Ferrite grinding

Answering my own post ?

[Dkr20.93 48% OFF]HILDA 4/4.4/5mm Diamond Grinding Head Polishing Tool for Chain Saw Sharpening Tool Accessories from Tools on banggood

--
Klaus Kragelund

if you only need to reduce the height you could also use a disc mounted like a slitting saw

Wouldn't a surface grinder be a better bet than a mill?

--
Best regards,  
Spehro Pefhany

This sounds like a diamond abrasive rotary "point".

.

There are lots of options, options intended for the purpose (unlike a chainsaw sharpener.)

First a few questions.

What is the purpose of grinding the ferrite? Air gap? Do the ground surfaces need to be flat? If so, how flat? How much material is to be removed?

Joe Gwinn

Yes, for air gap. So needs to be flat If so, how flat? How much material is to

Up to 0.3mm, which I know takes a long time

--
Klaus Kragelund

Yes, we have one of those at work

I was thinking of another way so I don't have to invest in other equipment

A band grinder could do it, but is sensitive to alignment of the ferrite

--
Klaus Kragelund

Am 09.02.21 um 01:18 schrieb Klaus Kragelund:

Can't you just place a plastic foil or sheet of paper into the prospective air gaps, like everybody else?

Avoid having copper close to the gaps b/c of eddy currents.

Gerhard

Grinding dry will muck up every surface nearby.

A glass grinder does this with a water reservoir and wick, in order to contain the slurry that will develop. Still messy.

Getting grinding bits that are broad enough for larger thicknesses or narrow enough for center legs of smaller parts can be an issue.

I think you will have to acid-etch ground Ferrite surfaces in order to avoid local heating at the machined surface or in loose particles, particularly if these surfaces appear in or near a high-flux gap.

Pre-gapped parts can be ordered fairly reliably. There may be a good reason why larger gaps are not offered in the parts you're addressing.

RL

I was think mount the disc (or maybe a cup wheel) in the cnc and approach the work from what ever angle to do what you want

Or use the trick of holding the halves together with epoxy loaded with spacer beads.

--
Best regards,  
Spehro Pefhany

Lasse Langwadt Christensen wrote in news: snipped-for-privacy@googlegroups.com:

That will make a pretty uneven surface with that tiny diameter.

on disc typr.

Regular abrasive wheel like 2.5" or three inch.. on the end of a die grinder. You can get fine grained honed finish surface types too. You could probably get away with the glued on pad to a disc type and use like 120 grit, slowly. But a ring on the leg the keeps the sanding from going to low of a step.

Joe Gwinn wrote in news: snipped-for-privacy@4ax.com:

If it is for a finished inductance measure best to remove small amounts and dial it in in steps.

Depending on how rough or tight the adjusment needs to be, the surface finish and coplanarity plays in to it more and more as precision requirements go up for circuit operation and stability and repeatability.

Klaus Kragelund wrote in news: snipped-for-privacy@nntp.aioe.org:

A couple minutes per unit once you have dialed in the finished value you seek to operate at.

legg wrote in news: snipped-for-privacy@4ax.com:

He's trying to do these in circuit?

Desolder that device and work on it on a bench by itself.

Spehro Pefhany wrote in news: snipped-for-privacy@4ax.com:

+1

We bought and used Nomex paper. One can get it from 1 mil through

100 mils IIRC, and 4 foot "tall" sheets. The thick stuff is usually orderd in short lengths so the 4 foot tall thing is because it stands up that way, whereas the 1 mil stuff one could buy a roll of and get several feet of 1 or 2 or 4 foot wide rolls. And locked them together with a dab of firm epoxy, but it needed a little give so as not to sheet upon thermal differentials, then we vacuum impregnated the whole thing in Dolph's transformer varnish, which locked every thing together and locked out moisture,

You also need to cover all the surfaces- the ferrite fragments and anything that comes off the grinding bit will embed in the ways etc. and shorten the life of your mill.

--
Best regards,  
Spehro Pefhany

You have to set a special workspace aside for this kind of work. It doesn't mix with any kind of 'clean' work. You wouldn't even want it to be near other precision machine tools.

RL

legg wrote in news: snipped-for-privacy@4ax.com:

That is what good air handling at the worksite is for. They put them on circular saws for wood and jigsaws and all other manner of power tools. This would be easy to use magnets and 'vacuum' type air removal during the grinding. Or one could just buy a replacement core that is already gapped. Less grinding to the finished need.

I could, but then the fringe fields are not in the correct place and I get higher ac losses

--
Klaus Kragelund