2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

[Brian Cryer]

I'm looking at a replacement laptop disk. Some sites now list some disks as
2.5" x 1/8H, 2.5" x 1/6H, 2.5" x 1/4H (or just simply as 2.5"). I'm not
familiar with the 1/4H (etc) designation, could someone tell me what it
means and how I can tell from my existing disk which I need?

TIA.

 

[Dave]

I'm looking at a replacement laptop disk. Some sites now list some disks
as 2.5" x 1/8H, 2.5" x 1/6H, 2.5" x 1/4H (or just simply as 2.5"). I'm not
familiar with the 1/4H (etc) designation, could someone tell me what it
means and how I can tell from my existing disk which I need?

TIA.

It refers to the height, but I'm not sure of the correspondence between the
number given and the physical height (thickness). 1/8H corresponds to .4"
(about 10mm) in the randomly chosen spec below:
http://www.provantage.com/toshiba-hdd2d15-50pk~7TOSD036.htm

on another 1/4H corresponded with 19 mm.

 

[GT]

It refers to the height, but I'm not sure of the correspondence between
the number given and the physical height (thickness). 1/8H corresponds to
.4" (about 10mm) in the randomly chosen spec below:
http://www.provantage.com/toshiba-hdd2d15-50pk~7TOSD036.htm

on another 1/4H corresponded with 19 mm.

I think it refers to the size of drive bay the disk is intended for, rather
than the actual measurement of the drive.

 

[Dave]

I think it refers to the size of drive bay the disk is intended for,
rather than the actual measurement of the drive.

I think you are right, although it strikes me that if the folk on this
newsgroup are uncertain about it then the manufacturers are not giving very
clear data here!

 

[Joel]

I think you are right, although it strikes me that if the folk on this
newsgroup are uncertain about it then the manufacturers are not giving very
clear data here!

2.5" is the diameter of the DISC and 1/8" - 1/4" is the height of the CASE

Right now we have

- 1.8" (I believe I even read 1.3" or 1.5") you may see they use on some
digital portable storage devices

- 2.5" usually use on laptop

- 3.5" is usually use on desktop

Before we had

from around 8", 13", 25", 28" and up to around 36-42+" or so. and somewhere
in between I can't remember. I used to go through thousands of them daily
for years.

 

[kony]

I think you are right, although it strikes me that if the folk on this
newsgroup are uncertain about it then the manufacturers are not giving very
clear data here!

Manufacturers generally spec in actual millimeter height,
not 1/2H, etc. The surest bet is to measure the drive caddy
in the laptop, what max size drive would fit in it, and
compare to the specific drive model, manufacturer's
datasheet.

 

[kony]

2.5" is the diameter of the DISC and 1/8" - 1/4" is the height of the CASE

If only it were but it isn't. A typical case might be 9.(n)
millimeters tall, meant to be just under 10mm. That's
inbetween 1/8 and 1/4", closer to about 1/2.7 of an inch.

 

[CBFalconer]

I think you are right, although it strikes me that if the folk on
this newsgroup are uncertain about it then the manufacturers are
not giving very clear data here!

The original floppy drives, both 8 inch, and 5 inch, were 3 1/2"
high. The fractions are referred to that. When they got down to
1/2 size in 5 inchers the price dropped to about $50 each. Now
they go for 5 to 10. Hard drives just followed the same form
factor.

 

[Joel]

If only it were but it isn't. A typical case might be 9.(n)
millimeters tall, meant to be just under 10mm. That's
inbetween 1/8 and 1/4", closer to about 1/2.7 of an inch.

I have never paid any attention to the height of 2.5" drive, but right
after the original posted the question I did Google and saw 3 different
heights for the first time myself.

 

[Joel]

The original floppy drives, both 8 inch, and 5 inch, were 3 1/2"
high. The fractions are referred to that. When they got down to
1/2 size in 5 inchers the price dropped to about $50 each. Now
they go for 5 to 10. Hard drives just followed the same form
factor.

In either late 70's to early 80's while I was still working, they were
already testing the disc little larger than US 25-cent coin. But for some
reason it never got released, and they were also testing 1.8MB and 2.6MB
3-1/2 floppy

So many things have changed.

 

[~misfit~]

It refers to the height, but I'm not sure of the correspondence
between the number given and the physical height (thickness). 1/8H
corresponds to .4" (about 10mm) in the randomly chosen spec below:
http://www.provantage.com/toshiba-hdd2d15-50pk~7TOSD036.htm

on another 1/4H corresponded with 19 mm.

I believe that it's the 'height' of the drive, expressed as a fraction of
the old 'full height' drives.

A full height drive is around 80mm. (An optical drive is classed as
half-height, around 40mm.) Therefore the numbers represent one eigth of
~80mm, or one quarter of ~80mm etc.

At least that's my take on it.

 

[leew]

I can't say I've ever seen the 1/8, 1/6, 1/4 designations before.

Most sites measure drives in height by mm - millimeter. I'd suggest
looking up the drive that's in your laptop and confirming it's size at
the manufacturer's web site and then find one with comparable physical
specifications.

-Lee

 

[CBFalconer]

leew wrote: *** and top-posted - fixed ***

I can't say I've ever seen the 1/8, 1/6, 1/4 designations before.

Most sites measure drives in height by mm - millimeter. I'd
suggest looking up the drive that's in your laptop and confirming
it's size at the manufacturer's web site and then find one with
comparable physical specifications.

Please don't top-post. Your answer belongs after (or intermixed
with) the material you quote, after snipping irrelevancies.

IIRC "Full Height" refers to 3 3/4 inch high units, thus 1/2 is 1
7/8 inches, etc.