Hi, I'm not sure, machine oil is too crude maybe. Maybe weapon oil (Balistol? Doesn't resin) or silicone grease is better suited ?

Edit: Please make sure the "breathing hole" isn't covered (a plastic membrane could be there, that's okay).
It's there to compensate for air pressure.
I've seen quite a few HDDs that had a sticker put onto it.

Air pressure/height is another factor, btw.
There's that story about HDDs used in PCs in observatories in the high mountains that failed over and over again.
The cause was the low air pressure. The HDD heads couldn't build up a proper air cushion and crashed on the platters.

Nunoalex wrote on 2023-05-06, 16:05:

My question is if it is possible or if it would help to drop a drop of machine oil on the spot the motor center, there seems to be a little hole just at the center
Also the stepper motor could receive the same treatment?

That hole probably doesn't go anywhere, the ones I've seen looked to be some sort of centering/support for shaft manufacturing process. You could maybe try to get some very thin oil on the dust cover and it will eventually seep through (the thicker the oil the longer it will take, if at all) since these are dust-proof but not hermetic. I've managed to quiet down a bearing like that in a floppy drive clamping arm, I used oil for sewing machine maintenance. It's almost like water and it still took like 10 to 15 minutes of putting some tiny droplets on the crack between the cover and race, and spinning by hand, to make any difference.

That being said the bearing in the HDD is way higher speed than FDD, if it makes noise now it's most likely gone for good. Some oil should quiet it down, for a time, but it will come back. It's hard to say how many times you can try to repeat that before it makes no difference or the excess oil contaminates the insides - but it's better than just throwing the HDD away right now.

Ok that said I.m going to warm up the drive to something like 40C to see if the old grease inside comes to life and then turn it on just with power cable so the heads dont move around so much

Maybe this will help spread what little active grease there is left

Heads will move anyway as part of the self-test, and on 3.5" drives these are parked on the platters (closest to the spindle/shaft) but the warming up idea is good. BTW the noise can also be a broken off head scrapping the platter, I don't think I have to explain this is always a KO for the disk. Oh and in case you are thinking about opening the cover to get better access to insides - this will not not help you oil the main bearing, not unless you remove the heads, and all the platters - and with a stepper motor rather than coil you will misalign the heads. Just not worth the trouble if you can't do anything from the outside.

Deunan wrote on 2023-05-06, 21:35:

Heads will move anyway as part of the self-test, and on 3.5" drives these are parked on the platters (closest to the spindle/shaft) but the warming up idea is good. BTW the noise can also be a broken off head scrapping the platter, I don't think I have to explain this is always a KO for the disk. Oh and in case you are thinking about opening the cover to get better access to insides - this will not not help you oil the main bearing, not unless you remove the heads, and all the platters - and with a stepper motor rather than coil you will misalign the heads. Just not worth the trouble if you can't do anything from the outside.

Thank you Deunan for you precious advice
I will never ever open an old hard drive because I know only BAD things can come out of it ... I am not a clockmaker, high tech engineer or someone with gold hands.

Anyway an update on my ST351A/X
I did put a drop of oil on the stepper motor axel opening and another on the center notch of the main motor (had to remove the PCB for that
I did put it in the oven when the temperature never exeeded 60-65 ºC (the oven was already switched off when I inserted it)

Results: I didn't help much and it might have actually made it worse a bit
The hard disk now at boot in the initializing sequence seems to make an extra little noise ... some "dan dan dan" and now struggles to start track zero
I had to run NDD, Fdisk it, and then NDD again ... always will a lot of retry errors
Then I run Spinrite 5 on it and it reported the same bad sectors as before... at least it seems not be developing any more and it stopped at around 240k (0.5%)
So now the hard disk is formatted it boots with MS DOS 5 and the first bytes (boot sector) seems to have been moved to avoid the first inaccessible area....

All that been said the main motor makes a much healthier noise now and the stepper motor runs smooth as I recall it from the old days so maybe the oil and oven treatment did make a little positive difference
Or it may just be because the disk was turned on for many hours for the spinrite that did manage to heal those bearings a bit

Who knows..

Thank for all who replyed !

FYI high temperatures will tend to erase the magnetic media (even if not really that close to Curie point) - so you might need to do a reformat. But running Spinrite is usually doing the same thing since it rewrites the data. If that HDD gets worse try low-level format on a mobo with BIOS that has that option. This is not MFM but some of these early IDEs actually do respond to low-level format commands with actual format. This is in case the data is OK now but the HDD has problems finding the sector headers and that's what causing read/write errors.

Deunan wrote on 2023-05-27, 20:10:

If that HDD gets worse try low-level format on a mobo with BIOS that has that option.

good luck low level formatting anything IDE in general
https://forum.vcfed.org/index.php?threads/sea … 880/post-556937

rasz_pl wrote on 2023-05-31, 04:54:

Deunan wrote on 2023-05-27, 20:10:

If that HDD gets worse try low-level format on a mobo with BIOS that has that option.

good luck low level formatting anything IDE in general
https://forum.vcfed.org/index.php?threads/sea … 880/post-556937

thanx

I decided for now that 0.5% of bad sectors is good enough

I've run spinrite a few times and it has returned some sectors to use... and also marked a few more... but the situation seems to be stable
spinrite has also "moved" the mbr or "track 0" so it can be made bootable by DOS

so for now it is alive and it works... it has DOS 5.0 installed and it boots fine 😀

rasz_pl wrote on 2023-05-31, 04:54:

Deunan wrote on 2023-05-27, 20:10:

If that HDD gets worse try low-level format on a mobo with BIOS that has that option.

good luck low level formatting anything IDE in general
https://forum.vcfed.org/index.php?threads/sea … 880/post-556937

I managed it aeons ago on one of those old connors that have a smooth pocket of a disk package held in a frame.. needed it to work in a compaq with limited disk types and I think I forced a type 17 or type 42 format on it, whereupon the Compaq liked it.... made horrible noises though.