Looking for someone to make a custom pair of magnets for me

[TDavenport]

Is there a person or shop out there that could make a pair of semicircular magnets about 8" in diameter and 1/2 x 1/2" cross section?  I have precise specs I have attached, but only the outer diameter is critical  (can't be exceeded . . smaller ok).

Thank you!

John  -  MA

[ThomasPowers]

Plain steel magnets will not be very strong.  You may note that the speaker magnets and the scary strong rare earth magnets are not made from steel.  Also forging is done above the curie temperature so any magnetic material will lose it's magnetism and only have a weak induced magnetism when cooled below the temp, (not to mention that hammering on steel can jar the magnetic domains even below curie temp.)

If I needed a magnet like that myself I would try to make it from a large car shaker speaker magnet and use a machinist to work it not a blacksmith!

As you don't list a location and this is an international forum; you are willing to pay for customs and shipping from say Australia?

Have you checked out a commercial place like apexmagnets.com?  (I know nothing about them save that they advertise they make custom Neodymium magnets,  browser search on: custom made strong magnets 

Note that for cost reasons it is often best to design for easily sourced items than to have custom made specialty items required.

[Frosty]

Ditto Thomas, this isn't a part to have made by a blacksmith. Have you shopped companies that make magnets?

Before you do, you might want to learn how blue prints are drawn and dimensioned. You've used non-existent lines for your ID and OD dimensions. This is NOT a good thing.

You can write the dimensions easily enough but you have to use proper terms. For example rather than writing a sentence describing a tolerance every machinist worth the title reads and or writes it as, OD= 0.867+0 /  - 0.015 whatevers, nanometers or miles? You have to include increments on prints, even working shop sketches.

You can NOT expect a manufacturer to figure out what you mean, not a good one. If you draw and spec slop you'll GET slop.

Yeah, I grew up in a machine shop and took enough drafting classes to be a professional. Could read a print when I was 9. This stuff matters, honest. I'm not just picking on you I'd much prefer you're project was successful.

Frosty The Lucky.

[TWISTEDWILLOW]

Off topic and boarding on the ridiculous but…

I wonder if a body fixed a bunch of those little Neodymium magnets in a pair of gloves if they could Spider-Man crawl up a metal wall?

or would your hands just stick to the wall and the fire department have to come rescue you?

Inquiring minds want to know?

[TDavenport]

Long ago blacksmiths made magnets.  How did they do it?

(am located in MA which is short for Massachusetts, USA)

[Frosty]

There was a Mythbusters episode that covered it nicely, Billy. 

T, We aren't going to remember your location once we open a different post. If this question is the ONLY interest you have in the forum it doesn't matter. However if you hang around, maybe learn a new craft and become properly addicted to hammering HOT iron you'll want folks to know where you live in general. It makes it so much more likely you'll be able to meet up with folk living within visiting distance.

A magnet made by a blacksmith would be a piece of wrought iron or mild steel perhaps magnetized by passing it between a couple strong magnets or with a DC electromagnet as it cooled. 

Don't expect it to be very strong if you don't use a modern material and process.

Frosty The Lucky.

[ThomasPowers]

They didn't make POWERFUL magnets.  Today most folks are commonly using magnets way more powerful than most made in blacksmithing days.  Computer disk drives use magnets that are amazinging strong compared to the magnets I played with 60 years ago.  I wonder if you are asking a "Model T mechanic to work on your Tesla"?  Are you willing to use weak ones?  If so look up how old motors were remagnetized .   Back in grade school we used to magnetize nails by running a DC current through wire wrapped around it.  Yes it was an electro magnet; but there was residual magnetism in the nail afterwards.  Lifting paper clips or showing the magnetic lines of force with iron filings was about as strong as they got.

One other thing when spec'ing a magnet: you need to include things like temperature range and strength of the field.

Blacksmiths also used to pull teeth, been blacksmithing 41 years now and still paying a professional dentist to pull mine when needed.

[TWISTEDWILLOW]

3 minutes ago, Frosty said:

There was a Mythbusters episode that covered it nicely, Billy

Never saw that, I’ll have to look it up!

back on topic you got me curious about what you need some 8” magnets for? 

I had a buddy bring over some crazy strong magnet on a rope a couple years ago and we stuck it on a 12”x4” post piece of ibeam 12’ long! And had a terrible time trying to get it back off again! Lol, and that magnet wasn’t half that big!

[TDavenport]

I am looking to see what possibilities exist.  As I said, a person or shop who might be capable.  Better yet, done it. 

Good metaphor!  I am looking for a Model T mechanic in a Tesla world perhaps.

Field strength?  Take what I can get.

It would be part  (the field) of a recreation of an antique motor.

Have tried a number of known techniques but the material seems the lacking factor.   Ya, paper clip level strength or a magnetized screwdriver about it.

[Frosty]

If you're going to magnetize it with an induction field, wrap it in electrified wire it's the number of wraps that determine the strength of the field, not the strength of the current. 

A science teacher in jr. high school (middle school) made a magnetizing ring by wrapping wire around a short piece of pipe. Passing a nail through it made a permanent bar magnet, stronger than heating the nail to non-magnetic and letting it cool aligned with magnetic north.

Billy: he wants a magnet that is 0.0867 OD, not 8". he didn't specify a scale so I can't say what the size is. Oh, T just responded.

Frosty The Lucky.

[Anachronist58]

May I ask what type of device you intend to apply this pair of magnets to?

Robert Taylor

[TWISTEDWILLOW]

4 minutes ago, Frosty said:

Billy: he wants a magnet that is 0.0867 OD, not 8". he didn't specify a scale so I can't say what the size is. Oh, T just responded.

I thought he said 8” diameter with 1/2”x1/2” cross sections in his first post?

either way I’m still curious whatcha makin?

[TDavenport]

Goal is to recreate an electric motor.  One of Davenport's originals.

Electromagnetic fields , we're fine on.  Trying to get one that runs on a permanent magnet.

About 8" in diameter will work fine.  

From Thomas Davenport

 

link removed

[Scott NC]

  It's probably been said before, but be careful with the stronger magnets of today.  I pinched my cuticle and cracked the nail on my thumb once.  Bled very badly but I suppose it could have been worse.  Your motor sounds like a fun project!  Like I need another one on the list....

[ThomasPowers]

OK, so you are trying to recreate a historical device and so historical materials and methods should work fine; it would have saved a lot of hassle it you had included that in the first place...If you want to be authentic as possible you would use triply refined wrought iron for the magnet. (Though there is the possibility of Huntsman's cast steel; however I highly doubt it!).

Thinking about how I would do it---

Firstly that drawing is useless.  What I would need to know to make it is the ID and the thickness of the material.  Given 1/2 sq stock then what the heck is the id?   6.813" is not the id of an 8" diameter toroid made from 1/2" stock!  8" minus 2x1/2" = 7"

If you can find a person with a DC welder you should be able to use it's output to magnetize your real wrought iron by winding it with insulated wire.  Note that an early steam pioneer used to complain that the blacksmiths could only work to the tolerance of "the thickness of a worn shilling"! 

I have some fairly high grade real wrought iron; but it's over an inch in diameter.  Using my screw press with stop blocks I could forge it to a fairly clean 1/2" square with quite a bit of work, however wrapping it in a helix hot would have scale losses, (as would flattening it after you sawed the coil to get the arc pieces.   

How close to your dimensions can you tolerate? It would be nice if you could tolerate the saw kerf as then each wrap would make 2 pieces instead of one and a slightly shorter one.  The 1/8 gap on each end from being a complete half circle should cover that nicely.

Can you provide  the interior diameter as the OD of a steel pipe or solid piece to wrap the stock hot around?  A 1" hardy stem attached would help. (If it has to be very exact; count in the expansion of the iron at say 1600 degF and how much it will contract on cooling). Or are you paying the blacksmith to have a machinist lathe one out? Not a common size to have on the shelf in the smithy! (He may have chosen a size that he did have to hand in his smithy and built around that!)

How much filing are you willing to do to clean things up and can you access a DC arc welder?

So each wrap will take around 24" of stock, two wraps would make 4' and getting harder to ship.  What did the New England Blacksmiths ABANA affiliate say when you contacted them?  www.newenglandblacksmiths.org    buy local!

Note using modern mild steel would be much easier and cheaper to source and work; however the Bessemer Process dates to 1856 and real wrought iron was used even into the 1930's in parallel to mild steel.  I would suggest 1018 or if you can get it; 1005, if you go with a modern alloy.

 

[TDavenport]

thanks for your time and information!  I will look into all suggestions.

[ThomasPowers]

Hey it's fun working on modern stuff; I'm generally trying to source bloomery iron to do pre Y1K stuff!

[TWISTEDWILLOW]

Sounds like a cool project keep us posted with progress an pictures!

[Frosty]

T: your original drawing here specs the OD as 0.0867. Did you MEAN 8" or what?

If you're going to present a dimensioned drawing it needs to BE what you're talking about. Now it seems to be a pretty vague iffy maybe concept sketch. I'm good with concept sketches I do most of my trouble shooting at the drawing board after I've debugged the concept sketches. 

You really need to pick a size to model and build around that. However as it seems we're talking about the concept rather than the device itself we can blue sky things.

For instance Thomas is suggesting you wrap the magnet stock around a mandrel and cut sections to flatten for the magnets. But is thinking the kerf from the saw cut is causing an issue needing adjustment. However, as drawn your 2 magnet ring  has a .25" space between halves eliminating the kerf issue.

If you can't locate triple wrought iron you can contact Pure Iron and see what they have in stock. I don't know if they carry any that small, 1/2" square is pretty unusual. Most blacksmiths working in wrought or pure iron would draw a common size down to suit.

Were I making the model and there wasn't a good reason to go to the expense and trouble of procuring wrought that size, I'd use cold rolled mild steel or shine up hot rolled mild.  

There are other alternatives for 12v DC than a DC welder, a model RR transformer or battery charger were my first thought. It doesn't need to be 12v the only MUST is it be DC current. I would however go with 12v DC but I have a couple few battery chargers. You still want LOTS of windings to magnetize your permanent magnets.

This is going to be a fun project I'm glad you asked us to join in.

Frosty The Lucky.

[TDavenport]

I would say more the concept.  I am trying to get a sense of what realistic possibilities there are and then go from there.

So for example whether the two magnets are square or round in cross section is not critical.  8.67 "  is a maximum outside diameter.  Less than that is OK.

If someone comes up with a possibility, we can take measurements and see how that would work, but there is flexibility.

There is also the goal, aside from an actual pair of magnets, of getting a better sense of how an 1837 blacksmith might have gone about such, both technique and materials.  An area you fellows might well have a sense of.  And perhaps be interested in.

Thomas Davenport was a remarkable person, blacksmith and scientist, and well worth learning about.

[Frosty]

Well, THANK YOU VERY MUCH! I started reading about Thomas Davenport and boy is that a warren of rabbit holes! A fascinating guy and some darned good reading. Thanks for dropping me down that rabbit hole!

I don't know why the link was removed but there are plenty of hit available through a search.

Not having specific plans the motor shouldn't be difficult to build. There are a number of approaches for making the permanent magnets. Find a piece of round material to be the mandrel to turn the magnets around. A piece of 7" OD pipe would work a treat. Or I could cut a 7" disk of steel plate with my oxy propane cutting torch and a circle guide AKA Circle Burner. clean the disk up with the most convenient or accurate grinder.

Then drill a center hole to fix a bending arm, heat and bend the stock chosen for the magnets. You can use ply wood for the bending mandrel if all you need are two magnets. 

Other than flattening I wouldn't use a hammer on the circular magnets, it'd all be bending and sawing with some filing or sanding to finish. I'd bend it hot if I had to use a wooden mandrel. Bending it cold would require a cheater on the arm.

I'd have  to play around a little to determine the best way to magnetize it. I'm pretty sure Mr. Davenport could make strong permanent magnets so I'd keep it in his tech level. 

Hmmmm, if I'm going to keep the project within period tech, there goes the grinders. Files and sand paper it is after my wheel grinder. 

It's pretty straight forward though. 

What do you want to know? Be as specific as you can.

Frosty The Lucky.

[ThomasPowers]

I have some 1/2" round real wrought iron, they were the bars used for cross bracing on old, mainly wood, RR boxcars.  They are a bit pitted and not as high a grade as my 1"+ stock.

There is an old story about a new engineer designing a bracket and taking the drawing down to the machine shop to get a price quote. Machinist quotes him US$100 per item.  He goes back up and is talking to an old engineer about the ridiculous price and shows him the drawing of the simple item.  The older engineer makes one change to the drawing and tells him to get another quote. That one was for 10 cents an item.  What was the change?   He added a tolerance that was easily achievable by the machine shop!

[BillyBones]

Thomas, you may find this interesting. At THE Ohio State University researchers there a few years back have made magnets out of plastic. They had very little attraction but they proved it could be done. 

Frosty, many of my prints now will have : OD = .500, then down at the bottom of the page it will have tolerances listed as : .xx = +/- .01",  .xxx = +/- .005, etc". ( i would give my left pinky toe to have a +/- .001" on the parts i am running right now, i got +/- .0003") 

[Irondragon Forge ClayWorks]

My tolerances would be +/- a worn schilling.

[anvil]

I'm not interested in making magnets, but there is no problem making your piece to a 64th" or closer as a blacksmith. It makes no difference what material you use, the method is the same. 

Looking at your top drawing, to find the length of material you need, measure the center line of your drawing. Why? When you bend it, the outside edge is drawn out and gets longer. The inside edge is upset and gets shorter. The center line maintains its original length so measure the center line. The only dimension needed is from the center to the center line.

To bend your radius, no jig or mandrel is needed. Transfer your drawing full size in chalk to your table and just use bending forks, a scrolling wrench, and your post vice. Bend your half square or round cold and match your drawing, no cheater needed on half inch square or round.  Check for edge bend and twist as you go to keep in plane. If you want to turn your half circle hot, well then go for it.  Any farrier or blacksmith should be able to do this in about 5 minutes or so.

Seems like you could magnetize however it suits you.