relapping tape heads with 3M scouring pads???

[honinbou]

Multipurpose 3M scouring pads are great for stainless steel cookware. But has anyone tried on tape heads?

[Conrad Hoffman]

Very rarely am I at a loss for words...

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Actually I've lapped tape heads quite successfully using metallurgical lapping film in the sub-micron region, on a sheet of plate glass. I suppose scouring pads would be useful if you've got burnt on scrambled eggs or maybe pot roast, but I don't think they'd cut it in the geometry or surface finish department.

[rcavictim]

Originally posted by honinbou
Multipurpose 3M scouring pads are great for stainless steel cookware. But has anyone tried on tape heads?

If you are after loud sound effects steel wool will be better than non magnetic synthetic polishing pads. Don`t have the playback volume too high first time as you could easily blow out your speakers.

Personally, I would not do this on my own deck.

[sreten]

Hmmm.......

Seems to me the concept of relapping is not understood.
And scouring pads are the last thing you would use ......
They are also the last thing you would use for normal "dirt".

/sreten.

[gto127]

How do you lap heads? I thought you shouldn't use anything abrasive on heads

[honinbou]

I experimented with a junk set of heads after my post. I start with heavy duty scouring pads (that's what I have at home) to remove the oxidation on the heads. It's very good in removing some rusted spots, but you damage the glossy surface on the head.

Then I rub the head on the scouring pad for another 30 minutes. The wear is less "angular" now but hey this is taking forever... and besides it is eating away the plastic faster than the metal. So I begin to sand the surface with 180, 360, 600, 1000 grit sandpaper.

rubbing the head ~30 times on 180 grit sandpaper restores the head contour. Then progress to higher grit sandpaper to polish the surface.

I tried with 1000 grit and the surface is still not smooth. So I have to get higher grit sandpaper before continuing this "head reconditioning" thing.

So to conclude - don't waste your time with scouring pads

[Conrad Hoffman]

For those who haven't put a lot of hours on a tape deck, the heads will eventually develop a wide shallow groove where the tape runs. Ideally one would replace the heads at that point, but some are difficult or impossible to get, others are studio heads that are actually designed to be reconditioned. The curved head surface is, I hate to use the word, sanded such that the groove is removed, and polished back to a mirror finish. IMO, nothing you can buy at the hardware store is fine enough for this sort of work. Maybe 1200 or 1500 grit paper would be a starting point, but after that you want a precision lapping film, I'm guessing 12 micron, followed by 9, followed by 3, followed by 1, and maybe finer. The downside is that as you remove material from the gap area, it gets wider, and the high frequency response deteriorates. Usually the cheaper the head, the worse the problem, so you wouldn't put this kind of time and effort into a cheap head. No doubt people who do this for a living have a far more rigorous process than I've described.

[anatech]

Hi Conrad,
Completely agree. I have lapped a couple heads in my time, but never with heads that are not designed for refinishing. I have seen it done, with less than satisfactory results. Lapping a head requires training and a level of natural skill. Most people can learn how to do this.

Heads not designed for lapping do not have much core material in the wear area. In fact, often the gap size is also not well controlled either. You are beat before you begin with heads like these. Now, even if the lap looks good and the gap is still even all the way, the inductance change will probably be out of range of the adjustments. It may even saturate much more easily.

The lapping paper is not sold in your average store. It will require some hunting to locate the good stuff.

One more point. Once the tape has established a path in the head, do not attempt to change anything! Certainly not the azimuth. If you try, the tape will ride up on the lip and you'll lose tape to head contact. Professional heads normally have a pair of cuts near the ends of the outer poles, thereby eliminating this problem. If the heads do not have this feature, you can not change anything in the tape path.

Glass heads (like Akai). Those things are ferrite. They saturate very easily and they do wear, but differently. The gap ends tend to chip off, widening the gap. Once you see any wavy surface where the tape contacts the head, it's too late. The head is really scrap. Look carefully, possibly with a magnifying glass and under a good light. Look across the heads front surface.

-Chris

[disco]

Don't know what a precision lapping film is but I've once witnessed a Revox playback head been done. Grinded wet up to 1500 grid and then polished with Commandant (used on car paint to restore shine). It was a 1960s model 36, which suffered from tapecurl as described above. Revox heads are very soft...

[oshifis]

I used plain white paper sheet on glass for the final polish. The head is tilted back and forth while it is moved horizontally, so that the polishing is more even. One can see the metal smeared on the white paper.