What metal could this be?

I have had this assembly for over 20 years and not yet found a use for it!

It came out of an old hard disk drive and the carriage (made of a very light/soft alloy but has very thick/hard plating) had a stack of read/write heads that traversed the 10 or so disks.

The mystery bit is the body of the high precision dovetail bar, its very heavy, hard as nails and not intrinsically shiny. It is very slightly magnetic and has a tough dark grey coating or possibly has just oxidised. It produces no sparks when I touch it on a grindstone and has no machining marks other than almost invisible lines on the ends which look to be from some sort of cut disk. I have just tried to use an automatic centrepunch on it but it made no impression! The only other observation is that the grey coating looks slightly burnished where the ballraces track along.

It weighs 1.9Kg and is 65x15x245mm long.

Does anyone know what is likely to have been used to make this out of?

Ian

Might be Stellite Colin

The IBM labs in the village of Hursley, Hampshire is about five miles from the city of Winchester and it's possible that that your metal came out of a 'Winchester' disc pack, but please do not be mis-led, the name has more to do with a rifle than the city. . As you've hinted, this technology is, at the very least, 20 years old, my guess is more like 40 years old . I had many friends who worked at the complex but all have been retired for five years or more, nevertheless, you could make enquiries.

>gasp<

Pure unobtainium!

Neil

Sounds like tungsten to me!

Based on the dimensions and weight that you give the density works out at 7.95 g/ml so it is definitely not an exotic heavy metal like tungsten which has a density of 19.3 g/ml. The density 7.95 g/ml is very close to that of iron (density 7.87 g/ml) so I think it is likely to be a ferrous alloy. However, the lack of sparking when touched on a grindstone is strange for a hard ferrous alloy.

Mike

Mike

As you say its density rules out the heavy metal so its most likely some sort of steel. My guess would be Stainless 400 as even the strongest rare earth magnet I have is hardly attracted to it. 400 grade is used for some ballraces so it could certainly be hard enough. I can just about put a scratch in the surface by pressing hard with a sharp tungsten carbide scriber so its not that tough.

I was hoping someone here might have been involved in hard disk hardware and knew what sort of lengths manufacturers went to in the earlier days of computing.

Ian

hi The carriage is possibly magnesium and plated with electroless nickel,Early files with linear actuators,used ball slides on hardened steel rods ,later on ball races ran on hard ceramic rods ,though a number of files had rotary actuators, ,I never saw a bar as you described in a Hursley designed actuator, How big are the discs in this file? I have never seen the original US designed Winchester file. Lots and lots of problems with all files as one might expect in leading edge technology, Regarding mechanical manufacture,one problem were the very tight tolerances required,and it took a long time before very good cnc machines were available not only to reliably achieve the tolerances but to also make parts at an economical cost.Thermal expansion is another problem ,files used to get hot and expand and the design has to cater for the heads to register with the disc tracks within a temperature range. Your rod is the brainchild of some scientist somewhere and unless you had the dwg and specification you will have trouble finding out what it is,as there were many wierd and wonderful parts and materials used in files.

I worked on multi-platter disks at IBM in the late '60s & '70's. ish

EG types 2311, 2314, 3340 which had linear actuators. There were a lot of other manufacturers like Memorex, Raytheon, Telex [?] etc.

Piccy would be nice

A sort of sintered material was used on some machines for wearing surfaces. For some reason 'Carballoy' springs to mind but whether this is significant in your case I don't know.

Dave

I worked on this style of disk drive in the late 70's. I worked on repairing them and regular maintenance. Every 3 months or so we had to replace absolute air filters and check the head alignment against a reference disk pack. This would take a couple of hours. I had nothing to do with the manufacturing so I do not know anything about the materials used. Here is a link I found on the web to a service manual for one of this type of disk drive. These were removable pack drives not Winchesters. The manual shows the type of linear actuator used to position the heads. It was driven by a giant loudspeaker voice coil.

Les.

Ahh disk pack drives, that takes me back. Had loads of these and used to maintain them back in the early eighties. Ours had two spindles per 300Kg cabinet which took multi platter disks with a whopping 65Mb (unformatted) capacity. They had six heads including a servo head and it was always the wires on the servo head that went so you then had to align the flippin lot of them from scratch!

We did have a couple of Winchester drives over here but I'm afraid I have no idea on the construction, ours were made in either Scotland or Detroit. I do remember that you had to regularly check what they called the Christmas Tree, a bunch of resistors in parallel and series, which affected head alignment and occasionally drifted.

Les, yours looks very similar to the ones that were sold by Memorex, never had the pleasure (?) of working on those.

Paul

Try grinding it on a green disk to see if it cuts

Bri

Try grinding it on a green disk to see if it cuts

Bri

I did put a picture in the first post but it vanished after the first day. I have taken another picture which shows the other parts that came with it. The main dovetail bar was what I was curious about but I'm pretty sure now that is some sort of steel.

I think I paid about 30 shillings for it in about 1975 from a shop selling all sorts of surplus electronic junk.

The ballraces on the carriage must be quite high tolerance versions, the outer race has a higher than usual surface finish and it has virtually no lateral movement. The 'T' block is light alloy but not plated like the carriage.

Ian

The shop was on Lowfield Road in Stockport, does anyone remember it?

Edited By Ian Phillips on 02/08/2014 10:28:10

(I know 1975 was post decimalisation!)

Edited By Ian Phillips on 02/08/2014 10:40:56

Hi Paul,
The basic disk drive was made by Sperry Univac but we also had RP05/6 drives made by Memorex that were very similar. DEC added the controller to the side to interface it with the "massbus" which was the interface DEC used at the time for disk drives and tape drives. I was working for DEC at the time. Who were you working for ?

Les.

That's an interesting arrangement for a high-precision slide. It could be an economical way to make slides for something like a 3D printer which needs low friction and precision without having to take heavy loads.

Neil

Hi Les,

Thought it was familiar, I worked for Burroughs Machines which then acquired/merged with Sperry to become Unisys.

Paul

I always like to see the old spec sheets for hardware like that. I have a couple of Easi-Disk stand-along RS232 driver floppy drives, as used fro driving CNC machines and other processes without a computer!. They still work. I found them at a boot sale, left by someone who had just abandoned their stuff in the rain. I thought teh cases would eb handy, abut I eventually tracked down a manual on the net.

Neil;

Try grinding it on a green disk to see if it cuts

Bri

I would if I had a green disk. I have a normal wheel that came with a cheap bench grinder and have a diamond wheel at the other end.

No sparks from either, although I did not press very hard as I did not want to spoil the regular geometric appearance of the part.

I am convinced its a very hard grade of stainless

Ian