Thread: Making magnetic blocks

Nice work as usual Ueee

Try a page out of a phone book between the mag chuck and the job, it makes it easier to remove
the job and protects the bottom of the job and the mag chuck from scratches

Hi Ewan,
Are some of blocks made with Alum for the gaps?

Looks great.

Did you solder them with a flame or oven?

Stuart

Nice work Ewan,

The only thing I would do different is drill for the through pins before soldering, I used threaded brass rod and tightened a couple of times while it was in the oven.

To thin the solder paste you can use metho, if you want a really thin layer, you could make a thin slurry and brush on.

I love that you are now surface grinding everthing...

Regards
Ray

Why do i get the feeling the phone book in the shed might start getting thinner soon Thanks John, i will try that.

Stuart, yes the small blocks are ally, they were just epoxied together, was a nightmare in the end as the epoxy didn't hold very well at all. I wanted to use urethane glue but my bottle had gone crunchy......Of course you cannot solder ally with lead/tin solder.
The big block was just done with a flame, on the gas camping stove actually. I'd loved to have used an oven but as i don't have one yet.....still looking though!

Ray, it probably would have been better for the little blocks in the end, but with the big one i don't see a problem with drilling then post solder, its just the length of drill bit required that has stopped me at this point. There is one on its way. I was going to make an excuse about not having brass threaded rod but of course i could have easily threaded the ends of the rod i used. That way the solder should have flowed along the rods too, really holding it all together.

My mind still boggles at just how accurate the grinder is....its alarming when you grind .001" of a milled surface and there are still marks from the cutter there. It really is on another level to the mill and lath.
All food for thought......

Cheers,
Ew

Originally Posted by Ueee

Why do i get the feeling the phone book in the shed might start getting thinner soon Thanks John, i will try that.

Stuart, yes the small blocks are ally, they were just epoxied together, was a nightmare in the end as the epoxy didn't hold very well at all. I wanted to use urethane glue but my bottle had gone crunchy......Of course you cannot solder ally with lead/tin solder.
The big block was just done with a flame, on the gas camping stove actually. I'd loved to have used an oven but as i don't have one yet.....still looking though!

Ray, it probably would have been better for the little blocks in the end, but with the big one i don't see a problem with drilling then post solder, its just the length of drill bit required that has stopped me at this point. There is one on its way. I was going to make an excuse about not having brass threaded rod but of course i could have easily threaded the ends of the rod i used. That way the solder should have flowed along the rods too, really holding it all together.

My mind still boggles at just how accurate the grinder is....its alarming when you grind .001" of a milled surface and there are still marks from the cutter there. It really is on another level to the mill and lath.
All food for thought......

Cheers,
Ew

Good thing about the phone book is that you get an automatic restock every year....

Loving the work Ewan, I would normally give myself a little extra going from a machined surface to a ground surface, 25µm ~(13 minimum passes) would be the minimum that I would want to work with per a side, with a workpiece say 100x100mm.

Another tip on the final debur is to use a course whetstone to deburr, something about a 320grit (~50µm grains) works well.

Pls more vids....

-J

Originally Posted by Brobdingnagian

Good thing about the phone book is that you get an automatic restock every year....

Loving the work Ewan, I would normally give myself a little extra going from a machined surface to a ground surface, 25µm ~(13 minimum passes) would be the minimum that I would want to work with per a side, with a workpiece say 100x100mm.

Another tip on the final debur is to use a course whetstone to deburr, something about a 320grit (~50µm grains) works well.

Pls more vids....

-J

Yeah the .005" (the .003" block must have not been seated properly when milled) got me in trouble with the ally blocks as the ally was only .122" not 1/8". If it wasn't going to solder them i probably would have given myself more....hang one, 25um, thats only .001"per side? Do you mean .010"/.25mm?

There is more vids, just need to cut out all the bits were i go silent in deep thought. I'll definitely be doing some on making a 450 x 150 sine plate for my new chuck.
I like vids of other guys working "in full" and not just edited together snippets. They always give an incite into other ways to do things.

Ew

Looking forward to the other parts of your lesson ........... interesting stuff

Originally Posted by Ueee

Yeah the .005" (the .003" block must have not been seated properly when milled) got me in trouble with the ally blocks as the ally was only .122" not 1/8". If it wasn't going to solder them i probably would have given myself more....hang one, 25um, thats only .001"per side? Do you mean .010"/.25mm?

There is more vids, just need to cut out all the bits were i go silent in deep thought. I'll definitely be doing some on making a 450 x 150 sine plate for my new chuck.
I like vids of other guys working "in full" and not just edited together snippets. They always give an incite into other ways to do things.

Ew

Sorry Ewan I should clarify, 25µm is the absolute minimum I would need per a side. I prefer to have 50-150µm per side total much more than that It's back to the mill, I would normally take 60% off the first side, 30% opposite and 10% on the flip flop, This also lets me check my wheel wear/dressing and creep up on final dimensions and also check for distortions. My mantra is "more than 1/2 a mil(mm) back to the mill"

Keith Fenner does some great cuts in his videos where know know he has hit the "what do the ^*&! do I do now" moments. But he comes back and works through the solution.

If I had a go pro or something I would do a few videos, but as it stands having a camera where it needs to be is harder than it sounds.

-J

Originally Posted by Ueee

they were just epoxied together, was a nightmare in the end as the epoxy didn't hold very well at all.

Did you use interface membrane?

Originally Posted by Ueee

but with the big one i don't see a problem with drilling then post solder,

I do, solder under pressure cold flows. Now it will depend how thick and even the solder joints are and how much pressure you put on them......Now I doubt its going to move much... but I wouldnt really know....and you're going to be grumpy if it moves at all......just remember you heard it here first .

Is there really a need to pin it after soldering? just how high would you have to drop it from to break one of those joints?

Stuart

Originally Posted by Stustoys

Did you use interface membrane?

Ewan might not get that reference. Its a fly wire spacer to get a good bond thinkness. Which improves shear strenght. Its a highly scienintific excersive which involves a trip to Bunnings with a micromiter in hand.

Phil.

Ah, and here was me reaching for the wife's sewing interface Next time i'm in bunnies i'll go mic in hand!

Stu, your super power has let you down! It wouldn't bother me a bit if the big block moved a little whilst drilling. But only if it moved a little. The finish on it may be reflecting nicely but its not ground. I can only thank Michael G and a new box of SEKR inserts for that. (ok and maybe Mlle) And if you wouldn't mind making a block up of your own and dropping it then i'll know whether i need to pin it or not

Ew

Well done Ueee.

This is quite an interesting thread. I have a couple of questions if I may,

The magnets, are they just rectangular neodymium of say N32 or N40 etc?
There is mention of both epoxy glue and soldering. Specifically, how does that work? Do you put them in the oven AFTER epoxying to melt the solder?
When you machine them flat/square etc, how do the magnets machine? I would have thought they would shatter.

Thanks,

Simon

The magnets are in the magnetic chuck on the grinder Simon - the things that Ewan has made are the magnetic versions of parallels.
By alternating layers of magnetic and non-magnetic materials the blocks can transfer the magnetic holding force. From what I understand the epoxy is because Ewan used Aluminium for one of the blocks which is difficult to solder so instead used the glue.

At one place we did grind ferrite transformer cores, but it required diamond wheels, lots of coolant and very small feeds. I imagine a ceramic magnet would need the same

Michael

Hi Simon,
They are not magnets.....they are just steel and brass/ally plates. The ally ones are epoxied as you can't soft solder ally (except maybe with some AgSn solders?) The brass one is soldered.
If you watch the first vid, the one i linked above, i give a brief (and probably poor) description of how a mag chuck and the mag blocks work. The blocks are designed to extend the N and S poles of the mag chuck up, without the poles "shorting" each other (i'm sure there are technical terms for that) so that a workpiece can sit on the blocks and be on both N and S poles.

Ew

Edit, i'm too slow Michael!