magnetic base's

Hi all

Could someone help me please, I want to make some magnetic base's for a project I have I like to make, I have downloaded some information and it states that the box it self is made from cast iron, when I have searched for materials I have seen cast iron in any form other than rounds bars, after this bit of rabbiting what I would like to know is could I use steel instead of cast iron for the construction, if not why not?

Thank you for any help it will be much appreciated

Bill

Maybe it's something to do with magnetic saturation properties.

A lot of transformers and electromagnets use an iron core, not a steel core.

http://en.wikipedia.org/wiki/Saturation_(magnetic)

No doubt you could make them out of any metal you like

They just wouldn't be as efficient

Iron may be the most magnetic(or anti-magnetic for saturation purposes) and cost effective route for mass production of devices which get switched on and off a lot

If you don't mind spending the cash I'm afraid I wouldn't know what "the very best" magnetic devices would be made from

edit: would actually be interested to know the answer to that one

Edited By Ady1 on 22/04/2012 10:46:53

Edited By Ady1 on 22/04/2012 10:55:12

Hi Bill

Plenty of places advertising cast iron rounds, Macc Models, MKMetals, College Engineering supplies to name a few. For "used" cast iron round bar try sash window weights.

Keith

Edited By Keith Long on 22/04/2012 11:40:14

Bill,

Some confusion here! Efficient electromagnets use fairly pure iron, or iron with some silicon content, to give the highest magnetic permeability, the lowest residual magnetism (when the magnetic flux is removed) and the lowest hysteresis losses. But ... what is know as "cast iron" is in fact considerably further removed from this than mild steel. Mild steel is virtually pure iron, with very small amounts of carbon and silicon. Cast iron contains 2-4% of carbon, along with silicon and other impurities depending on source. You are likely to get as good a result with mild steel (a.k.a. iron-purer-than-anything-else-in-your-workshop) as you are with any other common workshop material.

And as for the recommendation to use sash weights, they are usually made of the most crappy cast iron around, and full of glass hard chill spots that will ruin your tools.

Not clear from your post whether you are looking for round or square bases, but if you do decide to go with cast iron (and not to go down the sash weight crap route) there are plenty of suppliers who will sell you top quality continuous-cast grey cast iron, in rounds, squares or rectangular sections, which machines like a dream.

David

PS WHY does this blody stupid forum software INSIST on changing the (sometimes gramatically required) close quotes/end bracket with a stupid smiley? GRRR!

Edited By David Littlewood on 22/04/2012 15:57:37

It depends entirely on your application.

Years ago I used to use "MuMetal" (an 80% nickel alloy) for magnetic screening of cathode ray tubes as it has a very high permiability (about 100,000).

For mains transformers, grain oriented silicon steel as it has a high operating flux density

Ferrite for high frequency devices.

Etc.

Russell.

Hi

I dont know if im right in thinking that cast is used because it does not retain the magnatisum? In that if steel was used then over time it would start to keep and get more magnetised the more it was used.. Sorry if this has been said Iv read but may have been said in a way iv nut understood..

Osh..

Hi,

This discussion made me wonder why the cast iron did not shunt the magnetic path. Looking at a magnetic base it looks like one lump of cast iron. As I could not understand how it could possibly work I decided to dismantle one. I found that it was not one piece of cast iron but two separated by non magnetic material. (Probably aluminium.) The cast iron forms the two pole pieces. This explains how they work. When the poles of the magnet are horizontal a pole is lined up with each pole piece. When the poles of the magnet are vertical they are shunted by the cast iron so there is very little magnetic field.

Here are the pictures of the dismantled unit.

Les.

"He who destroys a thing fto find out how it works has surely left the path of wisdom".

I'm sure you will put it back together, but it's one of my favourite quotes. Virtual pint for someone who can say who I'm quoting without resorting to google.

Neil

Edited By Stub Mandrel on 24/04/2012 20:11:08

If it's any help, ready-made magnetic bases are available now from the far east via ebay, etc at a much lower price than they cost 10 or 15 years ago so a ready-made solution might be the answer. Modern Neodymium magnets give you a much stronger field than their predecessors.

Quote is from the works of Epicuras - 300BCE

Hi Neil,

It still works when re assembled.

Les.

I started to dismantle things to see how they worked when I was about six and haven't stopped in the last sixty years. Most things have worked again after reassembly

Russell.

The reassemblies fine.

Its the urge to "improve" I need to resist.

Oh and plastic "NIBS"

... and ultrasonic welding of cases...

"no user servicable parts inside ? " Yes there are! but the case is a S*D to open

Hello All

Thank you all so much for replies, they were very interesting reading, one big problem your replies set me of searching again, yes David that is what I found with steel,now I am of to find out how they make a cast iron bar that has just two strips down the side to give you the N & S, I have search again for flat or strip but all I have found round bars.

Yes it is the cost but if I have pay out so be it, but all my life because circumstances I have made any thing I wanted was out of scrap materials so I have been in the "recycle club" for 77 years but that is gone as you all know you cannot go into scrap yards to serch

Well thats the end of my rambling, again thank you for your replies.

Regards, Bill

When I got my magnetic Base it was in bits, I was told 'its yours if you can work it out', so I took it home, and at first I thought ah a magneto, no I don't need one at the moment, so I assembled it, it gets a bit of use, but my non magnetic, home made one gets more use. Ian S C

You can where I live

Russell.

You can where I live

WHERE DO YOU LIVE??

WE NEED TO KNOW PLEASE !

Thankyou.

oh bugger...he lives in France...

The EU health and safety fascists are stopping us from being British

You French guys have an inbuilt resistance to blind obedience which the British never acquired and we are currently paying the price over here

Edited By Ady1 on 26/04/2012 00:27:55