Vinyl Record Centre Hole diameter

[mossboss]

Hi all
I am curious to know how the centre hole size on records was established
It is in imperial, 0.286" +001 -002 Thou or 7.264 MM
A rather odd size in both cases Any one can shed light on this?
Cheers

[Jesus H Chrysler]

from my experience a 9/32" (.28125) bit cuts a perfect record hole

[mossboss]

This is the standard

R. I. A. A. DIMENSIONAL CHARACTERISTICS
33 1/3 RPM PHONOGRAPH RECORDS FOR HOME USE
7" Records 10" Records 12" Records
Outside Diameter 6 7/8" + 1/32" 9 7/8" + 1/32" 11 7/8" + 1/32"
Thickness
a. Flush Design .075" + .010" -.015" .075" + .010" .075 + .010"
b. Contour Design
(See drawings) Fig. 2; Fig. 3 Figure 1 Figure 1
Center Hole Diameter (Same as 10") 0.286" + 0.001" -0.002" (Same as 10")
This is a short version of the standard as published in 1961
Well lets be realistic Indeed a 9/32" drill bit would cut a hole around that size indeed, as they do wonder while drilling
Record labels are either kiss and cut or drilled to that size 9/32" which is some 5 odd thou smaller in diameter so they hang on to the pins on the dies when you press records
In so far as standard metric sizes are concerned
7.20 mm is .2835"
7.30 mm is .2874"
I have often thought that this was the reason you can buy paper drill bits that size 9/32"
Any way I was wondering how and why it was decided to be this size

[Aussie0zborn]

Mmmm... good quesiton. I hope you're not losing sleep over this????

There is also a British Standard for grammophone records and you might find some information there. Part of the British Standard is that each label would include the speed and the song titles. Would be nice if this part of the standard (song titles on every lable) extended to CDs! "Refer to inlay card" is fine, but what if you have lost the inlay card???)

[mossboss]

There is allways a reason for these things to come about I mean why this and not say 1/2" or a standard reamer size It often annoys the hell out of me since we have to have replacement pins and they cost a lot to get them made since they have to get a special size reamer so as to have a sliding fit from the pin plate holder combination
No I am not loosing sleep but I am sure there will be some obscure reason that this size was chosen
Cheers

[drdub]

in everything we cut, we widen the hole to 7.20mm (.2835").
it seems to fit all pins and no one ever complaining.

[mossboss]

Dr Dub
Do you do it with a drill bit? Cheers

[drdub]

yes, a drill bit fitted with a screwdriver handle

[mossboss]

Still curious as to why this size was chosen I am sure there is a reason No one just decides that this is it without a reason There are to many instances where a particular size method or whatever was adopted for a reason This must fall into one as well I am sure ther someone out there to shed light on it
Cheers

[cuttercollector]

Well, the flat disc was developed in Europe, so why is it not based on a even metric number? Did it get standardized later? Is it a compromise between inch and metric? Who has an original Berliner disc they can measure?
My Revox table has a spindle which is just a shade over .285 or so and seems tight on most records.

[MEGAMIKE]

hi mossy
i think that the size of the hole is the size of a universal drill tip ..iam not sure if it is the first measure of a drill bit, but hey thats just my hunch.
.like a drill press and they are 100s of years old ....
.

[markrob]

hi mossy
i think that the size of the hole is the size of a universal drill tip ..iam not sure if it is the first measure of a drill bit, but hey thats just my hunch.
.like a drill press and they are 100s of years old ....
.

Hi,

As far as I can see, its smack dab in between a K (.281") and an L (.290") drill. So, I don't see that its a standard size hole. Very strange.

[mossboss]

Hey All and Bob
I am in the same boat It's got me bugged, it is not K=7.15 mm or L=7.35 mm or as pointed out above their imperial sizes All letter and Numbered drills are imperial measures anyway and since it was a German trip it would have been metric one assumes It gets further confusing since there is no standard size reamer that suits My initial thoughts where that it was a K drill and ream it out but it is not the case in both meric and imperial size reamers
I am convinced there is a reason for it So the search is still on So here we are Anothe arcane bit of missing info
Cheers

[mossboss]

Hey All and Bob
I am in the same boat It's got me bugged, it is not K=7.15 mm or L=7.35 mm or as pointed out above their imperial sizes All letter and Numbered drills are imperial measures anyway and since it was a German trip it would have been metric one assumes It gets further confusing since there is no standard size reamer that suits My initial thoughts where that it was a K drill and ream it out but it is not the case in both meric and imperial size reamers
I am convinced there is a reason for it So the search is still on So here we are Another arcane bit of missing info
Cheers

[mossboss]

Well, the flat disc was developed in Europe, so why is it not based on a even metric number? Did it get standardized later? Is it a compromise between inch and metric? Who has an original Berliner disc they can measure?
My Revox table has a spindle which is just a shade over .285 or so and seems tight on most records.

Hey All
Just won a set of 5 x 9/32" expanding reamers for the princely sum of $14 They will expand to the infamous hole size of a record
It beats paying $120 Each for them custom msde, as they no longer available here We gone all metric so imperial stuff is hard to get and a set of five was quoted at nearly $250 And guess what these are USA made
Still want to know Why that silly size

Cheers

[W.B.]

0.286" sounds like a nearest rounding off to the nearest thousandth of 0.285714285714..." (2/7"). As for center holes on center labels, I've seen them vary from 0.28" (7/25") to 0.28125" (9/32") to 0.2890625" (37/128"). (And I have a few label sheets, printed on paper ranging from C2S to uncoated to Kromekote [printed on the uncoated side if LP label], so I can attest to that; how much the label shrinks after being pressed onto the record is a story in and of itself, to be examined on another thread.)

Also, metric-wise there's 7.25mm whose English measurement equivalent is 0.28543307086614..." .

Why this was chosen . . . sounds like it was made up as they all went along, dating back to way before the onset of the "electrical era" of disc recording.

[emidisc]

By coincidence I today produced a stack of Polystyrene blanks for my own use,
I have set up a Routing fixture to machine 7", 10" & 12" blanks but have struggled for a while to get the centre holes just right and usually need to open them up a little so glad it's not just me with this problem.

[mossboss]

A 9/32" drill bit will do the job
Drill bits never drill a perfect hole any way due to wobbles on the chuck so it will be slightly larger but good enough
In so far as labels shrinking, PVC, as well as pins which are a bit on the questionable size resulting in tight holes Tra La la
Its a never ending battle
At least on the auto trimming record machines machines one can get a taper pin which is slightly larger by say 3-5 thou, so when the record is transferred there for trimming away the flash, it will get resized as it is pushed on the trimmer table
On the Leneds one needs to boost the silly vacuum pump which is standard on them
With the Alphas its quite OK
Also the manual trimmers are quite easy to deal with as well
It works quite well, saves a lot of hole size related issues
Now Back to the subject. He He

I am sure there is a reason for that silly size of 9/32" I do know things are never done for no reason may be Berliner had a stack of rods in his workshop or some arbitrary reason but I would have thought this would be quite improbable
It has become a bit of a holly grail chase Ha
Cheers

[W.B.]

Over the years, many sizes were used for die-cut centre holes for vinyl record labels in the U.S. From least to most (with those over 0.3" usually for styrene labels), they are:
J - 0.277" (7.096mm)
K - 0.281" (7.137mm)
9/32" - 0.28125" (7.144mm)
L - 0.290" (7.366mm)
M - 0.295" (7.493mm)
N - 0.302" (7.671mm)
5/16" - 0.3125" (7.938mm)
O - 0.316" (8.026mm)
R - 0.339" (8.611mm)
11/32" - 0.34375" (8.731mm)
S - 0.348" (8.839mm)
T - 0.358" (9.093mm)
3/8" - 0.375" (9.525mm)
V - 0.377" (9.576mm)
W - 0.386" (9.804mm)
X - 0.397" (10.084mm)

0.339" thru 0.358" were generally used for styrene 7" 33⅓ RPM labels on Columbia pressings. 0.375" thru 0.397" by PRC in Richmond, IN.

I do have a loose label, meant for one of the Beatles' reissues on the Oldies 45 label, which hole was either 17/64" - 0.265625" (6.747mm) or H - 0.266" (6.756mm).

There may be a possibility of some of the metric drills being used by certain printers or pressing plants, to wit:

7.0mm = 0.2756"
7.2mm = 0.2835"
7.3mm = 0.2874"
7.7mm = 0.3032"
8.9mm = 0.3504"
9.7mm = 0.3819"

[boogievan]

The RIAA didn't want the pressing center-hole standard to have more than three numbers to the right of the cipher for us to recall. So they forced it to work in fractions of an inch by invoking an unequal tolerance, plus and minus what they state to be the 'center' number. But it's offset, like.

Because of the uneven tolerance ("+ 0,001" / - 0,002" ") I'll venture that they're implying that it's really 0,2854330709 ", which is the standard metric bit-size, 7,25 mm, which Emil (as he originally spelled it) probably used.

Making the RIAA standard's tolerance equal (plus and minus) gives us quite nearly that metric standard.

Try adding 0,0015" to the Imperial equivalent of 7,25 mm, and we get nearly right up to the RIAA's max, though, technically, 'only' at 0.2869330709" (which, though less, is very nearly RIAA's implied max of 0,287 (= 0,286 + 0,001, innit?)).

Similarly, by subtracting 0,0015" from the Imperial equivalent of 7,25 mm, we get only a very small amount less than the RIAA's min, at 0.2839330709" (which, though less, is very nearly RIAA's impled min of 0,284 (= 0,286 - 0,002)).

So, I'm rooting for 7,25 mm as Berliner's bore. 0;

- Boogie