hotozontal. I normally use my plate grab but I will it again with the magnet for you.
I try with a 12v, 24v and the 48v psu's


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## Dabbler (Jun 25, 2021)

Flyinfool said:


> Or is it that the steel is no longer magnetic above some certain temp



Anything ferrous has a 'currie point' the temperature where it loses its magnetic properties.  This differs a lot for each alloy, but usually molten steel does not respond (much) to magnetic forces.


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