Die grinder bit in milling machine

The thing that seems to eat diamond bits is heat and lack of lube. I know that running them dry will usually strip then diamond off in short order. I don't know if it is heat or lack of lube or both that strips the diamond. I use kerosene or WD40 or water or soapy water depending on what I'm grinding. For ferrite probably WD40. I use WD40 not because it is so superior to kerosene but because it doesn't smell so bad. Eric

Thanks, Erice. At $26 a bit, I'm not too eager to strip the diamonds off on the first try. I'll try the WD40.

If you use a die grinder bit as if it were a milling cutter, you'll leave a whole bunch of parallel grooves in your ferrite. In my (admittedly quite limited) experience, with abrasive media you need not only the obvious fore- and aft- movement of workpiece against wheel (or wheel against workpiece), but also side-to-side (or in a regular milling machine, up and down I guess).

I'm not sure how you'll achieve that in your application. Multiple swipes at slightly different quill height settings may do; if it were a CNC machine I'd suggest programming it to pump the quill up and down at the same time that it's moving the piece across the grinder.

Have fun gapping your cores, if that's what you're doing.

I may be able to leave the quill unlocked and just jiggle it up and down as it's fed in x or y. I doubt I'll get a mirror finish that way, but cranking the head up and down would not be pleasant.

if it were a

A similar motion to a surface grinder, which is what I don't have.

Usually I stick some plastic shim stock inbetween the E-core halves (using a set I got from McMaster), which gives effectively double the normal gap of the shim stock thickness, but I thought it might be nice to try just gapping the center leg, which would be more representative of the EMI situation, but mostly just because it would be fun to try.

The world needs ferrite shim stock.

I'll bet Kapton tape would work well, but I haven't tried it, so I'm nearly clueless there.

Report back on your results please? Probably on s.e.d, since the interesting results are going to be if it makes any real difference in shielding and other performance aspects (ultimately: is it worth the effort).

Kapton and Mylar tape work fine, but they don't come in such a range of thicknesses, and you have to take into account the adhesive thickness. Shim stock and wrap tape around the core (or use spring clips) gives you a pretty controlled gap.

For a mere $35 you get 15 sheets 5" x 20", color coded:0.0005"

0.00075" 0.001" 0.0015" 0.002" 0.003" 0.004" 0.005" 0.0075" 0.01" 0.0125" 0.015" 0.02" 0.025" 0.03", with tolerance +/-0.2 thou.

Ha. Okay, when I get to it. No promises on when the EMI testing will be done, I'm just playing with the new spectrum analyzer atm.

If you're concerned about damage to the bit, forget the idea. Unless you run such that the bit never sees red heat at the point of contact, you'll destroy the diamond, even if it isn't ripped from the matrix.

Reason?

Iron has an affinity for carbon. If you heat the diamond to the point of redness, the iron will absorb the carbon (diamond) dulling it quickly. It may still be there, but will have lost the sharp edge one relies upon for cutting.

If you can run it slow enough to not raise heat, sure, give it a go.

Harold