IBM Model F AT Bolt/Nut size?

anmq91 · 07 Dec 2019, 13:21

Hey guys,

My apologies if this thread has already been discussed, but my heavy-fisted google and DT searches yielded absolutely nothing. I've got an F AT that I am trying to open and cannot seem to find the correct driver size. I have the 5.5mm from my model M but that is too small. I read somewhere vaguely that it 'may' be 7.5mm (metric because I'm living in Germany). There seems to be not a single place where i can buy a 7.5mm driver (Can only find 7mm or 8mm) - let alone a slim fit one to fit into the recess. The closest I can find is purchasable online but it is 7.9mm and i do not know if it the head will fit in the recess.

Since many of you have done the AT restore/opening it up, would really appreciate it if someone could give me a correct size/sizes that would fit my AT screws. It's been days now that I've been trying to get it open and I have already spent north of 40 USD buying different drivers to no avail

cli · 07 Dec 2019, 13:51

You need something like this....
https://www.amazon.de/dp/B00TGUB52C

60mm

anmq91 · 07 Dec 2019, 14:14

Ah yeah I think this should fit in the recess, however just noticed that it is 6.5mm. Is that the correct size?

cli · 07 Dec 2019, 14:43

Just checked my bit, yes.. 6.5 mm should work

anmq91 · 07 Dec 2019, 15:17

Thank you so much! You're awesome. I'll run out and buy a bit today and hopefully get mine opened!

anmq91 · 07 Dec 2019, 15:56

And alas - no 6.5mm drivers to be had in Germany either. Would a 6.3mm driver work by any chance? :/

John Doe · 07 Dec 2019, 15:58

Well, why not bring the board to the local shop and give a shot directly?

kmnov2017 · 07 Dec 2019, 16:08

What nut are you trying to remove? My F AT only has screws in them...

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anmq91 · 07 Dec 2019, 16:13

Was trying to avoid lugging the board to the shop. Also, the shops here don't have much selection in this stuff. Most of this stuff has to be ordered online. @kmnov, my F AT has bolts like the Model M ones in the back, just bigger. I am not sure of the size in inches though, and cannot seem to find a 6.5mm bit.

kmnov2017 · 07 Dec 2019, 16:16

Have a look at the pic I posted. Thats how my AT shipped with.

anmq91 · 07 Dec 2019, 16:38

kmnov2017 wrote: 07 Dec 2019, 16:16 Have a look at the pic I posted. Thats how my AT shipped with.

Thats really lucky and odd, mine are standard bolts -

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Muirium · 07 Dec 2019, 16:45

All right folks, Mu to the rescue!

: IBM case bolts.jpg (1.28 MiB) Viewed 3948 times

Foreground: Model M SSK — gold coloured, recessed 5.5 mm hex headed bolt
Back left: XT — gold coloured, flush mounted large hex headed bot (>6 mm?) with handy flat screw cut
Middle back: Kishsaver — black, flush mounted circular headed 3 mm hex bolt
Right back: AT — silver, recessed, dome headed 2.5 mm hex bolt (3/32 inch also works)

The AT's bolts are recessed at least 1 cm from the case's outer surface. Just a smidge less deep than the SSK's.

Edit: Wait!? IBM really mixed and matched with the bots! That's your AT, right? Those bolts need a hex spinner, like a Model M. My kit of hex spinners maxes out at 5.5 mm…

anmq91 · 07 Dec 2019, 17:01

Muirium wrote: 07 Dec 2019, 16:45 All right folks, Mu to the rescue!

IBM case bolts.jpg

Foreground: Model M SSK — gold coloured, recessed 5.5 mm hex headed bolt
Back left: XT — gold coloured, flush mounted large hex headed bot (>6 mm?) with handy flat screw cut
Middle back: Kishsaver — black, flush mounted circular headed 3 mm hex bolt
Right back: AT — silver, recessed, dome headed 2.5 mm hex bolt (3/32 inch also works)

The AT's bolts are recessed at least 1 cm from the case's outer surface. Just a smidge less deep than the SSK's.

Edit: Wait!? IBM really mixed and matched with the bots! That's your AT, right? Those bolts need a hex spinner, like a Model M. My kit of hex spinners maxes out at 5.5 mm…

Thanks for the specs Mu! Yeah that's my F AT, and I guess they were mixing and matching. These seem to be the original bolts as well. The 5.5mm Hex spinner for my IBM model M is too small for it. So I'm still not sure which size driver I should order :/ Also considering that whatever I order had to be online, each one ends up being 14-20 usd so I can't just order many of them and hope on one of them to work :/

Muirium · 07 Dec 2019, 17:03

Yeah, looks like you need something very similar to, but larger than, your Model M hex spinner. Ordering a kit would tempt me, but then I'd just be taking up space with tools I don't need. Ordering individual drivers and returning all those that aren't a match may be a smart choice.

The upside is those AT holes can only take bolts up to a certain size. My pic is shot on the back of my AT, so there's a bolt hole just at the edge of frame, at the right. Can't be too much larger than the 5.5 mm spinner, I think.

For what it's worth, my XT's bolts are a touch too big for my biggest hex spinner. Hard to measure with a ruler (I don't have calipers) but I'd guess they're 6 mm.

kmnov2017 · 07 Dec 2019, 17:31

Conrad sells hex drivers individually for about 5/6 euros. If they don't work , you can return them.

anmq91 · 07 Dec 2019, 17:45

So I just ordered 6mm, 6.3mm, 7mm and 8mm. I'm sure the 8mm was overkill but I'd rather return one extra driver than pay 6.50 Euros for delivery a second time. Hopefully should be here by tuesday. I'll post back with more info as soon as I'm able to try them out! Thanks for the info and help everyone