Electromagnetic drill press clamp

[CopperCone]

So i see that people build these out of old microwave oven transformers but i dont really like those designs.

I am more interested in a magnetic table that has amore even distrivution of magnetic field.

Do you think its possible to get reasonable performance using mild steel as a magnetic flux path?

I thought about cutting a bunch of 1/4 inch steel plate and making a tray/box out of mild steel, then placing the little blocks i cut like buildings in a city or projects, making a even grid, then filling the space between them with magnet wire.

I would prefer to run at low voltage incase i accidentally drill into it (especially if drilling into something with the base angled.

My drill press is one horse power.

I never really messed with electromagnets before.. So i guess the questions are:

1) ratio of magnetic flux carrier and wire (by volume) in the magnetic base
2)gauge of wire to use
3) power source to use (thinking low drop diodes andcap bank)
4)interlock for safety - i had a few ideas here but i think the enclosure should be grounded and a circuit should be used to measure dc going through ground to disable a contactor for to disable the drill press. Also a thermal interlock on the magnet and standard precautions for the powrr supply. All interlocks would kill the drill press
5) can a thin aluminum sheet be placed on the top (1/8) of an inch to act as a removable millable durface so repairs can be conducted. I dont like the epoxy fill used on youtube. I dont feel plastic is a good durface for a drill press because it will get fucked up in short order due to machining fluids, grinding dust, etc

This is really brain storming i dont have a good idea in mind yet or any idea yo how much power you need to pull this off.

I would like this to be strong enough to work with a 3/4 inch bit, annular cutter or fairly large hole saw.

I would like it to be designed so that you can have up to 3/8 inch of free space between the electromagnets and the object being drilled, so that a 1/8 inch aluminum cover and a 1/4 inch piece of plywood can be used as a backet for using annular cutters and circular saws

Are these design goals realistic?

[Andy Watson]

Try searching for "DIY electromagnetic chuck". Also,
The video is about the "magnabend" - it uses an electromagnet to clamp the work piece - both the plans and design guide were available on the web - I can't find them now

If you use a DC power supply rather than AC, mild steel should be adequate for the magnetic flux path - it will probably be as good as whatever you're trying to hold.

A non-magnetic sacrificial surface plate will cripple the holding power - especially at 1/8" thick.
Edit: Found the link: http://aaybee.com.au/Magnabend/Building%20Your%20Own%20Magnabend.html

[CopperCone]

Will a magnetic plate rather then aluminum improve things significantly? I dont know how much flux will travel through it rather then the work piece. I also thought it would be annoying to remove grinding dust and chips off the plate due to residual magnetization if it was made of metal. Aluminum would wipe right off. But its not a strict requirement..

Is there some sweet thickness of feromagnetic metal that will conduct the field upwards but not shunt it too much? What should the geometric ratios be between the magnetic pillars and the flux path area through the top plate be to still make it useable.

I see he recommends using resin. I dont like this at all. And i dont want to use ac, i dont mind making a power pack for it that would sit on the bottom of the drill press with all the contactors and shit.

[IanB]

When I encountered a magnetic work piece clamp during metal shop class many years ago (ca 1975), it was mechanical rather than electrical. It was also extremely powerful. When the clamp was off there was no residual magnetism; when the clamp was on the work piece could not be budged at all. It was immovable. From memory, the clamping surface seemed to be made of steel rather than aluminium, but that was just an observation from the color and the hardness. (An effective clamping force could be arranged by having the surface consist of alternating pole pieces with some filler material between them.)

Given the ready availability of neodymium magnets these days, a mechanically operated clamp would still seem to be more convenient than an electromagnetic one.

[CopperCone]

I have some mechanical magnetic clamps (meant for welding). They are rather expensive and OK. I can't see myself being able to fabricate one. I also own a magnetic drill with a mechanical magnetic clamp, which is nice. 

They require a bit of force to turn. Electromagnet with a button is a bit different.

I can also see the safety benefits, especially for something like a milling machine or lathe that has alot of force. \
I still wanna investigate a electromagnetic one. I just think its cool.

for those interested in mechanical design:


Not my thing or budget though. Looks like you need a brazing furnace, blanchard grinder, general shop tools, in addition to the welding equipment (this I think Is all i can do).

I was hoping you can use higher power of electromagnets to hopefully get away from some of the precision that seems to be required with permament magnets.

Hopefully the residual magnetism, if not strong enough, would at least abosrb some energy from the drill press and make it less dangerous in the worst failure case.

[duak]

I've got a couple of electromagnetic door latch assemblies that I'm going to use to clamp a vise on the drill press when I get a round tuit.  These are about 8" x 2" x 2" and are supposed to have a clamping force of a few hundred pounds.  I don't think they are running at a current that saturates the core so I think I can increase it somewhat for short periods of time.

Unless the contact faces are extraordinarily large, the biggest loss in a magnet's "pulling power" is the area where the pieces touch.  If they're not flat or there's something in between the faces, the force drops a lot and/or creates a fulcrum that any sideways forces cause the vise to lift & detach.  The magnetic chucks mentioned above are used on surface grinders which usually grind the chuck to well under 1/1,000 of an inch of being perfectly flat.

If you do want something sacrificial, use a mild steel like 1008 or 1010 - there's nothing with high permeability that's as cheap - and keep it as flat as you can.  Talk to a machine shop with a surface or blanshard grinder or lap it with wet & dry paper on a piece of flat glass.

Best o' luck

[Muttley Snickers]

I have a Sieg Super X3 mill and also thought about doing something with the collection of magnetic locks that I have in stock, the fact is that in addition to metal objects I also work on other non magnetic materials such as plastics, aluminium and stainless steel so for the amount of time that magnetic work holding would be of any benefit would be rather minimal compared to my regular machining vices or other work holding arrangements.

Additionally, the rated holding forces of these locks are only valid when used with the accompanying face plate which must be mounted and used in the correct orientation, they would also be subject and prone to coolants and lubricants which might be of concern in regards to reliability. Setting up materials might also be a pain compared to an existing aligned and trammed machining vice, I never got around to doing it probably for good reason.   

https://www.fshlocking.com.au/en/products/electro-magnetic-locks.html